SPECTROSCOPIC PROPERTIES OF 2,5,8,11-TETRA-TERT-BUTYLPERYLENE IN POLYMER-FILMS

The spectroscopic properties of 2,5,8,11-tetra-tert-butylperylene in p oly(vinyl alcohol) have been studied. To this end, the absorption and fluorescescence excitation and emission spectra have been measured, Th e shape of the spec;ra in poly(vinyl alcohol) is virtually identical w ith that in propanediol and lipid systems. The Forster radius calculat ed from the spectra was found to be 3.7 +/- 0.3 nm, The natural fluore scence lifetime of 2,5,8,11-tetra-tert-butylperylene in poly(vinyl alc ohol) was also calculated from the spectra and found to be 5.3 +/- 0.2 ns. The fluorescence decay in paly(vinyl alcohol) exhibits monoexpone ntial behavior with a lifetime of 4.5 +/- 0.3 ns. It is shown that the fluorescence anisotropy of 2,5,8,11-tetra-tert-butylperylene in the p olymer matrix does not decay, indicating that its motion is quenched o n the time scale of the fluorescence decay. The initial value of the f luorescence anisotropy, r(0), for excitation at 260 nm and emission at 455 nm is -0.16 +/- 0.02 while for excitation at 440 nm and emission at 455 nm it is 0.35 +/- 0.02. The fluorescence transition dipole mome nts relative to the long molecular axis in the plane of the molecule w ere determined from angle-resolved fluorescence depolarization measure ments. This yields an emission dipole moment al 459 nm of 5 +/- 5 degr ees, an excitation dipole moment at 416 nm of -10 +/- 5 degrees, and a n excitation dipole moment at 256 nm of 80 +/- 5 degrees.