A [Mn-32] Double-Decker Wheel

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A nickel(II)-sulfur-based radical-ligand complex as a functional model of hydrogenase

A nickel(II) dithiolene complex [Ni<SUP>II</SUP>(L<SUP>2−</SUP>)(L<SUP>−</SUP>.)][PPh<SUB>4</SUB>] (1; see figure; L=1,2-dicarbomethoxyethylene dithiolate) electrocatalyzes hydrogen evolution at the lowest achievable reduction potential (−0.69 V) in CH3CN and also in aqueous medium (−0.71 V) to date. Compound 1 shows strikingly similar EPR and reduction potential values to those observed with native Ni-containing hydrogenases

Dangling thiyl radical: stabilized in [PPh<SUB>4</SUB><SUB>]2</SUB>[(bdt)W<SUP>VI</SUP>(O)(&#956; -S)<SUB>2</SUB>CuI(SC<SUB>6</SUB>H<SUB>4</SUB>S&#x2022;)]

The synthesis, crystal structure, and spectroscopic characterization of [PPh4]2[(bdt)W(O)(S2)Cu(SC6H4S&#183; )] (3; bdt= benzenedithiolate) relevant to the active site of carbon monoxide dehydrogenase are presented. Curiously, in 3, the copper(I) benzenemonothiolate subcenter possesses a dangling thiyl radical that is stabilized by a disulfido-bridged oxo tungsten dithiolene core. The benzenedithiolate ligand, which is generally bidentate in nature, acts as a bidentate and also as a monodentate in 3. The formation of an unusual dangling thiyl radical has been magnetically and spectroscopically identified and has been supported by the density functional theory level of calculation

From molecular to micro structure via nanostructure of a nickel(II) dithiolene complex

1257-1262The nanocrystal structure of a hetero-polyatomic metal-ligand complex, [PPh4][NiII(L2−)(L1−·)], (1) (L = 1,2-dicarbomethoxyethylene dithiolate) has been arrived at from its molecular structure obtained by X-ray crystallography. The complex (1) exhibits dimorphism, existing in two crystal habits at the micro level, viz., rectangular prismatic and hexagonal. Rectangular or hexagonal repeating motifs manifest in the lattice packing of the two crystal structures of (1) in two different solvents which extend up to nano dimension and result in nano sized rectangular and hexagonal prismatic crystals. This provides major clues to understand the shapes of hetero-poly atomic nanocrystals at the molecular level

Super reduced Fe₄S₄ cluster of Balch's dithiolene series

A super reduced Fe4S4 cluster with a sulfur based radical, [NBu4]4[Fe3IIIFeII(μ3-S)4(mnt)36−(mnt)1−˙]4−˙, (1) (mnt, which evolves H2S gas on treatment with acid under ambient conditions has been synthesized and structurally characterized. The Fe–S distances in 1 are in the range 2.246–2.383 Å, in stark contrast to that of the known n = −2 member of the series based on the [Fe4(μ3-S)4(S2C2R2)4]n unit (R = CF3, Ph) with Fe–S bond lengths of 2.149–2.186 Å. The EPR of 1 displays very weak signals at g, 4.03 and 2.38 along with a strong S-based radical EPR signal at g, 2.003 associated with five structured components tentatively assigned to hyperfine interaction arising out of the naturally abundant 57Fe with &lt;A&gt; = 88 G. The EPR profile resembles the reduced Fe–S cluster of CO inhibited Clostridium pasteurianum W5 hydrogenase or the Fe4S4 centers of wild-type enzyme, IspH treated with HMBPP or IPP

From the {Cu(μ2-S)N}4 butterfly architecture to the {Cu(μ3-S)N}12 double wheel

Copper(I) complexes with {Cu(μ2-S)N}4 and {Cu(μ3-S)N}12 core portions of butterfly-shaped or double wheel architectures have been isolated in the reaction of Cu(I) with the Schiff base ligand C6H4(CHNC6H4S)2, aiso-abtâ, under different conditions. View the MathML source containing the tetranuclear electroneutral complex View the MathML source is formed by the reaction of CuI in acetonitrilic solution and recrystallization from DMF, whereas View the MathML source containing dodecanuclear View the MathML source wheels is accessible starting from CuBF4. Complexes 2 and 4 represent the first examples of cyclic complexes with the same overall stoichiometry but different ring sizes. The ligand induces two different coordination environments around copper(I) by switching between μ2- and μ3-sulfur bridging modes

From molecular to micro structure via nanostructure of a nickel(II) dithiolene complex

The nanocrystal structure of a hetero-polyatomic metal-ligand complex, [PPh4][NiII(L2−)(L1−·)], (1) (L = 1,2-dicarbomethoxyethylene dithiolate) has been arrived at from its molecular structure obtained by X-ray crystallography. The complex (1) exhibits dimorphism, existing in two crystal habits at the micro level, viz., rectangular prismatic and hexagonal. Rectangular or hexagonal repeating motifs manifest in the lattice packing of the two crystal structures of (1) in two different solvents which extend up to nano dimension and result in nano sized rectangular and hexagonal prismatic crystals. This provides major clues to understand the shapes of hetero-poly atomic nanocrystals at the molecular level

Synthesis, crystal structures and protease activity of amino acid Schiff base iron(III) complexes

473-479Iron(III) complexes, (NHEt3)[Fe(III)(sal-met)2] and (NHEt3)[Fe(III)(sal-phe)2], of amino acid Schiff base ligands, viz., N-salicylidene-L-methionine and N-salicylidene-L-phenylalanine, have been prepared and their binding to bovine serum albumin (BSA) and photo-induced BSA cleavage activity have been investigated. The complexes are structurally characterized by single crystal X-ray crystallography. The crystal structures of the discrete mononuclear monoanionic complexes show FeN2O4 octahedral coordination geometry in which the tridentate dianionic amino acid Schiff base ligand binds through phenolate and carboxylate oxygen and imine nitrogen atoms. The imine nitrogen atoms are trans to each other. The Fe-O and Fe-N bond distances range between 1.9 and 2.1 Å. The sal-met complex has two pendant thiomethyl groups. The high-spin iron(III) complexes ( Normal 0 false false false MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} μeff ~ 5.9 Normal 0 false false false MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} μB) exhibit quasi-reversible Fe(III)/Fe(II) redox process near -0.6 V vs. SCE in water. These complexes display a visible electronic band near 480 nm in tris-HCl buffer assignable to the phenolate-to-iron(III) charge transfer transition. The water soluble complexes bind to BSA giving binding constant values of ~105 M-1. The complexes show non-specific oxidative cleavage of BSA protein on photo-irradiation with UV-A light of 365 nm