Exploring qualitative and quantitative contributions of intermolecular interactions, DNA-binding and in vitro cytotoxic activity of isostructural and isomorphous Cd and Zn complexes

Two isostructural and isomorphous Cd and Zn metal complexes of sulfapyridine, 4-amino-N-[2-pyridinyl] benzene sulfonamide, namely [M(C11H10N3O2S)(2)(C5H5N)(2)] (M = Cd (1)/Zn (2)) have been synthesized and characterized. Both complexes have a distorted octahedral geometry, with the metal center occupying a special position while coordinating to four N-atoms of two bidentate ligands in the equatorial plane and two N atoms of two solvent pyridine molecules in the apical positions. EDAX analysis and cyclovoltammetry confirm the presence of Cd and Zn atoms in the respective complexes. Similarities and differences in these two isostructural complexes are correlated by investigating qualitative and quantitative contributions of both strong and weak intermolecular interactions to the molecular packing through Hirshfeld surface analysis, 2D fingerprint plots and energy framework analysis. The DNA binding and in vitro cytotoxic properties of both these complexes are evaluated. The groove binding intercalation mode of DNA binding is confirmed for both complexes 1 and 2. Despite the structural similarities, the DNA binding affinity of complex 1 (Cd-SPY) is much stronger than that of complex 2 (Zn-SPY). A cytotoxicity assay reveals that the LC50 value of complex 2 is lower than that of complex 1, indicating a better inhibitory effect of the Zn complex compared to the Cd complex. Hence, in spite of being isostructural, the complexes presented different microbiological behaviour, revealing the role of metal ion. (C) 2020 Elsevier Ltd. All rights reserved.