We present herein the synthesis, crystal structure, and electric and magnetic properties of the spin‐crossover salt [Mn(5‐Cl‐sal‐N‐1,5,8,12)]TCNQ1.5⋅2 CH3CN (I), where 5‐Cl‐sal‐N‐1,5,8,12=N,N′‐bis(3‐(2‐oxy‐5‐chlorobenzylideneamino)propyl)‐ethylenediamine, containing distinct conductive and magnetic blocks along with acetonitrile solvent molecules. The MnIII complex with a Schiff‐base ligand, [Mn(5‐Cl‐sal‐N‐1,5,8,12)]+, acts as the magnetic unit, and the π‐electron acceptor 7,7,8,8‐tetracyanoquinodimethane (TCNQ−) is the conducting unit. The title compound (I) exhibits semiconducting behavior with room temperature conductivity σRT≈1×10−4 ohm−1 cm−1 and activation energy Δ ≈0.20 eV. In the temperature range 73–123 K, it experiences a hysteretic phase transition accompanied by a crossover between the low‐spin S=1 and high‐spin S=2 states of MnIII and changes in bond lengths within the MnN4O2 octahedra. The pronounced shrinkage of the basal Mn−N bonds in I at the spin crossover suggests that the dx2-y2 orbital is occupied/deoccupied in this transition. Interestingly, the bromo isomorphic counterpart [Mn(5‐Br‐sal‐N‐1,5,8,12)]TCNQ1.5⋅2 CH3CN (II) of the title compound evidences no spin‐crossover phenomena and remains in the high‐spin state in the temperature range 2–300 K. Comparison of the chloro and bromo compounds allows the thermal and spin‐crossover contributions to the overall variation in bond lengths to be distinguished. The difference in magnetic behavior of these two salts has been ascribed to intermolecular supramolecular effects on the spin transition. Discrete hydrogen bonding exists between cations and cations and anions in both compounds. However, the hydrogen bonding in the crystals of II is much stronger than in I. The relatively close packing arrangement of the [Mn(5‐Br‐sal‐N‐1,5,8,12)]+ cations probably precludes their spin transformation.

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Three tetraphenylborates of mononuclear Mn(III) cation complexes with hexadentate ligands, the products of the reaction between a N,N'-bis(3-aminopropyl) ethylenediamine and salicylaldehydes with the different haloid substitutions at the 5 or 3,5 positions, have been synthesized: [Mn(5-F-sal-N-1,5,8,12)]BPh 4 (1), [Mn(3,5-diCl-sal-N-1,5,8,12)]BPh 4 (2) and [Mn(3,5-Br,Cl-sal-N-1,5,8,12)]BPh 4 (3). Their crystal structure, dielectric constant (ɛ) and magnetic properties have been studied. Ligand substituents have a dramatic effect on the structure and magnetic properties of the complexes. With decreasing temperature, the complex (1) shows a gradual spin crossover from the high-spin state (HS) to the HS:LS intermediate phase, followed by an abrupt transition to the low-spin state (LS) without changing the crystal symmetry. The complexes 2 and 3 are isostructural, but have fundamentally different properties. Complex 2 demonstrates two structural phase transitions related to

Crystals of (ET) 2 Mn[N(CN) 2 ] 3 (1) and (ET) 2 CuMn[N(CN) 2 ] 4 (2) with mono-and first bimetal dicyanamide anions were obtained and their structure, conducting and magnetic properties were investigated. The structure of 2 is not typical for ET radical cation salts and is characterized by the presence of a 3D polymeric anion built into the ET radical cation layers. The crystals of 1 exhibit a semiconducting behavior of conductivity and 2 undergoes a semiconductor I-semiconductor II phase transition at 295-291 K, which is specified by a jump of resistivity and the appearance of a hysteresis in the R(T) curves. The phase transition is accompanied by changes in the charge state of the ET molecules and intermolecular interactions in the crystal. Antiferromagnetic correlations of spins associated with anionic subsystems were found in both salts at temperatures lower than 25 K. Antiferromagnetic ordering in 1 has a long-range character. The effect of the spin frustrated state of localized spins on conducting electrons of ET subsystem was found in 1.

The crystal structure and low-temperature transport properties of the recently synthesized Ј-͑BEDT -TTF͒ 2 Cu͓N͑CN͒ 2 ͔Cl radical cation salt are investigated. The crystals exhibit metallic conductivity and are ambient-pressure superconductors with critical temperature in the range ͑11.3-11.9͒ K. The crystals show some distinctions in structure as compared to that of the Mott insulator -͑BEDT-TTF͒ 2 Cu͓N͑CN͒ 2 ͔Cl: smaller size of the unit cell and deficiency in the occupancy of the copper positions. Anisotropy of superconducting properties as well as a nontrivial temperature dependence of the upper critical field were observed.