101
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Epifanovsky E, Kowalski K, Fan PD, Valiev M, Matsika S, Krylov AI. On the Electronically Excited States of Uracil. J Phys Chem A 2008; 112:9983-92. [DOI: 10.1021/jp803758q] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Evgeny Epifanovsky
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, Pacific Northwest National Laboratory, Richland, Washington 99352, and Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122
| | - Karol Kowalski
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, Pacific Northwest National Laboratory, Richland, Washington 99352, and Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122
| | - Peng-Dong Fan
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, Pacific Northwest National Laboratory, Richland, Washington 99352, and Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122
| | - Marat Valiev
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, Pacific Northwest National Laboratory, Richland, Washington 99352, and Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122
| | - Spiridoula Matsika
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, Pacific Northwest National Laboratory, Richland, Washington 99352, and Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122
| | - Anna I. Krylov
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, Pacific Northwest National Laboratory, Richland, Washington 99352, and Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122
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102
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Mercier Y, Santoro F, Reguero M, Improta R. The Decay from the Dark nπ* Excited State in Uracil: An Integrated CASPT2/CASSCF and PCM/TD-DFT Study in the Gas Phase and in Water. J Phys Chem B 2008; 112:10769-72. [DOI: 10.1021/jp804785p] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yannick Mercier
- Department de Química Física i Inorgànica, Universitat Rovira i Virgili, Marcel.lí Domingo, s/n-Campus Sescelades, 43007 Tarragona, Spain, Istituto per I Processi Chimico-Fisici - CNR, Area della Ricerca del CNR, Via Moruzzi 1, I-56124 Pisa, Italy, and Dipartimento di Chimica, Università Federico II, Via Cintia, I-80126 Napoli, Italy
| | - Fabrizio Santoro
- Department de Química Física i Inorgànica, Universitat Rovira i Virgili, Marcel.lí Domingo, s/n-Campus Sescelades, 43007 Tarragona, Spain, Istituto per I Processi Chimico-Fisici - CNR, Area della Ricerca del CNR, Via Moruzzi 1, I-56124 Pisa, Italy, and Dipartimento di Chimica, Università Federico II, Via Cintia, I-80126 Napoli, Italy
| | - Mar Reguero
- Department de Química Física i Inorgànica, Universitat Rovira i Virgili, Marcel.lí Domingo, s/n-Campus Sescelades, 43007 Tarragona, Spain, Istituto per I Processi Chimico-Fisici - CNR, Area della Ricerca del CNR, Via Moruzzi 1, I-56124 Pisa, Italy, and Dipartimento di Chimica, Università Federico II, Via Cintia, I-80126 Napoli, Italy
| | - Roberto Improta
- Department de Química Física i Inorgànica, Universitat Rovira i Virgili, Marcel.lí Domingo, s/n-Campus Sescelades, 43007 Tarragona, Spain, Istituto per I Processi Chimico-Fisici - CNR, Area della Ricerca del CNR, Via Moruzzi 1, I-56124 Pisa, Italy, and Dipartimento di Chimica, Università Federico II, Via Cintia, I-80126 Napoli, Italy
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103
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Carlotto S, Polimeno A, Ferrante C, Benzi C, Barone V. Integrated Approach for Modeling the Emission Fluorescence of 4-(N,N-Dimethylamino)benzonitrile in Polar Environments. J Phys Chem B 2008; 112:8106-13. [DOI: 10.1021/jp076676z] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Silvia Carlotto
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1-35131 Padova, Italy, and Dipartimento di Chimica, Università di Napoli “Federico II”, Complesso Universitario di Monte Sant’Angelo Via Cintia, I-80126 Napoli, Italy
| | - Antonino Polimeno
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1-35131 Padova, Italy, and Dipartimento di Chimica, Università di Napoli “Federico II”, Complesso Universitario di Monte Sant’Angelo Via Cintia, I-80126 Napoli, Italy
| | - Camilla Ferrante
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1-35131 Padova, Italy, and Dipartimento di Chimica, Università di Napoli “Federico II”, Complesso Universitario di Monte Sant’Angelo Via Cintia, I-80126 Napoli, Italy
| | - Caterina Benzi
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1-35131 Padova, Italy, and Dipartimento di Chimica, Università di Napoli “Federico II”, Complesso Universitario di Monte Sant’Angelo Via Cintia, I-80126 Napoli, Italy
| | - Vincenzo Barone
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1-35131 Padova, Italy, and Dipartimento di Chimica, Università di Napoli “Federico II”, Complesso Universitario di Monte Sant’Angelo Via Cintia, I-80126 Napoli, Italy
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104
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Gustavsson T, Bányász Á, Sarkar N, Markovitsi D, Improta R. Assessing solvent effects on the singlet excited state lifetime of uracil derivatives: A femtosecond fluorescence upconversion study in alcohols and D2O. Chem Phys 2008. [DOI: 10.1016/j.chemphys.2008.02.032] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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105
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106
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d’Ischia M, Crescenzi O, Pezzella A, Arzillo M, Panzella L, Napolitano A, Barone V. Structural Effects on the Electronic Absorption Properties of 5,6-Dihydroxyindole Oligomers: The Potential of an Integrated Experimental and DFT Approach to Model Eumelanin Optical Properties. Photochem Photobiol 2008; 84:600-7. [DOI: 10.1111/j.1751-1097.2007.00249.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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107
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De Boni L, Toro C, Masunov AE, Hernández FE. Untangling the Excited States of DR1 in Solution: An Experimental and Theoretical Study. J Phys Chem A 2008; 112:3886-90. [DOI: 10.1021/jp711552e] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Leonardo De Boni
- Department of Chemistry, University of Central Florida, P.O. Box 162366, Orlando, Florida 382616-2366
| | - Carlos Toro
- Department of Chemistry, University of Central Florida, P.O. Box 162366, Orlando, Florida 382616-2366
| | - Artëm E. Masunov
- Department of Chemistry, University of Central Florida, P.O. Box 162366, Orlando, Florida 382616-2366
| | - Florencio E. Hernández
- Department of Chemistry, University of Central Florida, P.O. Box 162366, Orlando, Florida 382616-2366
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108
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Kwok WM, Ma C, Phillips DL. A doorway state leads to photostability or triplet photodamage in thymine DNA. J Am Chem Soc 2008; 130:5131-9. [PMID: 18335986 DOI: 10.1021/ja077831q] [Citation(s) in RCA: 158] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ultraviolet irradiation of DNA produces electronic excited states that predominantly eliminate the excitation energy by returning to the ground state (photostability) or following minor pathways into mutagenic photoproducts (photodamage). The cyclobutane pyrimidine dimer (CPD) formed from photodimerization of thymines in DNA is the most common form of photodamage. The underlying molecular processes governing photostability and photodamage of thymine-constituted DNA remain unclear. Here, a combined femtosecond broadband time-resolved fluorescence and transient absorption spectroscopies were employed to study a monomer thymidine and a single-stranded thymine oligonucleotide. We show that the protecting deactivation of a thymine multimer is due to an ultrafast single-base localized stepwise mechanism where the initial excited state decays via a doorway state to the ground state or proceeds via the doorway state to a triplet state identified as a major precursor for CPD photodamage. These results provide new mechanistic characterization of and a dynamic link between the photoexcitation of DNA and DNA photostability and photodamage.
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Affiliation(s)
- Wai-Ming Kwok
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
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109
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Meng S, Ma J. Solvatochromic Shift of Donor−Acceptor Substituted Bithiophene in Solvents of Different Polarity: Quantum Chemical and Molecular Dynamics Simulations. J Phys Chem B 2008; 112:4313-22. [DOI: 10.1021/jp710456p] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Suci Meng
- Institute of Theoretical and Computational Chemistry, Key Laboratory of Mesoscopic Chemistry of MOE, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, People's Republic of China
| | - Jing Ma
- Institute of Theoretical and Computational Chemistry, Key Laboratory of Mesoscopic Chemistry of MOE, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, People's Republic of China
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110
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Preat J, Jacquemin D, Vercauteren DP, Perpète EA. A quantitative prediction of the electronic spectra of thiocarbonyl chromophores: TD-DFT versus SAC-CI. Theor Chem Acc 2008. [DOI: 10.1007/s00214-007-0405-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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111
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Improta R, Barone V. The excited states of adenine and thymine nucleoside and nucleotide in aqueous solution: a comparative study by time-dependent DFT calculations. Theor Chem Acc 2008. [DOI: 10.1007/s00214-007-0404-5] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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112
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Santoro F, Barone V, Improta R. Can TD-DFT calculations accurately describe the excited states behavior of stacked nucleobases? The cytosine dimer as a test case. J Comput Chem 2008; 29:957-64. [DOI: 10.1002/jcc.20853] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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113
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Improta R. The excited states of π-stacked 9-methyladenine oligomers: a TD-DFT study in aqueous solution. Phys Chem Chem Phys 2008; 10:2656-64. [DOI: 10.1039/b718562f] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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114
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Bányász Á, Gustavsson T, Keszei E, Improta R, Markovitsi D. Effect of amino substitution on the excited state dynamics of uracil. Photochem Photobiol Sci 2008; 7:765-8. [DOI: 10.1039/b800764k] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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115
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Scalmani G, Frisch MJ, Mennucci B, Tomasi J, Cammi R, Barone V. Geometries and properties of excited states in the gas phase and in solution: theory and application of a time-dependent density functional theory polarizable continuum model. J Chem Phys 2007; 124:94107. [PMID: 16526845 DOI: 10.1063/1.2173258] [Citation(s) in RCA: 918] [Impact Index Per Article: 54.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this paper we present the theory and implementation of analytic derivatives of time-dependent density functional theory (TDDFT) excited states energies, both in vacuo and including solvent effects by means of the polarizable continuum model. The method is applied to two case studies: p-nitroaniline and 4-(dimethyl)aminobenzonitrile. For both molecules PCM-TDDFT is shown to be successful in supporting the analysis of experimental data with useful insights for a better understanding of photophysical and photochemical pathways in solution.
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116
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Improta R, Scalmani G, Frisch MJ, Barone V. Toward effective and reliable fluorescence energies in solution by a new state specific polarizable continuum model time dependent density functional theory approach. J Chem Phys 2007; 127:074504. [PMID: 17718617 DOI: 10.1063/1.2757168] [Citation(s) in RCA: 364] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A state specific (SS) model for the inclusion of solvent effects in time dependent density functional theory (TD-DFT) computations of emission energies has been developed and coded in the framework of the so called polarizable continuum model (PCM). The new model allows for a rigorous and effective treatment of dynamical solvent effects in the computation of fluorescence and phosphorescence spectra in solution, and it can be used for studying different relaxation time regimes. SS and conventional linear response (LR) models have been compared by computing the emission energies for different benchmark systems (formaldehyde in water and three coumarin derivatives in ethanol). Special attention is given to the influence of dynamical solvation effects on LR geometry optimizations in solution. The results on formaldehyde point out the complementarity of LR and SS approaches and the advantages of the latter model especially for polar solvents and/or weak transitions. The computed emission energies for coumarin derivatives are very close to their experimental counterparts, pointing out the importance of a proper treatment of nonequilibrium solvent effects on both the excited and the ground state energies. The availability of SS-PCM/TD-DFT models for the study of absorption and emission processes allows for a consistent treatment of a number of different spectroscopic properties in solution.
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Affiliation(s)
- Roberto Improta
- Dipartimento di Chimica, Università Federico II, Complesso Monte S. Angelo, via Cintia, I-80126 Napoli, Italy.
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117
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Brancato G, Rega N, Barone V. A quantum mechanical/molecular dynamics/mean field study of acrolein in aqueous solution: analysis of H bonding and bulk effects on spectroscopic properties. J Chem Phys 2007; 125:164515. [PMID: 17092113 DOI: 10.1063/1.2359723] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
A novel molecular dynamics methodology recently proposed by our group [Rega et al., Chem. Phys. Lett. 422, 367 (2006)], which is based on an integrated hybrid potential rooted in high level quantum mechanical methods using localized basis functions and nonperiodic boundary conditions, has been applied to study acrolein in aqueous solution. The solute structural rearrangement and its hydrogen-bonding pattern due to the interactions with water have been analyzed in some detail. Moreover, the solvent effects on the UV n-->pi* vertical transition and on the NMR 13C and 17O shielding constants of acrolein have been investigated theoretically by performing a posteriori quantum mechanical calculations on a statistically significant number of snapshots extracted from both gas-phase and aqueous solution simulations. Results show that such effective computational strategy can be successfully used to improve our understanding, at atomic level, of important spectroscopic observables.
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Affiliation(s)
- Giuseppe Brancato
- Dipartimento di Chimica, Università Federico II, Complesso Monte S. Angelo, Via Cintia, I-80126 Napoli, Italy
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118
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Lange A, Herbert JM. Simple Methods To Reduce Charge-Transfer Contamination in Time-Dependent Density-Functional Calculations of Clusters and Liquids. J Chem Theory Comput 2007; 3:1680-90. [DOI: 10.1021/ct700125v] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Adrian Lange
- Department of Chemistry, The Ohio State University, Columbus, Ohio 43210
| | - John M. Herbert
- Department of Chemistry, The Ohio State University, Columbus, Ohio 43210
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119
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Shukla MK, Leszczynski J. Electronic Spectra, Excited State Structures and Interactions of Nucleic Acid Bases and Base Assemblies: A Review. J Biomol Struct Dyn 2007; 25:93-118. [PMID: 17676942 DOI: 10.1080/07391102.2007.10507159] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
A comprehensive review of recent theoretical and experimental advances in the singlet electronic transitions, excited state structures and dynamics of nucleic acid bases (NABs) and base assemblies are presented. It is well known that NABs absorb ultraviolet radiation, but the absorbed energy is efficiently dissipated in the form of ultrafast internal conversion processes believed to occur in the subpicosecond time scale and, therefore, enabling NABs highly photostable. It is not known how much evolutionary role was played in evolving these molecules and the ultimate selection by nature as genetic materials, but it is well accepted that survival-of-fittest prevails. Recently, significant efforts have been continuously paid to understand the mechanism of electronic excitation deactivation, but universally acceptable mechanism is still elusive. However, recent investigations reveal that electronic excited state geometries of DNA bases are usually nonplanar and this structural nonplanarity may facilitate nonradiative deactivation. Investigation of excited state structures is challenging and, therefore, it is not surprising that despite the impressive theoretical and computational advances, this research area is still hampered by the methodological and computational limitations. Further, stacking has significant influence on the emission properties of molecules. The 2-aminopurine, a fluorescent adenine derivative frequently used in studying DNA dynamics, shows significant attenuations in fluorescence quantum yield when incorporated in the DNA. Theoretical and computational bottlenecks limit a thorough theoretical understanding of effect of stacking interactions on the excited state dynamics of NABs. Despite these limitations the investigations of excited state properties are progressing in the right direction and our better understanding of excited state structure and dynamics of NABs and nucleic acids may help to design preventive strategy for radiation induced illness and photostable materials.
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Affiliation(s)
- M K Shukla
- Computational Center for Molecular Structure and Interactions, Department of Chemistry, Jackson State University, Jackson, Mississippi 39217, USA
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120
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Jacquemin D, Wathelet V, Preat J, Perpète EA. Ab initio tools for the accurate prediction of the visible spectra of anthraquinones. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2007; 67:334-41. [PMID: 16959534 DOI: 10.1016/j.saa.2006.07.023] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2006] [Revised: 05/25/2006] [Accepted: 07/14/2006] [Indexed: 05/11/2023]
Abstract
The UV/vis absorption spectra of 101 anthraquinones solvated in two protic solvents (methanol and ethanol) has been theoretically predicted using the time-dependent density functional theory (TD-DFT) for the excited state calculations and the polarizable continuum model (PCM) for evaluating bulk solvent effects. Two functionals (B3LYP and PBE0) have been used and they provide similar mean absolute deviations (approximately 0.09 eV) but mean signed errors presenting opposite signs. The errors can be minimized by using simple or multiple linear regression, the latter combining the results of both functionals to reach an optimal estimation of the lambda(max) (mean absolute error 0.06 eV). Specific fittings for the two media have been performed and it turned out that our approach is even more efficient for anthraquinones solvated in ethanol.
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Affiliation(s)
- Denis Jacquemin
- Laboratoire de Chimie Théorique Appliquée, Facultés Universitaires Notre-Dame de la Paix, rue de Bruxelles 61, B-5000 Namur, Belgium.
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121
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Gustavsson T, Sarkar N, Bányász A, Markovitsi D, Improta R. Solvent Effects on the Steady-state Absorption and Fluorescence Spectra of Uracil, Thymine and 5-Fluorouracil. Photochem Photobiol 2007; 83:595-9. [PMID: 17576372 DOI: 10.1111/j.1751-1097.2007.00052.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
We report a comparison of the steady-state absorption and fluorescence spectra of three representative uracil derivatives (uracil, thymine and 5-fluorouracil) in alcoholic solutions. The present results are compared with those from our previous experimental and computational studies of the same compounds in water and acetonitrile. The effects of solvent polarity and hydrogen bonding on the spectra are discussed in the light of theoretical predictions. This comparative analysis provides a more complete picture of the solvent effects on the absorption and fluorescence properties of pyrimidine nucleobases, with special emphasis on the mechanism of the excited state deactivation.
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Affiliation(s)
- Thomas Gustavsson
- Laboratoire Francis Perrin, CEA/DSM/DRECAM/SPAM - CNRS URA 2453, CEA Saclay, F-91191 Gif-sur-Yvette, France.
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122
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Pezzella A, Crescenzi O, Natangelo A, Panzella L, Napolitano A, Navaratnam S, Edge R, Land EJ, Barone V, d'Ischia M. Chemical, Pulse Radiolysis and Density Functional Studies of a New, Labile 5,6-Indolequinone and Its Semiquinone. J Org Chem 2007; 72:1595-603. [PMID: 17266371 DOI: 10.1021/jo0615807] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The chemical and spectroscopic characterization of 5,6-indolequinones and their semiquinones, key transient intermediates in the oxidative conversion of 5,6-dihydroxyindoles to eumelanin biopolymers, is a most challenging task. In the present paper, we report the characterization of a novel, relatively long-lived 5,6-indolequinone along with its semiquinone using an integrated chemical, pulse radiolytic, and computational approach. The quinone was obtained by oxidation of 5,6-dihydroxy-3-iodoindole (1a) with o-chloranil in cold ethyl acetate or aqueous buffer: it displayed electronic absorption bands around 400 and 600 nm, was reduced to 1a with Na2S2O4, and reacted with o-phenylenediamine to give small amounts of 3-iodo-1H-pyrrolo[2,3-b]phenazine (2). The semiquinone exhibited absorption maxima at 380 nm (sh) and 520 nm and was detected as the initial species produced by pulse radiolytic oxidation of 1a at pH 7.0. DFT investigations indicated the 6-phenoxyl radical and the N-protonated radical anion as the most stable tautomers for the neutral and anion forms of the semiquinone, respectively. Calculated absorption spectra in water gave bands at 350 (sh) and 500 nm for the neutral form and at 310 and 360 (sh) nm for the anion. Disproportionation of the semiquinone with fast second-order kinetics (2k = 1.1 x 1010 M-1 s-1) gave a chromophore with absorption bands resembling those of chemically generated 1a quinone. Computational analysis predicted 1a quinone to exist in vacuo as the quinone-methide tautomer, displaying low energy transitions at 380 and 710 nm, and in water as the o-quinone, with calculated absorption bands around 400 and 820 nm. A strong participation of a p orbital on the iodine atom in the 360-380 nm electronic transitions of the o-quinone and quinone-methide was highlighted. The satisfactory agreement between computational and experimental electronic absorption data would suggest partitioning of 1a quinone between the o-quinone and quinone-methide tautomers depending on the medium.
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Affiliation(s)
- Alessandro Pezzella
- Department of Organic Chemistry and Biochemistry, University of Naples Federico II, Via Cintia, I-80126 Naples, Italy.
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123
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Savko M, Kaščáková S, Mojzeš P, Jancura D, Miškovský P, Uličný J. Ground and excited state properties of naphthazarin: Absorption spectroscopy and theoretical modeling study. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/j.theochem.2006.10.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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124
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125
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Ludwig V, Coutinho K, Canuto S. A Monte Carlo-quantum mechanics study of the lowest n–π* and π–π* states of uracil in water. Phys Chem Chem Phys 2007; 9:4907-12. [PMID: 17912421 DOI: 10.1039/b704335j] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The solvatochromic shifts of the n-pi(*) and pi-pi(*) states of uracil in water are analyzed using a combined and sequential Monte Carlo/quantum mechanics (MC/QM) approach. The role of the solute polarization and electronic delocalization into the solvent region are investigated. Electronic polarization of the solute is obtained using the HF/6-31G(d), the polarizable continuum model (PCM) and an iterative procedure using MP2/aug-cc-pVDZ in the MC/QM. The in-water dipole moment of uracil is obtained, respectively, as 5.12 D, 6.12 D and 7.01 +/- 0.05 D. This latter result, corresponding to an increase of 60% with respect to the gas phase value, is used in the classical potential of the MC simulation to obtain statistically uncorrelated configurations for subsequent QM calculations of the ultraviolet-visible absorption spectrum of uracil in water. QM calculations are performed at the time-dependent density-functional theory (TD-DFT) combined with the B3LYP and B3PW91 functionals, multiconfigurational (CASSCF) and the semi-empirical all-valence electron INDO/CIS methods. Using 60 solute-solvent configurations with the explicit inclusion of 200 water molecules the solvatochromic shift is obtained as a blue shift of 0.50 eV for the n-pi(*) state and a red shift of 0.19 eV for the pi-pi(*) state, in good agreement with experimentally-inferred values. These results are compared with TD-DFT results in conjunction with PCM approaches and the importance of solute polarization and wave function delocalization over the solvent region is discussed. Our results suggest that the elusive n-pi(*) state of uracil in water lies around 255 nm hidden by the intense and broad pi-pi(*) transition with a maximum at 260 nm, inverting the relative locations of these states compared to the gas phase. This is further supported by considering the in-water dipole moment changes upon excitation, as obtained from CASSCF calculations.
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Affiliation(s)
- Valdemir Ludwig
- Instituto de Física, Universidade de São Paulo, CP 66318, São Paulo, 05315-970, SP Brazil
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126
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Santoro F, Barone V, Gustavsson T, Improta R. Solvent Effect on the Singlet Excited-State Lifetimes of Nucleic Acid Bases: A Computational Study of 5-Fluorouracil and Uracil in Acetonitrile and Water. J Am Chem Soc 2006; 128:16312-22. [PMID: 17165786 DOI: 10.1021/ja0657861] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The first comprehensive quantum mechanical study of solvent effects on the behavior of the two lowest energy excited states of uracil derivatives is presented. The absorption and emission spectra of uracil and 5-fluorouracil in acetonitrile and aqueous solution have been computed at the time-dependent density-functional theory level, using the polarizable continuum model (PCM) to take into account bulk solvent effects. The computed spectra and the solvent shifts provided by our method are close to their experimental counterpart. The S0/S1 conical intersection, located in the presence of hydrogen-bonded solvent molecules by CASSCF (8/8) calculations, indicates that the mechanism of ground-state recovery, involving out-of-plane motion of the 5 substituent, does not depend on the nature of the solvent. Extensive explorations of the excited-state surfaces in the Franck-Condon (FC) region show that solvent can modulate the accessibility of an additional decay channel, involving a dark n/pi* excited state. This finding provides the first unifying explanation for the experimental trend of 5-fluorouracil excited-state lifetime in different solvents. The microscopic mechanisms underlying solvent effects on the excited-state behavior of nucleobases are discussed.
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Affiliation(s)
- Fabrizio Santoro
- Istituto per i Processi Chimico-Fisici del CNR, Area della Ricerca del CNR di Pisa, via Moruzzi 1, I-56124 Pisa, Italy
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127
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Pezzella A, Panzella L, Crescenzi O, Napolitano A, Navaratman S, Edge R, Land EJ, Barone V, d'Ischia M. Short-Lived Quinonoid Species from 5,6-Dihydroxyindole Dimers en Route to Eumelanin Polymers: Integrated Chemical, Pulse Radiolytic, and Quantum Mechanical Investigation. J Am Chem Soc 2006; 128:15490-8. [PMID: 17132016 DOI: 10.1021/ja0650246] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The transient species formed by oxidation of three dimers of 5,6-dihydroxyindole (1), a major building block of the natural biopolymer eumelanin, have been investigated. Pulse radiolytic oxidation of 5,5',6,6'-tetrahydroxy-2,4'-biindolyl (3) and 5,5',6,6'-tetrahydroxy-2,7'-biindolyl (4) led to semiquinones absorbing around 450 nm, which decayed with second-order kinetics (2k=2.8x10(9) and 1.4x10(9) M-1 s-1, respectively) to give the corresponding quinones (500-550 nm). 5,5',6, 6'-Tetrahydroxy-2,2'-biindolyl (2), on the other hand, furnished a semiquinone (lamdamax=480 nm) which disproportionated at a comparable rate (2k=3x10(9) M-1 s-1) to give a relatively stable quinone (lamdamax=570 nm). A quantum mechanical investigation of o-quinone, quinonimine, and quinone methide structures of 2-4 suggested that oxidized 2-4 exist mainly as 2-substituted extended quinone methide tautomers. Finally, an oxidation product of 3 was isolated for the first time and was formulated as the hydroxylated derivative 5 arising conceivably by the addition of water to the quinone methide intermediate predicted by theoretical analysis. Overall, these results suggest that the oxidation chemistry of biindolyls 2-4 differs significantly from that of the parent 1, whereby caution must be exercised before concepts that apply strictly to the mode of coupling of 1 are extended to higher oligomers.
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Affiliation(s)
- Alessandro Pezzella
- Department of Organic Chemistry, University of Naples Federico II, Via Cintia, I-80126 Naples, Italy
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128
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Benzi C, Barone V, Tarroni R, Zannoni C. Order parameters of alpha,omega-diphenylpolyenes in a nematic liquid crystal from an integrated computational and 13C NMR spectroscopic approach. J Chem Phys 2006; 125:174904. [PMID: 17100476 DOI: 10.1063/1.2363994] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The orientational order parameters and conformational behavior of five relatively large rodlike molecules, biphenyl, trans-stilbene, 1,3-diphenyl-butadiene, 1,3,5-diphenyl-hexatriene, and 1,3,5,7-diphenyl-octatetraene, dissolved in the thermotropic liquid crystal ZLI-1167, have been studied using an integrated approach combining (13)C NMR measurements and quantum mechanical computations of carbon chemical shift tensors. Besides biphenyl, the phenyl moiety of all structures has been found to have a high rotational mobility in the temperature range of the present experiments. The rank-two order parameter <P(2)> in the nematic phase is found to increase steadily from the shortest to the longest term of the series at any temperature within the nematic range. The molecular biaxiality order parameter <D(02) (2)> is found to be small and essentially constant with temperature, giving further support to the common assumption of effective uniaxiality for these probes.
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Affiliation(s)
- Caterina Benzi
- Dipartimento di Chimica, Università Federico II, Complesso Monte S. Angelo, Via Cintia, I-80126 Naples, Italy.
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129
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Bertolino CA, Ferrari AM, Barolo C, Viscardi G, Caputo G, Coluccia S. Solvent effect on indocyanine dyes: A computational approach. Chem Phys 2006. [DOI: 10.1016/j.chemphys.2006.07.045] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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130
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Gustavsson T, Sarkar N, Lazzarotto E, Markovitsi D, Improta R. Singlet excited state dynamics of uracil and thymine derivatives: A femtosecond fluorescence upconversion study in acetonitrile. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2006.08.058] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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131
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Hare PM, Crespo-Hernández CE, Kohler B. Solvent-Dependent Photophysics of 1-Cyclohexyluracil: Ultrafast Branching in the Initial Bright State Leads Nonradiatively to the Electronic Ground State and a Long-Lived1nπ* State. J Phys Chem B 2006; 110:18641-50. [PMID: 16970494 DOI: 10.1021/jp064714t] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The modified nucleic acid base, 1-cyclohexyluracil, was studied by femtosecond transient absorption spectroscopy in protic and aprotic solvents of varying polarity. UV excitation at 267 nm populates the lowest-energy bright state, a (1)pipi* state, which has a lifetime of 120-270 fs, depending on the solvent. In all solvents, this initial bright state population bifurcates with approximately 60% undergoing subpicosecond nonradiative decay to the electronic ground state and the remaining population branching to a singlet dark state. The latter absorbs between 340 and 450 nm. The latter state is assigned to the lowest-energy (1)npi* state. It decays to the electronic ground state with a lifetime that varies from 26 ps in water to at least several nanoseconds in aprotic solvents. The results suggest that the two nonradiative decay pathways identified for photoexcited uracil in recent quantum chemical calculations (Matsika, S. J. Phys. Chem. A. 2004, 108, 7584) are simultaneously operative in a wide variety of solvent environments. The lowest-energy triplet state was also detected by transient absorption. The triplet population appears in a few picoseconds and is not formed from the thermalized (1)npi* state. It is suggested that high spin-orbit coupling is found only along initial segments of the nonradiative decay pathways. Efficient intersystem crossing prior to vibrational cooling offers a possible explanation for the wavelength-dependent triplet yields seen in single DNA bases.
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Affiliation(s)
- Patrick M Hare
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA
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132
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Jacquemin D, Preat J, Wathelet V, Perpète EA. Time-dependent density functional theory determination of the absorption spectra of naphthoquinones. Chem Phys 2006. [DOI: 10.1016/j.chemphys.2006.07.037] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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133
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Improta R, Barone V, Scalmani G, Frisch MJ. A state-specific polarizable continuum model time dependent density functional theory method for excited state calculations in solution. J Chem Phys 2006; 125:054103. [PMID: 16942199 DOI: 10.1063/1.2222364] [Citation(s) in RCA: 554] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
An effective state specific (SS) model for the inclusion of solvent effects in time dependent density functional theory (TD-DFT) computations of excited electronic states has been developed and coded in the framework of the so-called polarizable continuum model (PCM). Different relaxation time regimes can be treated thus giving access to a number of different spectroscopic properties together with solvent relaxation energies of paramount relevance in electron transfer processes. SS and conventional linear response (LR) models have been compared for two benchmark systems (coumarin 153 and formaldehyde in different solvents) and in the limiting simple case of a dipolar solute embedded in a spherical cavity. The results point out the complementarity of LR and SS approaches and the advantages of the latter model especially for polar solvents. The favorable scaling properties of PCM-TD-DFT models in both SS and LR variants and their availability in effective quantum mechanical codes pave the route for the computation of reliable spectroscopic properties of large molecules of technological and/or biological interest in their natural environments.
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Affiliation(s)
- Roberto Improta
- Dipartimento di Chimica, Università Federico II, Complesso Monte S. Angelo, via Cintia, I-80126 Napoli, Italy.
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134
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Jacquemin D, Wathelet V, Perpète EA. Ab Initio Investigation of the n → π* Transitions in Thiocarbonyl Dyes. J Phys Chem A 2006; 110:9145-52. [PMID: 16854027 DOI: 10.1021/jp062580d] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The n --> pi* transitions in more than 100 thiocarbonyl dyes have been calculated with an ab initio procedure relying on the combination of time-dependent density functional theory (TD-DFT) for evaluating excited states and the polarizable continuum model (PCM) for modeling the bulk solvent effects on both the geometrical and electronic structures. Two hybrid functionals (B3LYP and PBE0) and several basis sets, some including f polarization functions, have been used. B3LYP provides the most accurate raw estimates, but once simple linear regression is performed, both functionals give similar results with a small advantage for PBE0. By use of the latter, the mean absolute deviation with respect to experiment is limited to 0.06 eV whereas less than 20% of the estimates differ from absorption data by more than 0.10 eV. To assess the validity limits of our model, compounds containing multiple C=S chromophores have also been considered.
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Affiliation(s)
- Denis Jacquemin
- Laboratoire de Chimie Théorique Appliquée, Facultés Universitaires Notre-Dame de la Paix, rue de Bruxelles, 61, B-5000 Namur, Belgium.
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135
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Gustavsson T, Sarkar N, Lazzarotto E, Markovitsi D, Barone V, Improta R. Solvent Effect on the Singlet Excited-state Dynamics of 5-Fluorouracil in Acetonitrile as Compared with Water. J Phys Chem B 2006; 110:12843-7. [PMID: 16805579 DOI: 10.1021/jp062266j] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The excited-state dynamics of 5-fluorouracil in acetonitrile has been investigated by femtosecond fluorescence upconversion spectroscopy in combination with quantum chemistry TD-DFT calculations ((PCM/TD-PBE0). Experimentally, it was found that when going from water to acetonitrile solution the fluorescence decay of 5FU becomes much faster. The calculations show that this is related to the opening of an additional decay channel in acetonitrile solution since the dark n/pi* excited state becomes near degenerate with the bright pi/pi* state, forming a conical intersection close to the Franck-Condon region. In both solvents, a S1-S0 conical intersection, governed by the out-of-plane motion of the fluorine atom, is active, allowing an ultrafast internal conversion to the ground state.
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136
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Improta R, Barone V, Newton MD. A Parameter-Free Quantum-Mechanical Approach for Calculating Electron-Transfer Rates for Large Systems in Solution. Chemphyschem 2006; 7:1211-4. [PMID: 16680796 DOI: 10.1002/cphc.200600069] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Roberto Improta
- Dipartimento di Chimica, Università Federico II, Complesso Monte S. Angelo, via Cintia, 80126 Naples, Italy.
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137
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Barone V, Newton MD, Improta R. Dissociative Electron Transfer in Donor−Peptide−Acceptor Systems: Results for Kinetic Parameters from a Density Functional/Polarizable Continuum Model. J Phys Chem B 2006; 110:12632-9. [PMID: 16800595 DOI: 10.1021/jp0557969] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The main structural and electronic factors playing a role in intramolecular dissociative electron transfer of a simple donor-peptide-acceptor (D-peptide-A) model have been investigated by an integrated computational protocol based on the density functional theory, its time-dependent extension, and the polarizable continuum model. Our results allow us to elucidate the electronic states involved in the process and how they are perturbed by the orientation of the donor and the acceptor with respect to the peptide chain and by the presence of the solvent. We also report a semiquantitative estimation of the rate constant governing electron transfer obtained by a direct quantum mechanical evaluation of all the terms entering the kinetic expressions based on the Marcus theory and its extensions.
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Affiliation(s)
- Vincenzo Barone
- Dipartimento di Chimica, Università Federico II, Complesso Monte S. Angelo, via Cintia, I-80126 Napoli, Italy
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138
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Fabian J. Symmetry-lowering distortion of near-infrared polymethine dyes—a study by first-principles methods. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/j.theochem.2006.02.003] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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139
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Jacquemin D, Bouhy M, Perpète EA. Excitation spectra of nitro-diphenylaniline: Accurate time-dependent density functional theory predictions for charge-transfer dyes. J Chem Phys 2006; 124:204321. [PMID: 16774346 DOI: 10.1063/1.2202735] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Using time-dependent density functional theory (TD-DFT) and the polarizable continuum model (PCM), we have computed the absorption spectra of nitro-diphenylamine dyes. It turns out that the 6-311+G(2d,p) and 6-311G(d,p) basis sets provide, respectively, almost perfectly converged excitation spectra and geometries. Using the PBE0 hybrid functional, we obtain a valuable correlation between PCM-TD-DFT and experimental lambdamax with mean signed/absolute deviations of -4 nm (0.03 eV)8 nm (0.06 eV) and relatively small extreme discrepancies, although the excitations responsible for the color of this class of dyes present a charge-transfer character. The changes in the electron density upon absorption are analyzed through an orbital picture. In addition, a relationship between the light fastness and a well-identified vibrational frequency is proposed.
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Affiliation(s)
- Denis Jacquemin
- Laboratoire de Chimie Théorique Appliquée, Facultés Universitaires Notre-Dame de la Paix, rue de Bruxelles 61, B-5000 Namur, Belgium.
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140
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Zazza C, Grandi A, Bencivenni L, Aschi M. On the performance of gradient-corrected approximation functionals and polarizable continuum model in the study of 1,2,3-triazine in water. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/j.theochem.2006.02.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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141
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Perpète EA, Preat J, André JM, Jacquemin D. An ab Initio Study of the Absorption Spectra of Indirubin, Isoindigo, and Related Derivatives. J Phys Chem A 2006; 110:5629-35. [PMID: 16640356 DOI: 10.1021/jp060069e] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The UV/visible spectra of a series of indirubin, isoindigo, and other indigo/thioindigo related dyes have been evaluated in various solvent environments by using the time-dependent density functional theory in conjunction with the polarizable continuum model. Even for molecules of the same family, significant differences in the excitation processes have been noted. Two hybrid functionals have been selected: B3LYP and PBE0. For a set of the 50 selected molecular cases, both functionals provide accurate lambda(max), with mean absolute deviations limited to 0.1 eV. Actually, isoindigo is the main challenging series, with systematically underestimated excitation energies, due to the different nature of the excitation process. In most cases, we found that PBE0 is more efficient in reproducing the experimental values than B3LYP for sulfur-containing dyes not featuring internal hydrogen bonds, the reverse assertion being also true. In addition, the spectra of a series of unknown dyes have been predicted.
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Affiliation(s)
- Eric A Perpète
- Laboratoire de Chimie Théorique Appliquée, Facultés Universitaires Notre-Dame de la Paix, Namur, Belgium
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142
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Jacquemin D, Perpète EA, Scalmani G, Frisch MJ, Ciofini I, Adamo C. Absorption and emission spectra in gas-phase and solution using TD-DFT: Formaldehyde and benzene as case studies. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2006.01.068] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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143
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Sebek J, Kejík Z, Bour P. Geometry and Solvent Dependence of the Electronic Spectra of the Amide Group and Consequences for Peptide Circular Dichroism. J Phys Chem A 2006; 110:4702-11. [PMID: 16599437 DOI: 10.1021/jp060813v] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The influence of geometry variations and solvent environment of N-methylacetamide on its energies and absorption intensities was systematically analyzed with the aid of the time-dependent density functional theory (TD DFT). Selective and often complicated reactions of individual electronic levels on the perturbations were found important for the resultant spectral profile. For example, the n-pi band position varied by tens of nanometers due to the C=O bond length oscillations, while it was rather unaffected by surrounding water. On the contrary, pi-pi type transition energies and intensities were broadly dispersed by the aqueous environment but exhibited a modest coordinate dependence. A simple electrostatic model used previously for absorption in the IR region (J. Chem. Phys. 2005, 122, 144501) explained these changes only partially. Additionally, electronic transfer between the solute and the solvent had to be considered for faithful modeling of the ultraviolet light absorption. The inclusion of the environment and dynamics in the modeling then provided more accurate positions, intensities, and realistic inhomogeneous widths of spectral lines. These factors were found important for absorption and circular dichroism spectra of larger peptides and proteins. This was demonstrated with a combined DFT/coupled oscillator model providing principal features observed in electronic circular dichroism spectra of standard peptide conformations.
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Affiliation(s)
- Jirí Sebek
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nam. 2, 166 10
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144
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Pavone M, Cimino P, De Angelis F, Barone V. Interplay of Stereoelectronic and Enviromental Effects in Tuning the Structural and Magnetic Properties of a Prototypical Spin Probe: Further Insights from a First Principle Dynamical Approach. J Am Chem Soc 2006; 128:4338-47. [PMID: 16569010 DOI: 10.1021/ja0574872] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The nitrogen isotropic hyperfine coupling constant (hcc) and the g tensor of a prototypical spin probe (di-tert-butyl nitroxide, DTBN) in aqueous solution have been investigated by means of an integrated computational approach including Car-Parrinello molecular dynamics and quantum mechanical calculations involving a discrete-continuum embedding. The quantitative agreement between computed and experimental parameters fully validates our integrated approach. Decoupling of the structural, dynamical, and environmental contributions acting onto the spectral observables allows an unbiased judgment of the role played by different effects in determining the overall experimental observables and highlights the importance of finite-temperature vibrational averaging. Together with their intrinsic interest, our results pave the route toward more reliable interpretations of EPR parameters of complex systems of biological and technological relevance.
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Affiliation(s)
- Michele Pavone
- Dipartimento di Chimica, Università di Napoli FedericoII, Complesso Universitario di Monte Sant'Angelo Via Cintia, Italy
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145
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Pavone M, Crescenzi O, Morelli G, Rega N, Barone V. Solvent Effects on the UV (n → π*) and NMR (17O) Spectra of Acetone in Aqueous Solution: Development and Validation of a Modified AMBER Force Field for an Integrated MD/DFT/PCM Approach. Theor Chem Acc 2006. [DOI: 10.1007/s00214-006-0098-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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146
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Jacquemin D, Preat J, Wathelet V, Perpète EA. Substitution and chemical environment effects on the absorption spectrum of indigo. J Chem Phys 2006; 124:74104. [PMID: 16497027 DOI: 10.1063/1.2166018] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The UV/visible spectra of a series of indigo derivatives have been evaluated by using ab initio methods. The combination of the Polarizable continuum model for estimating bulk solvent effects with the TD-B3LYP6-311 + G(2d,p)B3LYP6-311G(d,p) level of approximation, leads to an accurate description of the wavelength of maximum absorption of indigoids compounds. Using this procedure, we have assessed the effects of both the surroundings (solvent and solid state) and the substitution pattern. For the latter, we obtained a mean absolute deviation of only 7 nm (0.02 eV) compared to experiment, for a set of 86 molecules/solvents.
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Affiliation(s)
- Denis Jacquemin
- Laboratoire de Chimie Théorique Appliquée, Facultés Universitaires Notre-Dame de la Paix, Namur, Belgium.
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147
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Jacquemin D, Preat J, Wathelet V, Fontaine M, Perpète EA. Thioindigo Dyes: Highly Accurate Visible Spectra with TD-DFT. J Am Chem Soc 2006; 128:2072-83. [PMID: 16464110 DOI: 10.1021/ja056676h] [Citation(s) in RCA: 183] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The structure and visible spectra of a large panel of thioindigo dyes and derivatives have been evaluated using a TD-PBE0/6-311+G(2d,p)//PBE0/6-311G(d,p) approach explicitly taking bulk solvent effects into account by means of the polarizable continuum model. The influence of the solvent characteristics, the trans-cis isomerization, and the chemical substitution on the benzene rings have been investigated. In addition, hemi-thioindigo dyes, thiazine-indigo, chromophore-like molecules, and selenoindigo have been considered. Though the relative oscillator strengths of the two allowed visible transitions in the nonplanar cis isomers are not always correctly reproduced by theory, the agreement between theoretical and experimental results is far above expectations. For the 170 cases studied, we obtained a mean unsigned error on the predicted lambda(max) limited to 6.9 nm or 0.03 eV, with only 6 (4) cases for which the difference exceeds 20 nm (0.10 eV). These errors are 1 order of magnitude smaller than what has previously been reported for indigoids. A linear correlation between the central double bond length and the lambda(max) has been established, while the bond length and vibrational frequency of the carbonyl groups do not correlate with the thioindigo color. The higher excitation energies of the cis conformers, compared to the trans structures, result from a less stabilized LUMO in the former case. Indeed, for cis thioindigo, the two electron-rich (in the excited state) carbonyl units lie close to each other.
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Affiliation(s)
- Denis Jacquemin
- Laboratoire de Chimie Théorique Appliquée, Facultés Universitaires Notre-Dame de la Paix, rue de Bruxelles 61, B-5000 Namur, Belgium.
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148
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Zazza C, Amadei A, Sanna N, Grandi A, Chillemi G, Di Nola A, D'Abramo M, Aschi M. Theoretical modeling of the valence UV spectra of 1,2,3-triazine and uracil in solution. Phys Chem Chem Phys 2006; 8:1385-93. [PMID: 16633620 DOI: 10.1039/b515648c] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Assessment of the perturbed matrix method (PMM) ability in reproducing valence UV absorption spectra is carried out on two model systems: 1,2,3-triazine in methanol solution and uracil in water solution. Results show that even using the simplest definition of the quantum center, i.e. the portion of the system explicitly treated quantum mechanically, PMM provides rather good results. This paper further confirms the possibility of using PMM as a theoretical-computational tool, complementary to other methodologies, for addressing the electronic properties in molecular systems of high complexity.
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Affiliation(s)
- Costantino Zazza
- Consorzio Interuniversitario per le Applicazioni di Supercalcolo per Università e Ricerca (CASPUR), via dei Tizii 6b, 00185, Roma, Italy
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149
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Gustavsson T, Bányász A, Lazzarotto E, Markovitsi D, Scalmani G, Frisch MJ, Barone V, Improta R. Singlet Excited-State Behavior of Uracil and Thymine in Aqueous Solution: A Combined Experimental and Computational Study of 11 Uracil Derivatives. J Am Chem Soc 2006; 128:607-19. [PMID: 16402849 DOI: 10.1021/ja056181s] [Citation(s) in RCA: 306] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The excited-state properties of uracil, thymine, and nine other derivatives of uracil have been studied by steady-state and time-resolved spectroscopy. The excited-state lifetimes were measured using femtosecond fluorescence upconversion in the UV. The absorption and emission spectra of five representative compounds have been computed at the TD-DFT level, using the PBE0 exchange-correlation functional for ground- and excited-state geometry optimization and the Polarizable Continuum Model (PCM) to simulate the aqueous solution. The calculated spectra are in good agreement with the experimental ones. Experiments show that the excited-state lifetimes of all the compounds examined are dominated by an ultrafast (<100 fs) component. Only 5-substituted compounds show more complex behavior than uracil, exhibiting longer excited-state lifetimes and biexponential fluorescence decays. The S(0)/S(1) conical intersection, located at CASSCF (8/8) level, is indeed characterized by pyramidalization and out of plane motion of the substituents on the C5 atom. A thorough analysis of the excited-state Potential Energy Surfaces, performed at the PCM/TD-DFT(PBE0) level in aqueous solution, shows that the energy barrier separating the local S(1) minimum from the conical intersection increases going from uracil through thymine to 5-fluorouracil, in agreement with the ordering of the experimental excited-state lifetime.
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Affiliation(s)
- Thomas Gustavsson
- Laboratoire Francis Perrin, CEA/DSM/DRECAM/SPAM - CNRS URA 2453, CEA Saclay, Gif-sur-Yvette, France.
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Allonas X, Morlet-Savary F, Lalevée J, Fouassier JP. A Photodissociation Reaction: Experimental and Computational Study of 2-Hydroxy-2,2-dimethylacetophenone†. Photochem Photobiol 2006; 82:88-94. [PMID: 16097859 DOI: 10.1562/2005-05-20-ra-535] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The photophysical parameters controlling the cleavage process of 2-hydroxy-2,2-dimethylacetophenone (HDMA) were investigated in detail. Time-resolved picosecond absorption experiments show that the formation of the triplet state occurs within 20 ps after excitation and decays within hundreds of picoseconds depending on the solvent polarity. Molecular modeling reveals that three stable conformations exist in the ground state, the most stable one exhibiting an intramolecular hydrogen bond that modifies the electronic properties of the molecule. This explains quite well the steady-state absorption properties. The conformation of the most stable triplet state is twisted by 180 degrees with respect to the ground state. Computation of the potential energy surface along the molecular coordinate for the dissociation reaction evidences an electronic state crossing yielding a final sigmasigma* state, in perfect agreement with the state correlation diagram. Optimization of the transition state allows the calculation of the activation energy and the use of the transition-state theory leads to an estimate of 100 ps for the cleavage process in the gas phase. Single-point energy calculations using a solvent model predict an increase of the dissociation rate constant with the increase of the solvent polarity, in good agreement with the value deduced from kinetic measurements.
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Affiliation(s)
- X Allonas
- Département de Photochimie Générale, Université de Haute Alsace, Mulhouse, France.
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