1
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Imran M, Taddei M, Sukhanov AA, Bussotti L, Ni W, Foggi P, Gurzadyan GG, Zhao J, Di Donato M, Voronkova VK. Radical-Enhanced Intersystem Crossing in Perylene-Oxoverdazyl Radical Dyads. Chemphyschem 2022; 23:e202100912. [PMID: 35191573 DOI: 10.1002/cphc.202100912] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Indexed: 11/07/2022]
Abstract
Linking stable radicals to organic chromophores is an effective method to enhance the intersystem crossing (ISC) of chromophores. Herein we prepared perylene-oxoverdazyl dyads either by directly connecting the two units or using an intervening phenyl spacer. We investigated the effect of the radical on the photophysical properties of perylene and observed strong fluorescence quenching due to radical enhanced intersystem crossing (REISC). Compared with a previously reported perylene fused nitroxide radical compound (triplet lifetime = 0.1 µs), these new adducts show a longer-lived triplet excited state (9.5 µs). Based on the singlet oxygen quantum yield (7%), we propose that the radical enhanced internal conversion also plays a role in the relaxation of the excited state. Femtosecond fluorescence up-conversion indicates a fast decay of the excited state (<1.0 ps), suggesting a strong spin-spin exchange interaction between the two units. Femtosecond transient absorption (fs-TA) spectra confirmed direct triplet state population (within 0.5 ps). Interestingly, by fs-TA, we observed the interconversion of the two states (D1/Q1) at ~80 ps time scale. Time-resolved electron paramagnetic resonance (TREPR) spectral study confirmed the formation of the quartet sate , we observed triplet and quartet states simultaneously with weights of 0.7 and 0.3, respectively. DFT computations showed that the interaction between radical and chromophore is ferromagnetic ( J >0, 0.05~0.10 eV).
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Affiliation(s)
- Muhammad Imran
- State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, E-208 West Campus, 2 Ling Gong Road, Dalian, 116024, P.R. China
| | - Maria Taddei
- LENS (European Laboratory for Non-Linear Spectroscopy), Via N. Carrara 1, 50019, Sesto Fiorentino, Italy
| | - Andrey A Sukhanov
- Zavoisky Physical-Technical Institute, FRC Kazan Scientific Center of RAS, Kazan, 420029, Russia
| | - Laura Bussotti
- LENS (European Laboratory for Non-Linear Spectroscopy), Via N. Carrara 1, 50019, Sesto Fiorentino, Italy
| | - Wenjun Ni
- Institute of Artificial Photosynthesis, State Key Laboratory of Fine Chemicals, Dalian University of Technology, 2 Ling-Gong Road, Dalian, 116024, P.R. China
| | - Paolo Foggi
- LENS (European Laboratory for Non-Linear Spectroscopy), Via N. Carrara 1, 50019, Sesto Fiorentino, Italy
- Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia, Via Elce di Sotto 8, 06123, Perugia, Italy
| | - Gagik G Gurzadyan
- Institute of Artificial Photosynthesis, State Key Laboratory of Fine Chemicals, Dalian University of Technology, 2 Ling-Gong Road, Dalian, 116024, P.R. China
| | - Jianzhang Zhao
- State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, E-208 West Campus, 2 Ling Gong Road, Dalian, 116024, P.R. China
| | - Mariangela Di Donato
- LENS (European Laboratory for Non-Linear Spectroscopy), Via N. Carrara 1, 50019, Sesto Fiorentino, Italy
- ICCOM-CNR, Via Madonna del Piano 10, 50019, Sesto Fiorentino (FI), Italy
| | - Violeta K Voronkova
- Zavoisky Physical-Technical Institute, FRC Kazan Scientific Center of RAS, Kazan, 420029, Russia
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2
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Watkins EJ, Almhjell PJ, Arnold FH. Direct Enzymatic Synthesis of a Deep-Blue Fluorescent Noncanonical Amino Acid from Azulene and Serine. Chembiochem 2019; 21:80-83. [PMID: 31513332 DOI: 10.1002/cbic.201900497] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Indexed: 12/21/2022]
Abstract
We report a simple, one-step enzymatic synthesis of the blue fluorescent noncanonical amino acid β-(1-azulenyl)-l-alanine (AzAla). By using an engineered tryptophan synthase β-subunit (TrpB), stereochemically pure AzAla can be synthesized at scale starting from commercially available azulene and l-serine. Mutation of a universally conserved catalytic glutamate in the active site to glycine has only a modest effect on native activity with indole but abolishes activity on azulene, suggesting that this glutamate activates azulene for nucleophilic attack by stabilization of the aromatic ion.
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Affiliation(s)
- Ella J Watkins
- Division of Biology and Biological Engineering, California Institute of Technology, MC 210-41, 1200 E. California Boulevard, Pasadena, CA, 91125, USA
| | - Patrick J Almhjell
- Division of Chemistry and Chemical Engineering, California Institute of Technology, MC 210-41, 1200 E. California Boulevard, Pasadena, CA, 91125, USA
| | - Frances H Arnold
- Division of Biology and Biological Engineering, California Institute of Technology, MC 210-41, 1200 E. California Boulevard, Pasadena, CA, 91125, USA.,Division of Chemistry and Chemical Engineering, California Institute of Technology, MC 210-41, 1200 E. California Boulevard, Pasadena, CA, 91125, USA
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3
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Wang Z, Zhao J, Barbon A, Toffoletti A, Liu Y, An Y, Xu L, Karatay A, Yaglioglu HG, Yildiz EA, Hayvali M. Radical-Enhanced Intersystem Crossing in New Bodipy Derivatives and Application for Efficient Triplet–Triplet Annihilation Upconversion. J Am Chem Soc 2017; 139:7831-7842. [PMID: 28524657 DOI: 10.1021/jacs.7b02063] [Citation(s) in RCA: 112] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Zhijia Wang
- State Key Laboratory
of Fine Chemicals, Dalian University of Technology, E-208 West
Campus, 2 Ling-Gong Road, Dalian 116024, People’s Republic of China
| | - Jianzhang Zhao
- State Key Laboratory
of Fine Chemicals, Dalian University of Technology, E-208 West
Campus, 2 Ling-Gong Road, Dalian 116024, People’s Republic of China
| | - Antonio Barbon
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo, 1, 35131 Padova, Italy
| | - Antonio Toffoletti
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo, 1, 35131 Padova, Italy
| | - Yan Liu
- State Key Laboratory
of Fine Chemicals, Dalian University of Technology, E-208 West
Campus, 2 Ling-Gong Road, Dalian 116024, People’s Republic of China
| | - Yonglin An
- State Key Laboratory
of Fine Chemicals, Dalian University of Technology, E-208 West
Campus, 2 Ling-Gong Road, Dalian 116024, People’s Republic of China
| | - Liang Xu
- State Key Laboratory
of Fine Chemicals, Dalian University of Technology, E-208 West
Campus, 2 Ling-Gong Road, Dalian 116024, People’s Republic of China
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4
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Gosavi PM, Moroz YS, Korendovych IV. β-(1-Azulenyl)-L-alanine--a functional probe for determination of pKa of histidine residues. Chem Commun (Camb) 2016; 51:5347-50. [PMID: 25645241 DOI: 10.1039/c4cc08720h] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
β-(1-Azulenyl)-L-alanine (AzAla) can be incorporated into the influenza A virus M2 proton channel. AzAla's sensitivity to the protonation state of the nearby histidines and the lack of environmental fluorescence dependence allow for direct and straightforward determination of histidine pKa values in ion channels.
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Affiliation(s)
- Pallavi M Gosavi
- Department of Chemistry, Syracuse University, 111 College Place, Syracuse, NY 13244, USA.
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5
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Dyar SM, Margulies EA, Horwitz NE, Brown KE, Krzyaniak MD, Wasielewski MR. Photogenerated Quartet State Formation in a Compact Ring-Fused Perylene-Nitroxide. J Phys Chem B 2015; 119:13560-9. [DOI: 10.1021/acs.jpcb.5b02378] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Scott M. Dyar
- Department of Chemistry and
Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Eric A. Margulies
- Department of Chemistry and
Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Noah E. Horwitz
- Department of Chemistry and
Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Kristen E. Brown
- Department of Chemistry and
Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Matthew D. Krzyaniak
- Department of Chemistry and
Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Michael R. Wasielewski
- Department of Chemistry and
Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
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6
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Hughes BK, Braunecker WA, Ferguson AJ, Kemper TW, Larsen RE, Gennett T. Quenching of the Perylene Fluorophore by Stable Nitroxide Radical-Containing Macromolecules. J Phys Chem B 2014; 118:12541-8. [PMID: 25329883 DOI: 10.1021/jp506240j] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Barbara K. Hughes
- Chemical and Materials
Science Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Wade A. Braunecker
- Chemical and Materials
Science Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Andrew J. Ferguson
- Chemical and Materials
Science Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Travis W. Kemper
- Chemical and Materials
Science Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Ross E. Larsen
- Chemical and Materials
Science Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Thomas Gennett
- Chemical and Materials
Science Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
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7
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Wright K, d'Aboville E, Scola J, Margola T, Toffoletti A, De Zotti M, Crisma M, Formaggio F, Toniolo C. A Quaternary Nitronyl Nitroxide α-Amino Acid: Synthesis, Configurational and Conformational Assignments, and Physicochemical Properties. European J Org Chem 2014. [DOI: 10.1002/ejoc.201301765] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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8
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Moroz YS, Binder W, Nygren P, Caputo GA, Korendovych IV. Painting proteins blue: β-(1-azulenyl)-L-alanine as a probe for studying protein-protein interactions. Chem Commun (Camb) 2013; 49:490-2. [PMID: 23207368 PMCID: PMC3547328 DOI: 10.1039/c2cc37550h] [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: 12/15/2022]
Abstract
We demonstrated that β-(1-azulenyl)-L-alanine, a fluorescent pseudoisosteric analog of tryptophan, exhibits weak environmental dependence and thus allows for using weak intrinsic quenchers, such as methionines, to monitor protein-protein interactions while not perturbing them.
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Affiliation(s)
- Yurii S. Moroz
- Department of Chemistry, Syracuse University, 111 College Place, Syracuse, NY 13244, USA
| | - Wolfgang Binder
- Department of Chemistry, Syracuse University, 111 College Place, Syracuse, NY 13244, USA
- Department of Chemistry, Technical University of Graz, Graz, Austria
| | - Patrik Nygren
- Department of Hematology and Oncology, University of Pennsylvania Medical School, Philadelphia, PA 19014, USA
| | - Gregory A. Caputo
- Department of Chemistry and Biochemistry, Rowan University, Glassboro, NJ 08028, USA
| | - Ivan V. Korendovych
- Department of Chemistry, Syracuse University, 111 College Place, Syracuse, NY 13244, USA
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9
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Wright K, Alvarez AB, Crisma M, Toffoletti A, Formaggio F, Toniolo C. 2-Amino-1,2,3,6-tetrahydro-6-oxocyclopenta[c]fluorene-2-carboxylic Acid (FlAib), a Completely Rigidified, Fluoren-9-one-Basedα-Amino Acid. Helv Chim Acta 2012. [DOI: 10.1002/hlca.201200490] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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10
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Colvin MT, Smeigh AL, Giacobbe EM, Conron SMM, Ricks AB, Wasielewski MR. Ultrafast Intersystem Crossing and Spin Dynamics of Zinc meso-Tetraphenylporphyrin Covalently Bound to Stable Radicals. J Phys Chem A 2011; 115:7538-49. [DOI: 10.1021/jp2021006] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Michael T. Colvin
- Department of Chemistry and Argonne−Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Amanda L. Smeigh
- Department of Chemistry and Argonne−Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Emilie M. Giacobbe
- Department of Chemistry and Argonne−Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Sarah M. Mickley Conron
- Department of Chemistry and Argonne−Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Annie Butler Ricks
- Department of Chemistry and Argonne−Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Michael R. Wasielewski
- Department of Chemistry and Argonne−Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
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11
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Moons H, Goovaerts E, Gubskaya VP, Nuretdinov IA, Corvaja C, Franco L. W-band transient EPR and photoinduced absorption on spin-labeled fullerene derivatives. Phys Chem Chem Phys 2011; 13:3942-51. [DOI: 10.1039/c0cp01902j] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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12
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Colvin MT, Giacobbe EM, Cohen B, Miura T, Scott AM, Wasielewski MR. Competitive Electron Transfer and Enhanced Intersystem Crossing in Photoexcited Covalent TEMPO−Perylene-3,4:9,10-bis(dicarboximide) Dyads: Unusual Spin Polarization Resulting from the Radical−Triplet Interaction. J Phys Chem A 2010; 114:1741-8. [DOI: 10.1021/jp909212c] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Michael T. Colvin
- Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113
| | - Emilie M. Giacobbe
- Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113
| | - Boiko Cohen
- Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113
| | - Tomoaki Miura
- Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113
| | - Amy M. Scott
- Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113
| | - Michael R. Wasielewski
- Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113
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13
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Giacobbe EM, Mi Q, Colvin MT, Cohen B, Ramanan C, Scott AM, Yeganeh S, Marks TJ, Ratner MA, Wasielewski MR. Ultrafast Intersystem Crossing and Spin Dynamics of Photoexcited Perylene-3,4:9,10-bis(dicarboximide) Covalently Linked to a Nitroxide Radical at Fixed Distances. J Am Chem Soc 2009; 131:3700-12. [DOI: 10.1021/ja808924f] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Emilie M. Giacobbe
- Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208-3113
| | - Qixi Mi
- Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208-3113
| | - Michael T. Colvin
- Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208-3113
| | - Boiko Cohen
- Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208-3113
| | - Charusheela Ramanan
- Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208-3113
| | - Amy M. Scott
- Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208-3113
| | - Sina Yeganeh
- Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208-3113
| | - Tobin J. Marks
- Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208-3113
| | - Mark A. Ratner
- Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208-3113
| | - Michael R. Wasielewski
- Department of Chemistry, Argonne-Northwestern Solar Energy Research (ANSER) Center, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208-3113
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14
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Maretti L, Ferbinteanu M, Cimpoesu F, Islam SSM, Ohba Y, Kajiwara T, Yamashita M, Yamauchi S. Spin coupling in the supramolecular structure of a new tetra(quinoline-TEMPO)yttrium(III) complex. Inorg Chem 2007; 46:660-9. [PMID: 17257008 DOI: 10.1021/ic0610841] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The newly synthesized tetra(quinoline-TEMPO)yttrium(III) potassium salt shows interesting structural features at the molecular and supramolecular levels, revealed by the analysis of the X-ray diffraction data. The magnetic susceptibility and EPR data corroborated with structural considerations showed that the exchange and dipolar spin coupling interactions are taking place at the nodes assembling the supramolecular 2D structure. The Y(III) center shows antiprismatic octacoordination, close to the idealized D2 symmetry. The diamagnetic transition metal plays no role in mediating the radical interactions since the TEMPO-type fragments are remote from the chelating moieties of the ligand. In turn, significant interaction occurs on the nodes consisting in the quasi-rectangular coordination of potassium counterions by the spin-bearing TEMPO groups coming from four distinct complex units. The antiferromagnetic susceptibility was consistently modeled by a spin Hamiltonian based on the rectangle topology of four spins S = 1/2. The fitted exchange parameters are Ja = -5.1 cm-1 and Jb = -3.4 cm-1 for the edges, imposing Jd = 0 for the diagonal. These values are in excellent agreement with the ab initio results Ja = -4.83 cm-1, Jb = -3.44 cm-1, Jd = -0.07 cm-1 obtained in a CASSCF(12,8) calculation. Based on the reliability of the ab initio results we were able to select the presented J parameters among several versions of multiple solutions with acceptable goodness of the fit. A methodological caveat about the artifacts of the automatic use of best fit parameters, in the absence of supplementary criteria, in the context of relative blindness of magnetic susceptibility modeling, is raised. The details of the EPR spectrum at 10 K are also consistent, in the frame of dipolar approximation, with the model of four interacting spins at the nodes of the supramolecular assembling.
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Affiliation(s)
- Luca Maretti
- Institute for Chemical Reaction Science, Tohoku University, Aoba-ku, Katahira 2-1-1, Sendai 980-8577, Japan
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15
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Fabris L, Antonello S, Armelao L, Donkers RL, Polo F, Toniolo C, Maran F. Gold Nanoclusters Protected by Conformationally Constrained Peptides. J Am Chem Soc 2005; 128:326-36. [PMID: 16390162 DOI: 10.1021/ja0560581] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The preparation and properties of a series of gold nanoclusters protected by thiolated peptides based on the alpha-aminoisobutyric acid (Aib) unit are described. The peptides were devised to form 0-3 C=O...H-N intramolecular hydrogen bonds, as required by their 3(10)-helical structure. The monolayer-protected clusters (MPCs) were prepared, using a modified version of the two-phase Brust-Schiffrin preparation, and fully characterized with (1)H NMR spectrometry, IR and UV-vis absorption spectroscopies, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The MPCs were obtained with core diameters in the range of 1.1-2.3 nm, depending on the reaction conditions. Structured peptides formed smaller clusters. The smallest MPC obtained is in agreement with the average formula Au(38)Pep(18). The results showed that the chemical integrity of the peptide is maintained upon monolayer formation and that the average number of peptide ligands per gold cluster is typically 75-85% the value calculated for alkanethiolate MPCs of similar sizes. The IR and NMR spectra indicated that in the monolayer the peptides are involved in both intra- and interligand C=O...H-N hydrogen bonds.
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Affiliation(s)
- Laura Fabris
- Department of Chemistry, University of Padua, via Marzolo 1, 35131 Padua, Italy
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16
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Venanzi M, Valeri A, Palleschi A, Stella L, Moroder L, Formaggio F, Toniolo C, Pispisa B. Structural properties and photophysical behavior of conformationally constrained hexapeptides functionalized with a new fluorescent analog of tryptophan and a nitroxide radical quencher. Biopolymers 2005; 75:128-39. [PMID: 15356867 DOI: 10.1002/bip.20110] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The influence of the conformational properties on the photophysics of two de novo designed hexapeptides was studied by spectroscopic measurements (ir, NMR, steady-state, and time resolved fluorescence) and molecular mechanics calculations. The peptide sequences comprise two nonproteinogenic residues: a beta-(1-azulenyl)-L-alanine (Aal) residue, obtained by formally functionalizing the Ala side chain with the azulene chromophore, and a Calpha-tetrasubstituted alpha-amino acid (TOAC), incorporating a nitroxide group in a cycloalkyl moiety. Aal represents a new fluorescent, quasi-isosteric Trp analog and TOAC a stable radical species, frequently used as a paramagnetic probe in biochemical studies. The peptide chains differ in the sequence position of the two probes and are heavily based on Aib (alpha-aminoisobutyric acid) residues to generate conformationally restricted helical structures, as confirmed by both spectroscopic and computational results. The conformationally controlled, excited state interactions, determining the photophysical relaxation of the Aal*/TOAC pair, are also discussed.
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Affiliation(s)
- Mariano Venanzi
- Department of Chemical Sciences and Technologies, University of Tor Vergata, 00133 Rome, Italy.
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