M. Sc Claudie Hulin
email: claudie.hulin@cnrs-orleans.fr

Prof Lionel Mercury
email: lionel.mercury@univ-orleans.fr

Dr. habil Patrick Simon
email: patrick.simon@cnrs-orleans.fr.

Dr. habil Kirill I Shmulovich
email: kshmulovich@yandex.ru.

Mechanical weakening of massive quartz due to in-pore water tension

The present contribution specifically considers the tensile stress exerted by in-pore (or confined) capillary liquids and the role it possibly plays on the host solid mechanics, in absence of significant confining pressure. This situation stands for any unsaturated porous systems submitted to dryingwetting cycles. An original combination of micro-thermometric procedures applied to liquids occluded inside quartz closed cavity, with Raman scattering data collected in the solid quartz lattice, leads to conclude that not only tensile guest liquid can act on its host solid, but can result in solid cracking in subcritical conditions. These processes are of importance for natural or manmade materials present in the Earth's environment, where water and other active species are present, for which various combination of pore fluid and confining pressure/tension are possible, and displacements and stresses are small.

INTRODUCTION

Mechanical-chemical processes in pores are under growing focus, especially due to the related influence they may have on the porosity-permeability relationship. A very common example of such processes is the crystallization (positive) pressure, the damages (host rock failure) of which are due to guest secondary precipitates crystal growth in pores. This process is activated by salt accumulation in the host rock by rain or sea sprays and regular drying by evaporative demand, until reaching the required saturation to activate nucleation. An overlooked partner in this classic scheme, at least when extrapolating laboratory experiment in the fields, is the common occurrence of capillary processes in drying rocks. This special state of liquids trapped in small enough pores is known to control the physics of sandcastles (e.g., [START_REF] Fraysse | Humidity effects on the stability of a sandpile[END_REF], but can also modify the strength of cementitious materials (e.g., [START_REF] Pihlajavaara | A review of some of the main results of a research on the ageing phenomena of concrete: effect of moisture conditions on strength, shrinkage, and creep of mature concrete[END_REF][START_REF] Lagier | Numerical strategies for prediction of drying cracks in heterogeneous materials: Comparison upon experimental results[END_REF][START_REF] Scherer | Drying, Shrinkage, and Cracking of Cementitious Materials[END_REF], or deform cohesive materials (e.g., [START_REF] Tas | Capillarity induced negative pressure of water plugs in nanochannels[END_REF][START_REF] Tas | Capillary Negative Pressure Measured by Nanochannel Collapse[END_REF].

The present contribution aims to examining how and to what extent an occluded tensile water may create a volumetric stress onto its host rock, and possibly damage it. To do that, synthetic fluid inclusions were fabricated in pure quartz to stand for isolated pores in crystalline and cemented solid materials. The occluded liquid was put under variable high tensions, according to microthermometric procedure, and the stress arising all in the crystal hosting the inclusion were monitored using Raman scattering measurements. They showed that the solid lattice remained at subcritical conditions, while the two experiments resulted into quartz failure.

MATERIALS AND METHODS

Principle. Isochoric cooling of liquids trapped in closed cavities put them under tensile strength up to the stability limits (e.g., [START_REF] Shmulovich | Experimental superheating of water and aqueous solutions[END_REF][START_REF] Qiu | Exploration of the phase diagram of liquid water in the low temperature metastable region using synthetic fluid inclusion[END_REF]. In situ Raman spectroscopy can be used to record the temperature/pressure shift upon external strains such as temperature or hydrostatic pressure. The frequency shift of the 464 cm -1 peak of quartz at room temperature (23°C) linearly depends on pressure up to 0.5 GPa: d/dP = 8.7 cm 1 /GPa. The frequency shift for the 206 cm -1 mode is d/dP = 20 cm -1 /GPa [START_REF] Schmidt | In-situ Raman spectroscopy of quartz: A pressure sensor for hydrothermal diamond-anvil cell experiments at elevated temperatures[END_REF]. These two Raman modes of quartz have been recorded in mapping mode all around an inclusion, submitted to a thermal cycle from room temperature to various values of temperature corresponding to diverse tensile states. The d/dP relationships allowed to translate the frequency shifts into an internal pressure state, corresponding to the isotropic value of the stress tensor.

Samples. Synthetic fluid inclusions (SFIs) have been synthetized in a piece of quartz using classical procedure (e.g. [START_REF] Shmulovich | Experimental superheating of water and aqueous solutions[END_REF], and filled with a 0.2m NaOH dilute solution which makes the quartz more soluble at the synthesis conditions (0.6 GPa, 500°C, 45 days), and so produces inclusions having very good inner surfaces. According to previous datasets [START_REF] Shmulovich | Experimental superheating of water and aqueous solutions[END_REF], NaOH dilute solutions are efficiently superheated at room temperature or below (high density samples), and display very satisfactory negative crystal shape (Fig. 1). Raman scattering. The spectroscopic measurements on the SFI were performed on a Renishaw Invia Reflex spectrometer, using the 633nm excitation line of a He-Ne laser (less than 10mW on the sample). The grating was a 1800 grooves/mm one, giving a wavenumber step between two adjacent pixels of the CCD equal to 0.97 cm -1 . Each measurement was done after a wavenumber calibration procedure of the spectrometer on its internal silicon reference sample (520.5 cm -1 ), without moving the quartz sample, which ensures the calibration state and promotes the highest possible reproducibility. The microscope (DM2500 Leica) objective was a Leica 100X long front distance (NA=0.85). Mapping measurement were done in the Renishaw StreamlineHR mode; each individual Raman spectrum was obtained with an accumulation time of 8s, a full image consists in 3621 spectra (step of 0.8µm). This mode allows a very efficient confocal filtering, and so it was possible to evaluate how the stress tensor develop either in the same plane than the inclusion itself (the optical one), or all around, specifically some 10 microns above.

Micro-thermometric protocol. The starting pore material generally contains a biphasic liquid+vapour assemblage (L+V). By a progressive heating, the liquid density and bubble pressure change (A to B path, Fig. 2) up to a particular density, at which the trapped liquid invades the whole inclusion space: there is no more vapour and the inclusion is said to be homogenized (B point, Fig. 2), at the corresponding 'homogenization temperature' (TH). Further heating drives the P-T conditions in the inclusion along the isochore curve inside the stable domain of liquid (B to C path, Fig. 2). The second step is the progressive cooling of the sample, which follows the isochoric path as long as the inclusion remains homogeneously filled with liquid (C to D path without nucleation at B, Fig. 2). The temperature of the bubble appearance is called the (instantaneous) nucleation temperature (TIN) and is always located within the tensile domain: nucleation in fluid inclusions disobeys the saturation conditions. This protocol mimics the tension exerted by capillary liquids on host cohesive material in a unsaturated heterometric porous network with capillary menisci at the throat and the superheated (capillary) liquid hosted in the larger pore space [START_REF] Bouzid | Salt precipitation and trapped liquid cavitation in micrometric capillary tubes[END_REF]. This inclusion is readily superheated (Fig. 3) by cooling the homogenized inclusion down to room temperature (RT; 21°C), what corresponds in terms of liquid tension to PL = -132.5 MPa. After overheating to 145°C to ensure the homogenization state (sometimes nano-bubbles keep trapped in invisible corners), Raman maps were put at RT under tensile state of the trapped water. Further cooling provoked bubble cavitation, and moving back to RT made possible to get Raman maps under biphasic stable state (Fig. 3). This first experiment confirms without any ambiguities the mechanical role attributed to liquid tension: the Raman maps without (left) and with (right) liquid tension differ appreciably (top maps: blue to green; bottom maps: red to yellow-greenthe scale color is the same in both cases), and in the opposite direction between the in-plane and the above-plane laser focus. It is also straightforward to distinguish that the quartz does not "react" the same way in all the directions, what is especially visible with the yellow-green diagonal of the bottom right map, and highlight the role of local heterogeneities present originally in the crystal lattice itself may play in this game. The 3621 spectra of each Raman map were processed with Origin 2016 software to extract the histograms of the main peak position in each configuration (after fitting with a pseudo Voigt profile), turning the Raman shift between the biphasic and monophasic conditions into an additional "Raman pressure", averaging the stress tensor implied by the liquid tension. The "plane dependency" is put into light, and makes clear that the direct effect of local tension (in-plane quartz -5 -tension) with the compressive relaxation above it and forcibly below it too. Obviously, a solid lattice cannot be put under isotropic tension, but it is also obvious from these results that the quartz reacts differently under compression and tension. The anisotropy of the tension propagation with the in-plane measurements compared to the quite homogeneous stress distribution in the aboveplane experiment testify this contrasted behavior. This large difference is interpreted as a clear evidence of the role of the interfacial energy consuming in the tensile situation part of the volumetric energy along the liquid-solid interface all around the cavity [START_REF] Coussy | The equivalent pore pressure and the swelling and shrinkage of cement-based materials[END_REF], compared to the insensitivity of the compressive situation to surfaces effect. Pre-fragmented fluid inclusions. In a second experiment, a pre-fragmented sample was closely studied, a work mainly reported in a paper under examination (Mercury et al., submitted) and the corresponding results will not be repeated here. The present contribution reports on a current longterm study about the Raman shifts of quartz around this inclusion maintained under permanent tension at RT (PL = -135 MPa). The idea is to evaluate how the stress anisotropy may lead to mechanical relaxation, even under sub-critical stress. Practically speaking, the inclusions under study are checked regularly and put again under tension if a bubble becomes visible.

The color scale of the maps (Fig. 5) is exactly similar to the figure 3's. Focusing on the upper inclusion, with micro-fissures at each apex of the hexagonal structure, it appears that the signal is reddening from May to June, then goes back to zero (constant blue everywhere) in October, and redden again in November. Our present interpretation is that, despite no visible cracking event, the inclusion failed to support tensile strength from liquid and developed micro-fissures around October, before resuming tensile stress at the subsequent tensile loading. Unfortunately, Raman maps were not interpreted when the system was put again under tensile stress, so the demonstration is still speculative and qualitative. Another unclear behavior is the one displayed by the bubblebearing inclusion (bottom right) which is our non-tensile control. As visible on the top and the bottom map, it shows a blue-to-red shift making clear that stress is accumulating there, despite a no tension exists (visible bubble) inside the cavity. At the time, no clear explanation arises. On this

1  = -0.25 cm -1  = +0.1 cm -1
RT, LV biphasic state RT, tensile liquid /P = 9 cm -1 /MPa [START_REF] Schmidt | In-situ Raman spectroscopy of quartz: A pressure sensor for hydrothermal diamond-anvil cell experiments at elevated temperatures[END_REF] P raman = 11.5 MPa /P = 9 cm -1 /MPa [START_REF] Schmidt | In-situ Raman spectroscopy of quartz: A pressure sensor for hydrothermal diamond-anvil cell experiments at elevated temperatures[END_REF] P raman = -28.7 MPa -6 -respect, the "June behavior" is simpler to understand, without any Raman signature around the bubble-bearing inclusion. However, this situation may also linked to the further relaxation step, so that no clear reasoning still clarifies this succession. This dataset appears quite promising, with apparent fatigue effects coming into play into a complex sketch of liquid-to-solid interrelationship. Further data are expected to fill the present uncertainty and afford quantitative conclusions to this current experiment.

CONCLUSION

These findings give interesting insights into the potentially complex strain-stress relationships in natural porous rocks, and the porosity-permeability relationship in drying systems with the possible role of liquid tension in natural water-depleted aquifers. On this respect, the present study with synthetic fluid inclusions demonstrates that cavities in the range of ten of microns or more, may hold pretty high tensions (beyond -100 MPa), which may participate in the geomechanical balance and the resistance to fracture or weakening of brittle polycrystalline rocks submitted to drying conditions. Further study includes both improvement on the experimental procedure and quantitative comparison between those results and mechanical modeling prediction (finite elements).

Figure 1 .

 1 Figure 1. Fluid inclusions-bearing quartz fragments. The left one present a series of prefragmented fluid inclusions (Mercury et al., submitted), but the two fragments come from the same synthesis run, so have similar composition, density, and behavior.

Figure 2 .

 2 Figure 2. Micro-thermometric procedure on closed water-bearing cavities (or fluid inclusions), to promote liquid tension prone to pull upon the surrounding quartz. It mimics the role capillary liquid may have on host cohesive material.

Figure 3 .

 3 Figure 3. Left. Micro-thermometric procedure on closed water-bearing cavities (or fluid inclusions), to promote liquid tension prone to pull upon the surrounding quartz. Right. Raman maps of the 464 cm -1 peak position all around the inclusion, in the inclusion plane (bottom, cavity marked by the black area), and above it (see text).

Figure 4 .

 4 Figure 4. Left. Histograms of the main peak position (Raman shift) according to different thermodynamic conditions in the inclusion (monophasic superheated, biphasic stable).

Figure 5 .

 5 Figure 5. Raman maps of pre-fragmented inclusions (see the micro-fissures), taken at different times along a six months period under permanent tension.

Acknowledgement This work has received financial support from the French Agency for Research (Agence Nationale de la Recherche), through the grant CONGE BLAN-610-01, the Equipex Planex ANR-11-EQPX-36 and the Labex Voltaire ANR-10-LABX-100-01.


Matthieu Kauffmann

Pascal Roussel
email: pascal.roussel@ensc-lille.fr

Francis Abraham

Layered Ruthenium Hexagonal Perovskites: the new series [Ba 2 Br 2-2x (CO 3 ) x ][Ba n+1 Ru n O 3n+3 ] with n = 2, 3, 4, 5

Keywords: Perovskite-Related Ruthenium Oxybromides Hexagonal perovskite, ruthenium oxybromides, Ruthenium mixed valence, layered oxycarbonates

Single crystals of the title compounds were prepared by solid state reactions from barium carbonate and ruthenium metal using a BaBr 2 flux and investigated by X-ray diffraction method using Mo(Kα) radiation and a Charge Coupled Device (CCD) detector. A structural model for the term n=2, Ba 5 Ru 2 Br 2 O 9 (1) was established in the hexagonal symmetry, space group P6 3 /mmc, a=5.8344(2) Å, c=25.637(2) Å, Z=2. Combined refinement and maximum-entropy method unambiguously show the presence of CO 3 2-ions in the three other compounds (2, 3, 4). Their crystal structures were solved and refined in the trigonal symmetry, space group P 3 m1, a=5.8381(1)Å, c=15.3083(6)Å for the term n=3, Ba 6 Ru 3 Br 1.54 (CO 3 ) 0.23 O 12 (2), and space group R 3 m, a=5.7992(1) Å, c=52.866(2) Å and a=5.7900(1) Å, c=59.819(2) Å for the terms n=4, Ba 7 Ru 4 Br 1.46 (CO 3 ) 0.27 O 15 (3), and n=5, Ba 8 Ru 5 Br 1.64 (CO 3 ) 0.18 O 18 (4), respectively. The structures are formed by the periodic stacking along [0 0 1] of (n+1) hexagonal close-packed [BaO 3 ] layers separated by a double layer of composition [Ba 2 Br 2-2x (CO 3 ) x ]. The ruthenium atoms occupy the n octahedral interstices created in the hexagonal perovskite slabs and constitute isolated dimers Ru 2 O 9 of face shared octahedra in 1 and isolated trimers Ru 3 O 12 of face shared octahedra in 2. In 3 and 4, the Ru 2 O 9 units are connected by corners either directly (3) or through a slab of isolated RuO 6 octahedra (4) to form a bidimensional arrangement of RuO 6 octahedra. These four oxybromocarbonates belong to the family of compounds formulated [Ba 2 Br 2- 2x (CO 3 ) x ][Ba n+1 Ru n O 3n+3 ] where n represents the thickness of the octahedral string in hexagonal perovskite slabs. These compounds are compared to the oxychloride series.

Introduction

In the cubic and hexagonal barium-containing perovskite-type oxides, the stacking of compact hexagonal [BaO 3 ] layers creates octahedral holes occupied by a small metal atom M to give various structures depending on the stacking sequence of the [BaO 3 ] layers. If a layer (noted c) is surrounded by two different layers, the MO 6 octahedra on both sides of this layer are connected by a corner. On the contrary, if the layer (noted h) is surrounded by two identical layers, the MO 6 octahedra are then face-shared. Except for the simplest hh sequence where 1Darrangement of face-shared octahedra is formed, all the structures are built from a 3D-framework of edge-and corner-shared octahedra. For a given M atom, several sequences can be observed corresponding to various polymorphs with transitions in function of the temperature or the pressure. The example of BaRuO 3 is very informative [1]. At atmospheric pressure, BaRuO 3 adopts a 9R structure with (hhc) 3 . In these layered 2D structures, the mean oxidation degree of the M metal decreases from +5 for n=2 to +4 for n=∞ which corresponds to infinite thickness of the 2D fragment i.e. to 3D 9R-BaRuO 3 . Two similar compounds with [Ba 2 Br 2 ] double layers intercalated in the [BaO 3 ] stacking have been reported for n=4 and 5 in Ba 7 Ru 4 Br 2 O 15 [5] and Ba 8 Ru 3 Ta 2 Br 2 O 18 [6], respectively. In the present paper we describe the crystal structure of all the terms for the bromide series from n=2 to n=5 that contain only Ru as transition metal in octahedral sites. In fact, presence of carbonate ions in the double barium layers leads to the formula [Ba 2 Br 2-2x (CO 3 ) x ][Ba n+1 Ru n O 3n+3 ] for this series. The crystal structure of the term n=3 for the chloride series has been revisited and carbonate ions localized in the double barium layers.

Experimental

Synthesis

The starting materials, BaCO 3 (Fisher, 99%), Ru (Touzart & Matignon, 99%) and BaBr 2 ,2H 2 O (Prolabo, Rectapur, 99%), were used as received. Two compositions of these reactants corresponding to the stoichiometries 3/3/10 and 3/1/10, respectively were mixed and heated in an alumina crucible from room temperature to 1100°C in 10 hours. After a 48 hours maintenance at this temperature the samples were cooled to 500°C at 15°C/hr and finally to room temperature by cut off the furnace. After dissolving the excess of BaBr 2 with hot water, black hexagonal-plate crystals were found in the two experiments. For each synthesis, several single crystals were tested on a single crystal X-Ray diffractometer, hexagonal unit cells are always obtained with the same a-parameter (a~5.8 Å) and c-parameter depending on the starting synthesis compositions. For the first one, two types of crystals were identified with c~25. (4), respectively, were obtained. Several crystals from the two preparations were analyzed by energy dispersive spectroscopy using a JEOL JSM -5300 scanning microscope equipped with a PGT Digital Spectrometer, confirming the presence of Ba, Ru and Br.

Crystal structure determination

For structure determinations, crystals of the four compounds were selected, mounted on glass fibers and aligned on a Bruker X8 APEX 2 X-Ray diffractometer. Intensities were collected at room temperature using MoKα radiation (λ=0.71073 Å) selected by a graphite monochromator. Individual frames were measured using a strategy combining ω and φ scans with a rotation of 0.3° and an acquisition time of 20 s per frame. After every data collection, intensities were reduced and corrected for Lorentz, polarization and background effects using the Saint 7.12 software [START_REF]Bruker Analytical X-ray system[END_REF]. Once the data processing was performed, the absorption corrections were computed by a semi-empirical method based on redundancy using the SADABS 2006/1 program [START_REF] Scheldrick | SADABS, Bruker-Siemens Area Detector Absorption and Other Correction[END_REF].

Details of the data collection and refinement are given in Table 1.

Compound 1 crystallizes in the hexagonal system and a crystal structure approach was realized in the centro-symmetric P6 3 /mmc space group. The three other compounds crystallize in the trigonal system and the crystal structures were solved in the centro-symmetric space groups P 3 m1 for 2 and R 3 m for 3 and 4. The structures were determined by direct methods using SIR97 program [9], which readily established the heavy atom positions (Ba, Ru, Br). Oxygen atoms were localized from difference Fourier maps. The last cycles of refinement included atomic positions, anisotropic displacement parameters for all non-oxygen atoms, and isotropic displacement parameters for oxygen atoms. Full-matrix least squares structure refinements against F were carried out using the JANA 2000 program [START_REF] Petricek | The Crystallographic Computing System JANA2000[END_REF]. In a first step, the crystal structures were refined without carbonate ions and with the Br atoms in the same positions than the Cl atoms in the analogous chlorides which correspond, for n=4 and 5, to the positions used in the previously reported Ba 7 Ru 4 Br 2 O 15 [5] and Ba 8 Ru 3 Ta 2 Br 2 O 18 [6]. The obtained structural parameters (hereafter the ideal model) are in good agreement with the previously reported results and are given in Table 2 for compound 3, as example. However, large unusual values of the displacement parameters for Br atoms, particularly in the (0 0 1) plane, were obtained for the four compounds. Furthermore, significant residual electron densities were observed around the bromine sites. This fact strongly suggests that one should apply additional structure refinements, e.g. using displacement parameters together with lowering the site-symmetry for bromine atoms and/or further thermal parameters. For many types of disorder it is difficult to derive an appropriate model based on atoms and harmonic displacement parameters. It can be necessary to use many different sites with a partial occupancy of the atoms. Alternatively, information on disorder can be obtained from a Fourier map generated from the phases of the structure factors calculated for the "best" model and their observed intensities. Another possibility lies in the use of the Maximum-Entropy Method (MEM), a model-free method which may be used for calculating electron densities in solids using experimental phased structure factors as input [START_REF] Gilmore | [END_REF].

To calculate the precise electron density distribution, the MEM analysis was carried out with the computer program BAYMEM [START_REF] Palatinus | BAYMEM -A computer program for application of the Maximum Entropy Method in reconstruction of electron densities in arbitrary dimension[END_REF]. In the present analysis, the total number of electrons in the unit cell was fixed to the F(000) values (1020, 634, 2274 and 2646 e -for 1, 2, 3, 4, respectively) and the unit cell was divided into a grid of 72*72*486 pixels to ensure a good spatial resolution (better than 0.081 Å for all the studied compounds). All independent reflections were used in the process. A particular attention was paid to the strategy of the data collection in order to obtain high angle data (up to 2θ=96.5° for Ba 7 Ru 4 Br 2 O 15 , for example). All calculations were performed with an initial flat electron density. The reliability factor of the MEM, R MEM is indicated in Table 1, with

∑ ∑ - = obs MEM obs MEM F F F R
, where F obs is obtained by the structural refinement and F MEM is the structure factor calculated from the electron density obtained by the MEM.

The visualized three-and two-dimensional electron density (ED) images are shown on Figure 1a in the region of the bromine atom for 3, as example. These images clearly showed that the ED at the Br (6c) site broadened like a triangular form indicating that bromine ions are distributed over three split sites in a 18h site (Br( 1)) In the same manner, the Ba(1) site displayed a triangular shape indicating a small splitting over the 3-fold axis. The Ba(2) site showed a slightly elongated ED with an egg-shape (Figure 1b) indicating a two position splitting. The disorder observed using the MEM was then introduced in the refinement process and therefore the ideal structure model was modified in such a way that Br(1) and Ba(1) ions at the 6c sites were divided into three positions, corresponding to one third of 18h sites, while Ba(2) was split over two 6c positions. The occupancy parameters of the Ba ions were constrained to unity to fulfil the chemical composition (Ba 7 Ru 4 Br 2 O 15 at this stage). This model is called the split-atom model without CO 3 and allows reducing considerably the residual density in all structures (see Table 1). Finally, analysis of the ED also showed a density in form of clover centred on a 6c position with three petals corresponding to a 18h position with distances compatible with a carbonate ion (Figure 1c). Therefore a carbonate ion was introduced with an occupancy factor adjusted to respect the electro-neutrality of the compound considering the same oxidation degree of the ruthenium as in the corresponding oxychloride (see the discussion below). Henceforth this model is called the split-atom model with CO 3 . The refinement was somewhat improved (Robs=0.0298 and wRobs=0.0354 to compare to Robs=0.0479 and wRobs= 0.0541 for the ideal model) and the residual densities were acceptable (Max ∆ρ=5.63 e -/Å 3 in the split-atom model with CO 3 to compare to 15.05 e -/Å 3 ). Another formalism which was proved to lead to a good fit to the data is the formalism of anharmonic displacement parameters [START_REF] Kuhs | [END_REF]. This model was tested in the present study but without significant improvements of the R factors and with many parameters and consequently strong correlations. The "simple" split-atom model with CO 3 was then used in the final refinement. All the details and results are given in Table 1. The MEM analysis was conducted in the same way on all the prepared compounds and leads to the same conclusions concerning the disorder for compounds 2 and 4. Ba(1), Ba(2) and Br (1)

Crystal structures descriptions and discussion

The atomic coordinates and displacement parameters are given in Tables 4, 5 and6 for 2, 3, 4 respectively. Selected bond lengths are listed in Table 7. Valence bond sums reported in

The stacking sequences

The four structures can be described from the stacking along the c axis of [BaO 3 ] and (hhcchhh'h') 3 for n=5 with rhombohedral lattice (21R and 24R sequences, respectively).

The RuO 6 octahedral arrangement

The Finally in 2, the Ru -Ru distance within the trimer FSO is similar to that calculated for the corresponding chlorine compound and greater than in 9R-BaRuO

The Br, CO 3 disorder in the [Ba 2 X 2 ] 2+ layers

In the ideal structure, the Br atoms occupy all the tetrahedral sites created between two

[Ba] layers leading to a fluorite type sheet. However the Ba(2) atoms that border the perovskite slab belong to the coordination polyhedra of the Br atom better described as a trigonal bipyramid.

In the actual structure, the C atom of a carbonate anion is located above or below the octahedral site between the [Ba] layers, the oxygen atoms being directed towards the Br atoms that should be removed. So, three Br atoms are replaced by one carbonate anion leading to a slightly lower MOD of the ruthenium atoms or to the formation of clusters of carbonate ions. In fact, one can also suppose the existence of [Ba 2 Br 2 ] layers and [Ba 2 CO 3 ] layers (Figure 3a) identical to those met in BaCO 3 . In the mineral witherite [40], with aragonite-type structure, the carbonate anions are displaced from the octahedral site to a tetrahedral one within a hexagonal close-packing of

[Ba] layers (Figure 3b). In BaCO 3 -II [41], the carbonate ions are disordered on both sides of the octahedral sites (Figure 3c) as in the currently described compounds.

3 [ 2 ], 4 [ 3 ]

 3243 stacking sequence and contains Ru 3 O 12 trimers of face-shared octahedra linked together by corner sharing. At 15 kbar, BaRuO 3 transforms to a 4H structure with (hc) 2 stacking sequence and Ru 2 O 9 dimers of face-shared octahedra linked together by corner sharing. At 30 kbar, this structure transforms to a 6H structure with (hcc) 2 stacking sequence and contains Ru 2 O 9 dimers of face-shared octahedra linked by corner sharing with a layer of isolated octahedra. Finally, a cubic 3c perovskite structure is expected for BaRuO 3 at about 120 kbar [1]. The introduction of [Ba 2 Cl 2 ] double layers within the [BaO 3 ] stacking breaks the 3D-arrangement and results in the formation of [Ba n+1 M n O 3n+3 ] 2-slabs of n octahedra thickness in the compounds formulated [Ba 2 Cl 2 ][Ba n+1 M n O 3n+3 ] reported for M = Ru and n=2, and for a mixed site M = 3.33 Ru -1.67 Ta and n = 5 [4]

[

  BaBr] layers in various sequences. In [BaBr] layers, the barium atoms occupy the same positions as in the corresponding [BaO 3 ] layers but the oxygen atoms are removed. So in the stacking sequence they are noted with a ' to indicate the deficient [BaBr] layers. The four compounds differ by the number (n+1) of successive [BaO 3 ] layers, n=2, 3, 4, 5 for compounds 1, 2, 3, 4, respectively, resulting in the formation of [BaO 3 ] n+1 slabs stacked in the [0 0 1] direction and separated by two [BaBr] layers. For the two first terms the slabs contain only two types of [BaO 3 ]layers leading to (hhh) and (hhhh) sequences. For the two other terms, one or two cubic close-packed c layers are introduced at the middle of the (hhhh) sequence to give (hhchh) and (hhcchh) sequences. In the four compounds the [BaBr] layers correspond to a (h'h') slab, so the complete layers sequences of both [BaO 3 ] and [BaBr] layers are (hhhh'h') 2 for n=2, (hhhhh'h') for n=3, leading to hexagonal lattices (10H and 6H sequences respectively) and (hhchhh'h') 3 for n=4 and

  ruthenium atoms occupy the n octahedral holes created by the [BaO 3 ] layers leading to [Ba n+1 Ru n O 3n+1 ] slabs. For n=2, 4 and 5, Ru 2 O 9 dimers of face-shared octahedra (FSO) are formed, they are isolated for n=2, connected by corner sharing for n=4 and through isolated RuO 6 octahedra for n=5. Finally, for n=3, isolated Ru 3 O 12 columns of three face-shared octahedra are formed. The four slabs can be deduced from the three polytypes of BaRuO 3 by separating the blocks on both sides from a shear plane which is a c layer (Figure 2) and, of course, by adding a [BaO 3 ] layer to border one of the two blocks giving a sheet [Ba n+1 Ru n O 3n+1 ]. For n=2 and 4, the slabs are deduced from the same 4H polytype but with a single and a double stage separation respectively. For n=3, the slabs are deduced from the 9R polytype. Finally, the n=5 slabs are obtained from the 6H polytype by withdrawing one layer of isolated RuO 6 octahedra out of two.The n=1 slab could result from the supposed 3C polytype but is unexpected because it would be made only of isolated octahedra. The insertion between the perovskite-type blocks of cationic [Ba 2 Br 2-2x (CO 3 ) x ] 2+ layers leads to 2+ charge of the perovskite-type blocks that implies an oxidation of the ruthenium atom to the mean degree (4+2/n). Thus the transformation from BaRuO 3 to the oxyhalides compounds can be called oxidative intercalation.

3 [ 2 ]

 32 , in agreement with the increase of MOD. Both the average Ru -O distances and the BVS do not permit to determine unambiguously the charge repartition in the three sites although the most probable distribution is Ru 5+ -Ru 4+ -Ru 5+ as in Ba 5 Ru 3 O 12 [19].

Figures captionsFigure 1 :

 1 Figures captions

Figure 2 :

 2 Figure 2: Projection along [010] of (a) 4H-BaRuO 3 , (b) Ba 5 Ru 2 Br 2 O 9 n=2, (c) 9R-BaRuO 3 , (d)

Figure 3 :Figure 1 :

 31 Figure 3: View along [001] and [100] of the [Ba 2 CO 3 ] sheets in (a) Ba 6 Ru 3 Br 1.54 (CO 3 ) 0.23 O 12

Figure 2 :

 2 Figure 2: Projection along [010] of (a) 4H-BaRuO 3 , (b) Ba 5 Ru 2 Br 2 O 9 n=2, (c) 9R-BaRuO 3 , (d)

Figure 3 :

 3 Figure 3: View along [001] and [100] of the [Ba 2 CO 3 ] sheets in (a) Ba 6 Ru 3 Br 1.54 (CO 3 ) 0.23 O 12

  6 and c~15.3 Å corresponding to Ba 5 Ru 2 Br 2 O 9 (1) and Ba 6 Ru 3 Br 2 O 12 (2), respectively. For the second one, two other types of crystals with c~52.9 and c~59.8 Å corresponding to Ba 7 Ru 4 Br 2 O 15 (3) and Ba 8 Ru 5 Br 2 O 48

  Ba 2 Cl 2 ] layers and the split-atom model leads to the formula Ba 6 Ru 3 Cl 1.36 (CO 3 ) 0. 32 O 12 and to an improvement of the refinement (Robs=0.0323 and wRobs=0.0321 to compare to Robs=0.0391 and wRobs= 0.0572).

atoms are split in the same manner than in Ba 7 Ru 4 Br 2 O 15 and CO 3 carbonate ions localized. In summary, all the atoms in the vicinity of the [Ba 2 Br 2 ] layers are disordered, whereas the rest of the structure is perfectly ordered. For compound 1, ED was observed in the vicinity of Br(1) atoms and between the Ba(1) and Ba(2) layers. Unfortunately, in spite of many hypotheses and tests, the results of the structural refinement could not significantly be improved. Thus only the structural approach leading to the average model (Table

3

) is considered in this paper for compound 1. Considering these results, MEM analysis was carried out using the diffraction data collected for the oxychloride compound Ba 6 Ru 3 Cl 2 O 12 reported in

[2]

for which high atomic displacement parameter was refined for the chlorine atom. Analogous conclusions were obtained, carbonate ions are unambiguously observed within the double [

Table 8

 8 were calculated using the expression of bond valence Sij between two atoms i and j given by Brown [17], Sij = exp(Ro-Rij)b where Rij are the observed bond distances and R 0 and b are empirical constants. For these calculations R 0 = 1.834 Å for Ru Ru 2 Br 2 O 9 (1), Ba 6 Ru 3 Br 1.54 (CO 3 ) 0.23 O 12 (2), Ba 7 Ru 4 Br 1.46 (CO 3 ) 0.27 O 15 (3) and Ba 8 Ru 5 Br 1.64 (CO 3 ) 0.18 O 18 (4) can be described as an intergrowth of [Ba n+1 Ru n O 3n+3 ] 2-anionic hexagonal perovskite slabs and [Ba 2 Br 2-2x (CO 3 )

4+ [18] and 1.888 Å for Ru 5+ [19] with the commonly taken b value, b= 0.37 Å [20] were used. The crystal structures of the four compounds Ba 5 x ] 2+ double layers and thus can be formulated [Ba 2 Br 2-2x (CO 3 ) x ][Ba n+1 Ru n O 3n+3 ] with n=2, 3, 4, 5 for 1, 2, 3, 4, respectively.

  The same type of oxidative intercalation of [Ba 2 X 2 ] layers has been recently reported to explain the transformation of Ba 2 Co 9 O 14 [21, 22] in the oxyhalides [Ba 2 X 2 ]Ba 2 Co 8 O 14 , X = Cl, Br [23]. Dimers of face shared octahedra (FSO) are very common in ruthenium compounds. If the ruthenium atoms were at the center of the neighboring FSO, the Ru -Ru distance, which corresponds to the average thickness of close-packed layers, should be 2.37 Å. The repulsion between Ru atoms which would lead to the destabilization of the structure can be prevented by the formation of a Ru -Ru metal bond as observed in Ru 2 O 9 dimers containing Ru 4+ or Ru at the mean oxidation degree (MOD) of +4.5 with Ru -Ru distances smaller than in the metal itself (2.65 Å). For example the Ru -Ru distance is 2.537 Å in 4H-BaRuO 3 [24], 2.481 to 2.515 Å in 6H-Ba 3 M 4+ Ru 2 O 9 , M=Ce, Pr, Tb [25] and Ti [26], and 2.517 to 2.563 Å in Ba 3 M 3+ Ru 2 O 9 Ru distances reported in Ru 2 O 10 dimers of edge-shared octahedra with strong metal -metal bonding in La 4 Ru 6 O 19 (2.488 Å) [38] and no metal -metal bonding in La 3 Ru 3 O 11

	distance is even longer (2.780(3) Å) and comparable to that observed in the corresponding oxychloride compound (2.819(4) Å). The Ru 5+ -Ru 5+ repulsion is reduced by the shortening of the O(2) -O(2) edge of the common face to 2.56(2) Å. The [Ba 2 X 2 ][Ba 3 Ru 2 O 9 ] oxyhalides can be deduced from the Ba 3 M 2+ Ru 2 O 9 oxides by the replacement of M 2+ cations by [Ba 2 X 2 ] 2+ layers between [Ba 3 Ru 2 O 9 ] 2-slabs that leads to a greater distance between the slabs allowing a lengthening of the intradimer Ru -Ru distance. Finally, the change of the nature of the cationic species between the [Ba 3 Ru 2 O 9 ] slabs, monovalent-, divalent-, trivalent-ions or [Ba 2 X 2 ] 2+ or [Ba 2 (O 2 )] 2+ layers [36, 37], provides access to the Ru -Ru distances which cover all the range In 3 and 4 that contain ruthenium at the MOD +4.5 and +4.4 respectively, the Ru -Ru distances within the dimers indicate clearly that there is no metal -metal bond. Furthermore the distances are slightly lower to that calculated in 1, in agreement with the lower MOD of ruthenium and consequently weaker repulsion. In addition, whereas the average Ru -O distances do not allow to propose a charge distribution on the ruthenium atoms, the bond valence sums (BVS) indicate a tendency showing that ruthenium ions are mainly Ru 4+ at the Ru(2) site and between the Ru -(2.990 Å) [39]. Ru

compounds, M=Y [27, 28], In [27, 29], La, Nd, Sm -Tb, Ho, Er, Yb, Lu [27, 28, 30, 31]. The Ru 5+ atom with low spin configuration d 3 is more favorable than the Ru 4+ atom with low spin configuration d 4 to the formation of Ru -Ru bond. However in the Ba 3 M 2+ Ru 2 O 9 compounds, M=Co, Zn [29, 32], Mg, Ca, Sr, Cd [33-35], the Ru -Ru distances are in the range from 2.652 to 2.701 Å that indicates that the Ru -Ru metal bond no longer exists. In Ba 5 Ru 2 O 9 Br 2 , the Ru -Ru 5+ at the Ru(1) site in 3. On the contrary, in 4, the greater Ru(3) -O bonds and the smaller BVS value reveals the presence of Ru 4+ in the Ru(3)O 6 octahedra connecting the dimers, thus the charge repartition within the dimers is rather similar in 3 and 4.

49]. Conclusion Single

  The presence of carbonate ions has been reported in many compounds with perovskite-related structures as, for examples, in high-Tc superconductors [42-45], in Ruddlesden-Popper materials such as Sr 4 Fe 2-x M x O 6 CO 3 (M=Sc, Ni, Co) [46] where they substitute layers of metal octahedra. In 6H-Ba 3 (Ru 1.69 C 0.31 )(Na 0.95 Ru 0.05 )O 8.69 [47], part of the Ru 2 O 9 dimeric units of the parent compound Ba 3 Ru 2 NaO 9 [48], are replaced by one RuO 5 and one CO 3 group. Finally in Ba 3 Co 2 O 6 (CO 3 ) 0.60 , carbonate ions and Ba atoms form [Ba(CO 3 ) 0.60 ] rods, related to the BaCO 3 aragonite-type structure, intergrowth with 2H-[Ba 2 Co 2 O 6 ] columns [crystals of the terms n=2, 3, 4 and 5 of the series [Ba 2 Br 2-2x (CO 3 ) x ][Ba n+1 Ru n O 3n+3 ] have been isolated. For n=2 and 3, the [Ba n+1 Ru n O 3n+3 ] 2-slabs contain respectively Ru 2 O 9 and Ru 3 O 12 entities resulting from face-shared octahedra, and giving one-dimensional ruthenium octahedra arrangement. For n=4 and 5, the [Ba n+1 Ru n O 3n+3 ] 2-slabs contain also Ru 2 O 9 dimers of face-shared octahedral further connected directly or by layers of isolated RuO 6 octahedra giving two-dimensional arrangements. The mean oxidation state of Ru decreases from +5 for n = 2 to +4.4 for n = 5. One interesting point of this series is to show the possibility of [Ba 2 CO 3 ] layers between perovskite-type blocks that opens a new way of synthesis of interesting oxycarbonates.

Table 1 :

 1 Crystal data, intensity collection and structure refinement parameters for Ba 5 Ru 2 Br 2 O 9 (1), Ba 6 Ru 3 Br 1.54 (CO 3 ) 0.23 O 12 (2), Ba 7 Ru 4 Br 1.46 (CO 3 ) 0.27 O 15 (3) and Ba 8 Ru 5 Br 1.64 (CO 3 ) 0.18 O 18(4)

		1	2	3	4
	Crystallographic data
	Formula weight (g.mol -1 )	1192.7	1456.2	1738.6	2035.1
	Crystal system	Hexagonal	Trigonal	Trigonal	Trigonal
	Space group	P6 3 /mmc	P-3m1	R-3m	R-3m
	Unit cell dimensions (Å)	a = 5.8344(2)	a = 5.8381(1)	a = 5.7992(1)	a = 5.7900(1)
		c = 25.637(2)	c = 15.3083(6) c = 52.866(2)	c = 59.819(2)
	Cell volume (Å 3 )	755.77(7)	451.86(2)	1539.73(7)	1736.71(7)
	Z	2	1	3	3
	Density calculated (g.cm -3 ) 5.24	5.35	5.62	5.88
	F(000)	1020	625	2241	2625
	Crystal size	120 x 60 x 20	130 x 70 x 20	140 x 90 x 30	150 x 90 x 30
	Intensity collection
	Wavelength (Å)	0.71073	0.71073	0.71073	0.71073
	2 Theta range (deg)	3.18 -84.64	2.66 -87.26	4.62 -96.50	2.04 -82.20
	Index range	-11 ≤ h ≤ 9	-10 ≤ h ≤ 11	-7 ≤ h ≤ 11	-10 ≤ h ≤ 10
		-9 ≤ k ≤ 11	-10 ≤ k ≤ 11	-12 ≤ k ≤ 8	-10 ≤ h ≤ 10
		-48 ≤ l ≤ 43	-23 ≤ l ≤ 29	-73 ≤ l ≤ 106	-109 ≤ h ≤ 95
	Reflections collected	21589	14011	13472	18600
	Reflections observed	13719	9608	10510	11766
	Criterion for observation	I > 3σ(I)	I > 3σ(I)	I > 3σ(I)	I > 3σ(I)
	R int before abs. corr.	0.2696	0.1898	0.1732	0.1667
	Absortion correction	SADABS	SADABS	SADABS	SADABS
	T min / T max	0.51	0.68	0.62	0.63
	R int after abs. corr.	0.0720	0.0607	0.0352	0.0597
	Redundancy µ (MoKα) (mm -1 )	19.97 20.065	10.12 18.731	6.70 18.940	12.10 19.453
	Refinement
	Data/restrains/parameters	1074 / 0 / 20	1385 / 1 / 42	2010 / 1 / 50	1537 / 1 / 54
	Weighting scheme	Unit	Unit	Unit	Unit
	Ideal model
	Final R indices (R, wR) obs 0.1221 / 0.1198 0.0736 / 0.0809 0.0479 / 0.0541 0.0554 / 0.0603
	Final R indices (R, wR) all 0.1472 / 0.1309 0.0885 / 0.1052 0.0604 / 0.0602 0.0772 / 0.0900 Max, min ∆ρ (e-Å 3 ) 18.99 / -19.30 23.23 / -6.96 15.05 / -8.40 9.47 / -11.88
	Split-atom model without CO 3
	Final R indices (R, wR) obs	/	0.0625 / 0.0716 0.0373 / 0.0448 0.0488 / 0.0538
	Final R indices (R, wR) all	/	0.0766 / 0.0979 0.0500 / 0.0517 0.0703 / 0.0854
	Max, min ∆ρ (e-Å 3 )	/	8.71 / -7.77	7.59 / -6.14	7.54 / -9.81
	Split-atom model with CO 3
	Final R indices (R, wR) obs	/	0.0540 / 0.0619 0.0298 / 0.0354 0.0457 / 0.0492
	Final R indices (R, wR) all	/	0.0688 / 0.0942 0.0423 / 0.0435 0.0670 / 0.0841
	Final R indices (R, wR) mem	/	0.0628 / 0.0430 0.0260 / 0.0128 0.0462 / 0.0326
	Max, min ∆ρ (e-Å 3 )	/	6.72 / -3.97	5.63 / -2.81	7.05 / -9.10
	Extinction coefficient	0	0	0.070(4)	0

Table 2 :

 2 Atomic coordinates and isotropic displacement parameters for the average structure of 3 corresponding to Ba 7 Ru 4 Br 2 O 15 . Anisotropic displacement parameters

	Atom	Wyck. Occ.	x		y		z	U iso or U eq
	Ba(1)	6c	1	0		0		0.20567(2)	0.0236(2)
	Ba(2)	6c	1	0		0		0.91766(1)	0.0117(1)
	Ba(3)	6c	1	0		0		0.28692(1)	0.0085(1)
	Ba(4)	3a	1	0		0		0	0.0105(2)
	Ru(1)	6c	1	0		0		0.59518(2)	0.0067(1)
	Ru(2)	6c	1	0		0		0.64672(1)	0.0054(1)
	O(2)	18h	1	0.4949(5)	-0.4949(5)	0.08902(9)	0.012(1)
	O(3)	18h	1	0.8190(5)	-0.8190(5)	0.95596(8)	0.0086(9)
	O(4)	9e	1	1/2		0		0	0.010(1)
	Br(1)	6c	1	0		0		0.14228(5)	0.061(1)
	Atom	U 11		U 22	U 33		U 12	U 13	U 23
	Ba(1)	0.0293(3)	0.0293(3) 0.0121(3)	0.0147(1)	0	0
	Ba(2)	0.0092(1)	0.0092(1) 0.0167(3)	0.00462(7)	0	0
	Ba(3)	0.0079(1)	0.0079(1) 0.0099(2)	0.00393(6)	0	0
	Ba(4)	0.0079(2)	0.0079(2) 0.0157(3)	0.00393(9)	0	0
	Ru(1)	0.0056(1)	0.0056(1) 0.0089(3)	0.00278(7)	0	0
	Ru(2)	0.0049(1)	0.0049(1) 0.0066(2)	0.00244(7)	0	0
	O(2)	0.014(1)		0.014(1)	0.011(1)		0.010(1)	-0.0027(6) 0.0027(6)
	O(3)	0.009(1)		0.009(1)	0.009(1)		0.005(1)	0.0005(6) -0.0005(6)
	O(4)	0.011(2)		0.006(2)	0.012(2)		0.003(1)	0.0007(8) 0.001(2)
	Br(1)	0.081(2)		0.081(2)	0.0210(9)	0.0408(8)	0	0

Table 3 :

 3 Atomic coordinates and isotropic displacement parameters for the average structure of Ba 5 Ru 2 Br 2 O 9(1). Anisotropic displacement parameters for the non-oxygen atoms

	Atom	Wyck. Occ.	x		y		z	U iso or U eq
	Ba(1)	4f	1	1/3		2/3		0.91916(1)	0.0393(9)
	Ba(2)	4f	1	1/3		2/3		0.17207(8)	0.0140(4)
	Ba(3)	2d	1	1/3		2/3		3/4	0.0116(5)
	Ru(1)	4e	1	0		0		0.19579(9)	0.0096(4)
	O(2)	12k	1	0.164(2)	0.328(3)	0.8424(5)	0.017(2)
	O(3)	6h	1	0.146(1)	0.292(3)	1/4	0.002(2)
	Br(1)	4f	1	1/3		2/3		0.4520(3)	0.094(4)
	Atom	U 11		U 22	U 33		U 12	U 13	U 23
	Ba(1)	0.049(1)		0.049(1)	0.0189(9)	0.0247(6)	0	0
	Ba(2)	0.0117(4)	0.0117(4) 0.0185(7)	0.0059(2)	0	0
	Ba(3)	0.0081(5)	0.0081(5) 0.0187(9)	0.0041(3)	0	0
	Ru(1)	0.0075(5)	0.0075(5) 0.0138(8)	0.0038(2)	0	0
	Br(1)	0.126(6)		0.126(6)	0.028(3)		0.063(3)	0	0

Table 4 :

 4 Atomic coordinates and isotropic displacement parameters for Ba 6 Ru 3 O 12 Br 1.54 (CO 3 ) 0.23(2). Anisotropic displacement parameters for the non-carbonate atoms

	Atom	Wyck. Occ.		x		y	z	U iso or U eq
	Ba(1)	6i	0.333	0.658(4)	-0.658(4)	0.6331(1)	0.022(2)
	Ba(2a) 2d	0.916(8)	1/3		2/3	0.7898(1)	0.0108(3)
	Ba(2b) 2d	0.084(8)	1/3		2/3	0.760(2)	0.0108(3)
	Ba(3)	2d	1		1/3		2/3	0.07789(9)	0.0117(2)
	Ru(1)	2c	1		0		0	0.8271(1)	0.0090(3)
	Ru(2)	1a	1		0		0	0	0.0076(3)
	Br(1)	6i	0.257(6)	0.320(6)	-0.320(6)	0.5838(3)	0.037(5)
	C(1)	2c	0.115(9)	0		0	0.44(1)	0.0150
	O(1)	6i	0.115(9)	0.124(9)	-0.124(9)	0.566(5)	0.0150
	O(2)	6i	1		0.162(1)	-0.162(1)	0.2324(6)	0.014(2)
	O(3)	6i	1		0.8451(9)	-0.8451(9)	0.0791(5)	0.011(2)
	Atom	U 11		U 22		U 33		U 12	U 13	U 23
	Ba(1)	0.026(4)		0.026(4)	0.0159(6)	0.014(2)	0.003(2)	-0.003(2)
	Ba(2a)	0.0096(3)	0.0096(3) 0.0132(8)	0.0048(1)	0	0
	Ba(2b)	0.0096(3)	0.0096(3) 0.0132(8)	0.0048(1)	0	0
	Ba(3)	0.0093(3)	0.0093(3) 0.0166(5)	0.0046(1)	0	0
	Ru(1)	0.0070(3)	0.0070(3) 0.0130(5)	0.0035(1)	0	0
	Ru(2)	0.0058(4)	0.0058(4) 0.0111(7)	0.0029(2)	0	0
	Br(1)	0.043(6)		0.043(6)	0.012(2)		0.011(9)	0.005(3)	-0.005(3)
	O(2)	0.015(3)		0.015(3)	0.016(3)		0.010(3)	-0.003(1)	0.003(1)
	O(3)	0.012(2)		0.012(2)	0.011(3)		0.008(3)	0.001(1)	-0.001(1)

Table 5 :

 5 Atomic coordinates and isotropic displacement parameters for Ba 7 Ru 4 O 15 Br 1.46 (CO 3 ) 0.27(3). Anisotropic displacement parameters for the non-carbonate atoms

	Atom	Wyck. Occ.		x		y	z	U iso or U eq
	Ba(1)	18h	0.333	0.0065(6)	-0.0065(6)	0.20556(2)	0.0231(6)
	Ba(2a) 6c	0.919(8)	0		0	0.91787(3)	0.0100(2)
	Ba(2b) 6c	0.081(8)	0		0	0.9112(3)	0.0100(2)
	Ba(3)	6c	1		0		0	0.28691(1)	0.00872(8)
	Ba(4)	3a	1		0		0	0	0.0107(1)
	Ru(1)	6c	1		0		0	0.59517(1)	0.00688(9)
	Ru(2)	6c	1		0		0	0.64672(1)	0.00568(9)
	Br(1)	18h	0.243(3)	0.014(2)	-0.014(2)	0.14232(4)	0.039(2)
	C(1)	6c	0.135(4)	0		0	0.482(1)	0.0150
	O(1)	18h	0.135(4)	0.125(3)	-0.125(3)	0.5180(5)	0.0150
	O(2)	18h	1		0.4948(4)	-0.4948(4)	0.08886(7)	0.0125(9)
	O(3)	18h	1		0.8191(3)	-0.8191(3)	0.95597(6)	0.0085(7)
	O(4)	9e	1		1/2		0	0	0.010(1)
	Atom	U 11		U 22		U 33		U 12	U 13	U 23
	Ba(1)	0.0309(8)	0.0309(8) 0.0130(2)	0.0196(9)	-0.0045(4) 0.0045(4)
	Ba(2a)	0.0091(1)	0.0091(1) 0.0119(4)	0.00453(5)	0	0
	Ba(2b)	0.0091(1)	0.0091(1) 0.0119(4)	0.00453(5)	0	0
	Ba(3)	0.00803(9)	0.00803(9) 0.0101(1)	0.00402(5)	0	0
	Ba(4)	0.0080(1)	0.0080(1) 0.0160(3)	0.00401(6)	0	0
	Ru(1)	0.0058(1)	0.0058(1) 0.0091(2)	0.00289(5)	0	0
	Ru(2)	0.0051(1)	0.0051(1) 0.0068(2)	0.00255(5)	0	0
	Br(1)	0.041(2)		0.041(2)	0.0116(7)	0.002(4)	0.004(1)	-0.004(1)
	O(2)	0.014(1)		0.014(1)	0.012(1)		0.010(1)	-0.0028(5) 0.0028(5)
	O(3)	0.0085(7)	0.0085(7) 0.0093(9)	0.0048(8)	0.0004(4) -0.0004(4)
	O(4)	0.011(1)		0.007(1)	0.013(2)		0.0034(7)	0.0008(6) 0.002(1)

Table 6 :

 6 Atomic coordinates and isotropic displacement parameters for Ba 8 Ru 5 O 18 Br 1.66 (CO 3 ) 0.17(4). Anisotropic displacement parameters for the non-carbonate atoms

	Atom	Wyck. Occ.		x		y	z	U iso or U eq
	Ba(1)	18h	0.333	0.011(3)	-0.011(3)	0.36796(4)	0.022(2)
	Ba(2a) 6c	0.90(4)	0		0	0.7413(2)	0.0114(7)
	Ba(2b) 6c	0.10(4)	0		0	0.736(1)	0.0114(7)
	Ba(3)	6c	1		0		0	0.44046(2)	0.0103(2)
	Ba(4)	6c	1		0		0	0.81193(2)	0.0108(2)
	Ru(1)	6c	1		0		0	0.08422(3)	0.0086(3)
	Ru(2)	6c	1		0		0	0.13025(3)	0.0073(3)
	Ru(3)	3b	1		0		0	1/2	0.0165(6)
	Br(1)	18h	0.277(7)	0.983(3)	-0.983(3)	0.31205(9)	0.062(5)
	C(1)	6c	0.08(1)	0		0	0.006(5)	0.0150
	O(1)	18h	0.08(1)	0.87(1)	-0.87(1)	0.016(2)	0.0150
	O(2)	18h	1		0.161(1)	-0.161(1)	0.0687(1)	0.014(3)
	O(3)	18h	1		0.1525(9)	-0.1525(9)	0.8916(1)	0.010(2)
	O(4)	18h	1		0.164(1)	-0.164(1)	0.1476(1)	0.012(2)
	Atom	U 11		U 22		U 33		U 12	U 13	U 23
	Ba(1)	0.024(2)		0.024(2)	0.0142(6)	0.007(2)	-0.003(1)	0.003(1)
	Ba(2a)	0.0114(3)	0.0114(3) 0.011(2)		0.0057(2)	0	0
	Ba(2b)	0.0114(3)	0.0114(3) 0.011(2)		0.0057(2)	0	0
	Ba(3)	0.0093(3)	0.0093(3) 0.0122(4)	0.0047(1)	0	0
	Ba(4)	0.0100(3)	0.0100(3) 0.0122(4)	0.0050(1)	0	0
	Ru(1)	0.0080(3)	0.0080(3) 0.0097(5)	0.0040(2)	0	0
	Ru(2)	0.0068(3)	0.0068(3) 0.0081(5)	0.0034(2)	0	0
	Ru(3)	0.0160(7)	0.0160(7) 0.017(1)		0.0080(3)	0	0
	Br(1)	0.056(4)		0.056(4)	0.016(2)		-0.014(9)	-0.009(3)	0.009(3)
	O(2)	0.016(3)		0.016(3)	0.014(3)		0.010(3)	0.002(1)	-0.002(1)
	O(3)	0.012(2)		0.012(2)	0.010(3)		0.008(3)	-0.001(1)	0.001(1)
	O(4)	0.014(3)		0.014(3)	0.009(3)		0.008(3)	-0.002(1)	0.002(1)


8(CN) a 6] and Cs4[Re6Se i 8(CN) a 6] species. It results that the H-bonded networks displays featureless deep-red emission band centered at λem= 722 and 737 nm and average excited-state lifetimes ranging between 11.5 and 14.8 µs, in accordance with the triplet nature of the radiative process. These photoluminescence properties are similar to the Cs + homologous and are attributed to the [Re6Q i 8] 2+ emitting core.

Hydrogen bonded networks based on hexarhenium(III) chalcocyanide cluster complexes structural and photophysical characterization

are presented (Q = S or Se; where i and a denote inner and apical position, respectively). 1-2H + is built upon two imidazolium groups linked together by a -(CH2)2-alkyl chain. 2-2H + is built upon two hydroxypyrazinium groups linked together via a phenyl group and, in consequence, it exhibits planar geometry. This ionic association leads to either two or three-dimensional hydrogen-bonded networks in the solid state, as confirmed by X-ray crystallographic analysis. The solidstate structures arise from the recognition between the pendant -C≡N ligands of the cluster cores and the amidinium Hbond donors. The luminescent properties of the compounds are investigated in the solid state by means of steady-state and time-resolved techniques. Results are discussed and compared with those measured for the parental Cs4[Re6S i

Introduction

The preparation of molecular compounds with tuneable optical properties is of current interest that is driven by their potential application in various technological areas such as optoelectronics, 1,2 solar energy conversion, [START_REF] Hagfeldt | [END_REF]4,5,6 and sensing, 7 just to cite some. Nonetheless, design of molecules that possess the desired functions in the solid state is of paramount importance, yet still a challenge in the field of molecular materials. This is due to the fact that molecular optical properties might be largely influenced by the establishment of (extended) intermolecular interactions in the solid states as well as because of excitonic coupling, 8,9 triplet-triplet annihilation 10 aggregation caused quenching and aggregation induced emission enhancement processes may take place.

11

To provide structural organization during the formation of solid-state emissive materials, one possibility is the use of noncovalent interactions to direct molecular organization, thus leading fine mastering of the interactions between the different components enabling the enhancement of cooperative effects, like optical properties, for example. Supramolecular chemistry 12 enables straightforward preparation of interesting functional compounds even in the solid state, where components can be held into the crystals by weak hydrogen bonds, [START_REF] Etter | [END_REF][START_REF] Jeffery | An Introduction to Hydrogen Bonding[END_REF][START_REF] Taylor | [END_REF] being relatively directional, and that can be also strengthen by addition of electrostatic chargecharge interactions (Charge Assisted H-Bond). 16,[START_REF] Ward | Structure and Bonding[END_REF] Hydrogen bonds, also in combination with coordination and/or metalmetal interactions, is a powerful tool to obtain new molecular materials with peculiar optical properties. [START_REF]Hydrogen Bonded Supramolecular[END_REF] Along this line, we demonstrated the formation of a variety of functional hydrogen bonded networks using amidinium-based organic building blocks (Figures 1a-b), combined with mononuclear polycyanometallate complexes as H-bond acceptors, combined with transition metal ions. 33,34,35,36,37 In addition, the rhenium clusters have been evidenced as bright emissive both in solution and in the solid state. 38,39,40,41,42,43,44,45,46 The use of hydrogen bonds for the development of new compounds based on either hexarhenium or hexamolybdenum clusters has been documented, 47,48,49,50 anions present six pendant terminal -C≡N groups orthogonally disposed at the vertices of the octahedral Re 6 cluster (Figure 1c). As already reported in previous crystallographic studies, average distances between -C≡N groups within cluster are about 7 Å for -C≡N groups in cis position and 10 Å for the groups in trans position (Figure 1c). [51][52][53][54][55] This feature enables the dihapto recognition mode through H bond between the donors and acceptors.

Results and discussion

Structural investigations of the frameworks

The interaction of the hydrogen bonds donors 1-2H + present interatomic distances close to those already reported for related species (see Table S1).

Q i 8 (CN) a 6 ], {(1-2H) 2 -[Re 6 Q i 8 (CN) a 6 ]}, where Q = S or Se (see crystallographic Table 1). Both compounds (1-2H) 2 -[Re 6 Q i 8 (CN) a 6
] (Q = S or Se) crystallise in the P 2 1 /n space group. They are isomorphous and present the same connectivity pattern. Crystals are exclusively built up from the organic compound 1-2H

+ and the inorganic anion

[Re 6 Q i 8 (CN) a 6 ]
4-(Q=S or Se) and no solvent molecules were found. Each anion is surrounded by six cations oriented in the three space directions and each of this latter is surrounded by three anions so that the anion:cation ratio is equal to 1:2 (Figures 2a-b). The resulting architecture is 3D cubic-like H ) isostructural crystalline materials (Q = S or Se) that crystallize in the triclinic P-1 space group (Table 1). As found for the two previous described structures, there are no solvent molecules present within the crystal. Each anion is surrounded by six cations and each of this latter is surrounded by three anions, yielding an anion:cation ratio equal to 1:2 (Figures 3a-b), as in the case of ( 1

-2H) 2 -[Re 6 Q i 8 (CN) a 6 ].
At first glance, the connectivity between cations and anions can be described as a 1D ladder-like system due to the rigidity of the cationic units, with short

-C≡N•••H-N interactions between the [Re 6 Q i 8 (CN) a 6 ]
4-H bond acceptors and 2-2H + H bond donors The N•••N distances range is between 2.875(7) and 3.098(8) Å (see Table 1). The chains are interconnected leading to a 2D Hbonded system (Figure 3c). The parallel packing of these 2D units in the unit cell is depicted in Figure 3d. ] n moieties has been previously reported by several groups and the results rationalized by joint Raman spectroscopy, photophysical techniques and theoretical analysis. [38][39][40][41][42][43][44][45][46] The clusters appeared to be characterized by a low-lying absorption bands of ligandto-cluster charge transfer character involving the [Re 6 Q 2+ core. Excited-state lifetimes were found in the order of tens of microseconds, as consequence of the symmetry and spin forbidden nature of the radiative transition and with non-radiative kinetic constant, k nr , which mainly governs the overall emission process. In such derivatives, the nature of the Q ligand largely affects the emission properties. 40 On the other hand, the axial ligands L affects the emission only in terms of quantum yield and radiative decay by offering vibrational relaxation modes, while emission energies are influenced to a much smaller extent. derivatives were investigated as microcrystalline powders by means of steady-state and time-resolved techniques and the results compared with related systems previously reported. The photophysical data are listed in Table 2 and the excitation and emission spectra displayed in Figure 4. Upon excitation at 360 nm, all the investigated species display broad and featureless emission band falling in the red and near-infrared (NIR) region (λ em = 721-737 nm) that can be confidentially attributed to the [Re 6 Q i 8 ] 2+ scaffold, in accordance with previous reports (see Figure 4). 40,40 In addition, the nature of the ligand Q seems to do not sizeably affect the emission maximum in the series Q = Se, S as by comparison between (1-2H) ], being λ em = 723 and 721 nm, respectively. This is also in agreement with observations made for the Cs + parental species (see Table 2). Besides, the nature of the cation and, in particular, of the H-donor moiety seems to slightly affect the emission energy, although still to a minor extent. Indeed, going from 1-2H + to 2-2H + a slight bathochromic shift in the order of 170-300 cm -1 is observed for both cluster anions. ]. The spectra features appeared to have broad emission and are in qualitative agreement with already reported electronic absorption spectra for similar species. At higher energy, an excitation maximum at ca. 365 nm is observed for all the derivatives, independently of Q and cation. Indeed, they clearly shown a modulation of the lowest-lying excitation band upon variation of the nature of Q, with a bathochromic shift of the excitation onset going from Q = Se to S, indicative of the involvement of the chalcogenide atoms into the electronic transition. This lower-energy excitation process can be confidentially ascribed to a transition with ligand-tocluster charge transfer nature involving the [Re 6 Q i 8 ]

2+ scaffold.

Time-resolved photophysical measurements were performed on solid-state samples as well. Overall, the samples show longlived excited state with decay kinetics that were fitted by using multi-exponential decay models and the average lifetimes, 𝜏𝜏̅ , in the range of 11.5-14.2 µs, which are listed in ] counterparts suggests that the nonradiative rate constant, k nr , remains unaffected in spite of the presence of extended H-bond network in the solid state, which in principle are keen to provide access to nonradiative decay pathways. This finding is in line with the previously reported data which show that the [Re 6 Q

Conclusions

Through this study, we demonstrated that it was possible to reproducibly obtain two series of hydrogen bonded compounds, through the recognition of the amidinium H donor atoms with the cyano appended of the

Photophysical characterization

Steady-state emission spectra on solid-state powder in a quartz-tube were recorded at room temperature on a HORIBA Jobin-Yvon IBH FL-322 Fluorolog 3 spectrometer equipped with a 450 W xenon arc lamp as the excitation source, doublegrating excitation and emission monochromators (2.1 nm mm-1 of dispersion; 1200 grooves mm-1) and a PPD850 singlephoton-counting as the detector. Emission and excitation spectra were corrected for source intensity (lamp and grating) and emission spectral response (detector and grating) by standard correction curves. Time-resolved measurements were performed using the time-correlated single-photon counting (TCSPC) electronics available on the FL-322. A pulsed NanoLEDs (370 nm; FWHM <1 ns) with repetition rate between 10 kHz and 1 MHz was used to excite the sample. The excitation source was mounted on the sample chamber at 90° to a double grating emission monochromator (2.1 nm mm -1 dispersion; 1200 grooves mm -1

) and collected by a PPD singlephoton-counting detector. The photons collected at the detector are correlated by a time-to-amplitude converter (TAC) to the excitation pulse. Signals were collected using an IBH DataStation Hub photon counting module and data analysis was performed using the commercially available DAS6 software (HORIBA Jobin Yvon IBH). Fitting methods. The quality of the fit was assessed by minimizing the reduced χ 2 function and by visual inspection of the weighted residuals and multi-exponential decay model was used for fitting the experiental decay data In such model, the intensity, namely I(t), has been assumed to decay as the sum of individual single exponential decays (Eq. 1): eq. 1 where τ i are the decay times and α i are the amplitude of the component at t = 0. In the table, average lifetime, expressed by the following equation (Eqn. 2) as been provided for each sample on the basis of a multi-exponential decay, where the percentages of the pre-exponential factors, α i , are used upon normalization.

eq. 1

Crystallography

Data were collected at 173(2) K on a Bruker APEX8 CCD Diffractometer equipped with an Oxford Cryosystem liquid N2 device, using graphite-monochromated Mo-Kα (λ= 0.71073 Å) radiation. For all structures, diffraction data were corrected for absorption. Structures were solved using SHELXS-97 and refined by full matrix least-squares on F 2 using SHELXL-97. The hydrogen atoms were introduced at calculated positions and not refined (riding model). [START_REF] Sheldrick | Program for Crystal Structure Solution[END_REF] Structures can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/datarequest/cif. CCDC: 1813047-1813050.

Powder diffraction studies (PXRD)

Powder diffraction studies (PXRD) diagrams were collected on polycrystalline samples, on a Bruker D8 diffractometer using monochromatic Cu-Kα radiation with a scanning range between 3.8 and 40° using a scan step size of 2°/mn.

  Ledneva, Sylvie Ferlay, Nikolay G. Naumov, Matteo Mauro, Stéphane Cordier, Nathalie Kyritsakas, Mir Wais Hosseini To cite this version: Alexandra Ledneva, Sylvie Ferlay, Nikolay G. Naumov, Matteo Mauro, Stéphane Cordier, et al.. Hydrogen bonded networks based on hexarhenium(III) chalcocyanide cluster complexes structural and photophysical characterization. New Journal of Chemistry, 2018, 42 (14), pp.11888-11895. 10.1039/c8nj02310g. hal-01861410 a. Nikolaev Institute of Inorganic Chemistry 3 Acad. Lavrentiev pr., 630090 Novosibirsk, Russia b. Molecular Tectonics Laboratory, Université de Strasbourg, CNRS, CMC UMR 7140, F-67000 Strasbourg, France c. Novosibirsk State University 2 Pirogova str. 630090 Novosibirsk, Russia d. Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes) -UMR 6226, F-35000, France † Electronic Supplementary Information (ESI) available: Useful bonds and distances for (1-2H)2-[Re6Q i 8(CN) a 6] (Q=S or Se) and (2-2H)2-[Re6Q i 8(CN) a 6] (Q=S or Se), XRPD traces for (1-2H)2-[Re6Q i 8(CN) a 6] and (2-2H)2-[Re6Q i 8(CN) a 6] (Q=S, Se). See DOI: 10.1039/x0xx00000x Hydrogen bonded networks based on hexarhenium(III) chalcocyanide clusters complexes: structural and photophysical characterizations series of isostructural compounds resulting from the combination of the four-fold hydrogen bond donors bisamidinium cations, namely 1-2H + and 2-2H + , and the anionic chalcocyanide clusters of general formula [

  opens a way for the formation of porous multifunctional molecular materials due to their large size and rigid geometry. Employment of [M 6 M = Mo, W or Re; Q= S, Se or Te as inner ligands and L is an apical ligand) has been explored for the formation of new molecular networks and hybrid nanomaterials.26,27,28, 29,30,31,32 For example, three dimensional bimetallic coordination networks have been reported with μ 3 Q = S, Se or Te) compounds

Figure 1 :

 1 Figure 1: Dicationic bisamidinium compounds 1-2H + (a) and 2-2H + (a), acting as H bond donors

Figure 2 :

 2 Figure 2: Representations of the crystal structure of (1-2H)2-[Re6Q i 8(CN) a 6] (Q=S or Se, and here Q=S is represented). a) environment of the cationic unit, b) environment of the anionic cluster unit, c) the three-dimensional framework formed by the recognition of 1-2H + by [Re6Q i 8(CN) a 6] 4-and d) interpenetration of two three dimensional frameworks. For clarity, some of the H atoms have been omitted.

  ). By comparison of the XRPD diagrams of microcrystalline powders of (1-2H) 2 -[Re 6 the simulated XRD using structural data obtained by single crystal X-ray diffraction analysis of (1-2H) 2 -[Re 6 it can be concluded these microcrystalline powders do not exhibit traces of impurities (figureS1). The combination of [Re 6 Q = S or Se) with the more rigid 2-2H + dication (see experimental part) leads to (2-2H) 2 -[Re 6

Figure 3 : 2

 32 Figure 3: Representation of the structure of (2-2H)2-[Re6Q i 8(CN) a 6] (Q = S or Se). a) environment of the cationic unit; b) environment of the anionic cluster unit, c) the hydrogen bonded framework leading to a 2D framework work formed by the recognition of 2-2H + by [Re6Q i 8(CN) a 6] 4-and d) the packing of the 2D H-bonded framework. Some of the H atoms are not presented for clarity.

  •metal bonded core. On the other hand, following efficient internal conversion and intersystem crossing processes, photoluminescence arises from an excited state with mainly triplet manifold metal-centred character largely localized onto the [Re 6 Q i 8 ]

  centred excited state appears to be insulated from the high-energy vibrational levels of the axial moieties when cyano ligands are incorporated into the cluster unit. This finding offers a unique possibility for the construction of extended H-bonded networks via -C≡N•••H-N interactions with minor alteration of the photophysical properties of the polynuclear molecular cluster synthon [Thus, the photophysical properties of the four solid state networks of formula (1-2H) 2 -[Re 6

Figure 4 :

 4 Figure 4: Excitation (left) and emission (right) spectra in the solid state for (1-2H)2-[Re6Q i 8(CN) a 6], (2-2H)2-[Re6Q i 8(CN)

i 8 ] 40 Table 2 .a

 8402 2+ emitting core in not affected by high-energy vibration modes of the -C≡N axial ligands. Photophysical data recorded in the solid state for the species Cs4[Emission of the sample was monitored at λem = 690 nm; b Samples were excited at λexc = 360 nm; c Samples were excited at λexc = 370 nm; "sh" denotes a shoulder.

Table 2

 2 Under the hypothesis that the radiative constants k r are unaffected by the nature of the axial ligand and chalcogenide, as demonstrated elsewhere, 40 the close lifetime values observed H-bonded species and Cs 4 [Re 6 Q

	(see

+ H-bonding donor moiety.

i 8 (CN) a 6

  Two series of isomorphous and stable compounds are here reported displaying either 2D or 3D H-bonded networks depending on the rigidity of the employed four-fold H-bond donors. The luminescent properties of all the H-bonded networks have been investigated as solid-state microcrystalline powders and the findings compared to the reported parental derivatives.

	Upon photo-excitation, the investigated species display broad
	and featureless luminescence in the deep-red/NIR region
	arising from long-lived excited state with lifetimes in the few
	microseconds regime. This emission is confidentially attributed
	to the [Re 6 Q	i 8 ]	2+ scaffold with the nature of the chalcogenide
	atom that affects emission maximum to a minor extent. This is
	fully in accordance with the results obtained from other
	materials with isolated [Re 6 Q i	8 (CN) a	6 ]	4-(Q = S or Se) cluster
	building blocks.
	Experimental
	Characterization
	FT-IR spectra were recorded on a Perkin Elmer ATR
	spectrometer.
	Elemental analyses were performed by the Service de
	Microanalyses de la Fédération de Recherche Chimie of the
	University de Strasbourg.
					[Re 6 Q i	8 (CN) a	6 ]	4-

(Q = S or Se) cluster building blocks.

2H) 2 -[Re 6 S i 8 (CN)

  3H 2 O (C = 0.5 mM). Upon slow diffusion at the room temperature, yellow crystals, suitable for X-ray analysis, were obtained after one week. Formula C 22 H 32 N 14 Re 6 Se 8 . Anal. Calcd.: C, 11.78%; H, 1.44%; N, 8.74%; Found: C, 11.73%; H, 1.45 %; N, 8.76 %. IR ν(C≡N): 2102, 2120 cm Upon slow diffusion at the room temperature, yellow crystals, suitable for X-ray analysis, were obtained after one week. Formula C 34 H 40 N 14 O 4 Re 6 S 8 . Anal. Calcd.: C, 19.61%; H, 1.93%; N, 9.41%; Found: C, 19.58%; H, 2.01 %; N, 9.37 %. IR ν(C≡N): 2105, 2116, 2127 cm -1 . In a thin crystallization tube (length 100 mm, diameter 10 mm), 1 mL of an aqueous solution of 2-2HCl (C = 7.5 mM) was gently layered on 2 mL of an aqueous solution of Cs 4 [Re 6 Se 3H 2 O (C = 0.5 mM). Upon slow diffusion at the room temperature, yellow needle-like crystals, suitable for X-ray analysis, were obtained after one hour. Formula C 34 H 40 N 14 O 4 Re 6 Se 8 . Anal. Calcd.: C, 16.61%; H, 1.64%; N, 7.97%; Found: C, 16.57%; H, 1.68 %; N, 7.92 %. IR ν (C≡N) : 2088, 2103, 2126 cm -1 .

	Synthesis 1-2HCl, 24,66 Cs 4 [Re 6 Se i 8 (CN) a from concentrated 2-2HCl, 21,66 6 ]•3H 2 O were obtained by recrystallization Cs 4 [Re 6 S i (CN) a 6 ]•3H 2 O and aqueous solution of Cs 3 K[Re 6 S i 8 (CN) a 6 ]·2H 2 O 67 and K 4 [Re 6 Se i 8 (CN) a 6 ]·3.5H 2 O 57 with twenty-fold excess of CsCl. (1-a 6 ] In a thin crystallization tube (length 100 mm, diameter 10 mm), 1 mL of an aqueous solution of 1-2HCl (C = 7.5 mM) was gently layered on 2 mL of an aqueous solution of Cs 4 [Re 6 S i 8 (CN) a 6 ]•3H 2 O (C = 0.5 mM). Upon slow diffusion at the room temperature, yellow crystals, suitable for X-ray analysis, were obtained after one week. Formula C 22 H 32 N 14 Re 6 S 8 . Anal. Calcd.: C, 14.16%; H, 1.73%; N, 10.51%; Found: C, 14.08%; H, 1.69 %; N, 10.43 %. IR ν(C≡N): 2115, 2130 cm -1 . (1-2H) 2 -[Re 6 Se i 8 (CN) a 6 ] In a thin crystallization tube (length 100 mm, diameter 10 mm), 1 mL of an aqueous solution of 1-2HCl (C = 7.5 mM) was gently layered on 2 mL of an aqueous solution of Cs 4 [Re 6 Se i 8 (CN) a 6], (2-2H)2-[Re6S In a thin crystallization tube (length 100 mm, diameter 10 . (2-2H) 2 -[Re 6 S i 8 (CN) a 6 ] mm), 1 mL of an aqueous solution of 2-2HCl (C = 7.5 mM) was gently layered on 2 mL of an aqueous solution of Cs 4 [Re 6 S i 8 (CN) a 6 ]•3H 2 O (C = 0.5 mM). (2-2H) 2 -[Re 6 Se i 8 (CN) a 6 ] i 8 (CN) a 6 ]•Table 1: Crystallographic Parameters for (1-2H)2-[Re6S i 8(CN) a 6], (1-2H)2-[Re6Se i 8(CN) a i 8(CN) a 6] and (2-2H)2-[Re6Se i 8(CN) a 6] recorded at 173 K. (1-2H)2-[Re6S i 8(CN) a 6] (1-2H)2-[Re6Se i 8(CN) a 6] (2-2H)2-[Re6S i 8(CN) a 6] (2-2H)2-[Re6Se i 8(CN) a 6] Chemical formula C22H32N14Re6S8 C22H32N14Re6Se8 C34H40N14O4Re6S8 C34H40N14O4Re6Se8 Molecular weight, g/mol 1866.29 2241.49 2082.48 2457.68 Crystal system Monoclinic Monoclinic triclinic triclinic Space group P 21/n P 21/n P -1 P -1 a(Å) 10.7460(3) 10.7572(4) 10.2728(4) 10.7148(6) b(Å) 17.8776(6) 18.2885(8) 11.2485(4) 11.3369(5) c(Å) 11.2185(4) 11.3229(4) 12.1798(5) 12.3039(5) α(deg) 90 90 104.230(2)° 104.098(2)° β(deg) 116.7330(10) 117.0480(10) 107.332(2)° 107.653(2)° γ(deg) 90 90 107.185(2)° 109.245(2)° V(Å 3 ) 1924.85(11) 1983.95(13) 1194.45(8) 1242.73(10) Z 2 2 1 1 Colour orange orange yellow yellow Crystal dim (mm) 0.060x0.060x0.070 0.070x0.070x0.080 0.040x0.040x0.050 0.060x0.060x0.070 Dcalc (gcm -3 ) 3.220 3.752 2.895 3.284 F(000) 1680 1968 952 1096 μ (mm -1 ) 19.264 25.608 15.545 20.463 Wavelength (Å) 0.71073 0.71073 0.71073 0.71073 Reflections collected 144959 61065 24080 8941 Independent reflections 5223 [R(int) = 0.0480] 5521 [R(int) = 0.0340] 6447 [R(int) = 0.0439] 5744 [R(int) = 0.0285] R (all data) R1 = 0.0151, wR2 = 0.0351 R1 = 0.0169, wR2 = 0.0369 R1 = 0.0289, wR2 = 0.0600 R1 = 0.0446, wR2 = 0.1128 Rw (all data) R1 = 0.0178, wR2 = 0.0363 R1 = 0.0236, wR2 = 0.0391 R1 = 0.0363, wR2 = 0.0625 R1 = 0.0692, wR2 = 0.1282 GOF 1.188 1.093 1.047 1.015 6 ]•-1 Largest diff. peak / hole (eÅ -3 ) 0.559 and -1.429 0.880 and -2.146 2.166 and -2.629 3.745 and -3.267

Acknowledgements

The work was performed in terms of International Associate Laboratory CLUSPOM (2014-2017 N° 1144). A. Ledneva thanks program "Mechnikov" supporting mobility of scientists. Financial supports from the University of Strasbourg, the International Centre for Frontier Research in Chemistry (icFRC), Laboratory of excellence LabEx CSC, Strasbourg, the Institut Universitaire de France, the CNRS are acknowledged.

Notes and references ‡ Footnotes relating to the main text should appear here. These might include comments relevant to but not central to the matter under discussion, limited experimental and spectral data, and crystallographic data.

Conflicts of interest

The authors declare no conflict of interest.

Graphical abstract