A Propargyl-Functionalized Benzimidazole-Based Cu(II) Complex: Synthesis and Structure

Abstract

A new propargyl-functionalized 2,6-bis(benzimidazolyl)pyridine-based N3-donor ligand (L) and its copper(II) complex [Cu(L)(NO3)2] have been synthesized and characterized. The ligand was designed to provide a rigid tridentate coordination environment while incorporating a propargyl moiety to modulate its electronic properties. The resulting complex was obtained as green crystals and fully characterized by elemental analysis, FT-IR spectroscopy, and single-crystal X-ray diffraction. Structural analysis revealed that the Cu(II) center adopts a distorted octahedral geometry with a characteristic (4+2) coordination mode, involving three nitrogen atoms from the ligand and three oxygen atoms from nitrate groups. The observed elongation of the axial Cu–O bonds is consistent with Jahn–Teller distortion typical for d⁹ metal ions. The photophysical properties of the complex were investigated using UV–Vis absorption spectroscopy. The absorption spectrum displays characteristic π→π* and n→π* transitions along with charge-transfer bands in the visible region.