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Molecules 2018, 23(11), 2932; https://doi.org/10.3390/molecules23112932 (registering DOI)

Assessing Configurational Sampling in the Quantum Mechanics/Molecular Mechanics Calculation of Temoporfin Absorption Spectrum and Triplet Density of States

1
Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Str. 17, 1090 Vienna, Austria
2
Departamento de Química Universidad Autónoma de Madrid Francisco Tomas y Valiente, 7, Cantoblanco, 28049 Madrid, Spain
3
Biolitec Research GmbH, Otto-Schott-Str. 15, 07745 Jena, Germany
This paper is published as part of a thematic issue of Molecules on “Combined Quantum Mechanical and Molecular Mechanical Methods and Simulations”. https://www.mdpi.com/journal/molecules/special_issues/QM.
Current address: Research School of Biology, Australian National University, Canberra, ACT 2601, Australia
*
Authors to whom correspondence should be addressed.
Academic Editors: Hai Lin and Donald G. Truhlar
Received: 11 October 2018 / Revised: 5 November 2018 / Accepted: 6 November 2018 / Published: 9 November 2018
Full-Text   |   PDF [1479 KB, uploaded 9 November 2018]   |  

Abstract

The absorption properties of Temoporfin, a second-generation photosensitizer employed in photodynamic therapy, are calculated with an electrostatic-embedding quantum mechanics/molecular mechanics (QM/MM) scheme in methanol. The suitability of several ensembles of geometries generated by different sampling techniques, namely classical-molecular-dynamics (MD) and QM/MM-MD thermal sampling, Wigner quantum sampling and a hybrid protocol, which combines the thermal and quantum approaches, is assessed. It is found that a QM description of the chromophore during the sampling is needed in order to achieve a good agreement with respect to the experimental spectrum. Such a good agreement is obtained with both QM/MM-MD and Wigner samplings, demonstrating that a proper description of the anharmonic motions of the chromophore is not relevant in the computation of the absorption properties. In addition, it is also found that solvent organization is a rather fast process and a long sampling is not required. Finally, it is also demonstrated that the same exchange-correlation functional should be employed in the sampling and in the computation of the excited states properties to avoid unphysical triplet states with relative energies close or below 0 eV. View Full-Text
Keywords: Temoporfin; configurational sampling; QM/MM; absorption properties Temoporfin; configurational sampling; QM/MM; absorption properties
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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De Vetta, M.; Baig, O.; Steen, D.; Nogueira, J.J.; González, L. Assessing Configurational Sampling in the Quantum Mechanics/Molecular Mechanics Calculation of Temoporfin Absorption Spectrum and Triplet Density of States. Molecules 2018, 23, 2932.

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