The Nickel (II) complexes [Ni(Cl)2(metf)(o‐phen)] (1), [Ni(Cl)2(metf)(opda)] (2), [Ni(Cl)2(metf)(en)](3), [Ni(Cl)2(metf)(2,2'‐bipy)](4), (metf = metformin, o‐phen = ortho‐phenanthroline, opda = ortho‐phenylenediamine, en = ethylenediamine, 2–2′ bipy = 2–2′ bipyridyl) were synthesized and characterized using LC–MS, elemental analysis, molar conductance measurements, TGA‐DTA, IR spectroscopy, magnetic moment measurements and electronic spectroscopy. The central Ni2+ was found to be in octahedral geometry. The DNA interaction of these complexes have been studied by UV–visible absorption studies, fluorescence emission technique and viscosity measurement. The complexes showed absorption hyperchromism in UV–visible spectra with calf thymus DNA. The binding constants from UV–visible absorption studies were 7.42 × 104, 0.74 × 104, 3.19 × 104, 5.9 × 104 M−1 for 1, 2, 3 and 4, respectively and Stern‐Volmer quenching constants from fluorescence studies were 0.16, 0.41, 0.23, 0.18, respectively. Viscosity measurements revealed that the binding of the complexes with DNA could be surface binding, mainly due to groove binding. The highest DNA cleavage activity of the complexes is recorded for complex 1. The complexes were docked in to B‐DNA sequence, 5′(D*AP*CP*CP*GP*AP*CP* GP*TP*CP*GP*GP*T)‐3′ retrieved from protein data bank (PDB ID: 423D), using Discovery Studio 2.1 software. C Docker Intectraction energy of 1, 2, 3 and 4 complexes is 32.027, 31.427, 35.393 and 30.521 respectively. The highest docking score is seen for complex 3.

Three chromium ternary complexes with metformin (met) as a primary ligand and bipyridine (bipy) or ortho‐phenylenediamine (opda) or ortho‐phenanthroline (phen) as secondary ligand were synthesized. These complexes [Cr (Cl)2(Hmet)(bipy)]‐(1), [Cr (Cl)2(Hmet)(opda)]‐(2) and [Cr (Cl)2(Hmet)(phen)]‐(3) were characterized by LC–MS, elemental analysis, molar conductance, thermal analysis, infrared spectroscopy, electronic spectroscopy. The geometrical structures have been found to be octahedral. Degradation pattern of the compounds is shown by thermal studies. The Kinetic parameters‐ energy of activation (Ea), enthalpy (ΔH), entropy (ΔS) and free energy changes (ΔG) have been determined by thermogravimetric data. Coats‐Redfern integration method with thirteen kinetic models was used to calculate the kinetic and thermodynamic parameters for the degradation of all the complexes. The stabilities of the complexes were obtained from their molecular orbital structures from which the quantum chemical parameters were calculated using the HOMO‐LUMO energies. UV–Visible absorption, fluorescence, and viscosity measurements have been conducted to assess the interaction of the complexes with CT DNA. The complexes showed absorption hyperchromism in its UV–Vis spectrum with DNA. The binding constants Kb from UV–Vis absorption studies were 3.1x104, 4.4x104, 5x104 M−1 for 1, 2, 3 respectively and Stern–Volmer quenching constants (Ksq) from fluorescence studies were 0.137, 0.532, 0.631 for 1, 2, 3 respectively. Finally, viscosity measurements revealed that the binding of the complexes with CT‐DNA could be surface binding, mainly due to groove binding. The activity of complexes towards DNA cleavage decrease in the order of 3 > 2 > 1.The light switching properties of the complexes were also evaluated. The complexes were docked in to B‐DNA sequence, 5′(D*AP*CP*CP*GP*AP*CP*GP*TP*CP*GP*GP*T)‐3′ retrieved from protein data bank (PDB ID: 423D), using Discovery Studio 2.1 software.

The cobalt(II) complexes [Co(Cl)2(met)(o‐phen)] (1), [Co(Cl)2(en)(met)] (2) and [Co(Cl)2(met)(opda)] (3) (met = metformin, o‐phen = ortho‐phenanthroline, en = ethylenediamine, opda = ortho‐phenylenediamine) were synthesized and characterized using liquid chromatography–mass spectrometry, elemental analysis, molar conductance measurements, thermal analysis, infrared spectroscopy, magnetic moment measurements, electronic spectroscopy and X‐ray diffraction. The metal centre was found to be in an octahedral geometry. UV–visible absorption, fluorescence and viscosity measurements were conducted to assess the interaction of the complexes with calf thymus DNA. The complexes showed absorption hyperchromism in UV–visible spectra with DNA. The binding constants from UV–visible absorption studies were 1.38 × 105, 2.1 × 105 and 3.1 × 105 M−1 for 1, 2 and 3, respectively, and Stern–Volmer quenching constants from fluorescence studies were 0.146, 0.176 and 0.475, respectively. Viscosity measurements revealed that the binding of the complexes with DNA could be surface binding, mainly due to groove binding. The activities of the complexes in DNA cleavage decrease in the order 3 > 2 > 1. The complexes were docked into DNA topoisomerase II using Discovery Studio 2.1 software.

Two new water soluble oxovanadium(IV) complexes with formulae Na[VO(his) (met)SO 4 ] (1) and Na[VO(gly)(met)SO 4 ] (2), (gly=glycine his=histidine, and met=metformin) were synthesized and characterized by LCMS, UV-Visible absorption, infrared spectra, magnetic moment, elemental analysis, thermal analysis and electronic spectral studies. The metal center was found in an octahedral geometry. DNA binding interaction of these complexes with CT DNA has been explored by UV-Visible absorption, fluorescence, viscosity measurements and cleavage studies. Finally the binding of the complexes with CT-DNA could be surface binding, mainly in the groove binding. The complexes were docked in to B-DNA sequence, 5