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A series of five new mononuclear pentagonal bipyramidal Co(II) complexes with the equatorial 2,6-diacetylpyridine bis(semicarbazone) ligand (H2dapsc) and various axial pseudohalide ligands (SCN, SeCN, N(CN)2, C(CN)3, and N3) was prepared and structurally characterizated: [Co(H2dapsc) (SCN)2]·0.5C2H5OH (1), [Co(H2dapsc) (SeCN)2]·0.5C2H5OH (2), [Co(H2dapsc) (N(CN)2)2]·2H2O (3), [Co(H2dapsc) (C(CN)3)(H2O)](NO3)·1.16H2O (4), and {[Co(H2dapsc) (H2O) (N3)][Co(H2dapsc)(N3)2]}N3·4H2O (5). The combined analyses of the experimental DC and AC magnetic data of the complexes (1-5) and two other earlier described those of this family [Co(H2dapsc) (H2O)2)](NO3)2·2H2O (6) and [Co(H2dapsc)(Cl)(H2O)]Cl·2H2O (7), their theoretical description and the ab initio CASSCF/NEVPT2 calculations reveal large easy-plane magnetic anisotropies for all complexes (D = + 35 40 cm1). All complexes under consideration demonstrate slow magnetic relaxation with dominant Raman and direct spin-phonon processes at static magnetic field and so they belong to the class of field-induced single-ion magnets (SIMs). [ABSTRACT FROM AUTHOR]

Reactions of [Mn(H2dapsc)Cl2]⋅H2O (dapsc=2,6‐ diacetylpyridine bis(semicarbazone)) with K3[Fe(CN)6] and (PPh4)3[Fe(CN)6] lead to the formation of the chain polymeric complex {[Mn(H2dapsc)][Fe(CN)6][K(H2O)3.5]}n⋅1.5n H2O (1) and the discrete pentanuclear complex {[Mn(H2dapsc)]3[Fe(CN)6]2(H2O)2}⋅4 CH3OH⋅3.4 H2O (2), respectively. In the crystal structure of 1 the high‐spin [MnII(H2dapsc)]2+ cations and low‐spin hexacyanoferrate(III) anions are assembled into alternating heterometallic cyano‐bridged chains. The K+ ions are located between the chains and are coordinated by oxygen atoms of the H2dapsc ligand and water molecules. The magnetic structure of 1 is built from ferrimagnetic chains, which are antiferromagnetically coupled. The complex exhibits metamagnetism and frequency‐dependent ac magnetic susceptibility, indicating single‐chain magnetic behavior with a Mydosh‐parameter φ=0.12 and an effective energy barrier (Ueff/kB) of 36.0 K with τ0=2.34×10−11 s for the spin relaxation. Detailed theoretical analysis showed highly anisotropic intra‐chain spin coupling between [FeIII(CN)6]3− and [MnII(H2dapsc)]2+ units resulting from orbital degeneracy and unquenched orbital momentum of [FeIII(CN)6]3− complexes. The origin of the metamagnetic transition is discussed in terms of strong magnetic anisotropy and weak AF interchain spin coupling. [ABSTRACT FROM AUTHOR]

The structure and properties of the radical cation salt based on [pi]-donor BETS (BETS = bis(ethylenedithio)tetraselenafulvalence) with tri(dicyanaamido)manganate(II) anion, [(BETS).sub.2]Mn[N(CN).sub.2]].sub.3] are reported. The crystal structure shows a transition into a superconducting state with [T.sub.c] = 5 K at P = 0.3 kbar and at ambient pressure the compound exhibits a metal-insulator transition at [T.sub.1] = 21 K and an AFM ordering at [T.sub.0] = 5 K.

Analysis of the data of the experimental study of a large family of low-dimensional organic conductors based on trihalides of ET and some of its analogues is presented. It is shown that the family of radical cation salts (ET)(sub 2) X, is characterized by a wide variety of conducting properties, rich polymorphism, and phase transitions.

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. [ABSTRACT FROM AUTHOR]

Isostructural mononuclear complexes of heavy lanthanides with the pentadentate Schiff-base dapsc ligand were synthesized, [Ln(H2dapsc)(H2O)4](NO3)3 (Ln = Tb, Dy, Ho, Er), and characterized structurally and magnetically. AC magnetic susceptibility measurements revealed that complexes of Dy3+ and Er3+ Kramers ions are field-induced single-ion magnets whereas the Tb and Ho complexes show no slow magnetic relation in DC fields up to 6000 Oe. DC and AC magnetic properties of these complexes were rationalized in terms of superposition crystal-field model calculations for Ln3+ ions, which have resulted in good agreement between the experiment and the theory. It is shown that low single-molecule magnet characteristics of the Dy and Er complexes and the absence of slow-magnetic relaxation in the Tb and Ho complexes are primarily due to the low-symmetry coordination of Ln3+ ions. [ABSTRACT FROM AUTHOR]

New crystals (1-4) of organic conductors based on the radical cation salts of the bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) with paramagnetic and diamagnetic tris(oxalato)metallate anions {A+[M3+(ox)3]3-G}2-, where M is Cr, Ga; G is 2-chloropyridine, 2-bromopyridine; and A+ is [K0.8(H3O)0.2]+ have been prepared and their crystal structure and transport properties were studied. All crystals belong to the monoclinic group of the (BEDT-TTF)4A+[M3+(ox)3]G family with α"-packing type of conducting BEDT-TTF layers. In contrast to the known superconducting crystals with M3+ = Fe3+ and G = 2-chloro- or 2-bromopyridine (Tc = 4.0-4.3 K), crystals with Cr3+ and Ga3+ ions exhibit metallic properties down to 0.5 K without superconducting transition. Upon cooling these crystals, the incommensurate superstructure appears, which has never been observed before in the numerous β"-salts of the family. In addition, orthorhombic (sp. group Pbca) semiconducting crystals α"-(BEDT-TTF)5[Ga(ox)3]·3.4·H2O·0.6 EtOH (5) were obtained. It is a new compound in the family of BEDT-TTF crystals with tris(oxalato)metallate anions. [ABSTRACT FROM AUTHOR]

The crystals of a perylene complex with the polymeric cluster containing [Mn6O2(O2CCHCl2)10(H2O)2] units assembled by 3,10-perylenequinone bridges, {[Mn6O2(O2CCHCl2)10(H2O)2(C20H10O2)]2n·(C20H12)n} (I), were obtained in the reaction of [Mn12O12(O2CCHCl2)16(H2O)4] with perylene. Unlike the Mn12 oxodichloroacetate cluster, the reaction of the Mn12 oxobenzoate cluster, [Mn12O12(O2CPh)16(H2O)4], with perylene does not occur. However, it turned out that the crystals isolated from the reaction are a new Mn12 oxobenzoate cluster containing three molecules of coordinated H2O and solvate molecules of hexane, [Mn12O12(O2CC6H5)16(H2O)3]·2C6H12 (II). Crystal structures of complexes I and II as well as the magnetic properties of the former were studied. [ABSTRACT FROM AUTHOR]

Four new superconducting and metallic salts of the family of organic molecular conductors (BEDT-TTF)4AI[FeIII(C2O4)3]G [A = H3O+; G = 2-chloropyridine (1), 2-bromopyridine (2), 3-chloropyridine (3), and 3-bromopyridine (4); BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene] have been prepared, and their crystal structures, electronic structures, transport properties, and magnetotransport properties have been studied. All of the crystals obtained belong to the monoclinic group of the family with β''-type packing of the conducting BEDT-TTF layers. Crystals 1 and 2 are superconductors with Tc = 2.4-4.0 and 4.3 K, respectively, and possess structural phase transitions from monoclinic to triclinic symmetry at temperatures of 190-215 K, whereas 3 and 4 retain monoclinic symmetry at 90-300 K and do not show a superconducting transition above 0.5 K. Shubnikov-de Haas (SdH) oscillations were found in crystals of 1, 2, and 4. The structures and conducting properties of 1-4 are compared with those of the known monoclinic phases of the family containing FeIII ions and different monohalobenzenes and pyridine as "guest" solvent molecules (G). [ABSTRACT FROM AUTHOR]