Two-dimensional electronic spectroscopy of chlorophyll a: Solvent dependent spectral evolution

Moca, Roberta, Meech, Steve ORCID: and Heisler, Ismael (2015) Two-dimensional electronic spectroscopy of chlorophyll a: Solvent dependent spectral evolution. The Journal of Physical Chemistry B, 119 (27). pp. 8623-8630. ISSN 1520-6106

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The interaction of the monomeric chlorophyll Q-band electronic transition with solvents of differing physical-chemical properties is investigated through two-dimensional electronic spectroscopy (2DES). Chlorophyll constitutes the key chromophore molecule in light harvesting complexes. It is well-known that the surrounding protein in the light harvesting complex fine-tunes chlorophyll electronic transitions to optimize energy transfer. Therefore, an understanding of the influence of the environment on the monomeric chlorophyll electronic transitions is important. The Q-band 2DES is inhomogeneous at early times, particularly in hydrogen bonding polar solvents, but also in nonpolar solvents like cyclohexane. Interestingly this inhomogeneity persists for long times, even up to the nanosecond time scale in some solvents. The reshaping of the 2DES occurs over multiple time scales and was assigned mainly to spectral diffusion. At early times the reshaping is Gaussian-like, hinting at a strong solvent reorganization effect. The temporal evolution of the 2DES response was analyzed in terms of a Brownian oscillator model. The spectral densities underpinning the Brownian oscillator fitting were recovered for the different solvents. The absorption spectra and Stokes shift were also properly described by this model. The extent and nature of inhomogeneous broadening was a strong function of solvent, being larger in H-bonding and viscous media and smaller in nonpolar solvents. The fastest spectral reshaping components were assigned to solvent dynamics, modified by interactions with the solute.

Item Type: Article
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: 17 Aug 2015 15:22
Last Modified: 27 Oct 2023 01:43
DOI: 10.1021/acs.jpcb.5b04339


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