Photoprocesses; Evolution of the properties of excited states and transitions in series of laser-active N, O, S heterocyclic molecules and the influence of conditions

Within the framework of direct and inverse structure-properties problems of optics and spectroscopy, we consider the interrelation of the regularities of changes in spatial and electronic structure of N, O, S heterocyclic compounds forming quasi-homologous series and the evolution of the properties of excited electronic states of different spin and orbital structure with their spectral luminescent and lasing properties. We performed experimental measurements and quantum-chemical simulations of photophysical and photochemical parameters of quantum multiatomic systems in a free state (in the absence of any external disturbances) and for different forms of molecules (e.g., in the case of complex formation and protonation with acids at approximate to pH(+) 2.0) with the help of LCAO MO SCF CI-PPP (Pariser-Parr-Pople pi-approximation) and INDO/S (sp-basis) methods. Within the framework of the method of a priori structural modeling of structure-properties of organic molecules, we consider the fundamental problems associated with a control of parameters of excited states and transitions for the optimization of the choice of new laser-active molecules with predetermined properties and structure for various applied problems of science and engineering.