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Isolated model anion chromophores of the green and cyan fluorescent proteins were generated in an electrospray ion source, and their photodetachment spectra were recorded using photoelectron imaging. Vertical photodetachment energies of 2.85(10) and 4.08(10) eV have been measured for the model green fluorescent protein chromophore anion, corresponding to photodetachment from the ground electronic state of the anion to the ground and first excited electronic states of the radical, respectively. For the model cyan fluorescent protein chromophore anion, vertical photodetachment energies of 2.88(10) and 3.96(10) eV have been measured, corresponding to detachment from the ground electronic state of the anion to the ground and first excited electronic states of the neutral radical, respectively. We also find evidence suggesting that autoionization of electronically excited states of the chromophore anions competes with direct photodetachment. For comparison and to benchmark our measurements, the vertical photodetachment energies of deprotonated phenol and indole anions have also been recorded and presented. Quantum chemistry calculations support our assignments. We discuss our results in the context of the isolated protein chromophore anions acting as electron donors, one of their potential biological functions.

The development of methods for carbon-carbon bond formation under benign conditions is an ongoing challenge for the synthetic chemist. In recent years there has been considerable interest in using selective C-H activation as a direct route for generating reactive intermediates. In this article, we describe the use of aldehyde auto-oxidation as a simple, clean and effective method for C-H activation, resulting in the generation of an acyl radical. This acyl radical can be used for carbon-carbon bond formation and herein we describe the application of this method for the hydroacylation of alpha,beta-unsaturated esters without the requirement of additional catalysts or reagents. This methodology generates unsymmetrical ketones, which have been shown to have broad use in organic synthesis.

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