Phenomenal Observation of Attractive Intermolecular CH⋯HC Interaction in a Mercury (II) Complex: An Experimental and First‐Principles Study

Abstract

AbstractThe nature of the attractive intermolecular C−H…H−C interaction, which could affect the crystal packing and solid‐state molecular structure, is yet unknown. Here, a novel mercury (II) complex includingN‐(2‐biphenyl)pyrazine‐2‐carboxamide ligand, one such system, has been synthesized and characterized by a single crystal X‐ray diffraction. The existence of attractive intermolecular C−H⋯H−C interaction (‐2.64 to −9.30 kj/mol depending on computational levels) is a notable feature in the crystal packing of this complex, which is the first observation ofintermolecularC−H⋯H−C interaction in a metal complex. From crystallographic data, this contact has a distance of 2.172 Å which is 9.5% shorter than the sum of the van der Waals radii of two hydrogen atoms, which is the primary condition of having intermolecular interactions. We study the nature C−H…H−C interaction in the synthesized mercury (II) complex using periodic/non‐periodic density functional theory in conjunction with quantum theory of atoms in molecules, non‐covalent interaction reduced density gradient method, natural bond orbital, and energy decomposition analysis tools. Our results suggest that C−H⋯H−C interaction has closed‐shell, donor‐acceptor, and van der Waals nature.