Superalkali ligands as a building block for aromatic trinuclear Cu(i)–NHC complexes

Abstract

Imidazole and benz-imidazole based different NHC ligands have been designed to synthesize a Cu(I)@NHC complex. Calculated vertical electron affinity suggests that all the ligands belong to a special type of molecule, superalkali, and shows a very good non linear optical activity. All of them form Cu(I)@NHC complexes having a trinuclear Cu₃ core. Canonical Molecular Orbital contribution towards nucleus-independent chemical shift values suggest that the Cu₃ ring is both σ- and π-aromatic. Aromaticity and other reactivity parameters like electrophilicity and hardness change with different ligand environments. It has been found that pyrazine based NHC synthesizes a more reactive complex than pyridine. Natural localized molecular orbitals of these complexes suggest that they have sp² hybridization like BH₃.