Vibrational Coherence from the Dipyridine Complex of Bacteriochlorophyll a: Intramolecular Modes in the 10−220-cm-1 Regime, Intermolecular Solvent Modes, and Relevance to Photosynthesis
journal contributionposted on 09.09.2003, 00:00 by Katherine R. Shelly, Elizabeth A. Carson, Warren F. Beck
We present the first observations of vibrational coherence in the 10−220-cm-1 region from bacteriochlorophyll a (BChl) in solution. A distinction can be made for the first time between BChl's intramolecular normal modes and intermolecular modes between BChl and solvent. The results show that the low-frequency vibrations that accompany the initial electron-transfer reaction from the paired BChl primary electron donor, P, in photosynthetic reaction centers arise predominantly from intramolecular modes of histidine-ligated BChl macrocycles. The results also suggest that polar-solvent interactions can significantly perturb the electronic properties of BChl in a manner that might have important functional consequences.