354160-03-5Relevant articles and documents
Two dinuclear oxidovanadium(V) complexes of N2O2 donor amine-bis(phenolate) ligands with bromo-peroxidase activities: Kinetic, catalytic and computational studies
Debnath, Mainak,Dolai, Malay,Pal, Kaberi,Dutta, Arpan,Lee, Hon Man,Ali, Mahammad
, p. 149 - 158 (2018)
Two dinuclear oxidovanadium(V) complexes [LiVVO(μ2-O)VVO(Li)] (i = 1, H2L1, complex 1 and i = 2 for H2L2, complex 2) of two ONNO donor amine-bis(phenolate) ligands have been synthesized and characterized by X-ray diffraction studies which exhibited distorted octahedral geometry around each V center. In MeCN the complexes exist as dimers as indicated by HRMS studies, however, in the presence of 2 or more equivalents of H+ the dimers turned into monomers, ([LiVV = O]+ which exists in equilibrium with ([LiVV = OH]2+ and evidenced from the shift in λmax from 685 nm to 765 nm for complex 1 and 600 to 765 nm for complex 2. The complexes 1 and 2 efficiently catalyze the oxidative bromination of salicylaldehyde in the presence of H2O2 to produce 5-bromo-salicylaldehyde as the major product with TONs 405 and 450, respectively in the mixed solvent system (H2O:MeOH:THF = 4:3:2, v/v). The kinetic analysis of the bromide ion oxidation reaction indicates a mechanism which is first order in peroxidovanadium complex and bromide ion and limiting first-order on [H+]. The evaluated kBr and kH values are (8.82 ± 0.35) and (65.0 ± 2.23) M?1 s?1 for complex 1 and (6.74 ± 0.19) and (61.87 ± 2.27) M?1 s?1 for complex 2, respectively. The Ka of protonated species ([LiVV = OH]2+ are: Ka = (4.3 ± 0.40) × 10?3 (pKa = 2.37) and (4.7 ± 0.50) × 10?3 (pKa = 2.33) for complex 1 and 2 respectively. On the basis of the chemistry displayed by these model compounds, a mechanism of bromide oxidation and a tentative catalytic cycle have been framed which might be relevant to vanadium haloperoxidase enzymes and supported by DFT calculations.
Solvent dependent disproportionation of Cu(II) complexes of N2O2-type ligands: Direct evidence of formation of phenoxyl radical: An experimental and computational study
Debnath, Rajib Kumar,Kalita, Apurba,Sinha, Sourab,Bhattacharyya, Pradip Kr.,Mondal, Biplab,Ganguli, Jatindra Nath
, p. 4490 - 4500 (2015/11/27)
Four Cu(II) complexes (1, 2, 3 and 4) with N2O2-type ligand, H2L1, H2L2, H2L3 and H2L4, respectively have been synthesized as the functional model for galactose oxidase. In presence of acetonitrile the Cu(II) centres in the complexes, undergo reduction with simultaneous oxidation of the ligands. The ligand oxidized products are isolated and characterized. Spectroscopic studies indicate that this disproportionation goes through the formation of a Cu(II)-phenoxyl intermediate. The complexes also undergoes the same reaction with pyridine, which indicates the involvement of the exergonic N-donor ligand for the formation of Cu(II)-phenoxyl complex. The Cu(II)-phenoxyl complexes are found to be stable in methanol in presence of a strong base. The paramagnetic centers in the Cu(II)-phenoxyl complexes were found to be weakly ferromagnetically coupled. The complexes, in acetonitrile solvent, have been found to oxidize primary alcohols to corresponding aldehydes. In absence of single crystal structures of the complexes, we optimized the structures using density functional theory (DFT). The UV-visible peaks of complexes as found from time dependent density functional theory (TDDFT) calculations match well with the observed experimental results.
