Bioinspired oxidation of benzyl alcohol: The role of environment and nuclearity of the catalyst evaluated by multivariate analysis.

Inspired by copper-containing enzymes such as galactose oxidase and catechol oxidase, in which distinct coordination environments and nuclearities lead to specific catalytic activities, we summarize here the catalytic properties of dinuclear and mononuclear copper species towards benzyl alcohol oxidation using a multivariate statistical approach. The new dinuclear [Cu(μ-L)(μ-pz)] (1) is compared against the mononuclear [CuLCl] (2), where (L) and (L) are the respective deprotonated forms of 2,6-bis((bis(pyridin-2-ylmethyl)amino)methyl)-4-methylphenol, and 3-((bis(pyridin-2-ylmethyl)amino)methyl)-2-hydroxy-5-methylbenzaldehyde and (pz) is a pyrazolato bridge. Copper(II) perchlorate (CP) is used as control.

Electronic structures and spectroscopic signatures of diiron intermediates generated by O activation of nonheme iron(II)-thiolate complexes.

The activation of O at thiolate-ligated iron(II) sites is essential to the function of numerous metalloenzymes and synthetic catalysts. Iron-thiolate bonds in the active sites of nonheme iron enzymes arise from either coordination of an endogenous cysteinate residue or binding of a deprotonated thiol-containing substrate. Examples of the latter include sulfoxide synthases, such as EgtB and OvoA, that utilize O to catalyze tandem S-C bond formation and -oxygenation steps in thiohistidine biosyntheses.

Nonheme iron-thiolate complexes as structural models of sulfoxide synthase active sites.

Two mononuclear iron(ii)-thiolate complexes have been prepared that represent structural models of the nonheme iron enzymes EgtB and OvoA, which catalyze the O2-dependent formation of carbon-sulfur bonds in the biosynthesis of thiohistidine compounds. The series of Fe(ii) complexes reported here feature tripodal N4 chelates (LA and LB) that contain both pyridyl and imidazolyl donors (LA = (1H-imidazol-4-yl)-N,N-bis((pyridin-2-yl)methyl)methanamine; LB = N,N-bis((1-methylimidazol-2-yl)methyl)-2-pyridylmethylamine). Further coordination with monodentate aromatic or aliphatic thiolate ligands yielded the five-coordinate, high-spin Fe(ii) complexes [FeII(LA)(SMes)]BPh4 (1) and [FeII(LB)(SCy)]BPh4 (2), where SMes = 2,4,6-trimethylthiophenolate and SCy = cyclohexanethiolate.

Spectroscopic and Computational Comparisons of Thiolate-Ligated Ferric Nonheme Complexes to Cysteine Dioxygenase: Second-Sphere Effects on Substrate (Analogue) Positioning.

Parallel spectroscopic and computational studies of iron(III) cysteine dioxygenase (CDO) and synthetic models are presented. The synthetic complexes utilize the ligand tris(4,5-diphenyl-1-methylimidazol-2-yl)phosphine (TIP), which mimics the facial three-histidine triad of CDO and other thiol dioxygenases. In addition to the previously reported [Fe(CysOEt)(TIP)]BPh (; CysOEt is the ethyl ester of anionic l-cysteine), the formation and crystallographic characterization of [Fe(2-MTS)(TIP)]BPh () is reported, where the methyl 2-thiosalicylate anion (2-MTS) resembles the substrate of 3-mercaptopropionate dioxygenase (MDO).

A pentadentate nitrogen-rich copper electrocatalyst for water reduction with pH-dependent molecular mechanisms.

The new pentadentate 3d complex [Cu(L)](PF) (1) based on a nitrogen-rich framework acts as an electrocatalyst toward dihydrogen production from water. This species is active at pHs 7 and 2.5 yielding respective TON values of 1670 and 3900.