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The comparative detailed investigation of the Bication pyridinium systems (BCP) and corresponding model pyridinium cations (CP) has been carried out by the spectral luminescent methods. BCP consist of the two identical moieties bound by the various space bridges ensuring their very weak interaction in the ground state. The Adiabatic Structural Relaxation (ASR) followed by the photocyclization reaction is realized only in one of BCP fragments in accordance with the general scheme typical for CP. The ASR is not realized in another BCP fragment owing to the S 1 state deactivation by the extremely fast Interfragmental Intramolecular S-S Energy Transfer from the unchanged fragment to the cyclized one. The ASR mechanism, luminescent properties and photoproduct structures depend strongly on the solvent temperature (viscosity) and on the steric interactions typical for the BCP. The additional information concerning the N phenyl role in the fluorescence and photo-chemical properties’ formation in CP has been obtained by the study of the BCP.

Melt-processible (spinnable) polydiorganosiloxanes have been tested. The polymers offer advantages over previously explored thermosetting siloxane systems. Radiation damage to the optical properties of this polymer have been measured and are smaller than other known optical polymers. Most importantly, intramolecular proton transfer dyes (e.g. 3-Hydroxyflavone) exhibit large Stokes shifted fluorescence in the thermoplastic, unlike that in comparable thermosetting systems. A plastic scintillator based on this system should find application in the harsh radiation environment of the Superconducting Super Collider.

The photobiscyclization reaction of N-azomethine pyridinium derivatives was investigated and the final and intermediate photoproducts were isolated. The first step of the reaction involves dihydro intermediate self-trapping by a 1,5-sigmatropic proton shift.

The photophysics and photochemistry of N-amino-substituted pyridinium salts were investigated. Electron transfer from the amino group to the pyridinium ring takes place in the singlet excited state. The fluorescence quenching and photoreactivity of these compounds is conditioned by this process. Irradiation of N-aminopyridinium salts in solution leads to novel fused heterocycles or to triphenylpyridine, depending on the concentration of the initial compound. Free radical intermediates are involved in the photoreaction.