Quasi-equilibrium Processes of Relaxation of the Electronic Excitation of the Azidomalachite Green Molecule

Real prospects of application of results of scientific investigations for creation of element base of optoelectronics, development of luminescent sensors, for optical record of the information is the substantiation of urgency of studying the processes connected with electronic highly excited states of molecules. Based on the studies of physical and photochemical processes in solutions of para-azidomalachite green (AMG), it is shown that the absorption spectra of AMG are formed by π → π* quantum transitions. Among the intense absorption bands is a weak absorption band π → σ* (S₀ → S₃ quantum transition). It turned out that the corresponding singlet and triplet states of the molecule are characterized by dissociative energy surfaces, that is, there are two channels of photodissociation of the AMG molecule. It is shown that the processes of relaxation of the excitation of the AMG molecule, which occur with the involvement of high-frequency vibrations of C–H bonds, localized on the phenyl rings, proceed as quasi-equilibrium processes. That is, during the relaxation the electronic system of excitation stops at each energy level for a time that exceeds the period of the specified fluctuation. This fact provides the possibility of the processes of dissociation of the molecule from the corresponding energy states. With the increase in temperature from 77 K to 300 K, the role of high-frequency vibrations of C–H bonds increases significantly, that leads to a significant decrease in the quantum yield of AMG photodissociation from both singlet and triplet dissociative states.