Crystal structure, ferromagnetostructural behavior and evidence of cooperative Jahn–Teller interactions of the complex [CuL]Cl·H 2O (L= N-glycyl-2(aminomethyl)benzimidazol), synthesized by a novel simple method of peptide bond formation.

Abstract

[CuL]Cl·H 2O 1 (L= N-glycyl-2(aminomethyl)benzimidazol) compound crystallizes in the orthorhombic space group Pna2 1 with unit cell parameters a=7.140(5) A ̊ , b=17.621(5) A ̊ , c=9.941(5) A ̊ . Its structure shows that the copper(II) ion is tetra coordinated with a square planar geometry. The ligand acts as a tridentate and the chloride ion is the fourth ligand. Symmetry related units stack into helicoidal columns along the ā direction producing weakly bonded strips with dihedral angles of 2.6° between two consecutive molecular planes. UV/VIS spectrum of 1 shows one broad and weak band at 622 nm, characteristic of d–d transitions, indicative of low local Cu(II) symmetry. X band ESR spectra of 1 at 300 and 77 K are axial exchange narrow lines with g ∥=2.135 and g ⊥=2.028. However, the axial spectrum at 6.4 K shows an increment Δ g ∥=0.076(6) and Δ g ⊥=0.028(4) which suggests a cooperative Jahn–Teller interactions between complexes via the hydrogen-bonding network. Magnetic susceptibility data at 18–300 K and fitted to the modified Bleany–Bowers equation indicate a weak ferromagnetic coupling with 2J≅+17 cm −1, which is compatible with the helium temperature ESR results and with the helicoidal stacking into columns of the molecules along the a-axis with 78.9° Cu′–Cl′–Cu and 81.2° Cu′–N( 1)–Cu bonds angles. The synthesis is a novel, simple and efficient method: in aqueous conditions and heterogeneous phase with basic copper(II) carbonate, which carries out the formation of the stable peptide bond.