Analysis of Structural Conformation and Supramolecular Self-Assembly of Novel Oxalate-Bridged Tetranuclear Cu(II) Complex by Combined Crystallographic and Computational Studies

The heteroleptic tetranuclear copper(II) complex, [Cu(II)(4)(mu 2-Cl)(3) -(mu 1-Cl)(3) (mu-C2O4 - kappa(4) O1, O2: O1', O2')-(mu 1-1-4-dioxane) - (terpy-kappa(3) N', N '')]; have been synthesized and its crystal structure was solved using single crystal X-ray diffraction method under ambient conditions. Each Cu(II) ion is in a highly distorted square-pyramidal coordination environment in the title complex. In the crystal, the complex molecules are linked by C-H center dot center dot center dot Cl and C-H center dot center dot center dot O hydrogen bonds, forming propagating chains along the [110] direction. This complex exhibits a pi-pi interaction resulting from an overlap between pyridine rings of molecules A and B [intercentroid distance = 3.921(9)angstrom, 3. 813(9)angstrom and 3.724(9)angstrom] leading to the formation of a supramolecular framework. A detailed analysis of Hirshfeld surfaces and fingerprint plots show that van der Waals interactions constitute a further significant contribution to the intermolecular interactions, with H center dot center dot center dot H contacts accounting for 33.1% of the surface. In addition, the geometrical optimization of the tetranuclear Cu(II) complex was done by electronic structure method using density functional theory (DFT) to identify the active sites and to explore the chemically reactive parameters of the molecule and the HOMO-LUMO energy gap (0.5916 eV). QTAIM and the NCI index model analyses the vital role of distinct non-covalent interactions in the establishment of a unique structural topology. Furthermore, AChE/BChE and tyrosinase activity methods have been used to estimate the in vitro anti-Alzheimer effect of the synthesized complex, which has shown a potent AChE/BChE inhibition. (C) 2021 Elsevier B.V. All rights reserved.