Mobile triplets

There can be no doubt that mobile triplets do exist in solid solutions of aromatic polymers, but this does not mean that the phosphorescences observed are necessarily emitted from (hopping) excitons (41). 

In the case of polymers with high trapping efficiency, the heterofusion (8l) between mobile triplets (excitons) and trapped ones is likely to prevail. The delayed singlets can therefore be created as excitons or as trapped states. 

Characteristic of the delayed emission spectrum is the delayed fluorescence band centered at 3 6 nm and the structured phosphorescence emission between 90 nm and 370 nm. That mobile triplet states and... 

The comparatively small size of the simplest carbene (methylene) ensures that it has a definite mobility in frozen inert matrices, which leads to the formation of dimerization products under these conditions. It became possible only in 1981 to detect in the spectra of the diazomethane photolysis products bands at 1115 cm (Ar matrix) and 1109 cm (Xe matrix) which were attributed to the deformation vibration of methylene in its ground triplet state (Lee and Pimentel, 1981). 

Magnetic resonance (ESR, NMR) Chemical structure, tacticity, conformation, polymer mobility (NMR) Radical, triplet state structure and behaviour (ESR)... 

Several derivatives of Eosin have been prepared and employed to study biological systems. Their main applications are as singlet energy acceptors and as triplet probes [93-97] to measure the rotational mobility of virus particles [98] and proteins in membranes and in solution. Examples of proteins studied using Eosin derivatives include myosin [99,100], band 3 protein [101,102], pyruvate dehydrogenase [103,104], and Sarcoplasmic... 

Reticulum ATPase [105,106], Owing to the long-lived nature of the triplet state, Eosin derivatives are suitable to study protein dynamics in the microsecond-millisecond range. Rotational correlation times are obtained by monitoring the time-dependent anisotropy of the probe s phosphorescence [107-112] and/or the recovery of the ground state absorption [113— 118] or fluorescence [119-122], The decay of the anisotropy allows determination of the mobility of the protein chain that cover the binding site and the rotational diffusion of the protein, the latter being a function of the size and shape of the protein, the viscosity of the medium, and the temperature. 

An MO study of triplet coumarin has indicated that the mobile bond order for the 3,4-double bond decreases significantly on excitation (73MI22201). Furthermore, the electron density at C-3 is decreased but is increased at C-4 and hence an explanation of the orientational specificity of the photoaddition of coumarin to 1,1-diethoxyethylene is available (equation 1) (66TL1419). The reactivity of the 3- and 4-positions of triplet coumarin is also substantiated by the high spin-densities calculated for these positions (70JPC4234). 

A general phenomenon is observed in many solids that due to interaction of the electronically excited particles (donors) D with acceptors A the energy transfer occurs D + A —> D + A [11, 12], Its probability depends on the actual kind of interaction (dipole-dipole or triplet-triplet transfer). When molecules are mobile, their reaction rate K is defined by their mobility, i.e., energy transfer becomes diffusion-controlled [13]. 

At liquid nitrogen temperature, 77 K, matrix isolation in hydrocarbons is successful for many silylenes because they are singlet species and so do not abstract hydrogen from C—H bonds, as would be expected for triplet molecules. The usual hydrocarbon is 3-methylpentane (3-MP) which forms a rigid glass at 77 K, but sometimes mixtures of hydrocarbons are used which are softer at this temperature, to allow some mobility of the silylene in the matrix. In a few cases, silylenes have also been identified from transient spectra obtained in flash photolysis experiments. 

The use of transition or rare earth metal complexes as emitting materials for OLED has attracted much attention recently because of the enhancement in EL efficiency from triplet excited state.16 Chan and co-workers demonstrated that incorporation of ruthenium bipyridyl complexes into conjugated polymers would enhance the charge carrier mobilities.17 Through attachment of different transition metal complexes onto polymer chains, tuning of light-emitting properties could be achieved.18... 

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