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Herein, we report the synthesis and structural investigation of CuII-NaI heterobimetallic complex 1, which comprises of the compartmental Schiff-base ligand (H2L) derived from DACH (1,2-Diaminocyclohexane) and o-vanillin. B3LYP/TZVP DFT calculation was performed to get a deeper insight of the ground state electronic structure, and quantitative analysis of non-covalent interactions was carried out using Hirshfeld surface analysis to explore H-bonding, C-H···π, Cu···C-H and Cu···H-C interactions. Furthermore, in vitro DNA binding studies with Complex 1 demonstrated the electrostatic mode of interaction at the major groove of the DNA. Complex 1 showed the oxidative damage of pBR322 DNA via ROS generation. Additionally, in vitro cytotoxicity and genotoxicity of complex 1 were investigated on human breast cancer cells (MCF-7), revealed concentration-dependent cell viability at micromolar concentration level. Flow cytometric analysis confirmed the cytotoxic potential of complex 1 as the percentage of apoptotic cells were increased in the treatment group. Genotoxicity was evident in the induction of micronucleus and DNA fragmentation.

Two new homometallic Cu4O4 cubane clusters 1 and 2 have been synthesized by self-assembly of copper(II) acetate and ligand, 2-[(2-Hydroxy-3-methoxy-benzylidene)-amino]-2-hydroxymethyl-propane-1,3-diol (H4L) and characterized thoroughly by various spectroscopic techniques and single crystal X-ray diffraction analysis. Temperature-dependent magnetic susceptibility measurements have been performed to elucidate the antiferromagnetic and ferromagnetic nature in Cu4O4 clusters 1 and 2, respectively. In vitro DNA binding studies of cubane clusters were carried out by employing optical spectroscopic techniques. Gel electrophoretic mobility assay performed to examine the nuclease activity of the complexes 1 and 2 with pBR322 DNA, and results revealed oxidative DNA cleavage via reactive oxygen species (ROS) species viz., O2 ‾, 1O2, etc. In vitro cell proliferation via MTT assay was studied to calculate the cytotoxicity of complexes 1 and 2. The IC50 evaluated were ∼20 µM in MCF-7 (Breast) and ∼30–35 µM in HepG2 (Liver) cancer cell lines. Additionally, in the presence of 1 and 2, ROS and TBARS (Thiobarbituric acid reactive substance) levels amplified significantly, coupled with GSH (glutathione) levels in cancer lines. Hence, the results exhibited the major role of ROS in apoptosis induced by 1 and 2 clusters and validate their prospective to be efficient anticancer drug entities.

New open–cubane tetranuclear copper(II) complex of formulation {[Cu4(HL)4(H2O)2]·(CH3OH)2·(H2O)5}(1) derived from Schiff base ligand 2–((E)–(1,3–dihydroxy–2–methylpropan–2–ylimino)methyl)–6–methoxyphenol (HL) was synthesized. The characterization of both ligand (HL) and tetranuclear Cu complex was carried out by analytical, spectroscopic and single crystal X–ray diffraction. The structure analyses revealed that in the tetranuclear core, the metal centers are mutually interconnected via two phenoxo oxygen and two alkoxo oxygen atoms of four H2L2− ligand to generate a distorted single–open [Cu4(μ3–O)2]6+ open cubane core with the four Cu atoms disposed in an extended “butterfly–like” arrangement. Binding of complex 1 with CT DNA was investigated by using vivid spectroscopic techniques to study the mode of the interaction of 1 towards CT DNA. The results obtained indicated that 1 avidly binds to CT DNA via electrostatic mode with an intrinsic binding constant, Kb value 4.63 × 104 M–1. Complex 1 showed an impressive nuclease activity generating single–strand breaks and the mechanistic investigation confirms the contribution of the reactive oxygen species (ROS). Likewise, the interaction of 1 with human serum album (HSA) revealed the change in intrinsic fluorescence intensity of HSA and was supposed to be associated with the microenvironment of Trp residue. Furthermore, the interaction of complex 1 with DNA and HSA was further investigated by the molecular docking studies which corroborated well with above findings. We have also tested 1 for cytotoxicity against the PC3 (Prostate) and K562 (Leukemia) cancer cell lines. The results exhibited were moderate when compared to standard drug viz, adriamycin (ADR).

The crystal and molecular structure of the title compound is presented and discussed in detail, and compared with some related pyrazole compounds. Focus is given on the often overlooked intramolecular hydrogen-bond stabilization that determines the structural conformation and also explains some unusual spectral properties. Ligand-field, EPR and infrared spectra are presented to illustrate the case on the title compound and also on a few related Cu(II) and Co(II) pyrazole-based compounds, compared with earlier reported Zn and Ni compounds. The observed N–H⋯O H-bond contacts correlate with the observed N–H stretching vibrations.