Substituent control of the ultrafast twisted intramolecular charge transfer rate in dimethylaminochalcone derivatives

The rate of TICT relaxation in dimethylaminochalcone derivatives is shown to be controlled by acceptor strength. Variation in the charge pulling capacity of the acceptor modifies the torsional barrier along the TICT coordinate in the S1 state, resulting in a tunable TICT relaxation rate.

Site-dependent effects of methylation on the electronic spectra of jet-cooled methylated xanthine compounds

The torsional barrier of methylated xanthine compounds is affected by a methyl-adjacent carbonyl or methyl group in the ground state, whereas it is governed in the excited state by the hyperconjugation interaction in the LUMO.