Crystal and molecular structure stabilized by weak interaction in unique 3,5-diiodo-L-tyrosinato copper(II) complex – synthesis, experimental and theoretical studies

Abstract

The ternary Cu(II)/amino-acid/diamine systems have large positive logK values than binary Cu/amino systems, suggesting stabilization due to the effective stacking interaction between aromatic diamine and the aromatic side group of the amino acid. Thus, a hybrid 3,5-diiodo-L−tyrosinato copper(II) complex with an aromatic diamine, of formula [Cu(L−I2TyrO-)(H2O)(phen)]∙2H2O (1) was characterized in depth by using X-ray, TG/DTG, DSC, FT-IR, Raman, Q-band EPR, NIR-Vis-UV, magnetic methods and the theoretical calculations. The crystal structure is stabilized by weak π···π stacking, metal···π and intra- and intermolecular π···I non-covalent interactions. The computed interaction energies of Cg(1)∙∙∙Cg(2), Cg(3)∙∙∙I and Cg(1)∙∙∙Cu ranging from 0.69 kcal/mol− -2.20 kcal/mol. The weak interactions shift the bands assigned as ν(C-I) to higher frequency in the FT-IR spectrum. The g tensor is axial with g|| (2.239) > g⊥ (2.057) indicating that the unpaired electron residues in the dx2–y2 orbital. The exchange pathway occurs in the zig-zag chain with d(Cu···Cu) = 9.429 Å.