Resonance Energy Transfer from the Lowest Excited Triplet State of Diphenylcarbene to Dye Molecules:  Utilization for the Characterization of the Triplet−Triplet Fluorescence

Abstract

Triplet-triplet (T 1 f T 0 ) fluorescence spectra and decay curves of diphenylcarbene (DPC) in the absence and in the presence of dye molecules such as Rhodamine 6G and Rhodamine B were measured in several organic glasses at 77 K. In the absence of dye molecules, the T 1 f T 0 fluorescence signals exhibit biexponential decay with the lifetimes of ∼30 and ∼140 ns, which are attributable to the independent T 1 f T 0 emission from the individual T 1 sublevels of DPC. In the presence of dye molecules, fluorescence decay signals of both fast and slow components were well analyzed in terms of resonance energy transfer of Förster type from DPC to dye molecule. The reaction scheme of the energy transfer and their various parameters are discussed on the basis of the independent T 1 f T 0 emission from the individual T 1 sublevels of DPC at low temperature.

Laser-Induced Carbene–Carbene Rearrangement in Solution: The Diphenylcarbene–Fluorene Rearrangement

“…Thus, the S 1 lifetime is ∼120 ps in cyclohexane and ∼340 ps in acetonitrile. , The S 1 singlet state is formed from DPDM within 30 ps of a 266 nm laser pump pulse and decays to T 0 in 300 fs. , S 1 and T 0 have UV absorption maxima at ∼370 and 320 nm, respectively. , The excited T 1 state of DPC absorbs at ca. 360 nm in CH 3 CN, fluoresces at ∼500 nm, and decays to the ground state triplet, T 0 , on a time scale of 4–9 ns in hydrocarbon solution , or 30–140 ns time scale in an ethanol glass at 77 K . The T 1 state is formed under the high-intensity laser conditions used by Turro and co-workers, who observed its emission at 507 nm …”

Optical Limiting Chromophores. Correlation Effects in Computing Triplet−Triplet Absorption Energies of Organic Molecules

“…For example, it has been postulated by Garito et al that some organic molecules may exhibit far larger non-linear optical (NLO) responses in excited states than in the ground state . Preliminary NLO response studies of organic molecules in the first excited singlet state (2 1 A g ) and of excited triplet states of finite polyenes, indeed indicate that the excited-state responses are an order of magnitude larger than the ground state, as reported by Garito et al Resonant energy transfer from the T 1 state of organic molecules to suitable acceptor molecules has also been extensively studied . Such resonant energy transfer is accepted as one of the mechanisms of PDT and characterization provides useful information for the design of new PDT chromophores. , …”