Solvatomorphic Diversity in Coordination Compounds of Copper(II) with <span style="font-variant: small-caps">l</span>-Homoserine and 1,10-Phenanthroline: Syntheses, Crystal Structures and ESR Study

Abstract

In this study, we report the syntheses, crystal structures and magnetic properties of ternary copper(II) coordination compounds with l-homoserine (l-Hhser) and 1,10-phenanthroline (phen). Six new coordination compounds were obtained: [Cu(l-hser)(H2O)(phen)]2SO4·5H2O (1·5H2O), [Cu(μ-l-hser)(H2O)(phen)][Cu(l-hser)(H2O)(phen)]3(SO4)2∙12H2O (2·12H2O), {[Cu(μ-l-hser)(H2O)(phen)][Cu(μ-l-hser)(phen)]SO4·6H2O}n (3·6H2O), {[Cu(μ-l-hser)(H2O)(phen)]2SO4·3H2O}n (4·3H2O), [Cu(l-hser)(H2O)(phen)][Cu(l-hser)(CH3OH)(phen)]SO4·4H2O (5·4H2O) and {[Cu(l-hser)(CH3OH)(phen)][Cu(μ-l-hser)(phen)]SO4·5CH3OH}n (6·5CH3OH). It was shown that slight differences in water content in the synthetic mixtures highly influence the final product, so in some cases, two or three different products were obtained. The compounds were characterized by single-crystal X-ray diffraction and ESR spectroscopy. Crystal packings are based on intensive networks of hydrogen bonds and π interactions. Most water solvent molecules in these microporous compounds are found in discrete pockets (1∙5H2O, 2∙12H2O, 3∙6H2O, 4∙3H2O). In 5∙4H2O, water molecules are packed in pockets and 1D channels and in 6∙5CH3OH methanol solvent molecules form 1D channels. ESR spectroscopy measured from room down to liquid nitrogen temperature was used for local magnetic characterization of copper centers. The spin Hamiltonian parameters obtained from the spectral simulation revealed copper coordination geometry that is in agreement with the structural results. Furthermore, ESR spectra revealed no significant exchange coupling between copper ions. 3·6H2O showed pronounced antiproliferative activity toward human colon cancer cell lines (HCT116), human breast cancer cell line (MCF-7) and human lung cancer cell lines (H460).

Keywords

• crystal structures
• ESR spectroscopy
• magnetism
• single-crystal X-ray diffraction
• solid state
• solvatomorphism