The matrix-form integral encounter theory (IET) is generalized to consider bulk reversible association–dissociation reactions. The many-particle derivation of the IET kinetic equations is based on the extension of the formalism of “effective” particles developed earlier. As a result, an infinite hierarchy for vector correlation patterns is obtained and truncated in the way suggested earlier for elementary reactions. We believe that such an extension of the IET is utterly important for the kinetic description of a great number of diffusion-influenced chemical reactions.

Photoinduced elementary processes in chiral linked systems, consisting of drugs and tryptophan (Trp) residues, attract considerable attention due to several aspects. First of all, these are models that allow one to trace the full and partial charge transfer underlying the binding of drugs to enzymes and receptors. On the other hand, Trp fluorescence is widely used to establish the structure and conformational mobility of proteins due to its high sensitivity to the microenvironment. Therefore, the study of mechanisms of Trp fluorescence quenching in various systems has both fundamental and practical interest. An analysis of the photo-chemically induced dynamic nuclear polarization (CIDNP) and Trp fluorescence quenching in (R/S)-ketoprofen-(S)-tryptophan ((S/R)-KP-(S)-Trp) dyad carried out in this work allowed us to trace the intramolecular reversible electron transfer (ET) and obtain evidence in favor of the resonance energy transfer (RET). The fraction of dyad’s singlet excited state, quenched via ET, was shown to be 7.5 times greater for the (S,S)-diastereomer than for the (R,S) analog. At the same time, the ratio of the fluorescence quantum yields shows that quenching effectiveness of (S,S)-diastereomer to be 5.4 times lower than for the (R,S) analog. It means that the main mechanism of Trp fluorescence quenching in (S/R)-KP-(S)-Trp dyad is RET.

Non-Markovian kinetic equations of the reversible monomolecular-bimolecular reactions of the type A+B⇄C (at arbitrary ratio between A and B concentrations) derived earlier are used in the calculation of kinetics on macroscopic space–time scales. It is found that the kinetics of the systems with different structure of reactants is universal, and it is the direct generalization of the kinetic law of mass action of formal chemical kinetics. The analysis of the kinetics allows one to establish the time range of the applicability of the law of mass action. It is shown that beyond these limits the usual kinetic law of mass action becomes invalid, and correct description of the kinetics even in the most rough approximation calls for the non-Markovian corrections to usual kinetic laws.