title: Copper coordinated ligand thioether-S and NO2(-) oxidation: relevance to the CuM site of hydroxylases.
abstract: In order to gain insight into the coordination site and oxidative activity of the CuM site of hydroxylases such as peptidylglycine α-hydroxylating monooxygenase (PHM), dopamine β-monooxygenase (DβM), and tyramine β-monooxygenase (TβM), we have synthesized, characterized and studied the oxidation chemistry of copper complexes chelated by tridentate N2Sthioether, N2Osulfoxide or N2Osulfone donor sets. The ligands are those of N-2-methylthiophenyl-2'-pyridinecarboxamide (HL1), and the oxidized variants, N-2-methylsulfenatophenyl-2'-pyridinecarboxamide (HL1(SO)), and N-2-methylsulfinatophenyl-2'-pyridinecarboxamide (HL1(SO2)). Our studies afforded the complexes [(L1)Cu(II)(H2O)](ClO4)·H2O (1·H2O), {[(L1(SO))Cu(II)(CH3CN)](ClO4)}n (2), [(L1)Cu(II)(ONO)] (3), [(L1(SO))Cu(II)(ONO)]n (4), [(L1)Cu(II)(NO3)]n (5), [(L1(SO))Cu(II)(NO3)]n (6) and [(L1(SO2))Cu(II)(NO3)] (7). Complexes 1 and 3 were described in a previous publication (Inorg. Chem., 2013, 52, 11084). The X-ray crystal structures revealed either distorted octahedral (in 2, 4-6) or square-pyramidal (in 1, 3) coordination geometry around Cu(II) ions of the complexes. In the presence of H2O2, conversion of 1→2, 3-5→6 and 6→7 occurs quantitatively via oxidation of thioether-S and/or Cu(ii) coordinated NO2(-) ions. Thioether-S oxidation of L1 also occurs when [L1](-) is reacted with [Cu(I)(CH3CN)4](ClO4) in DMF under O2, albeit low in yield (20%). Oxidations of thioether-S and NO2(-) were monitored by UV-Vis spectroscopy. Recovery of the sulfur oxidized ligands from their metal complexes allowed for their characterization by elemental analysis, (1)H NMR, FTIR and mass spectrometry.
authors.affiliation: Department of Chemistry, National Institute of Technology Durgapur, Mahatma Gandhi Avenue, Durgapur 713209, West Bengal, India. apurba.patra.nitdgp@gmail.com.
authors.forename: Ram Chandra
authors.initials: RC
authors.lastname: Maji
authors.forename: Anirban
authors.initials: A
authors.lastname: Bhandari
authors.forename: Ravindra
authors.initials: R
authors.lastname: Singh
authors.forename: Suprakash
authors.initials: S
authors.lastname: Roy
authors.forename: Sudip K
authors.initials: SK
authors.lastname: Chatterjee
authors.forename: Faye L
authors.initials: FL
authors.lastname: Bowles
authors.forename: Kamran B
authors.initials: KB
authors.lastname: Ghiassi
authors.forename: Milan
authors.initials: M
authors.lastname: Maji
authors.forename: Marilyn M
authors.initials: MM
authors.lastname: Olmstead
authors.forename: Apurba K
authors.initials: AK
authors.lastname: Patra
mesh_terms: D001665:Binding Sites; D003300:Copper / Q000737:chemistry*; D004987:Ethers / Q000737:chemistry*; D008024:Ligands; D006899:Mixed Function Oxygenases / Q000737:chemistry*; D009569:Nitric Oxide / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010084:Oxidation-Reduction; D013455:Sulfur / Q000737:chemistry*
chemical_list: D004987:Ethers; D008024:Ligands; D009942:Organometallic Compounds; D009569:Nitric Oxide; D013455:Sulfur; D003300:Copper; D006899:Mixed Function Oxygenases