Abstract The role of metalloenzymes in important biological transformations has attracted increasing attention over the past several decades. Of many chemical mediated by enzymes, few are as challenging multielectron redox reactions. Recent studies have revealed a partial structural and mechanistic description these redox‐active metalloenzymes, but there is much still to be learned regarding mechanisms substrate transformation. Due complexity metalloenzyme systems, simplified model systems...

Reported are quantitative studies of the energy transfer from water-soluble CdSe/ZnS and CdSeS/ZnS core/shell quantum dots (QDs) to Cr(III) complexes trans-Cr(N(4))(X)(2)(+) (N(4) is a tetraazamacrocycle ligand, X(-) CN(-), Cl(-), or ONO(-)) in aqueous solution. Variation N(4), X(-), QD size composition allows one probe relationship between emission/absorption overlap integral parameter efficiency quenching photoluminescence (PL) by chromium(III) complexes. Steady-state PL presence different...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHydride transfer and dihydrogen elimination from osmium ruthenium metalloporphyrin hydrides: model processes for hydrogenase enzymes the hydrogen electrode reactionJames P. Collman, Paul S. Wagenknecht, Nathan LewisCite this: J. Am. Chem. Soc. 1992, 114, 14, 5665–5673Publication Date (Print):July 1, 1992Publication History Published online1 May 2002Published inissue 1 July...

The nicotinamide coenzymes consumed in alcohol dehydrogenase catalyzed enantioselective reduction of ketones are expensive and thus require recycling. We have demonstrated that ruthenium(II) rhodium(III) complexes effective catalysts for the with hydrogen, under conditions appropriate situ coupling enzymatic reductions.

Abstract Die Rolle von Metalloenzymen in wichtigen biologischen Prozessen hat den letzten Jahrzehnten zunehmend Beachtung gefunden. Von vielen chemischen Reaktionen, die durch Enzyme gesteuert werden, sind nur wenige eine so große Herausforderung wie Mehrelektronen‐Redoxreaktionen. In neueren Untersuchungen ist es gelungen, einige strukturelle und mechanistische Merkmale derartig redoxaktiver Metalloenzyme aufzuklären, doch im Hinblick auf Mechanismus der Substratumwandlung tappt man...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAn unprecedented, bridged dihydrogen complex of a cofacial metallodiporphyrin and its relevance to the bimolecular reductive elimination hydrogenJames P. Collman, James E. Hutchison, Paul S. Wagenknecht, Nathan Lewis, Michel Angel Lopez, Roger GuilardCite this: J. Am. Chem. Soc. 1990, 112, 22, 8206–8208Publication Date (Print):October 1, 1990Publication History Published online1 May 2002Published inissue 1 October...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCofacial bisorganometallic diporphyrins: synthetic control in proton reduction catalysisJames P. Collman, Yunkyoung Ha, Paul S. Wagenknecht, Michel Angel Lopez, and Roger GuilardCite this: J. Am. Chem. Soc. 1993, 115, 20, 9080–9088Publication Date (Print):October 1, 1993Publication History Published online1 May 2002Published inissue 1 October 1993https://pubs.acs.org/doi/10.1021/ja00073a025https://doi.org/10.1021/ja00073a025research-articleACS...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDihydrogen complexes of metalloporphyrins: characterization and catalytic hydrogen oxidation activityJames P. Collman, Paul S. Wagenknecht, James E. Hutchison, Nathan Lewis, Michel Angel Lopez, Roger Guilard, Maurice L'Her, Aksel A. Bothner-By, K. MishraCite this: J. Am. Chem. Soc. 1992, 114, 14, 5654–5664Publication Date (Print):July 1, 1992Publication History Published online1 May 2002Published inissue 1 July...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDihydrogen complexes of metalloporphyrins: characterization and hydrogen-transfer reactivityJames P. Collman, Paul S. Wagenknecht, Robert T. Hembre, Nathan LewisCite this: J. Am. Chem. Soc. 1990, 112, 3, 1294–1295Publication Date (Print):January 1, 1990Publication History Published online1 May 2002Published inissue 1 January 1990https://doi.org/10.1021/ja00159a087RIGHTS & PERMISSIONSArticle Views270Altmetric-Citations44LEARN ABOUT THESE...

Abstract Reported herein are the preparation and characterization of trans ‐[Cr(cyclam)(X‐ gem ‐DEE) 2 ]OTf compounds ( ‐DEE = σ‐ geminal ‐diethynylethene, OTf trifluoromethanesulfonate) 1 , which first examples 3d metal complexes containing ligands. All reported were characterized by visible, emission, infrared spectroscopy, electrochemistry (CV DPV), high‐resolution mass spectrometry, compound was further studied single‐crystal X‐ray diffraction. Both photophyiscal data structural indicate...

Alkynyl complexes of the type [M(cyclam)(CCR)(2)]OTf (where cyclam = 1,4,8,11-tetraazacyclotetradecane; M Rh(III) or Cr(III); and R phenyl, 4-methylphenyl, 4-trifluoromethylphenyl, 4-fluorophenyl, 1-naphthalenyl, 9-phenanthrenyl, cyclohexyl) were prepared in 49% to 93% yield using a one-pot synthesis involving addition 2 equiv RCCH 4 BuLi appropriate [M(cyclam)(OTf)(2)]OTf complex THF. The cis trans isomers alkynyl separated solubility differences, stereochemistry was characterized infrared...

Iron(II)-to-titanium(IV) metal-to-metal-charge transfer (MMCT) is important in the photosensitization of TiO2 by ferrocyanide, charge solid-state metal-oxide photocatalysts, and has been invoked to explain blue color sapphire, kyanite, some lunar material. Herein, a series complexes with alkynyl linkages between ferrocene (Fc) TiIV prepared characterized UV–vis spectroscopy electrochemistry. Complexes two substituents include Cp2Ti(C2Fc)2, Cp*2Ti(C2Fc)2, Cp2Ti(C4Fc)2. single utilize...

Complexes with ligand-to-metal charge-transfer (LMCT) excited states involving d0 metals represent a new design for photocatalysts. Herein, the photochemistry and photophysics of titanocenes type Cp2Ti(C2R)2, where C2R = ethynylphenyl (C2Ph), 4-ethynyldimethylaniline (C2DMA), or 4-ethynyltriphenylamine (C2TPA), have been investigated. Cp2Ti(C2Ph)2 Cp2Ti(C2DMA)2 also characterized by single-crystal X-ray diffraction. The two aryl rings in are nearly face-to-face solid state, whereas they...

Arylethynylchromium(III) complexes of the form trans-[Cr(cyclam)(CCC(6)H(4)R)(2)]OTf (where cyclam = 1,4,8,11-tetraazacyclotetradecane, R H, CH(3), or CF(3) in para position, and OTf trifluoromethanesulfonate) have been prepared characterized by IR spectroscopy X-ray diffraction. The are emissive with excited-state lifetimes a deoxygenated fluid solution between 200 300 micros.

Transition-metal complexes that undergo ligand-to-metal charge transfer (LMCT) to d0 metals are of interest as possible photocatalysts due the lack deactivating d-d states. Herein, synthesis and characterization nine titanocene formula Cp2Ti(C2Ar)2·MX (where Ar = phenyl, dimethylaniline, or triphenylamine; MX CuCl, CuBr, AgCl) presented. Solid-state structural demonstrates coordinates alkyne tweezers CuX coordination has a greater impact than AgCl. All complexes, including parent without...

The trifluoropropynyl ligand -C≡CCF(3) was studied as a possible surrogate for the cyano ligand. Complexes of type trans-[M(cyclam)(C≡CCF(3))(2)]OTf (where M = Cr(3+), Co(3+), and Rh(3+); OTf trifluoromethanesulfonate) were prepared then characterized by electronic spectroscopy cyclic voltammetry Co(3+) complex. UV-vis spectra all three bear remarkable similarity to that trans-M(cyclam)(CN)(2)(+) cations. complex shows electrochemical behavior nearly identical with its dicyano analogue....

Square-planar PtII complexes are of interest as dopants for the emissive layer organic light-emitting diodes. Herein, photophysics three Pt bipyridyl with strongly e- withdrawing, high-field, 3,3,3-trifluoropropynyl ligand has been investigated. One complex, (phbpy)PtC2CF3 (phbpy = 6-phenyl-2,2'-dipyridyl), also characterized by single-crystal X-ray diffraction. All reported in both RT CH2Cl2 solution (ΦPL 0.007 to 0.027) and PMMA film 0.25 0.42). The trifluoropropynyl elevates energy MLCT...

The synthesis and characterization of several Cr(III) complexes the constrained macrocyclic ligand 1,4-C(2)-cyclam = 1,4,8,11-tetraazabicyclo[10.2.2]hexadecane is reported. appears to form only trans complexes, structure trans-[Cr(1,4-C(2)-cyclam)Cl(2)]PF(6) presented. constraint imposed by additional C(2) linkage distorts bond angles significantly away from ideal values 90 180 degrees. effect distortion enhance aquation rate trans-[Cr(1,4-C(2)-cyclam)Cl(2)](+) (k(obs) for...

The Ru(2) and RuNi derivatives of 1,8-bis(10,15,20-trimesityl-5-porphyrinato)anthracene-a recently reported cofacial diporphyrin ligand comprising two hindered porphyrins spanned by an anthracene bridge-have been synthesized. Both Ru(2)(DPAHM) RuNi(DPAHM) are extremely reactive species that apparently contain 14-electron Ru(II) centers and, as is the case for their monoporphyrin analog, (5,10,15,20-tetramesitylporphyrinato)ruthenium [Ru(TMP)], must be rigorously protected from oxygen,...

Complexes that undergo ligand-to-metal charge transfer (LMCT) to d0 metals are of interest as possible photocatalysts. Cp2Ti(C2Ph)2 (where C2Ph = phenylethynyl) was reported be weakly emissive in room-temperature (RT) fluid solution from its phenylethynyl-to-Ti 3LMCT state but readily photodecomposes. Coordination CuX between the alkyne ligands give Cp2Ti(C2Ph)2CuX (X Cl, Br) has been shown significantly increase photostability, such complexes not RT solution. Herein, we investigate whether...

The luminescent properties of Au(I) and Pt(II) compounds are commonly tuned by exploiting the alkynyl ligand with varying electron density. Herein, we describe synthesis three new emissive transition metal compounds, tbpyPt(C2pym)2, Ph3PAuC2pym, Cy3PAuC2pym (where HC2pym = 2-ethynylpyrimidine), verified 1H-NMR, EA, a single-crystal X-ray diffraction analysis. tbpyPt(C2pym)2 complex crystallized as an Et2O solvate in orthorhombic space group Pbca Z 24 unique species within unit cell....