Structural Conformational Isomerism of Cu(II) Chelate Complexes
It is known that the interaction of metals with amino acids plays an important role in the electron transfer reactions and deprotonation of the action centers in the molecular systems. Metal ions interact with amino acids by N,O-chelation, forming a five-membered chelate ring. Also, Cu(II) ion is one of the most famous transition elements in biological systems. It was found that the participation of the Cu(II) ion in the complexation with N,O-ligands leads mainly to a square-planar structure. In this case, cis- or trans -configuration of the resulting complexes are possible. The conformational analysis allows identifying the most optimal conformers, which are formed as a result of different orientations of ligands in space. By DFT modeling (method M06, 6-311G(d)), the structural conformational trans- and cis -isomers of chelate complexes Cu(II) with S- and R,S -valine and S - and R,S -phenylalanine were studied. It was found that amino acid bis-chelates of Cu(II) are formed as conformational isomers of “bath” or “chair” in a square-planar configuration. This differences arise due to distortion of chelate rings relative to each other in the plane and depend on the absolute configuration of the chiral center ( R,S ) of amino acid substituent, which can take axial or equatorial position in space.