Dipole Moment and Polarizability of Tunable Intramolecular Charge Transfer States in Heterocyclic π-Conjugated Molecular Dyads Determined by Computational and Stark Spectroscopic Study

Rohwer, Egmont Johann; Akbarimoosavi, Maryam; Meckel, Steven E.; Liu, Xunshan; Geng, Yan; Lawson Daku, Latévi Max; Hauser, Andreas; Cannizzo, Andrea; Decurtins, Silvio; Stanley, Robert J.; Liu, Shi-Xia; Feurer, Thomas (2018). Dipole Moment and Polarizability of Tunable Intramolecular Charge Transfer States in Heterocyclic π-Conjugated Molecular Dyads Determined by Computational and Stark Spectroscopic Study. Journal of physical chemistry. C, 122(17), pp. 9346-9355. American Chemical Society 10.1021/acs.jpcc.8b02268

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The annulation of two redox-active molecules into a compact and planar structure paves the way toward a new class of electronically versatile materials whose physical properties can be tuned via a substitution of one of the constituting moieties. Specifically, we present tetrathiafulvalene−benzothiadiazole donor−acceptor molecules. The critical role played by the dielectric properties of these molecules is evident by the large spectral shifts of the ground-state absorption spectra in a range of solvents. Stark spectroscopy is performed to determine experimentally dipole and polarizability change over transitions in the visible range with particular attention to the transition from the highest-occupied molecular orbital (HOMO) to the lowest-unoccupied molecular orbital (LUMO). The experimental results are compared to the results of time-dependent density functional theory calculations, and we reciprocally validate results from calculation and experiment. This allows us to filter out effective models and reveal important insights. The calculations are initially performed in the gas phase and subsequently a polarizable continuum model is adopted to probe the in fluence of the solvent on the molecular dielectric properties. The results show a large charge displacement from the HOMO to the LUMO and confirm the intramolecular charge transfer nature of the lowest-energy transition. Substitution of the acceptor moiety with electron-withdrawing groups results in changes to the experimentally determined molecular properties consistent with the effects predicted by computational results. The dominant contribution to the electroabsorption signal is due to the change in dipole moment, which is measured to be roughly 20 D for all samples and forms a small angle with the transition dipole moment in a toluene solvent environment.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Applied Physics

UniBE Contributor:

Rohwer, Egmont Johann; Akbarimoosavi, Maryam; Decurtins, Silvio; Liu, Shi-Xia and Feurer, Thomas

Subjects:

600 Technology > 620 Engineering
500 Science > 570 Life sciences; biology
500 Science > 540 Chemistry

ISSN:

1932-7447

Publisher:

American Chemical Society

Language:

English

Submitter:

Silvio Decurtins

Date Deposited:

02 May 2018 10:48

Last Modified:

27 Nov 2018 12:00

Publisher DOI:

10.1021/acs.jpcc.8b02268

BORIS DOI:

10.7892/boris.114653

URI:

https://boris.unibe.ch/id/eprint/114653

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