Studying the Structure, BSA and FS-DNA Interaction, Fluorescence Sensing of Anions, Cytotoxicity, and Catecholase Activity of Cu(II) and Zn(II) Schiff base Complexes

Synthesis, characterization, X-ray crystallography, and the interaction with BSA/FS-DNA are reported for two new complexes, [{CuII2L(NCS)2}(μ1,3-NCS)]n (1) and [ZnII2L(μ1,1-N3)(N3)2] (2) (where L=[2,6-bis{N-(2-pyridylethThis section comprises references that occur in the reference list but not in the body of the text. Please position each reference in the text or, alternatively, delete it.yl)formidoyl}-4-methylphenol]). Characterization of the complexes was performed using elemental analysis, UV-vis, and FT-IR spectroscopy. X-ray analysis revealed a thiocyanate-bridged 1-D polymeric structure for complex 1 and a homodinuclear monophenoxo- and azido-bridged structure for complex 2. ‌‌Binding affinity and interaction mode with BSA/FS-DNA were investigated for both complexes using absorption and emission spectroscopy, viscosity measurement, circular dichroism, agarose gel electrophoresis, electrochemical study, and docking simulation. The EtBr replacement experiments clarified an effective binding affinity, Kb = 0.53 × 106 M−1 and Kb = 3.5 × 106 M−1 for complex 1 and 2, respectively, and intercalation as the dominant binding mode for both complexes. Furthermore, the cytotoxicity detection test of the complexes against AGS, MCF-7, PC3 cancer, and NIH/3T3 normal cell lines has shown a moderate selective anticancer activity against MCF-7 and AGS in complex 1. Both complexes triggered apoptosis-programmed cell death. Also, complex 2 showed a sensitive and selective turn-off fluorescence behavior (Kb = 1.1 × 1010 M−1) toward CrO42− among various anions with LOD of 5 × 10−7 M. Moreover, the ability of complex 1 to catalyze the oxidation of 3,5-di-tert-butyl catechol (3,5-DTBCH2) to its related quinone, was investigated and it showed an acceptable enzymatic activity.