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Nonradiative decay of the lowest excited singlet state of 2-aminopyridine is considerably faster than the radiative decay
KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.ORCID iD: 0000-0003-0007-0394
Beijing Normal University.
2009 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 130, no 14, 144315- p.Article in journal (Refereed) Published
Abstract [en]

Ab initio calculations reveal that radiative lifetime of the lowest excited singlet state of 2-aminopyridine (2AP) molecule should be around 20 ns, consistent with the molecules of the same type, but is about one order of magnitude larger than the claimed experimental fluorescent lifetime in recent years. A S1/S0 conical intersection close to the S1 state has been located which could be the possible nonradiative channel that is responsible for the fast decay observed in the experiment.

Place, publisher, year, edition, pages
America: American -institute of Physics , 2009. Vol. 130, no 14, 144315- p.
Keyword [en]
ab initio calculations, excited states, fluorescences, organic compounds, radiative lifetimes
National Category
Theoretical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-11898DOI: 10.1063/1.3113664ISI: 000265617200033Scopus ID: 2-s2.0-65249190165OAI: oai:DiVA.org:kth-11898DiVA: diva2:288468
Note
QC20100719 Copyright (2009) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of PhysicsAvailable from: 2010-01-29 Created: 2010-01-21 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Theoretical Studies on Kinetics of Molecular Excited States
Open this publication in new window or tab >>Theoretical Studies on Kinetics of Molecular Excited States
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

HTML clipboardKinetics on molecular excited states is a challenging subject in the field of theoretical chemistry. This thesis pays attention to theoretical studies on kinetics of photo-induced processes, including photo-chemical reactions, radiative and non-radiative transitions (intersystem crossing and internal conversion) in molecular and bio-related systems.

One- or multi- dimensional potential energy surfaces (PESs) not only provide qualitative mechanistic explanation for excited state decay, but also make it possible to perform kinetic simulations. We have constructed several types of PESs by using computational methods of high-accuracy for a variety of systems of interest. In particular, density functional theory (DFT) and couple cluster singles and doubles (CCSD) method are employed to build PESs of the ground and lowest triple states. For medium-sized molecules, the complete active space self-consistent (CASSCF) method is used for constructing the PESs of excited states.

Various kinetic theories for the decay processes of excite states are briefly introduced, in particularly adiabatic and nonadiabatic Rice–Ramsperger–Kassel -Marcus (RRKM) approaches for the kinetics of nonradiative decay of excited 2-aminopridine molecule. Special attention has been devoted to Monte Carlo transition state theory which can provide an efficient way to predict the rate of nonradiative transitions of polyatomic molecules on multi-dimensional PESs. Examples of Monte Carlo simulations on the intersystem crossing of isocyanic acid and a model molecule of hexacoordinate heme, as well as internal conversion process for 2-amininopyridine dimer and the adenine-thymine base pair are presented.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. 62 p.
Series
Trita-BIO-Report, ISSN 1654-2312 ; 2010:2
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-11994 (URN)978-91-7415-551-8 (ISBN)
Public defence
2010-03-05, FB 53 Svedbergssalen, Roslagstullsbacken 21, AlbaNova, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC20100720Available from: 2010-02-09 Created: 2010-02-08 Last updated: 2012-03-28Bibliographically approved
2. Theoretical studies on photophysics and photochemistry of DNA
Open this publication in new window or tab >>Theoretical studies on photophysics and photochemistry of DNA
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Theoretical studies on biological systems like nucleic acid and protein have been widely developed in the past 50 years and will continue to be a topic of interest in forefronts of natural science. In addition to experimental science, computational modeling can give useful information and help us to understand biochemical issues at molecular, atomic and even electronic levels.

Deoxyribonucleic acid (DNA), the hereditary basis of life’s genetic identity, has always been major topic of discussions since its structure was built in 1953. However, harmful UV radiation from sunlight can make damage to DNA molecules and eventually give rise to DNA damaging biological consequences, like mutagenesis, carcinogenesis, and cell death. Photostability, photodamage, and photorepair are of vital importance in the photophysics and photochemistry of DNA. In this thesis, we have applied high level computer-aided theoretical methods to explore the underlying mechanisms for these three critical issues of DNA. Special attentions are paid to the following aspects: the properties of the excited states, the design of relevant computational models and the effects of biological environments.

We have systematically studied the excited state properties of DNA from single base to base pair and oligonucleotides, where the concerted base pairing and base stacking effects was found to play important roles in DNA photostability. The UV-light induced isomerization mechanism between two photoproducts of DNA photodamage has been revealed in different biological environments. In association with DNA photodamage, the related photorepair processes have been proposed for different lesions in photolyase which is a catalytic enzyme for DNA, and the calculated results well explained the experimental observations. In particular, the internal and external properties of flavin cofactors have been extensively studied by combining the electronic structure and spectroscopic calculations. We have examined the effects of the intramolecular hydrogen bond on spectroscopic properties of flavins. The good agreements with the experimental spectra indicated that the biological self-regulation acted critical role in these biological systems.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2010. 76 p.
Series
Trita-BIO-Report, ISSN 1654-2312 ; 2011:15
National Category
Theoretical Chemistry
Research subject
SRA - Molecular Bioscience
Identifiers
urn:nbn:se:kth:diva-33531 (URN)978-91-7415-977-6 (ISBN)
Public defence
2011-06-14, FA32, AlbaNova University Center, Roslagstullsbacken 21,, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20110530Available from: 2011-05-30 Created: 2011-05-09 Last updated: 2011-05-30Bibliographically approved

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