New tetradentate long chain Schiff base and its cadmium(II) complexes: Antimicrobial, antioxidant and anticancer activities

Abstract

In the current study, a new long chain tetra-nitrogen donor Schiff base ligand (SB) entitled as N1,N2-bis(2-(((1E,2E)-3-(4-(dimethylamino)phenyl)allylidene)amino)ethyl)ethane-1,2-diamine and some its molecular cadmium (II) complexes formulated as Cd(SB)X2 (X = halide/pseudohalide) were prepared and characterized by various physicochemical and spectral methods such as melting point, micro-analytical data, thermal analysis (TG/DTG/DTA), molar conductivity and UV–Visible, FT-IR, 1H, and 13C NMR spectroscopies. Also nanostructured cadmium chloride and iodide chelate complexes approved by PXRD SEM and EDX techniques were synthesized to use as precursor to prepare nanostructure cadmium oxide. The particle sizes about 2–10 nm were estimated for nanostructured cadmium complexes and oxide. Thermo-gravimetric plots showed the compounds are decomposed via 2–4 steps with weight loss of 69–100% to leave out metallic Cd or cadmium salt as final residue. Thermo-kinetic activation parameters calculated based on TG plots suggested non-spontaneous thermal decomposition with activation Ea*, ΔH* and ΔG* parameters in the ranges of (13.54–160.48 kJ.mol−1), (8.22–155.95 kJ.mol−1) and (1.59 × 102-4.1 × 102 kJ.mol−1) respectively. Moreover, the pharmacological activities of the compounds were investigated against some pathogenic fungi and bacteria. According to screening data, the SB ligand showed lower antimicrobial activities than its complexes toward selected microbes so that the cadmium(II) nitrate, thiocyanate and azide were found the most active against B. subtilis, S. aureus, P. aeruginosa and E. coli respectively. The evaluation of DNA cleavage potency using the agarose gel electrophoresis technique suggested Cd(SB)Cl2 as the most destructive compound. Furthermore, the antioxidant assessment of the compounds as compared with the standard references by DPPH and FRAP methods proposed Cd(SB)Cl2 and Cd(SB)Br2 as the best antioxidant. In final, the cytotoxicity of the synthesized compounds was appraised toward human breast cancer (MCF-7) and prostate cancer (PC3) cell lines employing MTT and nitric oxide level assays. The results suggested Cd(SB)Br2 as more cytotoxic than other complexes against two studied cancer cell lines.