High pressure-controlled intramolecular-twist of flexible molecules in solid polymers

We report the effect of pressure on fluorescence of two flexible dye molecules of a series of para-substituted benzylidenemalononitriles dissolved in solid poly(methyl methacrylate). Under pressure these molecules exhibit a remarkable increase of intensity and slowing of excited state decay. We show that these changes can be well explained by a kinetic model in which the pressure is assumed to control the barrier for the intramolecular transformation of the flexible molecules in their excited state.