Halogen Bonding Channels for Magnetic Exchange in Cu(II) Complexes with 2,5-Di(methylthio)-1,3,4-thiadiazole.

Copper(II) complexes with 2,5-bis(methylthio)-1,3,4-thiadiazole (tda) formulated as [Cu(tda)n X2 ] (n=2, X=Cl- , Br- , C2 N3 - ; n= 1, X=C2 N3 - ) have been isolated and fully characterized. The crystal structures of all compounds have been determined using single-crystal X-ray diffraction (SCXRD). A study of the magnetic susceptibility in the range 1.77-300 K has shown that magnetic properties of the [Cu(tda)2 Cl2 ] and [Cu(tda)2 Br2 ] complexes match those of 1D chains of antiferromagnetically-coupled Cu2+ ions. The intrachain interaction J in [Cu(tda)2 Cl2 ] turns out to be ∼1.2 times weaker than in its bromide analogue. In its turn, [Cu(tda)2 (C2 N3 )2 ] exhibits J being an order of magnitude smaller and of the opposite ferromagnetic sign. Halogen bonding (HB) between adjacent complexes is much stronger than the H-bonds or π-π interactions between tda ligands according to the DFT calculations.

High-Temperature Spin Crossover in Iron(II) Complexes with 2,6-Bis(1H-imidazol-2-yl)pyridine.

Novel iron(II) coordination compounds containing a ligand 2,6-bis(1H-imidazol-2-yl)pyridine (L), having such a composition as [FeL2]SO4·0.5H2O, [FeL2]Br2·H2O, [FeL2](ReO4)2, [FeL2]B10H10∙H2O, [FeL2]B12H12∙1.5H2O had been synthesized and studied using UV-Vis (diffuse reflectance), infrared, extended X-ray absorption fine structure (EXAFS), and Mössbauer spectroscopy methods, as well as X-ray diffraction and static magnetic susceptibility methods. The analysis of the µeff(T) dependence in the temperature range of 80-600 K have shown that all the obtained complexes exhibit a high-temperature spin crossover 1A1 ↔ 5T2.

Three differently coloured concomitant polymorphs: synthesis, structure and packing analysis of (4-(3',5'-dimethyl-1H-pyrazol-1'-yl)-6-methyl-2-phenylpyrimidine)dichlorocopper(II).

A novel pyrazolylpyrimidine ligand (L) and its complex CuLCl(2) were prepared and structurally characterized. The simultaneous crystallization of three polymorphs of CuLCl(2), green (G), emerald green (EG) and orange (O), was discovered. The molecular structures vary only slightly between the three forms. The Cu atom forms four coordinate bonds with the two N and two Cl atoms, and a shortened Cu...H contact with an H atom of the phenyl ring in L. The structural difference between polymorphs was analyzed with the boundary surfaces of molecular Voronoi-Dirichlet polyhedra. The difference in colour of the polymorphs is likely to be due to the different pi-pi stackings. There is no stacking in the G modification, but EG and O polymorphs demonstrate face-to-face and slipped stacking, resulting in dimers and infinite chains, respectively. The EG and O polymorphs are packed according to the hexagonal close-packing motif, while in G no special topology is found.