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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.

A new polysiloxane-based plastic scintillator with substituted oligophenylene and tetraphenylbutadiene as a primary and secondary fluor, respectively, has been suggested. These dyes show excellent spectral properties and fluorescence decay time, and overall radiation stability of the scintillator is very good. The final scintillator appears suitable for use at the Superconducting Super Collider.

Radiation hardness of polysiloxane-based scintillators doped with oligophenylene fluors has been investigated. Radiation damage to the chromophores themselves is negligible. The main component of light output loss under irradiation is due to production of color centers by substituents introduced into the fluors to increase solubility. When these oligophenylenes are used as primary fluors they are stable to exposures in excess of 107 rad.

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.

A rather complete data set for 12 characteristics of 18 common benzo-fused heterocycles yields two significant principal components. The loadings of the characteristics show a close correlation with those found for the same characteristics of monocyclic heterocycles. The scores for each bicycle are also closely related to those for the corresponding monocycle. The method demonstrates considerable predictive power.