Structure, optical and electro-physical properties of tetramerized anion-radical salt (N-Xy-Qn)(TCNQ)2.

The (N-Xy-Qn)(TCNQ)2 anion-radical salt characterized by tetramerized stacks of the TCNQ acceptor molecules has been synthesized and characterized using vibrational spectroscopy and electrical resistivity measurements. The bond lengths analysis based on the crystal structure data, indicates that the TCNQ molecules are non-uniformly charged with -0.83 e localized on the inner B molecules and -0.33 e on the outer A molecules within ABBA tetramers. Both infrared and Raman spectra of (N-Xy-Qn)(TCNQ)2 are dominated by vibrational modes of TCNQ and display splitting related to the tetramerized structure. Many of these features are affected by the strong electron-molecular vibration (EMV) coupling. Other charge-sensitive modes allowed estimation of charge localized on TCNQ, with the results that confirm the charges estimated on basis of the crystal data. Electrical measurements revealed the low-conducting behavior with room temperature conductivity value of 2.6 mS cm-1 and temperature dependence of resistivity that can be explained within the band conduction model. The calculated activation energies range from 0.169 eV to 0.187 eV, depending on the crystallographic direction and thermal history of the sample.

Synthesis and study of C-substituted methylthio derivatives of cobalt bis(dicarbollide).

The C-methylthio derivatives of cobalt bis(dicarbollide) were synthesized by reaction of anhydrous CoCl2 with nido-carborane [7-MeS-7,8-C2B9H11]- and isolated as a mixture of rac-[1,1'-(MeS)2-3,3'-Co(1,2-C2B9H10)2]- and meso-[1,2'-(MeS)2-3,3'-Co(1,2-C2B9H10)2]- isomers. The structures of both isomers were studied using DFT quantum chemical calculations. The most preferable geometry of rotamers and the stabilization energy of C-methylthio derivatives of cobalt bis(dicarbolide) were calculated. The (BEDT-TTF)[1,1'-(MeS)2-3,3'-Co(1,2-C2B9H10)2] salt was prepared and its structure was determined by single crystal X-ray diffraction. The cisoid conformation of the rac-[1,1'-(MeS)2-3,3'-Co(1,2-C2B9H10)2]- anion is stabilized by short intramolecular CH⋯S hydrogen and BH⋯S chalcogen bonds between the dicarbollide ligands, that is in good agreement with the data of quantum chemical calculations.

Stabilization of Pancake Bonding in (TCNQ)2 .- Dimers in the Radical-Anionic Salt (N-CH3-2-NH2-5Cl-Py)(TCNQ)(CH3CN) Solvate and Antiferromagnetism Induction.

We report a new antiferromagnetic radical-anion salt (RAS) formed from 7,7,8,8-tetracyanquinonedimethane (TCNQ) anion and 2-amino-5-chloro-pyridine cation with the composition of (N-CH3-2-NH2-5Cl-Py)(TCNQ)(CH3CN). The crystallographic data indicates the formation of (TCNQ)2 .- radical-anion π-dimers in the synthesized RAS. Unrestricted density functional theory calculations show that the formed π-dimers characterize with strong π-stacking "pancake" interactions, resulting in high electronic coupling, enabling efficient charge transfer properties, but π-dimers cannot be stable in the isolated conditions as a result of strong Coulomb repulsions. In a crystal, where (TCNQ)2 .- π-dimers bound in the endless chainlets via supramolecular bonds with (N-CH3-2-NH2-5-Cl-Py)+ cations, the repulsion forces are screened, allowing for specific parallel π-stacking interactions and stable radical-anion dimers formation. Measurements of magnetic susceptibility and magnetization confirm antiferromagnetic properties of RAS, what is in line with the higher stability of ground singlet state of the radical-anion pair, calculated by means of the DFT. Therefore, the reported radical-anion (N-CH3-2-NH2-5Cl-Py)(TCNQ)(CH3CN) solvate has promising applications in novel magnetics with supramolecular structures.

Crystal structure of bis-(ethyl-enedi-thio)-tetra-thia-fulvalenium µ2-acetato-bis-[tri-bromido-rhenate(III)] 1,1,2-tri-chloro-ethane hemisolvate.

The asymmetric unit of the title salt, (C10H8S8)[Re2Br6(CH3COO)]·0.5C2H3Cl3, contains one bis-(ethyl-enedi-thio)-tetra-thia-fulvalene (ET) radical cation, one µ2-acetato-bis-[tri-bromido-rhenate(III)] anion and a 1,1,2-tri-chloro-ethane mol-ecule with half-occupancy disordered about a twofold rotation axis. The tetra-thia-fulvalene fragment adopts an almost planar configuration typical of the ET radical cation. The C atoms of both ethyl-enedi-thio fragments in the cation are disordered over two orientations with occupancy factors 0.65:0.35 and 0.77:0.23. In the anion, six Br atoms and a µ2-acetate ligand form a strongly distorted cubic O2Br6 coordination polyhedron around the Re2 dinuclear centre. In the crystal, centrosymmetrically related ET cations and Re2O2Br6 anions are linked into dimers by π-π stacking inter-actions [centroid-to-centroid distance = 3.826 (8) Å] and by pairs of additional Re⋯Br contacts [3.131 (3) Å], respectively. The dimers are further packed into a three-dimensional network by non-directional inter-ionic electrostatic forces and by C-H⋯Br and C-H⋯S hydrogen bonds. The disordered 1,1,2-tri-chloro-ethane mol-ecules occupy solvent-accessible channels along the b axis.

Molecular conductors with a 8-hydroxy cobalt bis(dicarbollide) anion.

Molecular conductors based on the 8-hydroxy cobalt bis(dicarbollide) anion, (TMTTF)[8-HO-3,3'-Co(1,2-C2B9H10)(1',2'-C2B9H11)] (1), (BMDT-TTF)[8-HO-3,3'-Co(1,2-C2B9H10) (1',2'-C2B9H11)] (2), and (BEDT-TTF)[8-HO-3,3'-Co(1,2-C2B9H10)(1',2'-C2B9H11)] (3), were synthesized, and their crystal structures and electrical conductivities were determined. Compounds 2 and 3 are isostructural to the corresponding radical-cation salts of the parent cobalt bis(dicarbollide). All of the radical-cation salts prepared were found to be semiconductors. The relative stability of the rotation conformers of the [8-HO-3,3'-Co(1,2-C2B9H10)(1',2'-C2B9H11)](-) anion was estimated using DFT/BP86 quantum chemical calculations.