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In the present work, we attempted to develop new metal complexes (Cu(II), Co(II), Ni(II) and Zn(II)) of the imine ligand which was synthesized from 9,10-phenanthrenequinone and para-anisidine. With an intention to make the complexes most stable, very special chelating amino acid has been coordinated to the metal centre. The resultant metal complexes have been characterized by variety of techniques including FT-IR, UV-Vis., (1)H NMR, (13)C NMR, powder XRD, EPR and mass spectral studies. The interaction of the complexes with DNA has been effectively examined and explored by fluorescence titration, UV-Vis absorption, viscometer titration, cyclic voltammetry (CV) and differential pulse voltammetry. Moreover, molecular docking analysis has been performed to understand the nature of binding of the complexes with DNA. These studies prove that CT DNA interaction of the complexes follows intercalation mode. The metal complexes exhibit effective cleavage of pUC19 DNA by an oxidative cleavage mechanism. The antimicrobial screening indicates that these complexes are good antimicrobial agents against various organisms.

Four new transition metal complexes incorporating a Schiff base ligand derived from propylenediamine and 4‐formyl‐N,N‐dimethylaniline have been synthesized using transition metal salts. The characterization of the newly formed complexes was done from physicochemical parameters and using various techniques like 1H NMR, 13C NMR, IR, UV, electron paramagnetic resonance and mass spectroscopies, powder X‐ray diffraction and magnetic susceptibility. All the complexes were found to be monomeric in nature with square planar geometry. X‐ray powder diffraction illustrates that the complexes have a crystalline nature. The interaction of metal complexes with calf thymus DNA was investigated using UV–visible absorption, viscosity measurements, cyclic voltammetry, emission spectroscopy and docking analysis. The results indicate that the Cu(II), Co(II), Ni(II) and Zn(II) complexes interact with DNA by intercalative binding mode with optimum intrinsic binding constants of 4.3 × 104, 3.9 × 104, 4.7 × 104 and 3.7 × 104 M−1, respectively. These DNA binding results were rationalized using molecular docking in which the docked structures indicate that the metal complexes fit well into the A‐T rich region of target DNA through intercalation. The metal complexes exhibit an effective cleavage with pUC19 DNA by an oxidative cleavage mechanism. The synthesized ligand and the complexes were tested for their in vitro antimicrobial activity. The complexes show enhanced antifungal and antibacterial activities compared to the free ligand.

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The NMR spectrum is exploiting to determine the identity of prepared ligand and its diamagnetic metal complexes. Ligand and Zn(II) complex were recorded in DMSO-d 6 , using tetramethylsilane (TMS) as internal standard. The 1 H NMR spectrum of ligand shows a singlet peak at 9.71 ppm (1H, CH=N), multiplet in the range 6.60-7.90 ppm for the aromatic ring protons and a multiplet peak at 2.80-3.40 ppm for (12H, N-CH 3 ) protons. The proton 1 H NMR spectrum of Zn complex shows (Fig. S2.) a singlet peak at 9.67 ppm (1H, CH=N), multiplet in peaks at 6.60-7.90 ppm for the aromatic ring protons and a multiplet peak at 2.80-3.40 ppm for (6H, N-CH 3 ) protons. From the above observation, it is inferred that the azomethine group (CH=N) is involved in metal co-ordination. Powder XRDX-ray powder diffraction has been obtained for further confirmation, regarding the structure of the metal complexes. They are complicated to isolate single crystal suitable for a single crystal X-ray crystallography; it might be due to powder or polycrystalline nature of the complexes. However, the structural information on the majority of inorganic metal complexes is not suitable, because the materials have been polycrystalline or powder in nature. Generally it is hard to develop good quality single crystals of these inorganic complexes. In this metal complex, powder X-ray diffraction studies may be useful. The X-ray diffraction of metal complex is given in Fig. S3. which exhibits reflecting peaks of 2θ scattering angles at 13.