EXCITATION-ENERGY TRANSFER AND PHOTODECOMPOSITION OF SOME DIOLEFINIC LASER-DYES

Energy transfer from 1,4-bis-(beta-pyridyl-2-vinyl)-benzene (P2VB, 1), 2,5-distyrylpyrazine (DSP, 2), and 2,5-bis-2-(1-naphthylvinyl)-pyrazi ne (BNVP, 3) to N,N'-bis-(2,5-di-tert-butylphenyl)-3,4:9, 1 10-perylen e-bis-dicarboximide (DBPI, 4) has been studied in dimethyl formamide b y steady state emission measurements. It was found that the Stern-Volm er relation is obeyed from which the rate constants of energy transfer were determined as 5.6x10(12), 6.8x10(12), and 9.1x10(12) l . mol(-1) . s(-1) for 1/4, 2/4, and 3/4, respectively. The corresponding experi mental critical transfer distances have been calculated as 5.3, 5.7, a nd 8.45 nm, indicating a Forster type energy transfer mechanism. The a ctivation energies associated with the fluorescence quenching of 1-3 b y 4 in DMF were calculated as 5.5, 5.2, and 4.8 kJ . mol(-1). The exci ted state lifetime and the role of molecular oxygen in deactivation of the excited singlet state of 1-3 have been studied and the second ord er quenching rate constants have been determined. The photochemical qu antum yields (lambda(ex) = 365 nm) of 1-3 were studied in CCl4.