ИСТИНА

The methods of low-temperature stabilization and matrix isolation are widely used for trapping highly reactive intermediates of the radiation-induced processes for several decades. To a certain extent, this approach of “time freezing” is complementary to direct probing early events using modern pulse techniques. Indeed, although real time resolution is typically missing in the low-temperature experiments, one gets access to detailed picture of molecular structure and local dynamics as characterized by most sensitive and informative spectroscopic methods. These results provide a solid basis for comparison with high-level quantum-chemical computations. The present talk focuses on recent development of low-temperature studies of the radiation-induced species performed in our laboratory using advanced experimental techniques and some novel approaches. First part will be concerned with the primary radical ions produced by ionization of isolated molecules in inert and electron-scavenging matrices. In particular, the mechanism and implications of matrix effects and the role of “fine tuning” in intramolecular reactions of bifunctional radical cations of the X-(CH2)n-Y type will be considered on the basis of matrix EPR studies and quantum-chemical calculations. Preliminary data on structure and stability of radical anions resulting from excess electron attachment to matrix isolated molecules with low gas-phase electron affinity will be also presented. Second part will present recent results on trapping and properties of neutral free radicals generated by irradiation of small molecules in solid noble gas matrices. High-resolution EPR spectra of such species in solid xenon were obtained for the first time using an unique monoisotopic 136Xe matrix due to the absence of magnetic matrix interactions (I = 0). Several examples of assignment of vibrational spectra of matrix isolated radicals from comparison of FTIR and EPR data will be given. Final part will deal with dynamics and low-temperature chemical reactions of the radiation-induced H atoms, which lead to formation of exotic metastable molecules of noble-gas hydrides (HNgY, where Y = Xe or Kr). Recent development in this novel area of extremely unusual chemistry include direct spectroscopic manifestation of the H—Xe chemical bond in the xenon hydrides and characterization of intermolecular complexes of HNgY with polar molecules. The photochemical manipulations with HNgY molecules may provide new insight in the local dynamics and tunable chemical transformations in matrices at very low temperatures.