Exploring solvent dependent catecholase activity in transition metal complexes: an experimental and theoretical approach

摘要: In contrast to polynuclear complex models for biomimetic activity, a series of mononuclear complexes are designed in this work order assess their catecholase activity and kinetics. Four new complexes, namely, [Mn(pdmH2)(Phen)Cl]Cl·H2O (1), [Mn(pmmH)2(SCN)2] (2), [Ni(pmmH)2(SCN)2] (3) [Zn(phen)3][(pdm)]·11H2O (4) utilizing an amino alcohol ligand, pyridine-2,6-dimethanol (pdmH2) or 2-pyridinemonomethanol (pmmH), auxiliary 1,10-phenanthroline (phen) thiocyanate (SCN−), synthesized. The characterized by elemental analysis, FTIR, UV-visible, EPR, fluorescence (solution solid state), Hirshfeld surface magnetic, single crystal X-ray DFT/TD-DFT studies. structures confirm the geometry around M(II) ions be octahedral all complexes. 1–3, primary aminoalcohol ligand binds metal ion neutral (pdmH2 pmmH) mode while 4 exists as cation–anion type where deprotonated (pdm2−) is present outer sphere having no coordination metal. Zn(II) also shows remarkable luminescence state photoluminescence spectrum. Variable temperature magnetic studies show presence antiferromagnetic exchange 1–3 (θ = −2.8, −1.7 −5.2, respectively) with observation anisotropy (D 4.0 E 3.4) 3. results provide ample information regarding structures, spin densities, charge distribution, electronic spectra along transitions. density values, ρ 4.793, 4.792 1.676, five, five two unpaired electrons on d-orbitals 1, 2 3, respectively. Interestingly, solvent dependent has been observed first time Mn(II) (1 2) Kcat 2602.8 h−1 (acetonitrile), 1490.4 (methanol) 1083.6 806.4 2. This can rationalized terms coordinating powers solvent, i.e., DMSO > MeOH MeCN. Further, 1 (i.e., inactivity 3 very well corroborated DFT which ascertains highest contribution [33% HOMO 2% LUMO Mn(II)] resulting formation most stable metal–substrate adduct, thus enhancing activity.