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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. [ABSTRACT FROM AUTHOR]

Abstract: A detailed study of the low-temperature magnetic state and the relaxation in the phase-separated colossal magnetoresistance Nd2/3Ca1/3MnO3 perovskite has been carried out. Clear experimental evidence of the cluster-glass magnetic behavior of this compound has been revealed. Well defined maxima in the in-phase linear ac susceptibility χ′(T) were observed, indicative of the magnetic glass transition at T g ∼60K. Strongly divergent zero-field-cooled and field-cooled static magnetizations and frequency dependent ac susceptibility are evident of the glassy-like magnetic state of the compound at low temperatures. The frequency dependence of the cusp temperature T max of the χ′(T) susceptibility was found to follow the critical slowing down mechanism. The Cole–Cole analysis of the dynamic susceptibility at low temperature has shown extremely broad distribution of relaxation times, indicating that spins are frozen at “macroscopic” time scale. Slow relaxation in the zero-field-cooled magnetization has been experimentally revealed. The obtained results do not agree with a canonical spin-glass state and indicate a cluster glass magnetic state of the compound below T g , associated with its antiferromagnetic–ferromagnetic nano-phase segregated state. It was found that the relaxation mechanisms below the cluster glass freezing temperature T g and above it are strongly different. Magnetic field up to about μ 0 H∼0.4T suppresses the glassy magnetic state of the compound. [Copyright &y& Elsevier]

Abstract: Crystal structure, thermodynamic properties and electron spin resonance spectra of Cu(NH3)2Ag2(CN)4 have been studied. The structure of the studied compound consists of interpenetrating wave-shaped two-dimensional (2d) arrays, in which CuN4N2 octahedra axially elongated due to the Jahn–Teller effect are linked by diamagnetic [Ag(CN)2]− anions forming a square lattice. Although the susceptibility and specific heat data confirm the existence of short-range order at about 2K, quantitative analysis of the experimental data reveals that the magnetic behavior differs from that of the crystal structure expected for 2d Heisenberg magnet on the square lattice. Structural features responsible for the observed difference are discussed. In addition, it is suggested, that additional degrees of freedom contribute to the thermodynamic equilibrium properties in the millikelvin temperature range. [Copyright &y& Elsevier]

Abstract: The polymeric complex, {[Cu(tmen)][Pt(CN)4]} n (tmen =tetramethylethylenediamine) has been synthesized and characterized by elemental analysis, infrared spectroscopy, single-crystal structure analysis and by measurement of magnetic properties. Four ν(C N) absorption bands have been recorded in the infrared spectrum of this compound, what corresponds with four different types of cyano groups in the structure. Crystal structure revealed that one cyano group is terminal whereas three crystallographically different cyano groups of [Pt(CN)4]2− anions bridge Pt(II) and Cu(II) atoms to form a two-dimensional structure with a weak antiferromagnetic exchange coupling. [Copyright &y& Elsevier]