Exploration of supramolecular and theoretical aspects of two new Cu(II) complexes: On the importance of lone pair •••π(chelate ring) and π•••π(chelate ring) interactions

An organic ligand, NL [4-(1-methylimidazole)-2,6-di(pyrazinyl)pyridine] has been synthesized and characterized by several spectroscopic methods. The ligand (NL) was then utilized for the preparation of two complexes, namely, [Cu(NL)(N-3)(H2O)]ClO4 center dot H2O (complex 1) and {[Cu(NL)(mu-NL)NCS]ClO4}(n) (complex 2). The crystal structures of these complexes have been established by single-crystal X-ray analysis. Complex 2 exhibits a one dimensional (1-D) polymeric chain, whereas complex 1 is a mononuclear one. It is noteworthy that the change in auxiliary ligands exhibit structural variations and different supramolecular behaviors for the present complexes. Mainly, lone pair center dot center dot center dot pi(chelate ring) and pi center dot center dot center dot pi(chelate ring) interactions are well investigated in governing the solid state architecture of complex 1 and 2 respectively. Besides, the other non-covalent interactions like pi center dot center dot center dot pi stacking, sulphur (lone pair)center dot center dot center dot pi and hydrogen bonding interactions play crucial role in the crystal packing for both the complexes. In complex 1, a chair-like perchlorate-water tetrameric cluster, [(ClO4)(2)-(H2O)(2)](2-) was observed. The aim of this work is to investigate the role of chelate rings in producing supramolecular architectures of both the complexes in the solid state. Theoretical (DFT) calculations including QTAIM and NCI Plot index were carried out to analyze the non-covalent interactions in the solid state for both the complexes. (C) 2022 The Author(s). Published by Elsevier B.V.