The quenching rate constant of the triplet state by molecular oxygen and the efficiency of singlet oxygen generation have been measured for 12 amines in cyclohexane and benzene. For the best electron donors, the average rate constant for quenching by energy transfer is 6.0 × 109 M-1 s-1. For the same compounds, the rate constant of quenching via enchancement of internal conversion is 1.2 × 1010...

Electrogenerated chemiluminescence (ecl) resulting from reaction of the thianthrene (TH) cation radical and the 2,5-diphenyl-l,3,4-oxadiazole (PPD) anion radical in acetonitrile solutions is characterized by emission at wavelengths of both TH and PPD fluorescence. A consideration of the enthalpy of the reaction shows the process to be energy sufficient with respect to formation of excited singl...

The supramolecular systems [Ru(Pyr(n)bpy)(CN)(4)](2-) (n = 1, 2), where one and two pyrenyl units are linked via two-methylene bridges to the [Ru(bpy)(CN)(4)](2-) chromophore, have been synthesized. The photophysical properties of these systems, which contain a highly solvatochromic metal complex moiety, have been investigated in water, methanol, and acetonitrile. In all solvents, prompt and ef...

We demonstrate measurements of the efficiency of competing Förster-type energy-transfer pathways in single bichromophoric systems by monitoring simultaneously the fluorescence intensity, fluorescence lifetime, and the number of independent emitters with time. Peryleneimide end-capped fluorene trimers, hexamers, and polymers with interchromophore distances of 3.4, 5.9, and on average 42 nm, resp...

A quantitative (multistep) excitation-deactivation model of rose bengal (RB) has been developed which includes energy and electron transfer to oxygen and the possibility of photoproduct formation via higher excited triplet-singlet states. The model is based on previous measurements of non-linear absorption (NLA) and emission of RB with picosecond pulses at 532 nm and on NLA measurements with na...

Cofactor-less oxygenases perform challenging catalytic reactions between singlet co-substrates and triplet oxygen, in spite of apparently violating the spin-conservation rule. In 1-H-3-hydroxy-4-oxoquinaldine-2,4-dioxygenase, the active site has been suggested by quantum chemical computations to fine tune triplet oxygen reactivity, allowing it to interact rapidly with its singlet substrate with...

We have studied the low-temperature photoluminescence of the two-dimensional electron gas in a single GaAs quantum well in magnetic fields up to 50 T over four orders of magnitude of illumination intensity. At the very highest illumination powers, where the recombination is excitonic at zero field, we find that the binding energy of both the singlet and triplet states of the negatively charged ...

Optical properties of biphenyl difluoroboron β-diketonates were studied in poly(lactic acid) (PLA) blends. Increased conjugation lowered the emission energy, decreased the singlet-triplet energy gap and yielded blue thermally activated delayed fluorescence (TADF). The properties of these biphenyl dyes may inform organic light emitting diode (OLED) and bioimaging agent design.

The binuclear homoleptic rhodium carbonyls Rh2(CO)n (n = 8, 7, 6, 5) have been examined theoretically. Three energetically low-lying equilibrium structures of Rh2(CO)8 were found, i.e., one doubly bridged C2v singlet structure and two unbridged singlet structures with D(3d) and D(2d) symmetry. The doubly bridged structure is the global minimum predicted to lie 3.4 kcal/mol below the D(2d) struc...