Investigation of the noncovalent interactions of the Cu (II) amine complex with flexible aromatic moiety to the interaction with bovine serum albumin

Abstract

In crystallographic studies, non-covalent interactions are identified based on which atom is involved. A more accurate and quantitative idea can be obtained from the Hirshfeld surface (HS) analysis of the crystal structure of the molecule. The crystal structure of the synthesized Cu(II) complex (azidobis(N-benzylethylenediamine)copper(II) azide) with N-benzylethylenediamine was investigated to identify all the non-covalent interactions present in the crystal. Apparently, the hydrogen bond was the leading force in constructing the crystal from the crystallographic study, and this idea was overruled by HS analysis. The HS study indicates van der Walls interactions majorly contribute to crystal formation. Again, the high energy gap between HOMO and LUMO showed the inertness of the molecule toward chemical reactions. The conformational analysis of the molecule showed that the Cu(II) complex has a flexible phenyl ring and covalent azide, which makes the complex adjustable according to the environment. All these features of the complex make it a good candidate for interaction with proteins. In the presence of bovine serum albumin (BSA), the complex preferred to go into the hydrophobic site of the protein from water due to its van der Walls interactions preference. The interaction of the complex with BSA was investigated with multi-spectroscopic methods like UV–vis, fluorescence, circular dichroism, and time-resolved fluorescence lifetime. The experimental results also support the theoretical prediction that the binding of the complex with BSA is through hydrophobic interactions. Molecular docking results also indicate the hydrophobic interactions play the BSA-complex conjugation.