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Optical absorption and magnetic circular dichroism spectra of thiouracils: a quantum mechanical study in solution
KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.ORCID iD: 0000-0002-1191-4954
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2017 (English)In: Photochemical and Photobiological Sciences, ISSN 1474-905X, E-ISSN 1474-9092, Vol. 16, no 9, 1415-1423 p.Article in journal (Refereed) Published
Abstract [en]

The excited electronic states of 2-thiouracil, 4-thiouracil and 2,4-dithiouracil, the analogues of uracil where the carbonyl oxygens are substituted by sulphur atoms, have been investigated by computing the magnetic circular dichroism (MCD) and one-photon absorption (OPA) spectra at the time-dependent density functional theory level. Special attention has been paid to solvent effects, included by a mixed discrete/continuum model, and to determining how our results depend on the adopted DFT functional (CAM-B3LYP and B3LYP). Whereas including solvent effects does not dramatically impact the MCD and OPA spectra, though improving the agreement with the experimental spectra, the performances of CAM-B3LYP and B3LYP are remarkably different. CAM-B3LYP captures well the effect of thionation on the uracil excited states and provides spectra in good agreement with the experiments, whereas B3LYP shows some deficiency in describing 2-TU and 2,4-DTU spectra, despite being more accurate than CAM-B3LYP for 4-TU.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2017. Vol. 16, no 9, 1415-1423 p.
National Category
Biochemistry and Molecular Biology
Identifiers
URN: urn:nbn:se:kth:diva-215374DOI: 10.1039/c7pp00105cISI: 000410665500008PubMedID: 28745752Scopus ID: 2-s2.0-85029509510OAI: oai:DiVA.org:kth-215374DiVA: diva2:1147912
Funder
Swedish Research Council, 621-2014-4646
Note

QC 20171009

Available from: 2017-10-09 Created: 2017-10-09 Last updated: 2017-11-29Bibliographically approved
In thesis
1. Derivation and application of response functions for nonlinear absorption and dichroisms
Open this publication in new window or tab >>Derivation and application of response functions for nonlinear absorption and dichroisms
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is titled ’Derivation and application of response functions for nonlinear absorption and dichroisms’ and was written by Tobias Fahleson at the Division of Theoretical Chemistry & Biology at KTH Royal Institute of Technology in Sweden. It explores and expands upon theoretical means of quantifying a number of nonlinear spectroscopies, including two-photon absorption, resonant inelastic x-ray scattering, Jones birefringence, and magnetic circular dichroism. Details are provided for the derivation and program implementation of complex-valued (damped) cubic response functions that have been implemented in the quantum chemistry package DALTON [1], based on working equations formulated for an approximate-state wave function. This is followed by an assessment of the implementation. It is demonstrated how two-photon absorption (TPA) can be described either through second-order transition moments or the damped cubic response function. A set of illustrative TPA profiles are produced for smaller molecules. In addition, resonant inelastic x-ray scattering (RIXS) is explored in a similar manner as two-photon absorption. It is shown for small systems how RIXS spectra may be obtained using a reduced form of the cubic response function. Linear birefringences are investigated for noble gases, monosubstituted benzenes, furan homologues, and liquid acetonitrile. Regarding the noble gases, the Jones effect is shown to be proportional to a power series with respect to atomic radial sizes. For monosubstituted benzenes, a linear relation between the Jones birefringence and the empirical para-Hammett constant as well as the permanent electric dipole moment is presented. QM/MM protocols are applied for a pure acetonitrile liquid, including polarizable embedding and polarizable-density embedding models. The final chapter investigates magnetically induced circular dichroism (MCD). A question regarding relative stability of the first set of excited states for DNA-related molecular systems is resolved through MCD by exploiting the signed nature of circular dichroisms. Furthermore, to what extent solvent contributions affect MCD spectra and the effect on uracil MCD spectrum due to thionation is studied.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018. 85 p.
Series
TRITA-BIO-Report, ISSN 1654-2312 ; 2018:01
Keyword
Theoretical spectroscopy, cubic response theory, damped response theory, magnetic circular dichroism, linear birefringence, two-photon absorption, TPA, resonant-inelastic x-ray scattering, RIXS, DALTON program
National Category
Theoretical Chemistry
Research subject
Theoretical Chemistry and Biology
Identifiers
urn:nbn:se:kth:diva-218662 (URN)978-91-7729-627-0 (ISBN)
Public defence
2018-02-28, FA32, Roslagstullsbacken 21, Albanova, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Knut and Alice Wallenberg Foundation, KAW- 2013.0020Swedish Research Council, 621-2014-4646
Note

QC 20180108

Available from: 2018-01-08 Created: 2017-11-29 Last updated: 2018-01-08Bibliographically approved

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