[Migration of electron excitation energy in mixed associates of chlorophyll and its derivatives].

The intracomplex migration is investigated of electron excitation energy between molecules which are a part of a mixed associate. Weakly fluorescent and nonfluorescent associates of chlorophyll and its analogues as well as of bacteriochlorophyll and neoxanthine have been used as donors and acceptors. The migration of excitation energy with variation of quantum yield of donor emission from 5-10(-3) to less than or equal to 10(-4) and also with very weak overlapping of luminescence and absorption spectra for the pair D leads to A is experimentally discovered by luminescence excitation spectra of mixed pigment aggregates. A specific disturbing action of Pd and Cu ions on chlorophyll a luminescence with formation of mixed complexes of chlorophyll with Pd-pheophytin a and Cu-pheophytin b is observed. The presence of Pd and Cu ions in the structure of the mixed complexes gives rise to a considerable reduction of chlorophyll apparently due to increasing intersystem crossing probability in the chlorophyll molecule. The probability of intracomplex energy migration in systems under investigation amounts to approximately 10(12) sec-1 according to the obtained estimations. The probable mechanism of energy migration in mixed associates is discussed. The obtained results may be used for elucidation of a possible role of the mixed aggregates and effective intracomplex migration of excitation energy in photosynthetic apparatus of green plants.