Synthesis, crystal structures, spectroscopy and magnetic properties of two cobalt molecules constructed from histidine

A complex with a new [CoIII(d-His)(l-His)] · ClO4 (1) configuration was synthesized and characterized. Compound 1 crystallizes in the monoclinic space group Cc, with a = 13.102(5) Å, b = 15.495(5) Å, c = 10.237(4) Å, β = 127.856(4) ° and Z = 4. It was obtained via in situ oxidation. The histidinato–cobalt complexes with a cis-imidazole, cis-amine and cis-carboxylate configuration form a 3D supramolecular architecture of 1 via hydrogen bonding. Upon the addition of isonicotinic acid under similar reaction conditions, a new polymer [Co2II(d-His)(l-His)(INT)] · H2O · ClO4 (2) was obtained. Compound 2 crystallizes in the monoclinic space group P21/n, with a = 9.848(2) Å, b = 11.844(2) Å, c = 21.444(4) Å, β = 92.09(3) ° and Z = 4. In polymer 2, a novel kind of 16 nucleus cyclohexane-like chair conformation grid is formed. Each grid consists of four tetranucleus cluster units and four isonicotinate spacers. The novel tetranucleus clusters which are made up of four adjacent O–Co–N octahedra can be seen as the secondary building units (SBUs) for 2. Finally the grids form the coupling strands of opposite helixes via a connection of SBUs and assemble to the zigzag layers which organize into an embedding 3D supramolecular structure through hydrogen bonding. The spectroscopy and magnetic properties of two compounds were also measured. The FT-IR spectra provide an additional evidence for coordination environments for two compounds. The XPS result can provide assistant evidence for the conclusion that the valence of Co ions in 1 is III, as it is tested mainly in single X-ray diffraction and magnetic measurement. The diamagnetic-like phenomenon is shown for 1 and the paramagnetic-like phenomenon is displayed for 2.