Triplet-doublet quenching

Em and Merrifield [3] found that paramagnetic defects in anthracene crystals quenched triplet excitons and changed the field dependence from a negative to a positive gradient. They interpreted these MFEs in terms of the triplet-doublet quenching expressed by... 

Thus, JV(fi>0.1T)=4. This also shows that a magnetic field higher than O.IT decreases the triplet-doublet quenching. 

The triplet exciton quenching by doublet species is well established. Annihilation of triplet excitons has been observed on... 

Acridinium ion as sensitizer fluoresence quenched both NH3 and NCS- released although NHS predominates in presence of 02, NCS-release decreased, hence triplet state of the sensitizer is involved nh / ncs-, 33 for quartet state, 8 for doublet state. 

In fluid solutions, Faulkner and Bard first found the MFEs on the electrogenerated chemiluminescence of anthracence triplet-triplet annihilation [4], The general features of the MFEs were similar to those observed in crystals the intensity of delayed fluorescence was found to decrease with increasing B from 0 T to 0.8 T and to approach as3miptotically a value which was about 4 % below the zero-field intensity. They also found the MFEs on the anthracene fluorescence in the presence of doublet species such as Wurster s Blue perchlorate [5] the fluorescence intensity was found to be quenched by the doublet species, but the quenched intensity was found to be increased by magnetic fields. Their typical results are shown in Fig. 12-2. Although these MFEs observed in fluid solutions were smaller than those in crystals due to rotational motion of triplet molecules, the MFEs in solutions could also be explained by Eqs. (13-3) and (13-9). The magnetically induced decrease in the... 

Quenching of the ( CT)[Ru(bipy)3] by [Cr(bipy)]3 has been studied. This is via electron transfer to the Cr complex and a rapid back reaction. The ruthenium complex will also quench the 727 nm emission of the metal-centred doublet excited state of the chromium species, by a similar mechanism. Evidently both ligand- and metal-centred excited states can be quenched by bimolecular redox processes. A number of Ru complexes, e.g. [Ru(bipy)3] and [Ru(phen)3] also have their luminescence quenched by electron transfer to Fe or paraquat. Both the initial quenching reactions and back reactions are close to the diffusion-controlled limit. These mechanisms involve initial oxidation of Ru to Ru [equation (1)]. However, the triplet excited state is more active than the ground state towards reductants as well as... 

For donors with triplet energies below 52 kcal/mol only doublet acceptor states are energetically accessible hence only the doublet encounter pair provides a spin-allowed excitation-transfer channel with a maximum rate constant of At higher donor energies excitation to a quartet excited state of the acceptor is also possible and both quartet and doublet encounter pairs can lead to excitation transfer. The combined maximum quenching rate constant when both doublet... 

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