On the importance of unconventional Cu??? interaction in tetrachloro-bis (1,10-phenanthroline)-dicopper(II) complex: Insights from experiment and theory

A copper-phenanthroline complex, namely [bis(mu(2)-chloro)-dichloro-bis(1,10-phenanthroline)-di-copper(II)] has been synthesized and structurally characterized by single-crystal X-ray diffraction. The X-ray structure of the complex is stabilized through the hydrogen bond, pi...pi, and Cu...pi interactions. The Cu...pi interactions of the title complex along with two other complexes (retrieved from CSD) are analyzed in great detail through various theoretical calculations. Hirshfeld surface analysis and fingerprint plot quantify the non-covalent interactions. The interaction energies associated with intermolecular interactions have been calculated based on QTAIM (Quantum Theory of atoms in molecule). The analysis of topological parameters of charge density at (3, -1) bond critical points characterize the interactions as "closed-shell" interactions. The non-covalent interactions are further characterized by the Non-Covalent Interaction (NCI) plot index, Independent Gradient Module based on Hirshfeld partition of molecular density (IGMH), and Intrinsic Bond Strength Index for Weak interaction (IBSIW).