Supramolecular chirality in the crystals of mononuclear and polymeric cobalt(ii) complexes with enantiopure and racemic N-thiophosphorylated thioureas

Abstract

Mononuclear and polymeric Co(II) complexes were obtained with enantiopure and racemic N-thiophosphorylated thioureas with a metal to ligand ratio of 1 : 2. To control the stereochemistry of the complexes synthesized from racemic ligands, pyridine and pyrazine were used as co-ligands, the latter bridging cobalt ions in 1D-coordination polymers. Single crystal X-ray diffraction shows that 1D and 2D supramolecular homochiral arrangements in racemic crystals of mononuclear complexes are transferred to their polymeric counterparts. The cobalt oxidation state in coordination polymers was proved by electrochemistry. Magnetization and ESR measurements reveal a typical magnetic behavior of Co(II) metal ions in a distorted octahedral coordination. The polymeric crystals start to lose crystallinity from the surface at 65 °C, the process being accompanied with a color change and the evolution of gas. The ESR spectrum reduces in intensity after sample heating, tentatively, due to the smearing of the ESR response from the amorphous part of the sample.