Copper(II) complex with L-arginine – Crystal structure, DFT calculations, spectroscopic, thermal and magnetic properties

Abstract

Abstract Complex of formula [Cu(L−Arg)(phen)Cl]Cl·2H2O (1) was synthesized in crystalline form (triclinic crystal system, P1 (No. 1) space group with a = 9.376(1) A, b = 10.415(1) A, c = 12.209(2) A and Z = 2). The relations between the crystal structure, DFT calculations, spectroscopic properties (FT−IR, FT−Raman, NIR−Vis−UV, EPR) as well as the parameters of magnetic data were investigated. The square pyramidal geometry around copper (II) cations is very slightly distorted toward bipyramid geometry. The DFT-calculated interaction energies (ΔE) for the L−Arg zwitterion and phen ligands are −135.31 and −54.17 kcal mol−1, respectively. The g tensor diagonal components obey the relationship g|| > g⊥ (g⊥ = 2.063, g|| = 2.23) which suggested the pure dx2-y2 ground state orbital. Analysis of the crystal structure shows two possible magnetic exchange pathways: the neighboring [Cu( l −Arg)(phen)Cl]+ cations are linked in dimeric units by the N−H⋯Cl type hydrogen bonds, and almost parallel phenanthroline molecules provide π–π stacking interaction between the dimers. Analysis of the magnetic data, using an alternating ferro− and antiferromagnetic chain model for S = 1/2 spins, reveals the existence of weak antiferromagnetic coupling within the dimers (JAF = −0.23 cm−1) and weak ferromagnetic interaction between dimers (JF = 0.11 cm−1).