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New nickel and copper bisdithiolene complexes were prepared as tetraphenylphosphonium (Ph4P+) salts, (Ph4P)n[M(3cbdt)2], [n = 1, 2; M = Ni, Cu; 3cbdt = 3-cyanobenzene-1,2-dithiolate]: (Ph4P)2[Ni(3cbdt)2] (1); Ph4P[Ni(3cbdt)2] (2); (Ph4P)2[Cu(3cbdt)2] (3); Ph4P[Cu(3cbdt)2] (4), and characterised by single crystal X-ray diffraction, cyclic voltammetry, EPR and static magnetic susceptibility for the paramagnetic species. These Cu and Ni complexes obtained as stable monoanionic and dianionic anions are the first members of this family of cyano benzene functionalized bisdithiolene transition metal complexes, opening the way to the preparation of analogous compounds with other transition metals and their future use as building blocks for the preparation of molecular materials. Their properties are discussed in comparison with the corresponding complexes based on the 4-cyanobenzene-1,2-dithiolate (4cbdt) ligand previously described by us. The salts (Ph4P)n[M(3cbdt)2], [n = 1, 2; M = Ni, Cu] present the metal complexes always in a square-planar coordination geometry with a ligand trans configuration, but revealing a rich polymorphism. The Ni and Cu compounds are isostructural and occur as two polymorphs (α, β) with the exception of the salt of the monoanionic Ni complex, that was found only as the α-polymorph. The salt of the dianionic Ni complex was found to crystallise also with one acetonitrile molecule, when recrystallised from this solvent. The salts of monoanionic [Ni(3cbdt)2] and dianionic [Cu(3cbdt)2] complexes have been characterised by EPR and static magnetic susceptibility as paramagnetic S = 1/2 species. [ABSTRACT FROM AUTHOR]

Five new salts of 5-cyanobenzene-ethylenedithio-tetrathiafulvalene (CNB-EDT-TTF), with the general formula (CNB-EDT-TTF)4A, and anions A = Ag(CN)2 (1), Ag(CN)2·H2O (2), Ag2(CN)3 (3), Ag(SCN)2 (4) and Hg2(SCN)5 (5), were prepared by electrocrystallisation and characterised by single crystal X-ray diffraction, electrical conductivity, thermoelectric power and magnetic susceptibility measurements. Their crystal structure is based on a double layer arrangement of the donors with a β′′ packing pattern identical to that previously observed in related salts with small discrete anions. The donor bilayers are separated by layers of anions which however are incoherently arranged perpendicular to the layers. The average structures obtained are compatible with anionic arrangements similar to those previously observed in single layer salts of BEDT-TTF and related donors, where, with the exception of 1, the anions are polymeric. While 2 presents electrical resistivity with a thermally activated regime, 1, 3, 4 and 5 show metallic behaviour at high temperatures, with room temperature values in the range 10–20 S cm−1 and sample dependent electronic localisation effects at lower temperatures. The thermoelectric power of these compounds is +82–90 μV K−1 at room temperature, following behavior identical to that of their analogues with small discrete anions. The paramagnetic susceptibility of 4 and 5, similar to those of their analogues with I3, PF6, AsF6 and ReO4 anions, has values of ≈1.0 × 10−3 emu mol−1 at room temperature, being significantly enhanced compared with the Pauli-type contribution predicted from electron band calculations. [ABSTRACT FROM AUTHOR]

The importance of C–H⋯N≡C interactions in the crystal engineering of conducting materials was recently evidenced by a new type of two-dimensional conducting material with the composition of (5-CNB-EDT-TTF)4A with a variety of anions A, where CNB-EDT-TTF denotes the electron donor cyanobenzene-ethylenedithio-tetrathiafulvalene, which has been described in the last few years, presenting a new type of bilayer structure. The unique bilayer donor structure of these compounds is due to the network of C–H⋯N≡C interactions, which although generally considered weak, are effective in the self-assembly of the crystal structure. The role of these weak interactions is made clear by a comparison of the salts of this donor and the related isomer 4-CNB-EDT-TTF, where no bilayer structure is obtained but a variety of related interactions are observed instead. This comparison allows different patterns of weak C–H⋯N≡C interactions to be identified in these compounds, which can be described as combinations of several different synthons of type R 22 (10), R 22 (24), R 22 (26), R 23 (10), R 24 (8), R 24 (10), R 48 (20), and R 34 (30) or C(5) and C(6) infinite chains. The different patterns of interactions are comparable with those observed in other cyano compounds, as well as the magnitude of the interaction enthalpy associated with the different synthons, as estimated by means of density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

The family of recently described salts based on the electron donor CNB-EDT-TTF (5-cyanobenzene-ethylenedithio-tetrathiafulvalene) and different anions A, with general formula (CNB-EDT-TTF)4A, constitutes an unprecedented type of molecular conductor based on a bilayer structure of the donors. The crystal structures of the bilayer conductors (CNB-EDT-TTF)4A with small discrete anions are reviewed and analyzed considering previously reported compounds with different anions (A = I3−, ClO4−, BF4−, ReO4−, PF6− and SbF6−), as well as three new members of this family described here with AsF6−, AuI2−and I2Br−. A common structural feature of this family of compounds is the head-to-head arrangement of the donors, induced by a network of weak C≡N⋯H–C interactions, which can be described as an effective combination of R 22 (10) and R 24 (10) synthons, forming donor bilayers alternating with anionic layers. The magnitude of the interactions associated with R 22 (10) and R 24 (10) synthons is estimated to be 4.7 and 10.0 kcal mol−1, respectively. In spite of the common donor bilayer arrangement, a rich diversity of structural variations and polymorphs is observed. These structures are related to different types of donor or anion arrangements, which are analyzed. For all anions a β′′-type packing pattern of the donor molecules arranged in virtually identical bilayers is observed. However, for (CNB-EDT-TTF)4I3, so far a unique exception in this family of compounds, a distinct κ-type packing of the donors, is also obtained as a metastable phase as shown also by DFT calculations that predict the κ-phase above the β′′-phase. Another type of polymorphism is observed in β′′-(CNB-EDT-TTF)4A, compounds with tetrahedral anions, related to the tilting of the donor molecules (either alternating or uniform) in successive bilayers, leading to monoclinic or triclinic unit cells, with doubling of one cell parameter corresponding to the thickness of one bilayer (∼25 Å). Finally, the anions, which often appear with fractional site occupation factors, can be ordered in the anionic plane, with different degrees of correlation between successive anion planes as shown in the AsF6.compound. The implications of these structural features in the electronic properties of these compounds are also discussed. [ABSTRACT FROM AUTHOR]

We report the relevance of cation–anion and cation–solvent–anion interactions to the crystal lattice rigidity and the corresponding effect on the SCO behaviour of six FeIII complexes with the hexadentate Schiff base ligand nsal2trien. Four of these compounds were synthesized and structurally and magnetically characterized for the first time. In the most rigid structures, the SCO behaviour is either not allowed or severely hampered. For lower structural connectivity, incomplete transitions are observed within the 4–300 K temperature range. The most flexible structure shows a complete transition. The interactions between the cationic units and the anions were found to be more important than the cation–cation interactions for the SCO phenomenon and for the overall cooperativity related to the abrupt/gradual character of the transition. Computational studies were performed in order to determine the crystal splitting gap Δoct. The calculated values for the HS and LS Δoct are very similar for all compounds suggesting that these parameters have very little influence on the SCO behaviour. [ABSTRACT FROM AUTHOR]