Charge-Transferring Ahead

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Science  23 Apr 2004:
Vol. 304, Issue 5670, pp. 493
DOI: 10.1126/science.304.5670.493a

Small molecules that transfer charge from donor to acceptor groups after absorbing light are of interest as models for the oxidation-reduction components in energy-transducing complexes. Being able to control the degree of charge transfer will be essential for the successful use of organic materials in optical and electronic contexts, yet assessing the degree of charge transfer in donor-acceptor species has proven challenging to quantify.

Rubtsov et al. show that vibrational spectra measured with an ultrashort probe pulse just after visible light excitation can provide a measure of the degree of charge transfer in the ground and charge-transferred states. They show that for the same acceptor group, small spacer units can cause a slight decrease in the amount of downfield shift of the asymmetric carbonyl stretch in the charge transfer state. The values measured in this way agree well with those obtained from analysis of the electronic charge transfer band. However, this pump-probe approach may be particularly helpful when charge transfer bands are not particularly strong or overlap with other bands. — PDS

J. Am. Chem. Soc. 10.1021/ja030674k (2004

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