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Two one-dimensional cyano-bridged coordination polymers, namely, {[MnII(dapsc)][MnIII(CN)6][K(H2O)2.75(MeOH)0.5]}n·0.5n(H2O) (I) and {[MnII(dapsc)][MnIII(CN)6][K(H2O)2(MeOH)2]}n(II), based on alternating high-spin MnII(dapsc) (dapsc = 2,6-diacetylpyridine bis(semicarbazone)) complexes and low-spin orbitally degenerate hexacyanomanganate(III) complexes were synthesized and characterized structurally and magnetically. Static and dynamic magnetic measurements reveal a single-chain magnet (SCM) behavior of Iwith an energy barrier of Ueff≈ 40 K. Magnetic properties of Iare analyzed in detail in terms of a microscopic theory. It is shown that compound Irefers to a peculiar case of SCM that does not fall into the usual Ising and Heisenberg limits due to unconventional character of the MnIII–CN–MnIIspin coupling resulting from a nonmagnetic singlet ground state of orbitally degenerate complexes [MnIII(CN)6]3–. The prospects of [MnIII(CN)6]3–complex as magnetically anisotropic molecular building block for engineering molecular magnets are critically analyzed.

ortho-Pyrovanadate (or ortho-diorthovanadate) K2Mn23+Mn2+O(OH)(VO4)(V2O7) synthesized hydrothermally crystallizes in the orthorhombic space group Pnmawith a= 17.9155(5), b= 5.8940(2), c= 10.9971(3) Å, V= 1161.23(6) Å3, and Z= 4. Its crystal structure features linear chains of edge-sharing Mn3+O6octahedra with every second pair of Mn3+O6octahedra condensed with a Mn2+O6octahedron on one side of a chain in a sawtooth pattern so that each sawtooth chain consists of a triangular trimer. These sawtooth chains, running parallel to the baxis and linked by the VO4and V2O7groups, form a framework with channels populated by K atoms. The new compound is a structural analogue of the mineral zoisite Ca2Al3O(OH)(SiO4)(Si2O7), showing a striking example of very different chemical compositions. K2Mn3O(OH)(VO4)(V2O7) undergoes a phase transition into an ordered antiferromagnetic (AFM) state at TN= 14.4 K, which was detected by high-frequency electron spin resonance as well as by both specific heat Cpand Fisher’s specific heat d(χT)/dTmeasurements. However, this phase transition was not detected by magnetic susceptibility measurements. The origin of this puzzling observation was resolved by evaluating the spin exchanges of K2Mn3O(OH)(VO4)(V2O7), which revealed that each triangular trimer is a ferromagnetically coupled cluster, and the observed ordering involves an AFM ordering between the ferromagnetic (FM) clusters. This ordering is shrouded in magnetic susceptibility measurements due to the susceptibility contributions from the individual FM triangular trimers even below TN. We showed that the magnetic susceptibility of K2Mn3O(OH)(VO4)(V2O7) between ∼30 K and room temperature is satisfactorily described by an AFM chain made up of ferromagnetically coupled triangular clusters, as described by a few spin-exchange parameters.

The radical anion salt [Fe{HC(pz)3}2](TCNQ)3demonstrates conductivity and spin-crossover (SCO) transition associated with Fe(II) complex cation subsystem. It was synthesized and structurally characterized at temperatures 100, 300, 400, and 450 K. The compound demonstrates unusual for 7,7,8,8,-tetracyanoquinodimethane (TCNQ)-based salts quasi-two-dimensional conductivity. Pronounced changes of the in-plane direct-current resistivity and intensity of the electron paramagnetic resonance (EPR) signal, originated from TCNQ subsystem, precede the SCO transition at the midpoint T* = 445 K. The boltzmannian growth of the total magnetic response and structural changes in the vicinity of T* uniquely show that half [Fe{HC(pz)3}2] cations exist in high-spin state. Robust broadening of the EPR signal triggered by the SCO transition is interpreted in terms of cross relaxation between the TCNQ and Fe(II) spin subsystems.

Four new BEDT-TTF radical cation salts with the OsNOCl52−anion have been synthesized: α′-BEDT-TTF4OsNOCl5·C6H5NO21, δ-BEDT-TTF4OsNOCl51.33·C6H5NO20.672, κ-BEDT-TTF4OsNOCl5·C6H5CN 3 and β-BEDT-TTF2OsNOCl54. The salts were characterized by single-crystal X-ray diffraction, electrical resistance measurements, and electronic band-structure calculations. Evidence for commensurate structural modulations was found for 2and 3. The crystals of 1, 3and 4are semiconductors while those of 2exhibit a metal-to-insulator transition around 160 K. Analysis of the correlation between the crystal structure, transport properties and electronic structure of these and related salts suggests the possibility of smoothly changing the conductivity of κ-phases with two types of donors and dimers from semiconducting to metallic as well as the need to reconsider the origin of the metal-to-insulator transitions of δ-type salts.