Yan Suffren
email: yan.suffren@unige.ch

Niall O'toole

Andreas Hauser

Erwann Jeanneau

Arnaud Brioude

Cedric Desroches
email: cedric.desroches@univ-lyon1.fr

Cédric Desroches

Discrete polynuclear manganese(ii) complexes with thiacalixarene ligands: synthesis, structures and photophysical properties

de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

The macrocycle p-tertbutylthiacalix [4]arene (ThiaS), a homologue of the calixarene family, consists of phenol moieties linked by sulphur atoms. Its ease of accessibility and strong multichelating power, arising from the proximity of the phenoxide groups to the bridging sulphur atoms, make this ligand a popular choice in coordination chemistry. Consequently, since the first synthesis of this molecule was described by the Myano group in 1997 1 (Scheme 1), a multitude of polynuclear metal complexes have been isolated, reinforcing: (i) its structuring role in the creation of either highnuclearity isolable paramagnetic metal aggregates, 2 or the coordination-based molecular 'building bricks' leading to nano-capsule formation by supramolecular assembly, 3 and (ii) its electronic properties, known as the antenna effect, for luminescence in ions such as Tb 3+ or even Eu 3+ . 4 Scheme 1 Representation of p-tertbutylthiacalix [4]arene (ThiaS with X = S), ptertbutylsulphoxylcalix [4]arene (ThiaSO with X = SO) and p-tertbutylsulphonylcalix [4]arene (ThiaSO 2 with X = SO 2 ).

In previous work, we found that under solvothermal conditions p-tertbutylthiacalix [4]arene and its sulphonyl and sulphoxide derivatives give rise to tetranuclear metallic complexes comprising Mn 2+ ions. Differences in both the optical and structural properties were observed between those complexes obtained with ThiaS and ThiaSO, 2d and those obtained with ThiaSO 2 . 2k For ThiaS and ThiaSO neutral complexes are attained, consisting of two macrocycles and four Mn 2+ ions in trigonal biprismatic geometry. In both of these cases, no specific luminescence properties have been observed. For ThiaSO 2 a similar structure is obtained with the sole difference being the presence of a µ 4 -OH -group at the centre of the square formed by the four Mn 2+ ions, which display capped trigonal biprism coordination geometry. This µ 4 -OH -results in a negative charge over the aggregate, which is compensated by the presence of an alkali metal ion. In the solid state this ion interlinks the aggregates by ways of coordination to the oxygen atoms of sulphonyl groups. This family of clusters demonstrates an ambient temperature luminescence at a wavelength of approximately 580 nm when excited by illumination of 360 nm. Replacing the µ 4 -OH -with µ 4 -F - considerably increases the luminescence lifetime of this system.

The strong luminescence of the Mn 2+ ion arising from 4 T 1 ( 4 G) state was put to use at the start of the 20 th century in luminescent mineral materials using red or green phosphors (neon discharge, fluorescent lamp). 5 Since then, intense spectroscopic studies have been carried out, which shed light on the importance of the environment of the Mn 2+ ion as regards its luminescence properties. 6 However, despite the development of coordination chemistry, few studies have shown Mn(II) complexes presenting such properties at ambient temperature. 7 For this reason, we have resolved to pursue further investigation on the [Mn 4 (ThiaSO 2 ) 2 F] -system by spectroscopic analysis, in both solution and the solid state. Moreover it has been shown that the conformation of the macrocycle, as well as the presence of sulphonyl groups, significantly modifies the electronic properties of the thiacalixarene family of complexes. 8 Herein we report the preparation, crystal structures and photophysical behaviour of the new compound [Mn 4 (ThiaSO 2 ) 2 F][K(18C6)] (2), 18C6 = 18-crown-6, and compare the latter to the one of [Mn 4 (ThiaSO 2 ) 2 F]K (1). We thus will study: (i) the effect of removing the K + -sulphonyl interaction, and (ii) the effect of the conformation of the macrocycle.

Results and discussion

Crystal structure

The compounds of the tetranuclear complex 1 and 2 were obtained as pale-yellow coloured crystals with a relatively high yield by solvothermal reaction of MnCl 2 •4H 2 O, p-tertbutylsulphonylcalix[4]arene (ThiaSO 2 ) and KF for 1 and by adding 18C6 for 2 in a 1/10 (v/v) H 2 O/MeOH mixed solvents (total 11 ml) at 170°C during at least 2 days.

Compounds 1 and 2 are composed of squares of four manganese (II) ions sandwiched between two ThiaSO 2 macrocycles as shown in Fig. 1 and 2. In the middle of the square formed by the four manganese(II) ions, the presence of µ 4 -F -gives a negative charge to the cluster. The electroneutrality of the complex is achieved by the presence of the K + cation, coordinated by sulphonyl and methanol groups for 1 and coordinated by 18C6 and two methanol molecules for 2.

The originality of this type of aggregate, with a sevenfold [MnO 6 F] coordination polyhedron having approximately C 2v symmetry and a square planar relationship to the fluoride group (Scheme 2), has already been discussed in a previous article. 2k Both compounds crystallise in the P1 space group (for details of the structure determination see experimental section and Supporting Information). 9

For both, the centre of symmetry positioned on the fluoride group requires that the macrocycles, on either side of the square formed by the manganese ions, are crystallographically equivalent. The 5); F2-Mn3 2.1732(5); Mn1-O8 2.169(2) < Mn-O < Mn1-O4 2.242(2). Symmetry transformations used to generate equivalent atoms: i (1-x, 1-y, 1-z); ii (-1+x, y, z); iii (-3-x, 1-y, 1-z); iv (1+x, y, z); v (2-x, 1-y, 1-z). The tetranuclear clusters in 1 are linked through the coordinated potassium ion and sulphonyl group, making 1 a one dimensional network (Fig. 3a). The coordination of K + by the crown ether in 2 prevents interactions between the sulphonyl groups and the potassium ion. The tetranuclear clusters in 2 stack upon each other along the c-axis of the network, forming columns which are isolated from one another by the inclusion of [K18C6] + groups (Fig. 3b). The shortest distance of the interaction between the K + ion and the tetranuclear cluster in compound 1 is 2.72 Å (distance O15 -K60) whereas for compound 2 it is 5.54 Å (distance O8 -K60).

Photophysical characterisation

Absorption and luminescence in DMF solution: Fig. 4 shows the absorption, excitation and emission spectra at room temperature in dimethylformamide (DMF) solution of [Mn 4 (ThiaSO 2 ) 2 F]K (1) and [Mn 4 (ThiaSO 2 ) 2 F][K(18C6)] (2) between 11000 and 38000 cm -1 (265 -910 nm). The absorption spectrum of 1 is identical to that of 2. The absorption bands observed are mainly the signature of the ThiaSO 2 calixarene ligand. In the UV region there are two band maxima and at 28490 cm -1 (351 nm) and 35300 cm -1 (283 nm), respectively. These two bands can be attributed to π → π* transitions of the ThiaSO 2 ligand. The molar extinction coefficient of the intense absorption band at 28490 cm -1 is within experimental accuracy identical for the two compounds with a value of ε max = 72000 M -1 cm -1 .

Fig. 4 Absorption (red and dark blue curves), excitation (red and blue dotted curves) and emission (orange and light blue curves) spectra in DMF solution of [Mn 4 (ThiaSO 2 ) 2 F]K 1 and [Mn 4 (ThiaSO 2 ) 2 F][K(18C6)] 2 at room temperature, c = 1.5×10 -4 M for 1 and c = 1.2×10 -4 M for 2

for the absorption and emission spectra, and c = 1.5×10 -6 M for 1 and c = 1.3×10 -6 M for 2 for the excitation spectra. The spectra of 2 are offset along the intensity/absorptivity axes for clarity.

The emission spectra of 1 and 2 in DMF (see Fig. 4) upon photoexcitation at 28570 cm -1 (350 nm) show an intense and broad luminescence band between 12000 and 18000 cm -1 (555 -833 Wavelength (nm)

% ν max1 % ν max 2
+ 15000 M -1 .cm -1
nm) with a maximum % ν max at 15010 cm -1 (666 nm). As expected, in solution the influence of the cation is negligible and no difference in the emission spectra between the two compounds has been observed. The orange-red luminescence with a very large gap between the strong absorption at 28490 cm -1 , a lifetime of 35 µs and a quantum efficiency of 0.4% in non-deoxygenated solution at 298 K (compared to 1.08 ms and therefore around 15% in a deoxygenated solution) originates from the lowest energy component of the 4 T 1 (t 2g 4 e g 1 ) → 6 A 1 (t 2g The above is further borne out be the excitation spectra of both compounds in DMF solution included in Fig. 4, which were collected at the emission maximum of 15380 cm -1 (650 nm) and at very low concentrations of c = 1.5×10 -6 M in order to minimise saturation effects in the region of the strong UV absorption bands. They are indeed perfectly superimposed to the absorption spectra thus proving unambiguously that the emission is intrinsic to the complexes.

Solid-state emission and excitation spectra:

The low temperature solid-state emission and excitation spectra for the compounds 1 and 2 are displayed in Fig. 5. Upon excitation at 28570 cm -1 (350 nm), 1 presents an intense broad and asymmetric emission band centred at 16600 cm -1 (602 nm) with a full width at half maximum (FWHM) of approximately 1700 cm -1 . In contrast, 2 shows an intense symmetric emission band at 15660 cm -1 (639 nm) and a FWHM of about 2000 cm -1 .

Thus there is a redshift of the luminescence band maximum by around 950 cm -1 and an increase by about 18% of the FWHM between compounds 1 and 2. As in solution, the orange-red luminescence band originates from the 4 T 1 → 6 A 1 transition of the Mn(II) in d 5 high-spin configuration.

Fig. 5 Solid-state emission spectra (solid curves) at 7.5 K upon photoexcitation at 28570 cm -1 (350 nm) and excitation spectra at 8 K (dotted curves) of [Mn 4 (ThiaSO 2 ) 2 F]K 1 (blue) and

[Mn 4 (ThiaSO 2 ) 2 F][K(18C6)] 2 (red).
The solid-state excitation spectra at 8 K for both compounds are included in Fig. 5. In the UV region of the strong ligand-centred π-π* absorption bands they are saturated. However, they show a broad and structured band with two maxima and localised at approximately 19200 cm -1 (521 nm) and 20800 cm -1 (481 nm), respectively, and an indication of a shoulder on the high-energy side. These can be attributed to the split components of the d-d 6 A 1 → 4 T 1 transition of the manganese(II) ion, as in C 2v the excited 4 T 1 state is split into three energy level in first order.

Temperature-dependence of the Mn 2+ luminescence: The luminescence of 1 and 2 in the solid state between 7.5 K and room temperature and in vacuum on excitation at 28570 cm -1 (350 nm) is shown in Fig. 6. The luminescence intensity of 1 decreases only slightly as temperature increases up to just below room temperature and then drops more rapidly to 70% of its low-temperature value, as shown in Fig. 7. At the same time the FWHM increases by 29%, that is, from 1700 to 2200 cm -1 , whereas the band maximum is stable between 7.5 and 100 K with a value of 16600 cm -1 , and shifts to slightly higher energies above 100 K.

% ν max1 % ν max 2 % ν max Fig. 6 Solid-state emission spectra of [Mn 4 (ThiaSO 2 ) 2 F]K 1 (a) and [Mn 4 (ThiaSO 2 ) 2 F][K(18C6)] 2 (b
) between 7.5 and 300 K upon photoexcitation at 28570 cm -1 (350 nm).

For 2 the luminescence shows the same temperature dependence as for 1 with a somewhat smaller decrease to 88% between 7.5 and 300 K. The variation of the FWHM is slightly larger for 2 than for 1, with an increase by approximately 39% from 2000 cm -1 to 2780 cm -1 in the same temperature range, and a slight redshift from 15660 to 15630 cm -1 between 7.5 and 25 K followed by a blueshift to 16090 cm -1 is observed for 2. At a given temperature, the FWHM for 2 is larger than for 1.

Fig. 7b includes the luminescence lifetimes for 1 and 2 between 3 K and 300 K under pulsed photoexcitation at 28170 cm -1 (355 nm). Decay curves are close to single exponential except for a small deviation at short times. At 3 K the lifetimes calculated by the Igor fitting software 11 are 2.12 ms for 1 and 2.31 ms for 2, respectively. They increase between 3 K and 75 K for 1 with a maximum value of 2.41 ms and between 3 K and 100 K for 2 with a maximum value of 2.48 ms.

Then, the lifetime values decrease gradually up to room temperature reaching 1.65 ms and 2.00 ms for 1 and 2, respectively. The luminescence quantum yield for 1 in the solid state at room O 2 pressure-dependence of the Mn 2+ luminescence-quenching in the solid state: As mentioned above, in solution the presence of oxygen quenches the Mn 2+ luminescence considerably, such that in a deoxygenated solution at room temperarature the luminescence quantum efficiency is around 15% whereas under atmospheric conditions it is only 0.4%. What about the influence of O 2 on the solid-state luminescence? Fig. 8 shows the luminescence spectra of 1 and 2 at 298 K as a function ) For 1, the luminescence intensity decreases only by approximately 15% between 0.1 and 1010 mbar. For 2, the intensity decreases quite rapidly to less than 5% of its initial value. The difference in behaviour between the two compounds must be due to the structural differences. In 1, the K + cations bridge the [Mn 4 (ThiaSO 2 ) 2 F] -entities leading to compact structure limiting the diffusion of the dioxygen into the lattice. In contrast, for 2 the isolated [K(18C6)] + cations create a porous structure with empty spaces between the [Mn 4 (ThiaSO 2 ) 2 F] -entities connected only by weak ionic interactions. The dioxygen can be removed or introduced more easily into the structure. The most probable mechanism for the quenching of the spin-forbidden Mn 2+ centred 4 T 1 → 6 A 1 luminescence is given by a spin-conserving energy transfer process from the excited complex to O 2 thereby exciting O 2 from its 3 Σ - g ground state to the excited 1 Σ + g state. 12 For comparison to the solid state, the O 2 pressure-dependence of the luminescence behaviour was studied for the two compounds in DMF solution where the [Mn 4 (ThiaSO 2 ) 2 F] - tetranuclear complex is considered as totally isolated. The luminescence spectra of solutions of 1 and 2 after different times (0 -900 s) of de-oxygenation by N 2 bubbling were recorded (see Fig. S1 and S2 in Supporting Information). The reversibility was checked as function of time (0 -3600 s)

Luminescence ν max [Mn 4 (ThiaSO 2 ) 2 F]K [Mn 4 (ThiaSO 2 ) 2 F][K(18C6)] Luminescence FWHM [Mn 4 (ThiaSO 2 ) 2 F]K [Mn 4 (ThiaSO 2 ) 2 F][K(18C6)]
of re-oxygenation of the N 2 saturated solution by exposing them to air (see Fig. S3 and S4 in Supporting Information). As for the solids, the luminescence behaviour is reversible, with an increase and a decrease of the luminescence intensities by bubbling N 2 (removal O 2 ) and by reoxygenation (exposing to air), respectively. The maximum luminescence intensities are observed after approximately 120 s of N 2 bubbling (see Fig. S5 in Supporting Information).

Pressure-dependence of the Mn 2+ luminescence: Fig. 9a and 9b show the luminescence spectra of 1 and 2, respectively, between ambient pressure and 10 GPa at room temperature. In addition to the broad band due the Mn 2+ luminescence, all show a series of sharp bands corresponding to BaFCl:Sm 2+ f-f luminescence introduced into diamond anvil cell (DAC) as in situ pressure sensor. 13 For 1 the luminescence intensity increases by approximately 10% between ambient pressure and 0.3 GPa, then it decreases gradually and becomes very weak at a pressure of 9.6 GPa. At the same time the luminescence band maximum shifts linearly to lower energies by -230 cm -1 /GPa (Fig. 10a). For 2, the behaviour at variable pressure is very similar to 1, except that the initial increase in intensity up to a pressure of 0.4 GPa is much larger. The luminescence band maximum is stable up to this pressure, above that pressure it likewise shifts to the red by -190 cm -1 /GPa, that is, close to the value obtained for compound 1 (Fig. 10a). Such a redshift is expected for the spin-forbidden ∆V ≈ 5 Å 3 /complex. This is in line with ligand-field theoretical considerations. As pressure increases, the Mn-O bond is slightly compressed and therefore the ligand-field strength increases.

According to the Tanabe-Sugano diagram 15 for d 5 this results in a decrease of the energy of the 4 T 1 state with respect to the 6 A 1 ground state. The pressure in the DAC has been determined by following the shift of the 5 D 0 → 7 F 0 emission band of the samarium(II) ion in BaFCl:Sm 2+ compound (room temperature rate of -21 cm -1 /GPa). 13 The luminescence lifetimes between ambient pressure and 10 GPa and are plotted in Fig. 14 orbital to an anti-bonding e g orbital results in an expansion of the coordination sphere during the emission process. Thus external pressure destabilises the ground state with respect to the first excited state by a work term of the form p∆V. 14 The shift of around -200 cm -1 /GPa corresponds to Fig. 10 a) The energy band maxima upon photoexcitation at 24690 cm -1 (405 nm) of 1 (circles) and 2 (squares). b) Luminescence lifetimes (left axis) and integrated luminescence intensities (right axis) of 1 (circles) and 2 (squares) as function of pressure. The luminescence lifetimes and intensities at 298 K were obtained upon photoexcitation at 28170 cm -1 (355 nm, pulsed laser) and 24690 cm -1 (405 nm, continuous laser) respectively.

For 2, the luminescence lifetime of 0.57 ms at ambient pressure in the DAC is lower than the lifetime of 2.00 ms measured at room temperature and ambient pressure in a helium gas medium. Indeed, the value of 0.57 ms for the luminescence lifetime in the DAC is close to the value of 0.53 ms in the solid state under atmospheric pressure, thus indicating that oxygen also quenches the luminescence in the sample prepared in the DAC. The luminescence lifetime for 2 then first increases from 0.57 ms at ambient pressure to 1.45 ms at 0.4 GPa, then it gradually decreases at Luminescence Lifetime

[Mn 4 (ThiaSO 2 ) 2 F]K [Mn 4 (ThiaSO 2 ) 2 F][K(18C6)] Luminescence Intensity [Mn 4 (ThiaSO 2 ) 2 F]K [Mn 4 (ThiaSO 2 ) 2 F][K(18C6)] a)
b) %ν max respectively. As pressure increases, the lifetime decreases continously from 1.71 ms to 0.55 ms.

Concommitantly, the luminescence intensity decreases likewise with increasing pressure.

higher pressure to 0.59 ms at 9.6 GPa, that is, above 0.4 GPa it shows the same behaviour as for compound 1. Likewise the luminescence intensity increases up to 0.4 GPa and the decreases concomitantly with the lifetime. The strong increase of the luminescence lifetime and intensity between ambient pressure and 0.4 GPa is unusual. The only possible reason to explain this behaviour is that the O 2 that has diffused into the lattice at ambient pressure is almost quantitatively expelled from lattice upon application of a comparatively low pressure, thus reducing the quenching of the Mn 2+ .

The decrease in luminescence lifetime and intensity with increasing pressure for 1 right from the beginning and for 2 for pressures above 0.4 GPa indicates a gradual decrease in luminescence quantum efficiency. Such a decrease is expected based on the energy gap law 16 which states that the non-radiative decay rate constant increases exponentially with a decreasing zero-point energy difference. Quantitatively, according to the decrease in lifetime the quantum efficiency should decrease from the maximum value of 50% at ambient pressure and room temperature to around 15% at 10 GPa. However, the actual luminescence intensity at 10 GPa is less than 5% of its maximum value. The reason for this apparent discrepancy is not entirely clear. It seems to indicate that concomitantly with the increase in the non-radiative decay rate constant the radiative lifetime increases. This could be related to the fact that the lowest excited state of Mn 2+ consists of a multiplet with components in thermal equilibrium having different radiative lifetimes and luminescence quantum efficiencies. Pressure would then not only shift the energy of this multiplet with respect to the ground state, but also influence the multiplet splittings and thus the observed lifetime and luminescence quantum efficiencies differently.

Conclusions

Thiacalixarene complexes have been studied since the late 1990's for their magnetic, electronic and optical properties, with various potential applications such as molecular recognition, catalysis, selfassembly, and nanomedicine. 17 The new calixarene compound, [Mn 4 (ThiaSO 2 ) 2 F][K(18C6)] has [START_REF] Crysalispro | Agilent Technologies[END_REF] Reflection indexing, unit-cell parameters refinement, Lorentz-polarisation correction, peak integration and background determination were carried out with the CrysalisPro software. [START_REF] Crysalispro | Agilent Technologies[END_REF] An analytical absorption correction was applied using the modeled faces of the crystal. [START_REF] Clark | [END_REF] The structures were solved by direct methods with SIR97 and the least-square refinement on F2 was achieved with the CRYSTALIS software. 22 All non-hydrogen atoms were refined anisotropically.

→
The hydrogen atoms were all located in a difference map, but those attached to carbon atoms were repositioned geometrically. The H atoms were initially refined with soft restraints on the bond were averages of 3 independent determinations. The spectra were displayed as photons versus energy (cm -1 ) on the bottom axis and versus wavelength (nm) on the top axis. Luminescence spectra under high pressure were recorded using a diamond anvil cell (MiniDAC of D'Anvils Ltd.), which could also be inserted into the closed cycle cryostat. Pressure was calibrated by using the 5 D 0 → 7 F 0 luminescence of Sm 2+ doped BaFCl with a shift rate of -21 cm -1 GPa -1 as internal pressure sensor. 13 The air pressure-dependent solid-state luminescence spectra have been realised in a cryostat equipped with a primary pump and an APG100 active Pirani vacuum gauge (Edwards). The degassed solutions were realised in a 1 cm corked cuvette with a Schlenk line equipped with a small Teflon-PTFE tube provided of a medical needle, and a N 2 bottle. The re-oxygenation of the solution were realised by removing the plug from the cuvette and leaving it open to ambient air. Spectra were recorded on the Fluorolog-3 spectrometer with different times of N 2 bubbling (0 -900 seconds) and O 2 re-oxygenation (0 -60 minutes).

macrocycles of 1

 1 and 2 are in a slightly distorted cone conformation: in 1 d(O12 -O33) / d(O27 -O4) = 0.98 and in 2 d(O4 -O19) / d(O12 -O30) = 0.98.

Fig. 1

 1 Fig. 1 ORTEP 10 diagram of 1 with thermal ellipsoids at 50% probability. Hydrogen atoms and tertbutyl groups are omitted for clarity. Selected atom-atom distances [Å]: Mn1-Mn3 i 3.0972(7); Mn1-F2 2.2018(5); F2-Mn3 2.1732(5); Mn1-O8 2.169(2) < Mn-O < Mn1-O4 2.242(2). Symmetry

Fig. 2

 2 Fig. 2 ORTEP 10 diagram of 2 with thermal ellipsoids at 50% probability. Hydrogen atoms and tertbutyl groups are omitted for clarity. Selected atom-atom distances [Å]: Mn1-F2 2.2091(4); Mn3-F2 2.1924(5); Mn1-Mn3 3.1057(7); Mn3-O15 2.177(2) < Mn-O < Mn3-O19 i 2.247(2). Symmetry transformations used to generate equivalent atoms: i (-x+1, -y+1, -z+1); ii (-x, -y, -z+1); iii (-x+1, -y, -z+1); iv (x, y-1, z); v (-x, -y+1, -z+1).

Fig. 3 a )

 a Fig. 3 a) Projection of the crystal packing of compound 1 in the (a, c) plane, b) projection of the crystal packing of compound 2 in the (a, b) plane.

  -d transition of the manganese(II) ions in d5 high-spin configuration. As mentioned above, the crystal structure reveals a sevenfold coordination sphere for the Mn(II) ions in a monocapped trigonal prism geometry and close to C 2v symmetry, resulting is a large splitting of the 4 T 1 state of octahedral parentage (see below). In essence, photoexcitation into the ligand centred π-π* transition at 28570 cm -1 is followed by fast intersystem crossing and internal conversion, thus resulting in the orange-red metal-centred d-d luminescence.

  Fig. 7 a) The energy band maxima

Fig. 8

 8 Fig. 8 Solid-state emission spectra of [Mn 4 (ThiaSO 2 ) 2 F]K 1 (a) and [Mn 4 (ThiaSO 2 ) 2 F][K(18C6)] 2 (b) at variable molecular oxygen pressure and upon photoexcitation at 24690 cm -1 (405 nm). The normalised luminescence intensities are plotted in the top and bottom insets for 1 and 2, respectively.

  pressure between 0.1 and 1010 mbar. The behaviour observed is reversible and reproducible. The luminescence intensities increase and decrease within a few seconds by removing from or introducing the O 2 into the sample compartment.

Fig. 9

 9 Fig. 9 Solid-state emission spectra of [Mn 4 (ThiaSO 2 ) 2 F]K 1 (a) and [Mn 4 (ThiaSO 2 ) 2 F][K(18C6)] 2 (b) between ambient pressure and 10 GPa upon photoexcitation at 24690 cm -1 (405 nm) at 298 K.

10b. For 1 ,

 1 the lifetime at ambient pressure in the DAC is 1.71 ms. This value is in line with the values of 1.65 and 1.68 ms determined for 1 in the presence and absence of atmospheric O 2 ,

  lengths and angles to regularise their geometry (C-H in the range 0.93 -0.98 Å, N-H in the range 0.86 -0.89 Å and O-H = 0.82 Å, and Uiso(H) in the range 1.2 -1.5 times Ueq of the parent atom), after which the positions were refined with riding constraints. For the experimental details see supporting information. CCDC-1050380 contain the supplementary crystallographic data for this paper. These may be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Spectroscopic Measurements. Electronic absorption spectra in the UV-Vis were recorded at 293 K from solutions in dimethylformamide (DMF) with a double beam absorption spectrometer (Agilent, Cary 5000) and a commercial fluorimeter (Jobin Yvon Horiba FL3-22, Fluorolog-3) equipped with a peltier-cooled photomultiplier (Hamamatsu R2658P, sensitivity: 185 -1010 nm) using quartz cells of 0.2 cm and 1 cm path length, for the absorption, and excitation-emission spectra, respectively. Powder samples were mounted directly onto copper plates using conductive silver glue and cooled in an optical closed-cycle cryostat capable of reaching temperatures down to 3 K in a helium atmosphere (Sumitono SHI-950/Janis Research CCS-500/204). The emission spectra at variable temperature (7.5 -293 K) were measured on the Fluorolog-3 spectrometer. High resolution emission spectra were recorded upon excitation with 405 and 473 nm diode lasers or with a Nd:YAG laser (Quantel Brillant B) using the third harmonic at 355 nm. The emitted light was analysed at 90° with a Spex 270M monochromator with holographic gratings (150 grooves/mm, blazed at 600). Light intensity was detected by a photomultiplier (Hamamatsu R928) or CCD camera. Appropriate filters were utilised to remove the laser light, the Rayleigh scattered light and associated harmonics from the emission spectra. The emission spectra were corrected for the instrumental response function. Luminescent lifetimes were measured using the excitation provided by a the third harmonic of the Nd:YAG. The output signal of the photomultiplier was fed into a multichannel scaler (Stanford Research SR-400) and transferred to a PC for data analysis. Lifetimes

  6 A 1 (t 2g 3 e g 2 ) d-d transition of the manganese(II) ions. This luminescence has been studied at variable temperature and ambient pressure as well as at variable pressure at room temperature. The presence of oxygen in solution and in the solid state quenches the Mn 2+ luminescence by energy transfer from the excited complex to O 2 thereby exciting O 2 from its 3 Σ - g ground state to the excited Compound 2 was obtained in the form of pale-yellow coloured crystals from the reaction mixture of p-tertbutylsulphonylcalix[4]arene been characterised by single crystal X-ray diffraction. The structural studies reveal a structure very similar to that of [Mn 4 (ThiaSO 2 ) 2 F]K, with a square of four manganese(II) ions sandwiched between two ThiaSO 2 macrocycles. The main difference between the two structures lies in the connection of the tetranuclear clusters in the form of a one dimensional network of the clusters for 1 by K + coordination, and to isolated clusters by the inclusion of [K18C6] + for 2. In both clusters, the manganese C 2v symmetry and the µ 4 -F -square planar geometry are rare examples in the literature.

	(ThiaSO 2 ) (0.05 g, 0.059 mmol) with MnCl 2 .4H 2 O (0.05 g, 0.252 mmol), KF (0.02 g, 0.357 mmol),
	18-crown-6 (0.02g, 0.075 mmol), methanol (10 mL) and water (1 ml) in a 23 mL Teflon-lined
	autoclave under an autogenous pressure at 170°C for 3 days. The crystals were isolated upon
	filtration and were washed with methanol. Yield: 60%. IR (cm -1 ) MS ESI (negative mode):
	[(Mn 4 (ThiaSO 2 ) 2 F) -] calculated: 1927m/z, found: 1927,03m/z.
	Single Crystal X-Ray Diffraction XRD. Suitable crystals were selected and mounted on a Gemini
	1 Σ + g state. The quenching is more efficient for the [K(18C6)] + containing compound with its open structure, which facilitates O 2 diffusion into the lattice. This is the first compound of a calixarene complex showing such a strong O 2 pressure dependence in the solid state. Interestingly, a comparatively low hydrostatic pressure squeezes out the O 2 , thus restoring the luminescence intensity. Experimental All chemicals and solvents were used as received (solvents: Carlo Erba RPE; chemicals: Aldrich); all preparations and manipulations were performed under aerobic conditions. The ligands, p-tert-butylthiacalix[4]arene (ThiaS) 1a,18 , p-tert-butylsulphonylcalix-[4]arene (ThiaSO 2 ) 2a,19 and compound 1 2k were synthesised by the published procedures. FT-IR spectra were recorded on a Nicolet 380 spectrometer. Mass spectra were performed on a MicroTOF-QII Bruker mass spectrometer (ESI Source). 4 e g 1 ) kappa-geometry diffractometer (Agilent Technologies UK Ltd) equipped with an Atlas CCD detector and using Mo radiation (λ= 0.71073 Å). Intensities were collected at 100 K by means of the Synthesis of [Mn 4 (ThiaSO 2 ) 2 (F)][K(18C6)]•2CH 3 OH (2). Both compounds present an intense and broad luminescence band originating from the 4 T 1 (t 2g CrysalisPro software.

Accepted Manuscript

Acknowledgements

We thank the Swiss National Science Foundation (grant number 200020_152780) for financial support.


Guillaume Pellecuer
email: guillaumepellecuer@umontpellier.fr

Jean-Jacques Huselstein

Thierry Martir

Andr É Chrysochoos

Olivier Arnould

Impact of Thermal Cycling Frequency on IGBT Power Module Lifetime

The paper presents the impact of thermal cycling frequency on the lifetime of IGBT power module. The first part will be devoted to a quick presentation of the test bench. Then, the test protocols will be detailed as well as the measurement protocol to characterise the ageing of the power module wirebonds. An important part will be devoted to the results of ageing. Before concluding, mechanical tensile tests on bondwires will complete the ageing tests.

Introduction to the power module reliability

Semiconductor power modules are active components widely used in electrical power conversion. Their use in many fields such as electric vehicles, networks interconnection for example, makes the reliability of this component an important issue.

In normal operation, these devices are subject to variations in electrical loadings which, through the Joule effect, create cyclic thermal stresses within the assembly. As the module consists of a stack of different materials, cyclic thermal variations lead to mechanical strains which are limited by the mechanical cohesion of the assembly. These strains then lead to the development of mechanical stresses within the module, particularly in the upper part (bonding, metallization, die, solder). The appearance of these mechanical stresses then leads to the appearance of ageing mechanisms.

In many applications, the cycling thermal frequencies are low, a few tenths of a Hz for temperature ranges of around 50°C. These thermal cycling lead to very long lifetime (a few months or years). The study of ageing by means of experimental tests therefore involves long test times. These test times justify the need for accelerated ageing tests. This is possible if the lifetime of the modules is not dependent on the cycling frequency.

Then, the main objective of this study is to analyse the possibility of accelerated testing.

IGBT module and experimental test bench

This study focuses on IGBT modules (MICROSEMI APTGT200A60T3AG 600V-200A), representative of the current technology. This module is an inverter leg and is made of two elementary switches (2 IGBT chips associated with 2 diodes). Fig. 1 shows the module being studied. The test benches (Fig. 2) used to provide the results presented below have been described in previous papers [1][2]. The tested IGBT modules are assembled in pairs to form a pulse width modulated inverter (full bridge) feeding an inductive load allowing to use the opposition method in order to provide only the losses of the converters. The digital control of the inverter by an FPGA allows the bench to be used in a wide range of electrical stresses and therefore to study a wide range of thermal cycle profiles.

Fig. 2: IES power test bench schema

To generate the thermal power cycling, the current in the load inductor can be modulated in amplitude and frequency. The switching frequency can be varied to adjust the power profile. The current shapes are configurable for to maximize the junction temperature while respecting the maximum current allowed in each module. Figure 3 shows an example of a current shape.

Accelerated ageing protocol

To check whether there is a frequency dependence of the lifetime, three different cycling frequencies were applied: 0.1 Hz, 1 Hz and 5 Hz. The range of the junctions temperature variation was set at 50°C for all cycling tests with a minimum temperature of 80°C. This value is close to the maximal values typically encountered in embedded applications and is therefore realistic. The temperature variation of the junctions is achieved by modulating the conductive and switching losses of the components. The minimum cycle temperature is set by the air cooling system. In addition, it induces reasonable test durations and previous tests have shown that aging modes are similar for lower temperatures, at a given frequency [START_REF] Forest | Fast power cycling protocols implemented in an automated test bench dedicated to IGBT module ageing[END_REF]. Before each measurement campaign, a thermal study is carried out on each module to determine the necessary electrical parameters to obtain the desired thermal profile at a given frequency. To do this, the modules are prepared for analysis by infrared thermography [START_REF] Chrysochoos | Infrared thermography applied to the analysis of material behavior: a brief overview[END_REF] (silicone gel removed, black paint applied to improve emissivity). The Tab. 1 shows the electrical parameters used for the different test frequencies. The trapezoidal current mode corresponds to operation with a trapezoidal current shape (Fig. 3). This mode maximises the thermal cycle amplitude while respecting the maximal current allowed in the IGBT chips [START_REF] Forest | A power cycling test bench dedicated to the test of power modules in a large range of cycling frequency[END_REF]. The temperature variation measurement is the result of the average of eight temperature measurements on defined areas near the bonding foot (Fig. 4). Each of the eight zones is also the result of the integration of each pixel defined in the zone. Fig. 5 shows the different thermal profiles measured with an infrared thermal camera directly on the IGBT chip.

V CE monitoring

The ageing indicator chosen in the monitoring of the samples is the collector emitter voltage drop V CEsat in the on state of the IGBT [START_REF] Durand | Power cycling reliability of power module: A survey[END_REF]. By injecting a high current into the IGBT to be analysed, we can detect an increase in the voltage drop V CEsat which would reflect the degradation of the bonding wires (lift off) [START_REF] Hamidi | Reliability and lifetime evaluation of different wire bonding technologies for high power igbt modules[END_REF]. The on-state voltage drop of IGBT depends on the injected current I c , the control voltage V GE and the junction temperature T j (Fig. 6). To be valid, this measurement must be performed under constant parametric conditions (same V GE , I c , T j ).

In this test campaign, the junction tempera-ture was not measured, contrary to what had been done in previous work [START_REF] Smet | Evaluation of Vce Monitoring as a Real-Time Method to Estimate Aging of Bond Wire-IGBT Modules Stressed by Power Cycling[END_REF]. The choice of the injected current makes it possible to circumvent this difficulty by choosing an operating point where the temperature dependence of V CEsat is low. The characteristic in Fig. 6 shows that for a current I c of 75A, this voltage V CE varies little with temperature.

Fig. 6:

V CE (I c , T j ) pour V GE = 15V
An assessment of the temperature impact on the increase in V CE voltage was carried out beforehand. The 75A current is imposed using a current-limited power supply. The V GE voltage is maintained at 15V. The temperature control of the bench allows the reference temperature to be set at 60°C. With these constraints, the losses in an IGBT are 90W resulting in a junction temperature T j of 85°C. Assuming a test stop for a 10% increase in V CEsat (9W of added losses), the increase in junction temperature would be about 2.5°C for the same current.

-

T ref = 60 • C, V CE T 1 = 1.2440V and V CE T 2 = 1.2258V -T ref = 70 • C, V CE T 1 = 1.2497V and V CE T 2 = 1.2314V
The difference of about 6mV obtained for two reference temperatures, separated by 10°C, corresponds to a variation of 0.5% in the V CEsat measurement. It can therefore be seen that the impact of a temperature uncertainty on the detection of an increase between 5 and 10% is not significant. A measurement of V CE , the on-state voltage drop, is performed every 50 000 cycles to estimate the ageing of the connections. The estimated endof-life time of the IGBT modules is the number of cycles for which an increase in the V CE voltage of 3 to 5% is detected [START_REF] Smet | Evaluation of Vce Monitoring as a Real-Time Method to Estimate Aging of Bond Wire-IGBT Modules Stressed by Power Cycling[END_REF].

About ten samples were studied according to the protocols described above. The on-state voltage drop of the IGBTs is monitored to detect an increase in the order of 3-10%, indicating component failure [START_REF] Coquery | Failure criteria for long term accelerated power cycling test linked to electrical turn off soa on igbt module. a 4000 hours test on 1200a-3300v module with alsic base plate[END_REF]. After each test the module is prepared (dissolving the silicone gel) for analysis under a SEM (Scanning Electron Microscopy) to observe the state of the wirebond. The Fig. 7 shows the state of the bonding wires and a metallization before power cycling. The frequency of 0.1Hz is representative of the cycling frequency experienced by the modules in traction applications for example. It can then be considered as a reference for cycling tests. For a ∆T j of 50°C the lifetime is around 400 000 cycles. The disadvantage of testing at 0.1Hz is that the tests can take up to 2 months. Tests at 1Hz and 5Hz were then carried out to drastically reduce the test time.

The Fig. 8 shows the evolution of the onstate voltage drops of the IGBT ∆V CE during cycling for the three selected frequencies. For 0.1Hz and 1Hz, the evolution of ∆V CE suggests degradation of the connections in the upper part of the module reflecting a wirebond lift-off. SEM analyses confirm this hypothesis (Fig. 9). For 5Hz, the lifetime is much higher. We can then observe degradations by wirebond lift-off but also reconstructions of the transmitter metallization. The results are similar for 0.1Hz and 1 Hz, considering the unavoidable disparities in device manufacturing and the difficulty in setting strictly the same thermal cycle for all samples. For 2Hz, lifetime increases significantly (about 50%). For 5 Hz, it increases drastically (ratio of 5 to 10, the two latests 5Hz bars in Fig. 10 correspond to samples for which the test was stopped at 2 000 kcycles without any measured V CE increase). This test campaign highlights the impossibility of using time-temperature dependence to study the lifetime of power modules. The observed lifetime can increase by one decade with increasing frequency for the same temperature amplitude [START_REF] Bayerer | Model for Power Cycling lifetime of IGBT Modules -various factors influencing lifetime[END_REF] [START_REF] Scheuermann | A New Lifetime Model for Advanced Power Modules with Sintered Chips and Optimized Al Wire Bonds[END_REF]. The duration of the thermal pulse is an important issue to consider. This may be due to the visco-thermo-elasto-plastic behaviour of the junction zone, which may no longer be excited when the cycling frequency becomes too high. Another possible explanation is related to the temperature propagation time. Indeed, for high frequencies (>1 Hz), the temperature gradient cannot propagate on the surface of the chip, thus reducing the thermal amplitude under the bonding wire, which would lead to an increase in the lifetime [START_REF] Bayerer | Model for Power Cycling lifetime of IGBT Modules -various factors influencing lifetime[END_REF].

Tensile tests on aluminium wires

To analyse the influence of cycling speed and temperature on the mechanical characteristics, ten different tensile tests were performed using a TA Electroforce ® 3230 mechanical test instrument equipped with a hot-cold chamber and controlled by dedicated software. For these tests, test specimens were specially manufactured with 300µm diameter bonding wire made of aluminium. The grips for the two machine attachments (jaws) were made with a U-shaped FR4 support frame. This shape prevents damage and plastic deformation when handling the specimen and mounting it in the test fixture, it ensures correct alignment of the specimen and finally, it prevents slippage in the jaws during the test. The aluminium wire is bonded into the frame using a high thermal performance epoxy adhesive.

The choice of thermal conditions is based on previous experimental tests. Indeed, for the temperature, we have chosen five values (25°C, 50°C, 80°C, 100°C, 130°C) which are function of the amplitudes of the thermal cycles. For the displacement speeds, previous numerical tests with a elasto-plastic mechnaical curves shows a displacement speeds in order to 0.001s -1 and 0.01s -1 for 0.1 Hz and 1Hz cycling frequencies. The results of stress-strains curves are shown in Fig. 12. It should be noted that in these tests there is an initial stiffening due to the realignment of the sample in the machine. The Young's modulus measured in this way is not representative of the sample. In order to measure the Young's modulus, several elastic discharges during the cycle were carried out. For each test parameter, several samples were used and provided the same mechanical response to validate the repeatability of the tests.

The curves obtained shows an impact of the deformation rate reflecting a viscous behaviour of the material. In fact, during an imposed strain (thermal expansion in the context of ageing of adhesives), the stress increases when the speed increases. Consequently, the higher the stress rate, the greater the energy required to deform a material. However, this effect remains relatively small. It can also be seen that for a given strain, the stress decreases as the temperature increases. The material is more ductile.

These tests show that the time-temperature equivalence cannot be verified. However, due to the small influence of the strain rate, accelerated ageing tests can be performed under one condition.

It is necessary that the thermal cycle, whatever the frequency, is identical in shape to have identical lifetimes and equivalent ageing modes. This aspect explains why our results at 5Hz are so different. Given the power requirements and thermal module inertia, we cannot have the same thermal profiles at 1Hz as at 5Hz.

Conclusion

This paper presents the development of a test methodology focused on bonding aging, one of the weak points in power modules subject to active thermal cycling modes. The main objective is to define all the necessary conditions for defining accelerated tests whose results are representative of the reality of industrial applications.

In the paper, results of numerous aging tests carried out over different campaigns were presented, highlighting the possibility of applying cycling frequencies much higher than real frequencies while preserving degradation modes. Conversely, they also show a change in behavior if those frequencies become too high, indicating the likely existence of viscoplastic behavior but also the impact of the shape of the thermal cycle. However, they also show the possibility of accelerated testing but with a limit on the frequency of cycles.

Fig. 1 :

 1 Fig. 1: IGBT Power module

Fig. 3 :

 3 Fig. 3: Current in inductive load

Tab. 1 :

 1 Power cycling electrical parameters

Fig. 4 :

 4 Fig. 4: Infrared thermography measurement

2 Fig. 5 :

 25 Fig. 5: Junction temperature profiles for 0.1 Hz, 1 Hz and 5Hz

Fig. 7 :

 7 Fig. 7: SEM view of an IGBT chip before power cycling.

Fig. 8 :

 8 Fig. 8: V CEsat evolution for 0.1 Hz, 1 Hz and 5Hz

Fig. 9 :

 9 Fig. 9: Wirebond lift-off and metallization reconstruction

Fig. 10 :

 10 Fig. 10: Lifetime vs power cycling frequency

Fig. 11 :

 11 Fig. 11: Experimental setup for tensile tests

Fig. 12 :

 12 Fig. 12: Uniaxial stress-strain curves


Jamal El Abbadi

Christophe Coquelet

Céline Alain Valtz

Céline Houriez

,1,1,2-tetrafluoroethane (R134a) or 1,1difluoroethane (R152a) or trans-1-chloro-3,3,3-Trifluoropropene (R1233zd(E)) or 2-Chloro-3,3,3-trifluoropropene (R1233xf)

Keywords: Experimental measurements Working fluids, Hydrofluoroolefins, Hydrofluorocarbons, vapor-liquid equilibrium, modeling exp Experimental property i, j Molecular species

    Experimental measurements and modelling of vapor-liquid equilibria for four mixtures of 2,3,3,3-tetrafluoropropene (R1234yf) with 1,1,1,2-tetrafluoroethane (R134a) or 1,1-difluoroethane (R152a) or trans-1-chloro-3,3,3-Trifluoropropene (R1233zd(E)) or 2-Chloro-3,3,3-trifluoropropene (R1233xf)

Introduction

In the previous years, hydrofluorocarbons (HFCs) were used as alternative refrigerants in many industrial applications, due mainly to their thermophysical properties and their zero ozone depletion potential (ODP). Nevertheless, many HFCs have a global warming potential (GWP) greater than 150 and their use will probably be restricted in the upcoming years according to the European Union's F-Gas regulations [START_REF] Brown | Critical review of the latest thermodynamic and transport property data and models, and equations of state for R-1234yf[END_REF] More recently, hydrofluoroolefins (HFOs) have been introduced as replacement fluids to the HFCs thanks to their low GWP and their similar thermophysical properties. In particular, the 1,1,1,2-tetrafluoroethane (HFC-134a or R134a), which is widely used in automotive air conditioning, is gradually replaced by the 2,3,3,3-tetrafluoropropene (HFO-1234yf or R1234yf) which has a low GWP of 4 [START_REF] Minor | International Refrigeration and Air Conditioning Conference[END_REF] and similar thermophysical properties to those of R134a. Considering the environmental point of view, HFOs are unsaturated HFCs that have high reactivity and therefore shorter lifetimes in the atmosphere. Considering the mechanical engineering point of view, the latent heat of R1234yf is very low, which leads to larger mass flow rates, larger pressure drops in heat exchangers and connection pipes, and eventually, to lower coefficients of performance (COP). One approach to resolve this issue is to use a mixture of R1234yf with other refrigerants like HFCs, such as R134a or 1,1-difluoroethane (R152a).

For instance, R152a which has a GWP of 140 and a short atmospheric lifetime of 1.5 years [START_REF] Mcculloch | CFC and Halon replacements in the environment[END_REF], has been used for many years as a component in blends, and its latent heat is much larger than the R1234yf one. Also, mixing more than 36 wt% R134a with R1234yf has an additional advantage to cancel the mild flammability of R1234yf [START_REF] Yamada | Environmentally friendly non-flammable refrigerants[END_REF].

Furthermore, the mixtures of R1234yf with either R134a or R152a are characterized by the presence of a maximum-pressure azeotrope, which presents advantages for many industrial applications (refrigeration, heat pumps...), as to avoid an important temperature glide. These mixtures can be considered as candidate as working fluid for refrigeration and can be considered as very advantageous in the case of retrofit application in the case where lifespan of installation is very important with respect to F-gas regulations [START_REF] Lasserre | Le réglement F-Gas, objectifs et impacts[END_REF]. The phase equilibrium properties of the mixtures of these refrigerants are crucial for an investigation of their performance in refrigeration or the heat pump cycles.

For other applications like high temperature heat pump or Organic Rankine Cycle (ORC), working fluid with high critical point temperature value is highly recommended.

Unfortunately, it signifies the utilization of HFCs with high GWP values. Also, considering the technical point of view, utilization of high latent heat and high-density fluid in order to decrease the size of heat exchangers are recommended [START_REF] Liu | Investigation of a two stage Rankine cycle for electric power plants[END_REF]. R1233zd(E) (trans-1-chloro-3,3,3-trifluoroprop-1-ene ) is one of the most promising compounds (and can be used to replace R245fa). In order to better optimize the performance of heat pump or ORC, it can be judicious to use a blend. Another advantage of blends concerns the temperature glide which is very interesting when we use hot or cold sources with some variation of temperature.

The blend composed of R1234yf + R1233zd(E) can be investigated. In this case, vapour liquid equilibrium (VLE) data are essential for the parametrization of equation of state for the prediction of phase diagrams.

Finally, HFOs such as R1234yf have to be produced. According to [START_REF] Teinz | Catalytic formation of 2, 3, 3, 3-tetrafluoropropene from 2-chloro-3, 3, 3-trifluoropropene at fluorinated chromia: A study of reaction pathways[END_REF], R1233xf can be used as raw materials to synthesize R1234yf. The design of the separation column, important for the purification process, requires vapour-liquid equilibrium data. R1233xf can also be used as refrigerant and can be associated with R1234yf in a blend.

To the best of our knowledge, very few publications are available in the literature about VLE data of the systems R1234yf + R134a (Kiamika et al., 2013) and R1234yf + R152a [ [START_REF] Hu | Isothermal VLE measurements for the binary mixture of 2,3,3,3-tetrafluoroprop-1-ene (HFO-1234yf)+1,1-difluoroethane (HFC-152a[END_REF] and [START_REF] Yang | Vapor-Liquid Equilibria for the Binary and Ternary Systems of Difluoromethane (R32), 1, 1-Difluoroethane (R152a), and 2[END_REF]]. Also, there is no data concerning the binary system R1234yf + R1233zd(E) and one set of data published by [START_REF] Yang | Isothermal vapor-liquid equilibria measurements for binary systems of 2, 3, 3, 3-tetrafluoropropene (HFO-1234yf)+ 2-chloro-3, 3, 3-trifluoropropene (HCFO-1233xf) and 2-chloro-3, 3, 3trifluoropropene (HCFO-1233xf)+ 2-chloro-1, 1, 1, 2-tetrafluoropropane (HCFC-244bb)[END_REF] on the binary system R1234yf + R1233xf.

Regarding the nature of chemicals, all of these systems can be classified as type one according to Scott and van Konynenburg classification (Scott and van Konynerburg, 1980).

For such system, [START_REF] Coquelet | Experimental Determination of Phase Diagram and Modeling. Application to Refrigerant Mixtures[END_REF] have recommended to use an experimental technique based on static-analytic method [START_REF] Coquelet | Experimental Determination of Thermophysical Properties of Working Fluids for ORC Applications[END_REF].

In this study, the VLE of four systems, R1234yf + (R134a or R152a or R1233zd(E) or R1233xf) were measured using a "static-analytic" apparatus at temperatures T = 278.15 to 343.15 K. To correlate the VLE data and considering the type of phase diagram, the Peng-Robinson (PR-EoS) associated with the Mathias-Copeman α-function and classical mixing rules was considered. Comparison was also done, if possible, with REFPROP 10.0 predictions. Indeed, R1233xf is not available in the software and for the binary system R1234yf + R1233zd(E), no mixing rule parameters are available (alternative mixing rule parameters are considered, i.e. the ones for R1234yf + R1234ze(E) binary system).

Experimental

2.1.Materials

Five refrigerants were used for the vapour-liquid equilibrium (VLE) and density measurements. They are listed in Table 1, along with the details about their ASHRAE number, chemical formula, CAS number, the name of the supplier and the product purity given by the supplier. No further purification of the chemical products was needed, only degassing was realised when loading the chemicals into the equilibrium cell.

2.2.Experimental apparatus

The equipment used for the VLE measurements is based on a "static-analytic" method with liquid and vapour phase sampling using capillary samplers ROLSI ® (Armines's patent). The equipment can be categorized under "Analytical technique with sampling, isothermal AnT" according to Dohrn classification [ [START_REF] Dohrn | High-pressure fluid-phase equilibria: Experimental methods and systems investigated (2000-2004[END_REF] and [START_REF] Fonseca | High-pressure fluid-phase equilibria: Experimental methods and systems investigated (2005-2008)[END_REF]].

The equipment is very similar to the one used for the measurement of VLE data concerning the binary systems CO 2 + R1234yf [START_REF] Juntarachat | Experimental measurements and correlation of vapor-liquid equilibrium and critical data for the CO2 + R1234yf and CO2 + R1234ze(E) binary mixtures[END_REF], CO 2 + R1234ze(E) [START_REF] Wang | Vapor-liquid equilibrium and molecular simulation data for carbon dioxide (CO2) + trans-1,3,3,3-tetrafluoroprop-1-ene (R-1234ze(E)) mixture at temperatures from 283.32 to 353.02 K and pressures up to 7.6 MPa[END_REF] and R1234yf + R245cb [START_REF] Valtz | Experimental measurements and modeling of vapour liquid equilibrium of 2,3,3,3 tetrafluoropropene (R1234yf) + 1,1,1,2,2[END_REF]. The main part of the apparatus is the equilibrium cell, where the two-phase equilibrium takes place. The flow diagram of the apparatus is displayed in Figure 1. The apparatus is equipped with a thermo-regulated liquid bath where the equilibrium cell is immersed. The bath ensures the control of the temperature within 0.01 K.

The temperature measurements inside the equilibrium cell is performed using two platinum resistance thermometer probes (Pt100), one to measure the temperature at the top of the cell, and the other for the temperature at the bottom of the cell. Two other temperature probes are used to control the temperature inside the thermal presses used to load the chemical products into the equilibrium cell.

The Pt100 probes are connected to a data acquisition unit (HP34970A). The Pt100 probes are calibrated against a 25 Ω reference platinum resistance thermometer (Pt25 -Hart Scientific).

The Pt25 reference probe was calibrated by the "Laboratoire National d'Essais de Paris" based on the 1990 International Temperature Scale (ITS 90). The temperature accuracy is estimated to be within ± 0.03 K.

The pressure is measured using one of two pressure transducers (DRUCK, 0 -3 MPa, 0 -30 MPa) installed on the apparatus. The choice of pressure transducer is dependent upon the maximum pressures generated by the system being characterised. The two pressure transducers are also connected to the data acquisition unit (HP34970A). The pressure transducers were calibrated against a pressure automated calibrator (GE Sensing, model PACE 5000). The pressure accuracy of the transducers is estimated to be within ± 0.0004

V5

MPa. Type B uncertainties were considered for the determination of temperature and pressure uncertainties.

The molar compositions of the phases present within the cell are determined after analysis of liquid and vapour samples by a gas chromatograph (VARIAN, equipped with a thermal conductivity detector (TCD). The analytical column within the gas chromatograph is a RESTEK, 1% RT-1000 on Carboblack B, 60/80 mesh (length: 2.4m, diameter: 2 mm from Restek, ID Silcosteel).

The TCD is calibrated by introducing manually known amounts of each pure compound (for the system studied) into the injector of the gas chromatograph, using an automatic syringe.

The calibration equation was fitted to relate the response of the TCD to the amount of the component introduced. The relative accuracy for each mole number is given in Table 2. The determination of the uncertainty of the mole numbers [START_REF] Taylor | Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results[END_REF] takes into account the repeatability of the measurement, the calibration of the TCD and the purity of the chemicals. The molar fraction is determined from the number of moles of each compound in the analysed sample, given by for the liquid phase. The uncertainty of mole numbers is given by considering the calibration results (Table 2) and the purity of the chemicals. By definition, we can calculate the uncertainty on mole fraction by considering the relative uncertainties on each mole numbers determined by gas chromatograph after calibration (combined uncertainties). Uncertainty of type B is considered (see Eq. ( 1)).

(1)

Concerning the purity of the chemicals, we consider that it is not correlated to the mole number sensitivity coefficient (equal to one). The uncertainty due to the purity is considered as type B by where p is the purity. Consequently, the global uncertainty is given by Eq. ( 2).

(2) u rep (x 1 ) is due to repeatability, so it is a type A uncertainty given by Eq. ( 3) (standard deviation).

(3)

The uncertainty on relative volatility is given by Eq. (S1) in Supplementary Material.

Experimental procedure

At ambient temperature, the equilibrium cell and its loading lines are made under vacuum. A first thermal press is loaded with one of the compounds, the second press with the other compound. The liquid bath is set to the temperature desired. When the equilibrium temperature is reached (the equilibrium temperature is reached when the Pt100 probes give the same temperature value within their temperature uncertainty for at least 10 minutes), an amount of about 5 cm 3 of the heavier component (the component with the lower vapour pressure) is introduced into the equilibrium cell. Its vapour pressure is then measured at this temperature.

Then, given amount of the lightest component (the component with the higher vapour pressure) is introduced step by step in order to increase the pressure inside the cell, leading to successive equilibrium mixtures, in order to have enough points to cover the two-phase envelope.

The equilibrium inside the cell is assumed to be reached when the pressure does not change during a period of 10 minutes within ±0.001 MPa under continuous stirring.

For each equilibrium condition, six or more samples of both vapour and liquid phases are taken using the capillary sampler ROLSI ® (ARMINES's patent) and analysed in order to verify the repeatability of the measurements, as to have a standard deviation less than 1%.

Experimental measurements

The VLE measurements of four binary mixtures have been carried out in this work, considering three isotherms for each mixture. The binary systems studied are R1234yf + R134a, R1234yf + R152a, R1234yf + R1233zd(E) and R1234yf + R1233xf.

3.1.Binary mixture R1234yf + R134a

This system was studied at three isotherms ranging from 278.17 to 333.17 K. The experimental VLE results for this system, along with the number of samples (n), the standard deviation ( x 1 and y 1 ) and the measurements uncertainties are provided in Table 3.

3.2.Binary mixture R1234yf + R152a

This second system was also studied at three isotherms ranging from 278.18 to 333.29 K. The experimental results for this system, along with the number of samples (n), the standard deviation ( x 1 and y 1 ) and the measurements uncertainties are reported in Table 4.

3.3.Binary mixture R1234yf + R1233zd(E)

This second system was also studied at two temperatures, 303.22 and 333.27 K. The experimental results for this system, along with the number of samples (n), the standard deviation ( x 1 and y 1 ) and the measurements uncertainties are reported in Table 5.

3.4.Binary mixture R1234yf + R1233xf

This second system was also studied at three isotherms ranging from 298.31 to 348.25 K. The experimental results for this system, along with the number of samples (n), the standard deviation ( x 1 and y 1 ) and the measurements uncertainties are reported in Table 6.

Modelling and discussions

In order to correlate the data, we have considered the most popular cubic equation of state present in all process simulators, the Peng-Robinson equation of state (PR EoS) [START_REF] Peng | A New Two-Constant Equation of State[END_REF]. This model is also considered to correlate and check the quality of the experimental. This model doesn't require numerous parameters and is used to generate phase diagrams. The PR EoS is a two-parameter cubic EoS and is defined by Eq. ( 4).

(4) P is the pressure, T the temperature, v the volume, and R the universal constant for ideal gases. b is the volumetric parameter and a(T) the cohesive energy parameter. The cohesive energy parameter a(T) depends on the temperature and is defined by Eq. ( 5).

(5)

The parameters a c , and b are defined by and .

In order to have the best prediction of the pure component vapour pressure and considering the fact that all of our experimental data were obtained for temperature lower than the critical temperature of the lightest component, the Mathias-Copeman [START_REF] Mathias | Extension of the Peng-Robinson equation of state to complex mixtures: Evaluation of the various forms of the local composition concept[END_REF]) αfunction was selected. The α-function is defined by Eq. ( 6).

(

T and T c are respectively the temperature and the critical temperature. m 1 , m 2 and m 3 are three adjustable parameters fitted on the experimental data For the mixtures, the classical van der Waals (vdW) mixing and combining rules [START_REF] Kwak | Van der waals mixing rules for cubic equations of state. Applications for supercritical fluid extraction modelling[END_REF] were used for the calculations. They are defined by Eqs (7-8).

(

) (8) 7
With .

z i is the mole fraction of the component i, a i is the energy parameter, b i is the covolume parameter of the component i, and k ij is the binary interaction parameter (BIP). N is the number of components of the system. The vdW mixing rules were chosen for their simplicity, ease of computing and also to be able to use a predictive binary interaction parameter k ij . For the VLE modelling, the model parameters have been adjusted in order to have an accurate representation, especially with the presence of an azeotrope. The binary interaction parameter (BIP) was fitted on experimental VLE data to take into account the molecular interactions occurring, and the α-function parameters m 1 , m 2 and m 3 were fitted on the pure compound data, in order to accurately represent the vapour pressures and the critical point.

For the R1234yf + R152a and R1234yf + R134a binary systems, the BIP k ij is fitted on the VLE data of bubble pressure according to the Eq. ( 9). As there is no important difference between vapour and liquid phase mole fractions, we have preferred to not include mole fraction of vapour phase in the objective function used:

(9)

For the R1234yf + R1233zd(E) and R1234yf + R1133xf binary systems, the BIP k ij is fitted on the VLE data of bubble pressure and mole fraction of vapour according to the Eq. ( 10).

(10)

For the Eqs (9-10), N data is the number of data points, P exp the experimental bubble pressure, P cal the calculated bubble pressure, y exp the experimental vapour molar fraction and y cal the calculated vapour molar fraction.

The critical temperature and pressure, and the acentric factor ( ) of these refrigerants are reported in Table 7. We have used the pure component vapour pressure predicted by the NIST (REFPROP 10.0, [START_REF] Lemmon | NIST Standard Reference Database 23: Reference Fluid Thermodynamic and Transport Properties REFPROP, version 10[END_REF]). The relative uncertainties given by the NIST are 0.02 % for R134a, 0.1 % for R152a, 0.1 % for R1234yf and 0.131% for R1233zd(E). For R1233xf, we have considered the experimental data mentioned by [START_REF] Zhang | Vapor pressures of 2-chloro-3, 3, 3trifluoropropene (HCFO-1233xf)[END_REF]

4.1.Binary mixture R1234yf + R134a

The results of the modelling for the system R1234yf + R134a are displayed in Figure 2 (T = 278.17 K) and Figures S11 to S13 for the other temperatures, from which we can notice that the model, in overall, reproduces accurately the experimental results. The calculated values by our model are given in Table 3. This system exhibits an azeotropic behaviour, which can be expected due to the close values of the vapour pressures of the two refrigerants R1234yf and R134a. Also, we can observe that the VLE diagram is very narrow, due to the close mole fraction values of the vapour and liquid phases, which makes the modelling quite challenging.

In order to check our measurements, the relative volatility was calculated (Figure 3). We can verify that the relative volatility is a decreasing function of the mole fraction of liquid phase and is equal to one at the composition of the azeotrope. In Table 9, we report the results of the AAD and bias calculated for the bubble pressure and the mole fraction of vapour phase, along with the values of the BIP fitted on the experimental data. The AAD and bias are calculated according to Eqs. (11-12).

In addition to the data measured as part of this work, the VLE data from the literature (Kamiaka et al. ) were modelled by using the same thermodynamic model, and the results of the AAD and bias were reported as well in Table 9. We have also compared our results and those from Kamiaka et al. with the prediction given by REFPROP. In REFPROP 10.0, some mixing parameters are proposed for this binary system. We can observe that there is a good agreement between our data and literature data if we compare the values of binary interaction parameters (Figure 4) obtained after adjustment. But we can also see that the trend concerning the variation of the BIP with the temperature is different between our data and those from Kiamiaka et al. Moreover, concerning the data from Kiamiaka et al., we can observed that there are systematic deviation between experimental and calculated mole fraction of vapour phase values. The deviations between the experimental data and predictions from REFPROP are higher than the deviations obtained using the PR EoS.

Table 9. Deviations between the experimental data and modelling results (AAD and bias) for the binary system R1234yf (1) + R134a (2).

PR EoS REFPROP

Reference T/K

4.2.Binary mixture R1234yf + R152a

The VLE modelling results for the system R1234yf + R152a are displayed in Figure 5 4. Similarly to the previous system, this binary system has an azeotropic behaviour, which can be expected due to the close values of the vapour pressures of the two refrigerants R1234yf and R152a. Also, we can observe that the VLE diagram is very narrow, due to the close mole fractions of the vapour and liquid phases, which makes the modelling quite challenging. In order to check our measurements, the relative volatility was calculated (Figure 6). We can see that the relative volatility is a decreasing function of the mole fraction of the liquid phase and is equal to one at the composition of the azeotrope. where the mixing parameters used are given in the paper of [START_REF] Bell | Automatic fitting of binary interaction parameters for multifluid Helmholtz-energy-explicit mixture models[END_REF] As we can see, there is a good agreement between our data and literature data if we compare the values of binary interaction parameters (Figure 7). But we can also see that the variation of the BIP with the temperature obtained after data treatment for the three sets of data are similar and not too much temperature dependent (k ij close to 0.02). Also, according to the

4.3.Binary mixture R1234yf + R1233zd(E)

The VLE modelling results for the binary system R1234yf + R1233zd(E) are displayed in Figure 8, from which we can notice that the calculations are in good agreement with the experimental results. The calculated values by our model are given in Table 5. There is no azeotrope. In order to check our measurements, the relative volatility was calculated (Figure 9). We can see that the relative volatility is a decreasing function of the liquid molar fraction. The results of the AAD and bias calculated for the bubble pressure and the mole fraction of vapour phase, along with the values of the BIP fitted on the experimental data are reported in Table 11. We have also compared our results with the prediction given by REFPROP. Unfortunately, there is no specific mixing parameters for this binary system in REFPROP. In our version of REFPROP, the BIP of the binary system R1234yf + R1234ze(E) are thus considered (similar system). We can observe that the deviations between our model and the experimental data are higher than the deviations between our experimental data and REFPROP's predictions. This can be attributed to the low level of purity of the R1233zd(E) in comparison to the purity of R134a, R1234yf and R152a. One consequence of the presence of impurities is that the deviations are the highest at 333.27 K.

4.4.Binary mixture R1234yf + R1233xf

The VLE modelling results for the system R1234yf + R1233xf are displayed in figure 10, from which we can notice that the calculations are in good agreement with the experimental results. The calculated values by our model are given in Table 6. There is no azeotrope. In order to check our measurements, the relative volatility was calculated (Figure 11). We can see that the relative volatility is a decreasing function of the liquid molar fraction. The results of the AAD and bias calculated for the bubble pressure and the mole fraction of the vapour phase, along with the values of the BIP fitted on the experimental data are reported in Table 12. We have also compared our results with the results from [START_REF] Yang | Isothermal vapor-liquid equilibria measurements for binary systems of 2, 3, 3, 3-tetrafluoropropene (HFO-1234yf)+ 2-chloro-3, 3, 3-trifluoropropene (HCFO-1233xf) and 2-chloro-3, 3, 3trifluoropropene (HCFO-1233xf)+ 2-chloro-1, 1, 1, 2-tetrafluoropropane (HCFC-244bb)[END_REF]. The deviations are indicated in the Table12. As the R1233xf is not available in REFPROP 10.0, we do not compare the experimental data with REFPROP predictions. The variations of the BIP with the temperature are plotted on Figure 12. We can see that the orders of magnitude of the BIP are similar, reflecting a good agreement between the two sets of data.

Conclusions

In this paper, the isothermal VLE of two systems, R1234yf + (R134a or R152a) were measured using a static-analytic apparatus at temperatures between 278.15 and 348.15 K. The experiments were conducted by means of a "static-analytic" apparatus with phase analysis via gas chromatography, with resulting uncertainties of 0.06 K for temperature, 8 kPa for pressure and a maximum of 0.007 for vapour and liquid mole fractions. All the uncertainties were estimated taking into account the purities of the chemicals. The data obtained were correlated within 5% of absolute error with a Peng-Robinson cubic equation of state associated with a Mathias-Copeman alpha function and the classical van der Waals mixing rules (with a temperature-dependent binary interaction parameter).

  , Directive 2006/40/EC, European Union Regulation (EC) No 842/2006).

Figure 2 .

 2 Figure2. Phase diagrams for the R1234yf + R134a binary system at (▲) 278.17 K. Solid line: modelling results using the Peng Robinson EoS.

Figure

  Figure 3. Relative volatility of the (R1234yf + R134a) binary system at (▲) 278.17 K; () 303.16 K and (•) 333.17 K; solid line: modelling results using the Peng-Robinson EoS. Error bars (uncertainty on relative volatility): 2 %

Figure 4 :

 4 Figure 4: Variation of the binary interaction parameters (binary system R1234yf + R134a) with the temperature. (): this work, (): Kamiaka et al.

  K) and Figures S14 and S16 for the other temperatures, from which we can notice that the calculations are, in overall, in good agreement with the experimental results. The calculated values by our model are given in Table

Figure 5 .Figure

 5 Figure 5. Phase diagrams for the R1234yf + R152a binary system at (▲) 278.18 K Solid line: modelling results using the Peng Robinson EoS.

Figure 7 :

 7 Figure 7: Variation of the binary interaction parameters (binary system R1234yf + R152a with the temperature. (): this work; (): Hu et al.; (): Yang et al..

Figure 8 .Figure 9 .

 89 Figure 8. Phase diagrams for the R1234yf + R1233zd(E) binary system at (▲) 303.22 K; () 333.27 K; Solid line: modelling results using the Peng Robinson EoS.

FigureFigure 11 .

 11 Figure 10. Phase diagrams for the R1234yf + R1233xf binary system at (▲) 298.31 K; () 323.27 K (): 348.25 K. Solid line: modelling results using the Peng Robinson EoS.

Figure

  Figure 12: Variation of the binary interaction parameters (binary system R1234yf + R1233xf) with the temperature. (): this work, (): Yang et al. (2016)

Table 1 . Refrigerants used for the experimental measurements

 1

a ASHRAE: American Society of Heating, Refrigerating and Air-Conditioning Engineers b CAS: Chemical Abstracts Service c from supplier

Figure 1. Flow diagram of the "static-analytic" apparatus. EC: equilibrium cell; LV: loading valve; MS: magnetic stirrer; PP: platinum resistance thermometer probe; PT: pressure transducer; RT: temperature regulator; LB: liquid bath; TP: thermal press; C1: more volatile compound; C2: less volatile compound; V: valve; GC: gas chromatograph; LS: liquid sampler; VS: vapor sampler; SC: sample controlling; PC: personal computer; VP: vacuum pump.

	Compounds	ASHRAE a Number	Formula	CAS b Number	Supplier	Purity c (vol%)
	1,1,1,2-Tetrafluoroethane	R134a	C 2 H 2 F 4	811-97-2	Climalife	>99%
	1,1-Difluoroethane	R152a	C 2 H 4 F 2	75-37-6	Dehon	>99%
	2,3,3,3-Tetrafluoropropene	R1234yf	C 3 H 2 F 4	754-12-1	Honeywell	>99.5%
	Trans-1-chloro,3,3,3 trifluoropropene	R1233zd(E)	C 3 H 2 F 3 Cl	102687-65-0	Synquest	>97%
	2-chloro-3,3,3-trifluoropropene	R1233xf	C 3 H 2 F 3 Cl	2730-62-3	Synquest	>97%

Table 2 : Mole number relative accuracy (in %) of TCD for each component.

 2

	Binary system	Component 1	Component 2
	R1234yf(1) + R134a(2)	0.7	0.7
	R1234yf(1) + R152a(2)	0.7	1.0
	R1234yf(1) + R1233zd(E)(2)	0.6	1.8
	R1234yf(1) + R1233xf(2)	1.2	1.0

Table 3 . Vapor Liquid Equilibrium data for the binary system R1234yf (1) + R134a (2) and modelling results.

 3

	Experimental data

Table 4 . Vapor Liquid Equilibrium data for the binary system R1234yf (1) + R152a (2) and modelling results.

 4

	Experimental data

Table 5 . Vapor Liquid Equilibrium data for the binary system R1234yf (1) + R1233zd(E) (2) and modelling results.

 5

	Experimental data

Table 6 . Vapor Liquid Equilibrium data for the binary system R1234yf (1) + R1233xf (2) and modelling results.

 6

	Experimental data

  . They claimed a relative uncertainty of 0.5 %. The values of the Mathias-Copeman alpha function parameters for the five single compounds used in this study are provided in Table8with the corresponding AAD (Average Absolute Deviation) and Bias. The Mathias Copeman Alpha function is applicable in the whole range or pressure and temperature from 273.15K to the critical temperature. Of course, for temperature higher than the critical temperature higher than the critical temperature, only the first parameter m 1 have to be considered with the adapted expression for T>T C :). We have used the pure compound vapour pressures predicted by REFPROP 10.0. For the R1233xf, we have considered the experimental data measured by Zhang et al. The results are also presented in Supplementary Materials (ln(P) as a function of 1/T and the deviations, Figures S1 to S10).

Table 7 . Critical properties and acentric factor values from REFPROP (Lemmon et al., 2018) of the refrigerants studied.

 7

a

[START_REF] Zhang | Vapor pressures of 2-chloro-3, 3, 3trifluoropropene (HCFO-1233xf)[END_REF]

Table 8 . Mathias Copeman alpha function parameters adjusted for each pure component (range of Temperature from 273.15 K to the pure component critical temperature)

 8

	Component	m 1	m 2	m 3	AAD /%	Bias /%
	R1234yf	0.80519	-0.33942	1.01599	0.16	-0.04
	R134a	0.85811	-0.13358	0.49210	0.27	-0.13
	R152a	0.81002	-0.45981	1.59189	0.19	-0.18
	R1233zd(E)	0.85356	-0.53966	1.80195	0.13	-0.02
	R1233xf	0.31079	3.51330	-8.73344	0.44	0.02

Table 10 .

 10 In addition to the data measured in this work, the VLE data from the literature(Hue et al. 2014;[START_REF] Yang | Vapor-Liquid Equilibria for the Binary and Ternary Systems of Difluoromethane (R32), 1, 1-Difluoroethane (R152a), and 2[END_REF] were modelled by using the same thermodynamic model, and the results of the AAD and bias were reported as well in Table10. We have also compared our results and those fromHu et al. and Yang et al. with the predictions given by REFPROP

		1.7
		1.6
		1.5
		1.4
	a 12	1.2 1.3
		1.1
		1.0
		0.9
		0.8
		0.0	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9	1.0
							x 1

Table 10 ,

 10 we can observe a systematic deviation concerning the mole fraction of vapour phase for the data measured byYang et al. The deviations between the experimental data and predictions from REFPROP are higher than the deviations obtained using the PR EoS. The deviations between experimental data from Yang et al. and REFPROP predictions are the highest.

Table 10 . AAD and bias for the binary mixture R1234yf (1) + R152a (2).

 10

					PR EoS				REFPROP
	Reference T/K	k 12	AAD P /%	AAD y 1 /%	bias P /%	bias y 1 /%	AAD P /%	AAD y 1 /%	bias P /%	bias y 1 /%
		278.18 0.0171	0.10	0.40	0.03	-0.40	0.31	0.67	-0.22	0.53
	This work	303.16	0.0190	0.17	0.22	0.03	-0.18	0.25	0.29	-0.01	0.14
		333.29 0.0194	0.08	0.39	-0.02	-0.32	0.20	0.45	0.08	0.27
		283.15	0.0193	0.25	0.98	0.08	-0.82	0.22	0.88	0.12	0.64
		293.15	0.0193	0.18	0.87	0.06	-0.65	0.15	0.97	0.04	0.59
	Hu et al. 2014	303.15 313.15	0.0190 0.0196	0.18 0.15	0.67 0.80	0.03 0.03	-0.55 -0.61	0.19 0.15	0.73 0.82	-0.02 0.06	0.50 0.53
		323.15	0.0201	0.13	0.65	0.03	-0.46	0.19	0.69	0.14	0.36
		283.15	0.0195	0.09	0.32	0.03	0.32	0.13	5.44	0.07	-4.48
		293.15	0.0196	0.13	0.14	0.03	0.14	0.13	0.30	0.05	0.17
	Yang et al. 2018	303.15 313.15	0.0198 0.0199	0.11 0.11	0.14 0.11	-0.01 0.002	0.10 0.11	0.15 0.15	0.32 0.17	0.03 0.05	0.15 0.07
		323.15	0.0198	0.11	0.14	-0.02	0.14	0.15	0.17	0.05	0.08

Table 11 . AAD and bias for the binary mixture R1234yf (1) + R1233zd(E).

 11

				PR EoS				REFPROP
	T/K	k 12	AAD P /%	AAD y 1 /%	bias P /%	bias y 1 /%	AAD P /%	AAD y 1 /%	bias P /%	bias y 1 /%
	303.22	0.0205	1.5	0.6	1.5	-0.6	0.83	0.92	-0.83	0.55
	333.27	0.0358	1.6	1.7	-1.6	-1.3	0.52	0.77	-0.52	0.06

Table 12 . AAD and bias for the binary mixture R1234yf (1) + R1233xf.

 12

	Reference T/K	k 12	AAD P /%	AAD y 1 /%	bias P /%	bias y 1 /%
		298.31	0.0122	0.42	0.37	-0.29	-0.23
	This work	323.27	0.0172	0.41	0.88	-0.41	-0.88
		348.25 0.01502	0.33	0.65	0.04	-0.65
		293.15	0.0167	0.67	0.44	0.45	-0.41
	Yang et al. 2016	303.15	0.0174	0.66	0.14	0.57	-0.08
		313.15	0.0224	1.97	0.22	1.73	0.09

Acknowledgments

The authors are grateful to the French National Agency of Research (ANR) for funding this work as part of PREDIREF Project (ANR-13-CDII-0008).