We describe the photophysical properties of solid films of 6,14-bis(triisopropylsilylethynyl)-1,3,9,11-tetraoxa-dicyclopenta[b,m]pentacene (TP-5) and 2,2,10,10-tetraethyl-6,14-bis-(triisopropylsilylethynyl)-1,3,9,11-tetraoxa-dicyclopenta[b,m]pentacene (EtTP-5) dispersed in either tris(quinolin-8-olato)aluminum III (Alq3) or 4,4-bis[N-1-napthyl-N-phenyl-amino]biphenyl (a-NPD). Upon host excitation, bright red emission (lmax = 645 - 655 nm) from the pentacene guest is observed as a result of fast and efficient Förster energy transfer. High photoluminescence (PL) quantum yields (fPL ~ 60 - 90%) are measured at low concentrations (pentacene ~ 0.25 mol%). Dilute films also show that the molecular singlet excited state lifetimes of TP-5 and EtTP-5 in Alq3 or a-NPD are identical (t ~ 18.5 ns). Strong PL concentration quenching and abrupt shortening of the average PL lifetimes of the Alq3 composite films are observed at higher concentrations (TP-5 ≥ 1.00 mol% and EtTP-5 ≥ 1.50 mol%). None of these features are evident when EtTP-5 is dispersed at comparable concentrations in a-NPD, suggesting even dispersal of the guest monomers in this host.
New Reactions and Methodology, Materials, Total Synthesis, Process R&D
8:00 PM-10:00 PM, Sunday, 28 August 2005 Washington DC Convention Center -- Hall A, Poster