1
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Caliskanyürek V, Eulberg S, Lange O, Bröring M, Tschierlei S. Sb(V) dihalide corroles: efficient singlet oxygen photosensitisers. Chem Commun (Camb) 2024; 60:4096-4099. [PMID: 38512705 DOI: 10.1039/d4cc00675e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2024]
Abstract
Sb(V) dihalide corrole complexes, in particular difluoro-5,15-di(4-cyanophenyl)-10-(2,4,5-trimethoxyphenyl)corrolatoantimony(V) (complex 1), show distinct emission properties and efficient intersystem crossing rates. Furthermore, complex 1 is characterised by its extended triplet excited state lifetime and an impressive singlet oxygen quantum yield exceeding 95%. This emphasises its potential for effective photooxidation reactions, positioning it as a leader in Sb(V) complex applications.
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Affiliation(s)
- Volkan Caliskanyürek
- Department of Energy Conversion, Institute of Physical and Theoretical Chemistry, Technische Universität Braunschweig, Rebenring 31, 38106, Braunschweig, Germany.
| | - Simon Eulberg
- Institute of Inorganic and Analytical Chemistry, Technische Universität Braunschweig, Hagenring 30, 38106, Braunschweig, Germany.
| | - Oliver Lange
- Department of Energy Conversion, Institute of Physical and Theoretical Chemistry, Technische Universität Braunschweig, Rebenring 31, 38106, Braunschweig, Germany.
| | - Martin Bröring
- Institute of Inorganic and Analytical Chemistry, Technische Universität Braunschweig, Hagenring 30, 38106, Braunschweig, Germany.
| | - Stefanie Tschierlei
- Department of Energy Conversion, Institute of Physical and Theoretical Chemistry, Technische Universität Braunschweig, Rebenring 31, 38106, Braunschweig, Germany.
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2
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Lemon CM, Powers DC, Huynh M, Maher AG, Phillips AA, Tripet BP, Nocera DG. Ag(III)···Ag(III) Argentophilic Interaction in a Cofacial Corrole Dyad. Inorg Chem 2023; 62:3-17. [PMID: 36538590 DOI: 10.1021/acs.inorgchem.2c02285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Metallophilic interactions between closed-shell metal centers are exemplified by d10 ions, with Au(I) aurophilic interactions as the archetype. Such an interaction extends to d8 species, and examples involving Au(III) are prevalent. Conversely, Ag(III) argentophilic interactions are uncommon. Here, we identify argentophilic interactions in silver corroles, which are authentic Ag(III) species. The crystal structure of a monomeric silver corrole is a dimer in the solid state, and the macrocycle exhibits an atypical domed conformation. In order to evaluate whether this represents an authentic metallophilic interaction or a crystal-packing artifact, the analogous cofacial or "pacman" corrole was prepared. The conformation of the monomer was recapitulated in the silver pacman corrole, exhibiting a short 3.67 Å distance between metal centers and a significant compression of the xanthene backbone. Theoretical calculations support the presence of a rare Ag(III)···Ag(III) argentophilic interaction in the pacman complex.
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Affiliation(s)
- Christopher M Lemon
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States.,Department of Chemistry and Biochemistry, Montana State University (MSU), P.O. Box 173400, Bozeman, Montana 59717, United States
| | - David C Powers
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Michael Huynh
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Andrew G Maher
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Austin A Phillips
- Department of Chemistry and Biochemistry, Montana State University (MSU), P.O. Box 173400, Bozeman, Montana 59717, United States
| | - Brian P Tripet
- Department of Chemistry and Biochemistry, Montana State University (MSU), P.O. Box 173400, Bozeman, Montana 59717, United States
| | - Daniel G Nocera
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
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3
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Navrátilová T, Tatar A, Havlík M, Hajduch J, Drozdová M, Gurung K, Palatinus L, Čejka J, Sedláček J, Anzenbacher P, Dolenský B. Preparation and Characterization of Metalloporphyrin Tröger’s and Spiro-Tröger’s Base Derivatives. J Org Chem 2022; 87:15178-15186. [DOI: 10.1021/acs.joc.2c01716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Tereza Navrátilová
- Department of Analytical Chemistry, University of Chemistry and Technology, Prague, 166 28 Prague 6, Czech Republic
| | - Ameneh Tatar
- Department of Analytical Chemistry, University of Chemistry and Technology, Prague, 166 28 Prague 6, Czech Republic
| | - Martin Havlík
- Department of Analytical Chemistry, University of Chemistry and Technology, Prague, 166 28 Prague 6, Czech Republic
| | - Jan Hajduch
- Department of Analytical Chemistry, University of Chemistry and Technology, Prague, 166 28 Prague 6, Czech Republic
| | - Michaela Drozdová
- Department of Analytical Chemistry, University of Chemistry and Technology, Prague, 166 28 Prague 6, Czech Republic
| | - Kshitij Gurung
- Institute of Physics of the Czech Academy of Sciences, 182 21 Prague 8, Czech Republic
| | - Lukáš Palatinus
- Institute of Physics of the Czech Academy of Sciences, 182 21 Prague 8, Czech Republic
| | - Jan Čejka
- Department of Solid State Chemistry, University of Chemistry and Technology, Prague, 166 28 Prague 6, Czech Republic
| | - Jakub Sedláček
- Department of Analytical Chemistry, University of Chemistry and Technology, Prague, 166 28 Prague 6, Czech Republic
| | - Pavel Anzenbacher
- Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, United States
| | - Bohumil Dolenský
- Department of Analytical Chemistry, University of Chemistry and Technology, Prague, 166 28 Prague 6, Czech Republic
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4
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Lemon CM, Maher AG, Mazzotti AR, Powers DC, Gonzalez MI, Nocera DG. Multielectron C–H photoactivation with an Sb(v) oxo corrole. Chem Commun (Camb) 2020; 56:5247-5250. [DOI: 10.1039/c9cc09892e] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
An Sb(v) bis-μ-oxo corrole dimer performs photochemical multielectron C–H activation, oxidising toluene to benzaldehyde in a four-electron process.
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Affiliation(s)
| | - Andrew G. Maher
- Department of Chemistry and Chemical Biology
- Harvard University
- Cambridge
- USA
| | | | - David C. Powers
- Department of Chemistry and Chemical Biology
- Harvard University
- Cambridge
- USA
| | - Miguel I. Gonzalez
- Department of Chemistry and Chemical Biology
- Harvard University
- Cambridge
- USA
| | - Daniel G. Nocera
- Department of Chemistry and Chemical Biology
- Harvard University
- Cambridge
- USA
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5
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Lemon CM, Hwang SJ, Maher AG, Powers DC, Nocera DG. Halogen Photoelimination from SbV Dihalide Corroles. Inorg Chem 2018; 57:5333-5342. [DOI: 10.1021/acs.inorgchem.8b00314] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Christopher M. Lemon
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Seung Jun Hwang
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Andrew G. Maher
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - David C. Powers
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Daniel G. Nocera
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
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6
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Lemon CM, Karnas E, Han X, Bruns OT, Kempa TJ, Fukumura D, Bawendi MG, Jain RK, Duda DG, Nocera DG. Micelle-Encapsulated Quantum Dot-Porphyrin Assemblies as in Vivo Two-Photon Oxygen Sensors. J Am Chem Soc 2015; 137:9832-42. [PMID: 26149349 DOI: 10.1021/jacs.5b04765] [Citation(s) in RCA: 90] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Micelles have been employed to encapsulate the supramolecular assembly of quantum dots with palladium(II) porphyrins for the quantification of O2 levels in aqueous media and in vivo. Förster resonance energy transfer from the quantum dot (QD) to the palladium porphyrin provides a means for signal transduction under both one- and two-photon excitation. The palladium porphyrins are sensitive to O2 concentrations in the range of 0-160 Torr. The micelle-encapsulated QD-porphyrin assemblies have been employed for in vivo multiphoton imaging and lifetime-based oxygen measurements in mice with chronic dorsal skinfold chambers or cranial windows. Our results establish the utility of the QD-micelle approach for in vivo biological sensing applications.
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Affiliation(s)
- Christopher M Lemon
- †Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States.,‡Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Elizabeth Karnas
- ‡Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Xiaoxing Han
- §Edwin L. Steele Laboratory for Tumor Biology, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, 100 Blossom Street, Cox-7, Boston, Massachusetts 02114, United States
| | - Oliver T Bruns
- ‡Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Thomas J Kempa
- †Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Dai Fukumura
- §Edwin L. Steele Laboratory for Tumor Biology, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, 100 Blossom Street, Cox-7, Boston, Massachusetts 02114, United States
| | - Moungi G Bawendi
- ‡Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Rakesh K Jain
- §Edwin L. Steele Laboratory for Tumor Biology, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, 100 Blossom Street, Cox-7, Boston, Massachusetts 02114, United States
| | - Dan G Duda
- §Edwin L. Steele Laboratory for Tumor Biology, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, 100 Blossom Street, Cox-7, Boston, Massachusetts 02114, United States
| | - Daniel G Nocera
- †Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
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7
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Lemon CM, Halbach RL, Huynh M, Nocera DG. Photophysical Properties of β-Substituted Free-Base Corroles. Inorg Chem 2015; 54:2713-25. [DOI: 10.1021/ic502860g] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Christopher M. Lemon
- Department
of Chemistry and Chemical Biology, Harvard University, 12 Oxford
Street, Cambridge, Massachusetts 02138, United States
| | - Robert L. Halbach
- Department
of Chemistry and Chemical Biology, Harvard University, 12 Oxford
Street, Cambridge, Massachusetts 02138, United States
| | - Michael Huynh
- Department
of Chemistry and Chemical Biology, Harvard University, 12 Oxford
Street, Cambridge, Massachusetts 02138, United States
| | - Daniel G. Nocera
- Department
of Chemistry and Chemical Biology, Harvard University, 12 Oxford
Street, Cambridge, Massachusetts 02138, United States
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8
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Anderson BL, Maher AG, Nava M, Lopez N, Cummins CC, Nocera DG. Ultrafast Photoinduced Electron Transfer from Peroxide Dianion. J Phys Chem B 2015; 119:7422-9. [PMID: 25635708 DOI: 10.1021/jp5110505] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The encapsulation of peroxide dianion by hexacarboxamide cryptand provides a platform for the study of electron transfer of isolated peroxide anion. Photoinitiated electron transfer (ET) between freely diffusing Ru(bpy)3(2+) and the peroxide dianion occurs with a rate constant of 2.0 × 10(10) M(-1) s(-1). A competing electron transfer quenching pathway is observed within an ion pair. Picosecond transient spectroscopy furnishes a rate constant of 1.1 × 10(10) s(-1) for this first-order process. A driving force dependence for the ET rate within the ion pair using a series of Ru(bpy)3(2+) derivatives allows for the electronic coupling and reorganization energies to be assessed. The ET reaction is nonadiabatic and dominated by a large inner-sphere reorganization energy, in accordance with that expected for the change in bond distance accompanying the conversion of peroxide dianion to superoxide anion.
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Affiliation(s)
- Bryce L Anderson
- †Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138-2902, United States
| | - Andrew G Maher
- †Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138-2902, United States.,‡Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, United States
| | - Matthew Nava
- ‡Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, United States
| | - Nazario Lopez
- ‡Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, United States
| | - Christopher C Cummins
- ‡Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, United States
| | - Daniel G Nocera
- †Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138-2902, United States
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9
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Lemon CM, Nocera DG. Comparison of self-assembled and micelle encapsulated QD chemosensor constructs for biological sensing. Faraday Discuss 2015; 185:249-66. [DOI: 10.1039/c5fd00093a] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Whereas a variety of covalent conjugation strategies have been utilized to prepare quantum dot (QD)-based nanosensors, supramolecular approaches of self-assembly have been underexplored. A major advantage of self-assembly is the ability to circumvent laborious synthetic efforts attendant to covalent conjugation of a chemosensor to functionalized QDs. Here, we combine a CdSe/ZnS core–shell QD with gold(iii) corroles using both self-assembly and micelle encapsulation to form QD nanosensors. Appreciable spectral overlap between QD emission and corrole absorption results in efficient Förster resonance energy transfer (FRET), which may be initiated by one- or two-photon excitation. The triplet state of the gold(iii) corroles is quenched by molecular oxygen, enabling these constructs to function as optical O2 sensors, which is useful for the metabolic profiling of tumours. The photophysical properties, including QD and corrole lifetimes, FRET efficiency, and O2 sensitivity, have been determined for each construct. The relative merits of each conjugation strategy are assessed with regard to their implementation as sensors.
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Affiliation(s)
| | - Daniel G. Nocera
- Department of Chemistry and Chemical Biology
- Harvard University
- Cambridge
- USA
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10
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Haack P, Kärgel A, Greco C, Dokic J, Braun B, Pfaff FF, Mebs S, Ray K, Limberg C. Access to a Cu(II)-O-Cu(II) motif: spectroscopic properties, solution structure, and reactivity. J Am Chem Soc 2013; 135:16148-60. [PMID: 24134722 PMCID: PMC3946511 DOI: 10.1021/ja406721a] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
We report a complex with a rare Cu(II)-O-Cu(II) structural motif that is stable at room temperature, which allows its in-depth characterization by a variety of spectroscopic methods. Interest in such compounds is fueled by the recent discovery that a Cu(II)-O-Cu(II) species on the surface of Cu-ZSM-5 is capable of oxidizing methane to methanol, and this in turn ties into mechanistic discussions on the methane oxidation at the dicopper site within the particulate methane monooxygenase. For the synthesis of our Cu2O complex we have developed a novel, neutral ligand system, FurNeu, exhibiting two N-(N',N'-dimethylaminoethyl)(2-pyridylmethyl)amino binding pockets connected by a dibenzofuran spacer. The reaction of FurNeu with CuCl yielded [FurNeu](Cu2(μ-Cl))(CuCl2), 1, demonstrating the geometric potential of the ligand to stabilize Cu-X-Cu moieties. A Cu(I) precursor with weakly coordinating anions was chosen in the next step, namely [Cu(NCCH3)4]OTf, which led to the formation of [FurNeu](Cu(NCCH3))2(OTf)2, 3. Treatment of 3 with O2 or PhIO led to identical green solutions, whose UV-vis spectra were markedly different from the one displayed by [FurNeu](Cu)2(OTf)4, 4, prepared independently from FurNeu and Cu(OTf)2. Further investigations including PhIO consumption experiments, NMR and UV-vis spectroscopy, HR-ESI mass spectrometry, and protonation studies led to the identification of the green product as [FurNeu](Cu2(μ-O))(OTf)2, 5. DOSY NMR spectroscopy confirmed its monomeric character. Over longer periods of time 5 decomposes to give [Cu(picoloyl)2], formed through an oxidative N-dealkylation reaction followed by further oxidation of the ligand. Due to its slow decomposition reaction, all attempts to crystallize 5 failed. However, its structure in solution could be determined by EXAFS analysis in combination with DFT calculations, which revealed a Cu-O-Cu angle that amounts to 105.17°. Moreover, TDDFT calculations helped to rationalize the UV-vis absorptions of 5. The reactivity of complex 5 with 2,4-di-tert-butylphenol, DTBP, was also investigated; the initially formed biphenol product, TBBP, was found to further react in the presence of excessive O2 to yield 2,4,7,9-tetra-tert-butyloxepino[2,3-b]benzofuran, TBOBF, via an intermediate diphenoquinone. It turned out that 5, or its precursor 3, can even be employed as a catalyst for the oxidation of DTBP to TBBP or for the oxidation of TBBP to TBOBF.
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Affiliation(s)
- Peter Haack
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Str. 2, 12489 Berlin, Germany
| | - Anne Kärgel
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Str. 2, 12489 Berlin, Germany
| | - Claudio Greco
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Str. 2, 12489 Berlin, Germany
| | | | - Beatrice Braun
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Str. 2, 12489 Berlin, Germany
| | - Florian F. Pfaff
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Str. 2, 12489 Berlin, Germany
| | - Stefan Mebs
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Str. 2, 12489 Berlin, Germany
| | - Kallol Ray
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Str. 2, 12489 Berlin, Germany
| | - Christian Limberg
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Str. 2, 12489 Berlin, Germany
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11
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Lemon CM, Karnas E, Bawendi MG, Nocera DG. Two-photon oxygen sensing with quantum dot-porphyrin conjugates. Inorg Chem 2013; 52:10394-406. [PMID: 23978247 PMCID: PMC3881537 DOI: 10.1021/ic4011168] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Supramolecular assemblies of a quantum dot (QD) associated to palladium(II) porphyrins have been developed to detect oxygen (pO2) in organic solvents. Palladium porphyrins are sensitive in the 0-160 Torr range, making them ideal phosphors for in vivo biological oxygen quantification. Porphyrins with meso pyridyl substituents bind to the surface of the QD to produce self-assembled nanosensors. Appreciable overlap between QD emission and porphyrin absorption features results in efficient Förster resonance energy transfer (FRET) for signal transduction in these sensors. The QD serves as a photon antenna, enhancing porphyrin emission under both one- and two-photon excitation, demonstrating that QD-palladium porphyrin conjugates may be used for oxygen sensing over physiological oxygen ranges.
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Affiliation(s)
- Christopher M Lemon
- Department of Chemistry, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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12
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Symes MD, Lutterman DA, Teets TS, Anderson BL, Breen JJ, Nocera DG. Photo-active cobalt cubane model of an oxygen-evolving catalyst. CHEMSUSCHEM 2013; 6:65-69. [PMID: 23288784 DOI: 10.1002/cssc.201200682] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Indexed: 06/01/2023]
Abstract
A dyad complex has been constructed as a soluble molecular model of a heterogeneous cobalt-based oxygen-evolving catalyst (Co-OEC). To this end, the Co(4)O(4) core of a cobalt-oxo cubane was covalently appended to Re(I) photosensitisers. The resulting adduct was characterised both in the solid state (by X-ray diffraction) and in solution using a variety of techniques. In particular, the covalent attachment of the Re(I) moieties to the Co(4)O(4) core promotes emission quenching of the Re(I) photocentres, with implications for the energy and electron transduction process of Co-OEC-like catalysts.
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Affiliation(s)
- Mark D Symes
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
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13
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Tatar A, Dolenský B, Dvořáková H, Král V. Selective formation of either Tröger’s base or spiro Tröger’s base derivatives from [2-aminoporphyrinato(2-)]nickel by choice of reaction conditions. Tetrahedron Lett 2012. [DOI: 10.1016/j.tetlet.2012.08.097] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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14
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Yan L, Chen X, He Q, Wang Y, Wang X, Guo Q, Bai F, Xia A, Aumiler D, Vdović S, Lin S. Localized Emitting State and Energy Transfer Properties of Quadrupolar Chromophores and (Multi)Branched Derivatives. J Phys Chem A 2012; 116:8693-705. [DOI: 10.1021/jp305407s] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Linyin Yan
- The State
Key Laboratory of Molecular Reaction Dynamics,
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- Beijing National
Laboratory for Molecular Sciences
(BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
| | - Xudong Chen
- The State
Key Laboratory of Molecular Reaction Dynamics,
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- Beijing National
Laboratory for Molecular Sciences
(BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
| | - Qingguo He
- The State
Key Laboratory of Molecular Reaction Dynamics,
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- Beijing National
Laboratory for Molecular Sciences
(BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
| | - Yingying Wang
- The State
Key Laboratory of Molecular Reaction Dynamics,
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- Beijing National
Laboratory for Molecular Sciences
(BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
| | - Xuefei Wang
- The State
Key Laboratory of Molecular Reaction Dynamics,
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- Beijing National
Laboratory for Molecular Sciences
(BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
| | - Qianjin Guo
- The State
Key Laboratory of Molecular Reaction Dynamics,
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- Beijing National
Laboratory for Molecular Sciences
(BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
| | - Fenglian Bai
- The State
Key Laboratory of Molecular Reaction Dynamics,
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- Beijing National
Laboratory for Molecular Sciences
(BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
| | - Andong Xia
- The State
Key Laboratory of Molecular Reaction Dynamics,
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- Beijing National
Laboratory for Molecular Sciences
(BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
| | - Damir Aumiler
- The
State Key Laboratory of Molecular Reaction Dynamics,
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- Institute of Physics, Bijenička
cesta 46, 10000 Zagreb, Croatia
| | - Silvije Vdović
- The
State Key Laboratory of Molecular Reaction Dynamics,
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- Institute of Physics, Bijenička
cesta 46, 10000 Zagreb, Croatia
| | - ShengHien Lin
- Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan 30010, China
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15
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Cook TR, McCarthy BD, Lutterman DA, Nocera DG. Halogen Oxidation and Halogen Photoelimination Chemistry of a Platinum–Rhodium Heterobimetallic Core. Inorg Chem 2012; 51:5152-63. [DOI: 10.1021/ic300004x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Timothy R. Cook
- Department of Chemistry, 6-335, Massachusetts Institute of Technology, 77 Massachusetts
Avenue, Cambridge, Massachusetts 02139-4307, United States
| | - Brian D. McCarthy
- Department of Chemistry, 6-335, Massachusetts Institute of Technology, 77 Massachusetts
Avenue, Cambridge, Massachusetts 02139-4307, United States
| | - Daniel A. Lutterman
- Department of Chemistry, 6-335, Massachusetts Institute of Technology, 77 Massachusetts
Avenue, Cambridge, Massachusetts 02139-4307, United States
| | - Daniel G. Nocera
- Department of Chemistry, 6-335, Massachusetts Institute of Technology, 77 Massachusetts
Avenue, Cambridge, Massachusetts 02139-4307, United States
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16
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Young ER, Rosenthal J, Nocera DG. Energy transfer mediated by asymmetric hydrogen-bonded interfaces. Chem Sci 2012; 3:10.1039/C1SC00596K. [PMID: 24363889 PMCID: PMC3868475 DOI: 10.1039/c1sc00596k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Amidine-appended ferrocene derivatives form a supramolecular assembly with Ru(ii)(bpy-COOH) (L)22+ complexes (bpy-COOH is 4-CO2H-4'-CH3-bpy and L = bpy, 2,2'-bipyridine or btfmbpy, 4,4'-bis (trifluoromethyl)-2,2'-bipyridine). Steady-state, time-resolved spectroscopy and kinetic isotope effects establish that the metal-to-ligand charge transfer excited states of the Ru(ii) complexes are quenched by proton-coupled energy transfer (PCEnT). These results show that proton motion can be effective in mediating not only electron transfer (ET) but energy transfer (EnT) as well.
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Affiliation(s)
- Elizabeth R Young
- Department of Chemistry, Amherst College, P.O. Box 5000, Amherst, MA, 01002-5000, USA
| | - Joel Rosenthal
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, 19716, USA
| | - Daniel G Nocera
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139-4307, USA. ; Tel: +1 617 253 5537
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Gros CP, Mohammed Aly S, El Ojaimi M, Barbe JM, Brisach F, Abd-El-Aziz AS, Guilard R, Harvey PD. Through space singlet-singlet and triplet-triplet energy transfers in cofacial bisporphyrins held by the carbazoyl spacer. J PORPHYR PHTHALOCYA 2012. [DOI: 10.1142/s1088424607000308] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The through space singlet-singlet and triplet-triplet energy transfers in cofacial bis(etio-porphyrins) rigidly held by the carbazoyl spacer were investigated. The studies on singlet-singlet transfer, which operates via a Förster mechanism, were performed using the zinc porphyrin and free base chromophores as energy donor and acceptor, respectively, while the investigation on triplet-triplet processes was performed using the palladium porphyrin, and the zinc porphyrin and free base chromophores as donor and acceptors, respectively. The rate for singlet-singlet transfer ( k ET ( singlet )) is unexpectedly slower than that reported for other similar, rigidly held bisporphyrins such as H 2( DPO ) Zn ( DPO = 4,6- bis [5-(2,8,13,17- tetraethyl -3,7,12,18- tetramethylporphyrinyl )] dibenzofuran ) and H 2( DPS ) Zn ( DPS = 4,6- bis [5-(2,8,13,17- tetraethyl -3,7,12,18- tetramethyl - porphyrinyl )] dibenzothiophene )). This slower rate is interpreted by the presence of the H -atom exactly located between the two meso-carbons in the dyads. The rates for triplet-triplet transfer are also slow but not too different from that recently reported for H 2( DPX ) Pd ( DPX = 4,5- bis [5-(2,8,13,17- tetraethyl -3,7,12,18- tetramethylporphyrinyl )]-9,9- dimethylxanthene ) and H 2( DPB ) Pd ( DPB = 1,8- bis [5-(2,8,13,17- tetraethyl -3,7,12,18- tetramethylporphyrinyl )] biphenylene ) at 77 K. In such cases, the slow rate is interpreted by a through space energy transfer pathway which operates according to a (small range) Dexter mechanism (since the Förster mechanism is inoperative for triplet-triplet processes). The k ET (triplet) increases at 298 K which is tentatively interpreted by favorable excited state distortions in the triplet state and fluxion processes which ease intramolecular transfers for these dyads in fluid solution in comparison with former glassy matrices.
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Affiliation(s)
- Claude P. Gros
- Contribution from the Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB, UMR 5260), Université de Bourgogne, 9 avenue A. Savary, 21078 Dijon, France
| | - Shawkat Mohammed Aly
- Département de Chimie, Université de Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada
| | - Maya El Ojaimi
- Contribution from the Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB, UMR 5260), Université de Bourgogne, 9 avenue A. Savary, 21078 Dijon, France
| | - Jean-Michel Barbe
- Contribution from the Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB, UMR 5260), Université de Bourgogne, 9 avenue A. Savary, 21078 Dijon, France
| | - Frédéric Brisach
- Département de Chimie, Université de Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada
| | - Alaa S. Abd-El-Aziz
- Department of Chemistry, University of British Columbia Okanagan, 3333 University Way, Kelowna, British Columbia, Canada
| | - Roger Guilard
- Contribution from the Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB, UMR 5260), Université de Bourgogne, 9 avenue A. Savary, 21078 Dijon, France
| | - Pierre D. Harvey
- Département de Chimie, Université de Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada
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Constrained Digold(I) Diaryls: Syntheses, Crystal Structures, and Photophysics. Chemistry 2012; 18:2100-12. [DOI: 10.1002/chem.201101891] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Indexed: 11/07/2022]
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Pizano AA, Yang JL, Nocera DG. Photochemical Tyrosine Oxidation with a Hydrogen-Bonded Proton Acceptor by Bidirectional Proton-Coupled Electron Transfer. Chem Sci 2012; 3:2457-2461. [PMID: 23495362 DOI: 10.1039/c2sc20113e] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Amino acid radical generation and transport are fundamentally important to numerous essential biological processes to which small molecule models lend valuable mechanistic insights. Pyridyl-amino acid-methyl esters are appended to a rhenium(I) tricarbonyl 1,10-phenanthroline core to yield rhenium-amino acid complexes with tyrosine ([Re]-Y-OH) and phenylalanine ([Re]-F). The emission from the [Re] center is more significantly quenched for [Re]-Y-OH upon addition of base. Time-resolved studies establish that excited-state quenching occurs by a combination of static and dynamic mechanisms. The degree of quenching depends on the strength of the base, consistent with a proton-coupled electron transfer (PCET) quenching mechanism. Comparative studies of [Re]-Y-OH and [Re]-F enable a detailed mechanistic analysis of a bidirectional PCET process.
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Affiliation(s)
- Arturo A Pizano
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139-4307; Tel: 61d53 5537
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Photo-ribonucleotide reductase β2 by selective cysteine labeling with a radical phototrigger. Proc Natl Acad Sci U S A 2011; 109:39-43. [PMID: 22171005 DOI: 10.1073/pnas.1115778108] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Photochemical radical initiation is a powerful tool for studying radical initiation and transport in biology. Ribonucleotide reductases (RNRs), which catalyze the conversion of nucleotides to deoxynucleotides in all organisms, are an exemplar of radical mediated transformations in biology. Class Ia RNRs are composed of two subunits: α2 and β2. As a method to initiate radical formation photochemically within β2, a single surface-exposed cysteine of the β2 subunit of Escherichia coli Class Ia RNR has been labeled (98%) with a photooxidant ([Re ] = tricarbonyl(1,10-phenanthroline)(methylpyridyl)rhenium(I)). The labeling was achieved by incubation of S355C-β2 with the 4-(bromomethyl)pyridyl derivative of [Re] to yield the labeled species, [Re]-S355C-β2. Steady-state and time-resolved emission experiments reveal that the metal-to-ligand charge transfer (MLCT) excited-state (3)[Re ](∗) is not significantly perturbed after bioconjugation and is available as a phototrigger of tyrosine radical at position 356 in the β2 subunit; transient absorption spectroscopy reveals that the radical lives for microseconds. The work described herein provides a platform for photochemical radical initiation and study of proton-coupled electron transfer (PCET) in the β2 subunit of RNR, from which radical initiation and transport for this enzyme originates.
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Teets TS, Lutterman DA, Nocera DG. Halogen Photoreductive Elimination from Metal−Metal Bonded Iridium(II)−Gold(II) Heterobimetallic Complexes. Inorg Chem 2010; 49:3035-43. [DOI: 10.1021/ic902590u] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Thomas S. Teets
- Department of Chemistry, 6-335, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307
| | - Daniel A. Lutterman
- Department of Chemistry, 6-335, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307
| | - Daniel G. Nocera
- Department of Chemistry, 6-335, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307
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Gao L, Peay MA, Partyka DV, Updegraff JB, Teets TS, Esswein AJ, Zeller M, Hunter AD, Gray TG. Mono- and Di-Gold(I) Naphthalenes and Pyrenes: Syntheses, Crystal Structures, and Photophysics. Organometallics 2009. [DOI: 10.1021/om9005214] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Lei Gao
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106
| | - Miya A. Peay
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106
| | - David V. Partyka
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106
| | - James B. Updegraff
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106
| | - Thomas S. Teets
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Arthur J. Esswein
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Matthias Zeller
- Department of Chemistry, Youngstown State University, 1 University Plaza, Youngstown, Ohio 44555
| | - Allen D. Hunter
- Department of Chemistry, Youngstown State University, 1 University Plaza, Youngstown, Ohio 44555
| | - Thomas G. Gray
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106
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Young ER, Rosenthal J, Hodgkiss JM, Nocera DG. Comparative PCET study of a donor-acceptor pair linked by ionized and nonionized asymmetric hydrogen-bonded interfaces. J Am Chem Soc 2009; 131:7678-84. [PMID: 19489645 DOI: 10.1021/ja809777j] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
A Zn(II) amidinium porphyrin is the excited-state electron donor (D) to a naphthalene diimide acceptor (A) appended with either a carboxylate or sulfonate functionality. The two-point hydrogen bond (...[H(+)]...) formed between the amidinium and carboxylate or sulfonate functionalities establishes a proton-coupled electron transfer (PCET) pathway for charge transfer. The two D...[H(+)]...A assemblies differ only by the proton configuration within the hydrogen-bonding interface. Specifically, the amidinium ion transfers a proton to the carboxylate to form a nonionized amidine-carboxylic acid two-point hydrogen network, whereas the amidinium retains both protons when bound to the sulfonate functionality, forming an ionized amidinium-sulfonate two-point hydrogen bond network. These two interface configurations within the dyads thus allow for a direct comparison of the PCET kinetics for the same donor and acceptor juxtaposed by ionized and nonionized hydrogen-bonded interfaces. Analysis of the PCET kinetics ascertained from transient absorption and transient emission spectroscopy reveals that the ionized interface is more strongly impacted by the local solvent environment, thus establishing that the initial static configuration of the proton interface is a critical determinant in the kinetics of PCET.
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Affiliation(s)
- Elizabeth R Young
- Department of Chemistry, 6-335, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA
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Reece SY, Lutterman DA, Seyedsayamdost MR, Stubbe J, Nocera DG. Re(bpy)(CO)3CN as a probe of conformational flexibility in a photochemical ribonucleotide reductase. Biochemistry 2009; 48:5832-8. [PMID: 19402704 PMCID: PMC3340421 DOI: 10.1021/bi9005804] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Photochemical ribonucleotide reductases (photoRNRs) have been developed to study the proton-coupled electron transfer (PCET) mechanism of radical transport in Escherichia coli class I ribonucleotide reductase (RNR). The transport of the effective radical occurs along several conserved aromatic residues across two subunits: beta2((*)Y122 --> W48 --> Y356) --> alpha2(Y731 --> Y730 --> C439). The current model for RNR activity suggests that radical transport is strongly controlled by conformational gating. The C-terminal tail peptide (Y-betaC19) of beta2 is the binding determinant of beta2 to alpha2 and contains the redox active Y356 residue. A photoRNR has been generated synthetically by appending a Re(bpy)(CO)(3)CN ([Re]) photo-oxidant next to Y356 of the 20-mer peptide. Emission from the [Re] center dramatically increases upon peptide binding, serving as a probe for conformational dynamics and the protonation state of Y356. The diffusion coefficient of [Re]-Y-betaC19 has been measured (k(d1) = 6.1 x 10(-7) cm(-1) s(-1)), along with the dissociation rate constant for the [Re]-Y-betaC19-alpha2 complex (7000 s(-1) > k(off) > 400 s(-1)). Results from detailed time-resolved emission and absorption spectroscopy reveal biexponential kinetics, suggesting a large degree of conformational flexibility in the [Re]-Y-betaC19-alpha2 complex that engenders partitioning of the N-terminus of the peptide into both bound and solvent-exposed fractions.
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Affiliation(s)
- Steven Y Reece
- Department of Chemistry, Massachusetts Institute of Technology,77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA
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Love JB. A macrocyclic approach to transition metal and uranyl Pacman complexes. Chem Commun (Camb) 2009:3154-65. [DOI: 10.1039/b904189c] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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A porphyrin complex of gold(I): (phosphine)gold(I) azides as cation precursors. Proc Natl Acad Sci U S A 2008; 105:14293-7. [PMID: 18780788 DOI: 10.1073/pnas.0806520105] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A silver- and Brönsted acid-free protocol for generating the (tricyclohexylphosphine)gold(I) cation from the corresponding azide complexes is disclosed. The gold(I) cations so liberated are trapped by complexation with octaethylporphyrin. The first structurally authenticated gold(I) porphyrin complex crystallizes with formula C(72)H(112)Au(2)F(12)N(4)P(2)Sb(2), space group C2/c, a = 21.388 (4), b = 19.679 (4), c = 19.231 (3) A; beta = 111.030 (3) degrees. Solution spectroscopic studies indicate that the di-gold complex fragments on dissolution in organic solvents. Approximate density-functional theory calculations find an electrostatic origin for the binding of two gold(I) centers to the unprotonated nitrogen atoms, despite greater orbital density on the porphyrin meso carbons.
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Che C, Xiang H, Chui S, Xu Z, Roy V, Yan J, Fu W, Lai P, Williams I. A High‐Performance Organic Field‐Effect Transistor Based on Platinum(II) Porphyrin: Peripheral Substituents on Porphyrin Ligand Significantly Affect Film Structure and Charge Mobility. Chem Asian J 2008; 3:1092-103. [DOI: 10.1002/asia.200800011] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Rosenthal J, Nocera DG. Oxygen Activation Chemistry of Pacman and Hangman Porphyrin Architectures Based on Xanthene and Dibenzofuran Spacers. PROGRESS IN INORGANIC CHEMISTRY 2008. [DOI: 10.1002/9780470144428.ch7] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Abstract
The selective reduction of oxygen to water requires four electrons and four protons. The design of catalysts that promote oxygen reduction therefore requires the management of both electron and proton inventories. Pacman and Hangman porphyrins provide a cleft for oxygen binding, a redox shuttle for oxygen reduction, and functionality for tuning the acid-base properties of bound oxygen and its intermediates. With proper control of the proton-coupled electron transfer events, O-O bond breaking of oxygen, and more generally oxygenated substrates, may be achieved with high efficiencies. The rule set developed for oxygen reduction may be applied to a variety of other small molecule activation reactions of consequence to energy conversion.
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Affiliation(s)
- Joel Rosenthal
- Department of Chemistry, 6-335, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA
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Reece SY, Seyedsayamdost MR, Stubbe J, Nocera DG. Photoactive Peptides for Light-Initiated Tyrosyl Radical Generation and Transport into Ribonucleotide Reductase. J Am Chem Soc 2007; 129:8500-9. [PMID: 17567129 DOI: 10.1021/ja0704434] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The mechanism of radical transport in the alpha2 (R1) subunit of class I E. coli ribonucleotide reductase (RNR) has been investigated by the phototriggered generation of a tyrosyl radical, *Y356, on a 20-mer peptide bound to alpha2. This peptide, Y-R2C19, is identical to the C-terminal peptide tail of the beta2 (R2) subunit and is a known competitive inhibitor of binding of the native beta2 protein to alpha2. *Y356 radical initiation is prompted by excitation (lambda >or= 300 nm) of a proximal anthraquinone, Anq, or benzophenone, BPA, chromophore on the peptide. Transient absorption spectroscopy has been employed to kinetically characterize the radical-producing step by time resolving the semiquinone anion (Anq*-), ketyl radical (*-BPA), and Y* photoproducts on (i) BPA-Y and Anq-Y dipeptides and (ii) BPA/Anq-Y-R2C19 peptides. Light-initiated, single-turnover assays have been carried out with the peptide/alpha2 complex in the presence of [14C]-labeled cytidine 5'-diphosphate substrate and ATP allosteric effector. We show that both the Anq- and BPA-containing peptides are competent in deoxycytidine diphosphate formation and turnover occurs via Y731 to Y730 to C439 pathway-dependent radical transport in alpha2. Experiments with the Y730F mutant exclude a direct superexchange mechanism between C439 and Y731 and are consistent with a PCET model for radical transport in which there is a unidirectional transport of the electron and proton transport among residues of alpha2.
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Affiliation(s)
- Steven Y Reece
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA
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Givaja G, Volpe M, Leeland JW, Edwards MA, Young TK, Darby SB, Reid SD, Blake AJ, Wilson C, Wolowska J, McInnes EJL, Schröder M, Love JB. Design and Synthesis of Binucleating Macrocyclic Clefts Derived from Schiff-Base Calixpyrroles. Chemistry 2007; 13:3707-23. [PMID: 17245783 DOI: 10.1002/chem.200600989] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The syntheses, characterisation and complexation reactions of a series of binucleating Schiff-base calixpyrrole macrocycles are described. The acid-templated [2+2] condensations between meso-disubstituted diformyldipyrromethanes and o-phenylenediamines generate the Schiff-base pyrrolic macrocycles H(4)L(1) to H(4)L(6) upon basic workup. The single-crystal X-ray structures of both H(4)L(3).2 EtOH and H(4)L(6).H2O confirm that [2+2] cyclisation has occurred, with either EtOH or H2O hydrogen-bonded within the macrocyclic cleft. A series of complexation reactions generate the dipalladium [Pd2(L)] (L=L(1) to L(5)), dinickel [Ni2(L(1))] and dicopper [Cu2(L)] (L=L(1) to L(3)) complexes. All of these complexes have been structurally characterised in the solid state and are found to adopt wedged structures that are enforced by the rigidity of the aryl backbone to give a cleft reminiscent of the structures of Pacman porphyrins. The binuclear nickel complexes [Ni2(mu-OMe)2Cl2(HOMe)2(H(4)L(1))] and [Ni2(mu-OH)2Cl2(HOMe)(H(4)L(5))] have also been prepared, although in these cases the solid-state structures show that the macrocyclic ligand remains protonated at the pyrrolic nitrogen atoms, and the Ni(II) cations are therefore co-ordinated by the imine nitrogen atoms only to give an open conformation for the complex. The dicopper complex [Cu2(L(3))] was crystallised in the presence of pyridine to form the adduct [Cu2(py)(L(3))], in which, in the solid state, the pyridine ligand is bound within the binuclear molecular cleft. Reaction between H(4)L(1) and [Mn(thf){N(SiMe(3))2}2] results in clean formation of the dimanganese complex [Mn2(L(1))], which, upon crystallisation, formed the mixed-valent complex [Mn2(mu-OH)(L(1))] in which the hydroxo ligand bridges the metal centres within the molecular cleft.
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Affiliation(s)
- Gonzalo Givaja
- School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
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Harvey PD, Stern C, Gros CP, Guilard R. The photophysics and photochemistry of cofacial free base and metallated bisporphyrins held together by covalent architectures. Coord Chem Rev 2007. [DOI: 10.1016/j.ccr.2006.06.009] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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MURATA H, IAI Y, OTAKE T, OYAIZU K, KOZAWA K, YUASA M. Synthesis of Cobalt Complex Using Pyrrole Derivative with Basic Ligand and Application to Cathodic Catalyst for Oxygen Reduction. ELECTROCHEMISTRY 2007. [DOI: 10.5796/electrochemistry.75.964] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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YUASA M, OYAIZU K, MURATA H, TANAKA K, YAMAMOTO M, SASAKI S. Electrocatalytic Activities for the Reduction of Oxygen of Carbon Particles Modified with Polypyrrole Including Various Metal Ions as Electrocatalytic Sites. ELECTROCHEMISTRY 2007. [DOI: 10.5796/electrochemistry.75.800] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Faure S, Stern C, Guilard R, Harvey PD. Synthesis and photophysical properties of meso-substituted bisporphyrins: comparative study of phosphorescence quenching for dioxygen sensing. Inorg Chem 2006; 44:9232-41. [PMID: 16323904 DOI: 10.1021/ic0508573] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The 4,6-bis(10-mesityl-5,15-di-p-tolylporpyrinyl)dibenzothiophene (H4DPSN) free base was obtained in five steps from commercially available materials. The metalation of DPSN2- with zinc(II), copper(II), and palladium(II) led to three new homobimetallic systems, (Zn)2DPSN, (Cu)2DPSN, and (Pd)2DPSN, respectively. The cofacial structures of these molecules offer the possibility of having dioxygen molecules inside the cavity for a period of time, allowing dynamic (collisional) phosphorescence quenching to be more efficient. The bimolecular excited-state deactivation rate constant for deactivation by dioxygen (kQ: (Pd)2DPB, 2.98x10(9); (Pd)2DPSN, 3.99x10(9); (Pd)2DPX, 6.94x10(9); (Pd)TPP, 8.95x10(9); (Pd)2DPS, 8.95x10(9) M-1 s-1) of (Pd)2DPSN, which exhibits an intense phosphorescence at 699 nm, was compared to those observed for (Pd)TPP, (Pd)2DPS, (Pd)2DPX, and (Pd)2DPB (TPP2-=tetraphenylporphyrin dianion, DPS4-=4,6-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]dibenzothiophene tetraanion, DPX4-=4,5-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]-9,9-dimethylxanthene tetraanion, and DPB4-=1,8-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]biphenylene tetraanion). These collision-induced deactivation data were interpreted by estimating a series of physical parameters such as the surface area and bisporphyrin radii, the diffusion coefficient of the bismacrocycles, and the theoretical deactivation efficiency for the five compounds addressing the role of steric hindrance of the macrocycles on each other and the aryl groups at the meso positions. For sensing purposes, (Pd)2DPX is characterized by a Stern-Volmer constant kSV of 2.91x10(6) M-1, placing the lower detection limit for [O2] in solution at 0.58 ppm, which is better than that for (Pd)TPP (kSV=2.31x10(6) M-1; lower detection limit of 0.73 ppm), the classically used monoporphyrin complex.
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Affiliation(s)
- Sébastien Faure
- LIMSAG UMR 5633, Université de Bourgogne, 6 bd Gabriel, 21100 Dijon, France
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Hodgkiss JM, Damrauer NH, Pressé S, Rosenthal J, Nocera DG. Electron Transfer Driven by Proton Fluctuations in a Hydrogen-Bonded Donor−Acceptor Assembly. J Phys Chem B 2006; 110:18853-8. [PMID: 16986876 DOI: 10.1021/jp056703q] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The temperature-isotope dependence of proton-coupled electron transfer (PCET) for a noncovalent molecular dyad is reported. The system consists of an excited-state Zn(II) porphyrin that transfers an electron to a naphthalene diimide acceptor through an amidinium-carboxylate interface. Two different isotope effects are observed for variant temperature regimes. A reverse isotope effect (i.e., kH/kD < 1) is observed as T approaches 120 K (kH/kD = 0.9, 120 K), whereas a normal isotope effect (i.e., kH/kD > 1) is recovered as the temperature is increased (kH/kD = 1.2, 300 K). The transition between these limits is smooth, with a crossover temperature of T approximately 160 K. These observations are in accordance with charge-transfer dynamics that are susceptible to bath-induced fluctuations in the proton coordinate.
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Affiliation(s)
- Justin M Hodgkiss
- Department of Chemistry, 6-335, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA
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Seyedsayamdost MR, Reece SY, Nocera DG, Stubbe J. Mono-, Di-, Tri-, and Tetra-Substituted Fluorotyrosines: New Probes for Enzymes That Use Tyrosyl Radicals in Catalysis†. J Am Chem Soc 2006; 128:1569-79. [PMID: 16448128 DOI: 10.1021/ja055926r] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A set of N-acylated, carboxyamide fluorotyrosine (F(n)()Y) analogues [Ac-3-FY-NH(2), Ac-3,5-F(2)Y-NH(2), Ac-2,3-F(2)Y-NH(2), Ac-2,3,5-F(3)Y-NH(2), Ac-2,3,6-F(3)Y-NH(2) and Ac-2,3,5,6-F(4)Y-NH(2)] have been synthesized from their corresponding amino acids to interrogate the detailed reaction mechanism(s) accessible to F(n)()Y*s in small molecules and in proteins. These Ac-F(n)()Y-NH(2) derivatives span a pK(a) range from 5.6 to 8.4 and a reduction potential range of 320 mV in the pH region accessible to most proteins (6-9). DFT electronic-structure calculations capture the observed trends for both the reduction potentials and pK(a)s. Dipeptides of the methyl ester of 4-benzoyl-l-phenylalanyl-F(n)()Ys at pH 4 were examined with a nanosecond laser pulse and transient absorption spectroscopy to provide absorption spectra of F(n)()Y*s. The EPR spectrum of each F(n)()Y* has also been determined by UV photolysis of solutions at pH 11 and 77 K. The ability to vary systematically both pK(a) and radical reduction potential, together with the facility to monitor radical formation with distinct absorption and EPR features, establishes that F(n)()Ys will be useful in the study of biological charge-transport mechanisms involving tyrosine. To demonstrate the efficacy of the fluorotyrosine method in unraveling charge transport in complex biological systems, we report the global substitution of tyrosine by 3-fluorotyrosine (3-FY) in the R2 subunit of ribonucleotide reductase (RNR) and present the EPR spectrum along with its simulation of 3-FY122*. In the companion paper, we demonstrate the utility of F(n)()Ys in providing insight into the mechanism of tyrosine oxidation in biological systems by incorporating them site-specifically at position 356 in the R2 subunit of Escherichia coli RNR.
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Affiliation(s)
- Mohammad R Seyedsayamdost
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA
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YUASA M, OYAIZU K, MURATA H, KITAO M, FUJITA K. Investigation of Carbon Materials as Supports for Metalloporphyrins Used for Cathode Catalyst in Fuel Cells. KOBUNSHI RONBUNSHU 2006. [DOI: 10.1295/koron.63.607] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Makoto YUASA
- Department of Pure and Applied Chemistry, Faculty of Science and Engineering, Tokyo University of Science
- Institute of Colloid and Interface Science, Tokyo University of Science
| | - Kenichi OYAIZU
- Institute of Colloid and Interface Science, Tokyo University of Science
| | - Hidenori MURATA
- Department of Pure and Applied Chemistry, Faculty of Science and Engineering, Tokyo University of Science
| | - Mizuki KITAO
- Department of Pure and Applied Chemistry, Faculty of Science and Engineering, Tokyo University of Science
| | - Kenji FUJITA
- Department of Pure and Applied Chemistry, Faculty of Science and Engineering, Tokyo University of Science
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YUASA M, OYAIZU K, YAMAGUCHI A, IMAI T, KITAO M. Novel Electrocatalysts for Oxygen Reduction Using Cobaltporphyrins That Undergo Facile Electropolymerization. KOBUNSHI RONBUNSHU 2006. [DOI: 10.1295/koron.63.182] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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YUASA M, OYAIZU K, MURATA H, TANAKA K, YAMAMOTO M. Improved Activity of Cathode Catalysts for Fuel Cells by Optimizing the Conditions for Preparation of Carbon Particles Modified with Cobalt-polypyrrole Complex. KOBUNSHI RONBUNSHU 2006. [DOI: 10.1295/koron.63.601] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Makoto YUASA
- Department of Pure and Applied Chemistry, Faculty of Science and Engineering, Tokyo University of Science
- Institute of Colloid and Interface Science, Tokyo University of Science
| | - Kenichi OYAIZU
- Institute of Colloid and Interface Science, Tokyo University of Science
| | - Hidenori MURATA
- Department of Pure and Applied Chemistry, Faculty of Science and Engineering, Tokyo University of Science
| | - Ken TANAKA
- Department of Pure and Applied Chemistry, Faculty of Science and Engineering, Tokyo University of Science
| | - Masakuni YAMAMOTO
- Department of Pure and Applied Chemistry, Faculty of Science and Engineering, Tokyo University of Science
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OYAIZU K, YAMAGUCHI A, IAI Y, TANAKA K, YUASA M. Preparation of Novel Conductive Polymer Ligand-Coated Carbon Particles by Electropolymerization of Pyridylthiophene and Application as Metal Complex Catalysts for Oxygen Reduction. KOBUNSHI RONBUNSHU 2006. [DOI: 10.1295/koron.63.189] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Reece SY, Nocera DG. Direct Tyrosine Oxidation Using the MLCT Excited States of Rhenium Polypyridyl Complexes. J Am Chem Soc 2005; 127:9448-58. [PMID: 15984872 DOI: 10.1021/ja0510360] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Rhenium(I) polypyridyl complexes have been designed for the intramolecular photogeneration of tyrosyl radical. Tyrosine (Y) and phenylalanine (F) have each been separately appended to a conventional Re(I)(bpy)(CO)(3)CN framework via an amide linkage to the bipyridine (bpy) ligand. Comparative time-resolved emission quenching and transient absorption spectra of Re(bpy-Y)(CO)(3)CN and Re(bpy-F)(CO)(3)CN show that Y is oxidized only upon its deprotonation at pH 12. In an effort to redirect electron transport so that it is more compatible with intramolecular Y oxidation, polypyridyl Re(I) complexes have been prepared with the amide bond functionality located on a pendant phosphine ligand. A [Re(phen)(PP-Bn)(CO)(2)](PF(6)) (PP = bis(diphenylphosphino)ethylene) complex has been synthesized and crystallographically characterized. Electrochemistry and phosphorescence measurements of this complex indicate a modest excited-state potential for tyrosine oxidation, similar to that for the (bpy)Re(I)(CO)(3)CN framework. The excited-state oxidation potential can be increased by introducing a monodentate phosphine to the Re(I)(NN)(CO)(3)(+) framework (NN = polypyridyl). In this case, Y is oxidized at all pHs when appended to the triphenylphosphine (P) of [Re(phen)(P-Y)(CO(3))](PF(6)). Analysis of the pH dependence of the rate constant for tyrosyl radical generation is consistent with a proton-coupled electron transfer (PCET) quenching mechanism.
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Affiliation(s)
- Steven Y Reece
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA
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Rosenthal J, Bachman J, Dempsey JL, Esswein AJ, Gray TG, Hodgkiss JM, Manke DR, Luckett TD, Pistorio BJ, Veige AS, Nocera DG. Oxygen and hydrogen photocatalysis by two-electron mixed-valence coordination compounds. Coord Chem Rev 2005. [DOI: 10.1016/j.ccr.2005.03.034] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Faure S, Stern C, Espinosa E, Douville J, Guilard R, Harvey PD. Triplet-Triplet Energy Transfer Controlled by the Donor-Acceptor Distance in Rigidly Held Palladium-Containing Cofacial Bisporphyrins. Chemistry 2005; 11:3469-81. [PMID: 15812878 DOI: 10.1002/chem.200400990] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Eleven new complexes, including mono-, heterobi-, and homobimetallic cofacial bisporphyrins, (Pd)H2DPS, (M)H2DPX, (M)H2DPB, (PdZn)DPS, (PdZn)DPX, (Pt)2DPX, (M)2DPB (M = Pd, Pt), and (Pt)P (DPS4- = 4,6-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]dibenzothiophene tetraanion, DPX(4-) = 4,5-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]-9,9-dimethylxanthene tetraanion, DPB4- = 1,8-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]biphenylene tetraanion, P2- = 5-phenyl-2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrin dianion) have been synthesized and characterized. The photophysical properties of the donor (M)P (M=Pd or Pt, P=porphyrin chromophore) and the acceptor (free base H(2)P or (Zn)P) depend on the C(meso)-C(meso) distance and the presence of a heavy atom such as Pd(II) or Pt(II). The data were compared with those for the known compounds (Pd)2DPS, (Pd)2DPX, H4DPS, H4DPX, H4DPB, (Pd)P, (Zn)P, and H(2)P. The rate constants for triplet-triplet energy transfer (k(ET)) were measured for the heterobimetallic (PdZn) and monometallic [(M)H2] derivatives (M=Pd, Pt). The fluorescence lifetimes (Deltatau(F)) of the acceptors decrease as a result of the heavy-atom effect, and vary as follows: (Pd)H2DPS<<(Pd)H2DPX approximately (Pd)H2DPB. The k(ET) values calculated according to the equation k(ET)=(1/tau(emi)-1/tau(emi) (0)), where tau(emi) (0) is the emission lifetime of the homobimetallic bisporphyrins (no ET occurs), are equal to 0, 247+/-57 and 133+/-52 s(-1) for DPS, DPX, and DPB, respectively, in the (Pd)H(2) series. These measurements allowed the range of distance over which the Dexter mechanism for T(1)-T(1) energy transfer ceases to operate to be determined. This distance is somewhere between 4.3 and 6.3 A, in agreement with our recent findings on singlet-singlet energy transfer. During the course of this study, the X-ray crystal structure for (Pd)H2DPX was obtained; triclinic (P1), a = 11.1016(1), b = 14.9868(2), c = 20.6786(3) A, alpha = 102.091(1), beta = 100.587(1), gamma = 101.817(1) degrees , V = 3199.19(7) A(3), Z = 2.
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Affiliation(s)
- Sébastien Faure
- LIMSAG UMR 5633, Université de Bourgogne, 6 bd Gabriel, 21100 Dijon, France
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Reece SY, Stubbe J, Nocera DG. pH Dependence of charge transfer between tryptophan and tyrosine in dipeptides. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2005; 1706:232-8. [PMID: 15694351 DOI: 10.1016/j.bbabio.2004.11.011] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2004] [Revised: 11/11/2004] [Accepted: 11/15/2004] [Indexed: 11/20/2022]
Abstract
Time-resolved absorption spectroscopy has been employed to study the directionality and rate of charge transfer in W-Y and Ac-W-Y dipeptides as a function of pH. Excitation with 266-nm nanosecond laser pulses produces both W (or [WH](+), depending on pH) and Y. Between pH 6 and 10, W to was found to oxidize Y with k(X)=9.0x10(4) s(-1) and 1.8x10(4) s(-1) for the W-Y and Ac-W-Y dipeptide systems, respectively. The intramolecular charge transfer rate increases as the pH is lowered over the range 6>pH>2. For 10<pH<12, the rate of radical transport for the W-Y dipeptide decreases and becomes convoluted with other radical decay processes, the timescales of which have been identified in studies of control dipeptides Ac-F-Y and W-F. Further increases in pH prompt the reverse reaction to occur, W-Y-->W-Y(-) (Y(-), tyrosinate anion), with a rate constant of k(X)=1.2x10(5) s(-1). The dependence of charge transfer directionality between W and Y on pH is important to the enzymatic function of several model and natural biological systems as discussed here for ribonucleotide reductase.
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Affiliation(s)
- Steven Y Reece
- Department of Chemistry, 6-335, 77 Massachusetts Avenue, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA
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Givaja G, Blake AJ, Wilson C, Schröder M, Love JB. Macrocyclic diiminodipyrromethane complexes: structural analogues of Pac-Man porphyrins. Chem Commun (Camb) 2003:2508-9. [PMID: 14587755 DOI: 10.1039/b308443d] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The complexation of palladium(II) by a unique family of [2+2] diiminodipyrromethane macrocycles yields compounds that adopt structures reminiscent of Pac-Man porphyrins.
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Affiliation(s)
- Gonzalo Givaja
- School of Chemistry, University of Nottingham, University Park, Nottingham, UK NG7 2RD
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