Synthesis, characterization and DFT study on two copper(II) complexes with a naphthalene-based Schiff base: Examples of stronger chelate-chelate interactions than those reported for classical pi-pi complexes

摘要

A N,N,O donor Schiff base blocking ligand, [HL = (1-(2-(morpholinoethylimino)methyl)naphthalen-2-ol)] has been used to synthesize one end-to-end thiocyanate bridged dinuclear complex {[Cu-2(L)(2)(mu 1,3NCS)(2)] (1)) and one end-to-end dicyanamide (dca) bridged polynuclear complex {[Cu(L)(mu(1.5)-dca)](n) (2)). Both complexes have been characterized by elemental and spectral analysis. Their structures have been confirmed by single crystal X-ray diffraction studies. Copper(II) center in each complex is coordinated in an elongated square pyramidal fashion. Complex 1 is a centrosymmetric dimer, whereas complex 2 forms a one dimensional coordination polymer bridged by end-to-end dca bridges. The presence of an extended pi-system (naphthalene-based ligand) facilitates the formation of C-H center dot center dot center dot pi and pi center dot center dot center dot pi non-covalent interactions. DFT calculations have been performed to explore the contribution of conventional pi center dot center dot center dot pi and unconventional pi(arene)-pi(chelate ring) interactions using several computational tools. (C) 2018 Elsevier Ltd. All rights reserved.