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How method-dependent are calculated differences between vertical, adiabatic, and 0-0 excitation energies?
Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
2014 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 118, no 23, 4157-4171 p.Article in journal (Refereed) Published
Abstract [en]

Through a large number of benchmark studies, the performance of different quantum chemical methods in calculating vertical excitation energies is today quite well established. Furthermore, these efforts have in recent years been complemented by a few benchmarks focusing instead on adiabatic excitation energies. However, it is much less well established how calculated differences between vertical, adiabatic and 0-0 excitation energies vary between methods, which may be due to the cost of evaluating zero-point vibrational energy corrections for excited states. To fill this gap, we have calculated vertical, adiabatic, and 0-0 excitation energies for a benchmark set of molecules covering both organic and inorganic systems. Considering in total 96 excited states and using both TD-DFT with a variety of exchange-correlation functionals and the ab initio CIS and CC2 methods, it is found that while the vertical excitation energies obtained with the various methods show an average (over the 96 states) standard deviation of 0.39 eV, the corresponding standard deviations for the differences between vertical, adiabatic, and 0-0 excitation energies are much smaller: 0.10 (difference between adiabatic and vertical) and 0.02 eV (difference between 0-0 and adiabatic). These results provide a quantitative measure showing that the calculation of such quantities in photochemical modeling is well amenable to low-level methods. In addition, we also report on how these energy differences vary between chemical systems and assess the performance of TD-DFT, CIS, and CC2 in reproducing experimental 0-0 excitation energies.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2014. Vol. 118, no 23, 4157-4171 p.
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:liu:diva-109132DOI: 10.1021/jp501974pISI: 000337497300017PubMedID: 24848558OAI: oai:DiVA.org:liu-109132DiVA: diva2:737522
Available from: 2014-08-13 Created: 2014-08-11 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Computational Design of Molecular Motors and Excited-State Studies of Organic Chromophores
Open this publication in new window or tab >>Computational Design of Molecular Motors and Excited-State Studies of Organic Chromophores
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents computational quantum chemical studies of molecular motors and excited electronic states of organic chromophores.

The first and major part of the thesis is concerned with the design of light-driven rotary molecular motors. These are molecules that absorb light energy and convert it into 360° unidirectional rotary motion around a double bond connecting two molecular halves. In order to facilitate potential applications of molecular motors in nanotechnology, such as in molecular transport or in development of materials with photo-controllable properties, it is critical to optimize the rates and efficiencies of the chemical reactions that produce the rotary motion. To this end, computational methods are in this thesis used to study two different classes of molecular motors.

The first class encompasses the sterically overcrowded alkenes developed by Ben Feringa, co-recipient of the 2016 Nobel Prize in Chemistry. The rotary cycles of these motors involve two photoisomerization and two thermal isomerization steps, where the latter are the ones that limit the attainable rotational frequencies. In the thesis, several new motors of this type are proposed by identifying steric, electronic and conformational approaches to accelerate the thermal isomerizations. The second class contains motors that incorporate a protonated Schiff base and are capable to achieve higher photoisomerization rates than overcrowded alkene-based motors. In the thesis, a new motor of this type is proposed that produces unidirectional rotary motion by means of two photochemical steps alone. Also, this motor lacks both a stereocenter and helical motifs, which are key features of almost all synthetic rotary motors developed to date.

The second part of the thesis focuses on the design and assessment of composite computational procedures for modeling excited electronic states of organic chromophores. In particular, emphasis is put on developing procedures that facilitate the calculations of accurate 0−0 excitation energies of such compounds in a cost-effective way by combining quantum chemical methods with different accuracies.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2016. 64 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1794
National Category
Theoretical Chemistry Organic Chemistry Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-132611 (URN)10.3384/diss.diva-132611 (DOI)9789176856741 (ISBN)
Public defence
2016-12-15, Schrödinger (E324), Fysikhuset, Campus Valla, Linköping, 13:15 (English)
Opponent
Supervisors
Available from: 2016-11-16 Created: 2016-11-16 Last updated: 2016-11-17Bibliographically approved

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Fang, ChangfengOruganti, BaswanthDurbeej, Bo

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