Abstract
Molecules embedded in low-temperature matrices experience conformer interconversion processes due to IR- (or UV-)irradiation. This paper summarizes the known IR-induced conformational changes, of which the majority has been studied by using broad-band sources provided with filters. We focus at the thermal and IR-photochemical methods in obtaining information of conformational energetics of matrix isolated molecules, at the usefulness of ab initio calculations in assigning the spectra of conformers involved and in finding the reaction path on the ground state surface. The data obtained from a number of molecules is used to discuss possible mechanisms in both intramolecularly hydrogen-bonded and non-bonded molecules. Also possible indications of mode-selective phenomena in these processes are dealt with. In addition, common trends found for photorotamerization in different hosts are discussed.