Supramolecular and theoretical investigation of copper(II) complexes containing 2,2'-39;-bipyridine and substituted chalcone ligands: Estimation of non-covalent interactions

Copper complexes of type [Cu(L)(bpy)(NO3)] { 1 , L = L 1 ; 2 , L = L 2 ; L1H = 3-(4-benzyloxyphenyl)-1-(2-hydroxylphenyl)-prop-2-en-1-one, L2H = 1-(2-hydroxyphenyl)-3-(4-chlorophenyl) prop-2-en-1-one, bpy = 2,2'-bipyridine} have been synthesized and characterized using elemental analysis, spectroscopic (IR, UV-Vis) and single crystal X-ray diffraction techniques. In both complexes, Cu(II) adopts distorted square pyramidal geometry. The crystal packing of complex 1 displays an infinite 1D supramolecular architec-ture using C-H center dot center dot center dot O and pi-pi stacking interactions. The C-H center dot center dot center dot O and pi center dot center dot center dot pi interactions together with weak C-H center dot center dot center dot Cl interaction facilitate formation of a 2D supramolecular net like structure in complex 2 . The com-prehensive studies of these interactions have been made using hirshfeld surface, fingerprint plots analyses and energy frameworks. The molecular electrostatic potential (MEP) surface analysis shows the larger val-ues of negatively charged nitrate and larger positive values at aromatic ring in both complexes. It implies that C-H center dot center dot center dot O and pi center dot center dot center dot pi interactions are dominant. Additionally, the combination of non-covalent interac-tion (NCI) plot index and QTAIM analysis computational tools are used to explore energetic features of the synthons involving different non-covalent interactions such as C-H center dot center dot center dot O, pi center dot center dot center dot pi and C-H center dot center dot center dot Cl interactions. Both analyses show that the combined pi center dot center dot center dot pi and C -H center dot center dot center dot pi interactions are dominant in the complex 1 for the dimer stabilization and construction of supramolecular structure. Whereas, complex 2 dimerization is prominently due to pi center dot center dot center dot pi interaction. The complexes 1 and 2 display emissions lambda max 524 and 533 nm at lambda excit 438 and 440 nm, respectively. It indicates small bathochromic shift in emission of complex 2 to complex 1 due to substituted chalcone ligands.(c) 2022 Elsevier B.V. All rights reserved.