Issue 13, 2018

Evaluating excited state atomic polarizabilities of chromophores


Ground and excited state dipoles and polarizabilities of the chromophores N-methyl-6-oxyquinolinium betaine (MQ) and coumarin 153 (C153) in solution have been evaluated using time-dependent density functional theory (TD-DFT). A method for determining the atomic polarizabilities has been developed; the molecular dipole has been decomposed into atomic charge transfer and polarizability terms, and variation in the presence of an electric field has been used to evaluate atomic polarizabilities. On excitation, MQ undergoes very site-specific changes in polarizability while C153 shows significantly less variation. We also conclude that MQ cannot be adequately described by standard atomic polarizabilities based on atomic number and hybridization state. Changes in the molecular polarizability of MQ (on excitation) are not representative of the local site-specific changes in atomic polarizability, thus the overall molecular polarizability ratio Image ID:c7cp08549d-t1.gif does not provide a good approximation for local atom-specific polarizability changes on excitation. Accurate excited state force fields are needed for computer simulation of solvation dynamics. The chromophores considered in this study are often used as molecular probes. The methods and data reported here can be used for the construction of polarizable ground and excited state force fields. Atomic and molecular polarizabilities (ground and excited states) have been evaluated over a range of functionals and basis sets. Different mechanisms for including solvation effects have been examined; using a polarizable continuum model, explicit solvation and via sampling of clusters extracted from a MD simulation. A range of different solvents have also been considered.

Graphical abstract: Evaluating excited state atomic polarizabilities of chromophores

Supplementary files

Article information

Article type
21 Dec 2017
05 Mar 2018
First published
06 Mar 2018
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2018,20, 8554-8563

Evaluating excited state atomic polarizabilities of chromophores

E. Heid, P. A. Hunt and C. Schröder, Phys. Chem. Chem. Phys., 2018, 20, 8554 DOI: 10.1039/C7CP08549D

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