Time-resolved twisting dynamics in a porphyrin dimer characterized by two-dimensional electronic spectroscopy

Camargo, Franco V. A., Heisler, Ismael V. A., Anderson, Harry L. and Meech, Stephen R. ORCID: https://orcid.org/0000-0001-5561-2782 (2015) Time-resolved twisting dynamics in a porphyrin dimer characterized by two-dimensional electronic spectroscopy. The Journal of Physical Chemistry B, 119 (46). pp. 14660-14667. ISSN 1520-6106

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Abstract

Molecular conformational changes in electronic excited states play a key role in numerous light-activated processes. In the case of porphyrin oligomers intramolecular twisting influences energy and charge transport dynamics. Here we address the twisting reaction in both ground and excited states in a model porphyrin dimer, employing two-dimensional electronic spectroscopy (2D ES). By spreading the information over excitation and detection frequencies, cross-peaks reveal the twisting reaction in both the ground and excited states unambiguously and distinctly from other dynamics. A quasi-barrierless planarization reaction is observed in the excited state on a tens of picoseconds time scale. This is accompanied by a spectral narrowing, indicative of a reduction in conformational disorder. The reverse reaction is suppressed in the excited state due to a steep activation energy barrier. However, in the ground state the barrier is within the thermal energy distribution, and therefore contributions from reverse and forward reactions could be observed on the subnanosecond time scale. Crucially 2D ES enables simultaneous assessment of ground and excited state reactions through analysis of different spectral regions on the 2D spectral maps.

Item Type:	Article
Uncontrolled Keywords:	chromophore,reaction,nonlinear spectroscopy,ultrafast dynamics,global analysis
Faculty \ School:	Faculty of Science > School of Chemistry
UEA Research Groups:	Faculty of Science > Research Groups > Physical and Analytical Chemistry (former - to 2017) Faculty of Science > Research Groups > Chemistry of Light and Energy Faculty of Science > Research Groups > Centre for Photonics and Quantum Science
Depositing User:	Pure Connector
Date Deposited:	20 Nov 2015 16:01
Last Modified:	21 Aug 2023 00:52
URI:	https://ueaeprints.uea.ac.uk/id/eprint/55509
DOI:	10.1021/acs.jpcb.5b09964

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