Triplet states locally excited

The vibrationally excited singlet Si and triplet Tf, expected upon the annihilation of the lowest excited triplets Ti, have an energy below the autoionization threshold of typical aromatic crystals [26], thus, no intrinsic photoionization has been observed in these solids. However, the presence of intentional or non-intentional admixtures can allow the triplet-triplet interaction-induced photoionization forming a free carrier in the matrix and a trapped carrier on an admixture molecule. Also, such a process has been reported for the CT triplet states localized on the donor molecule, e.g. in polycrystalline samples of CT complex anthracene-tetracyanoben-zene, where the triplets are localized on the anthracene donor (3Di). Annihilation of 3Di results in the population of non-relaxed excited states of the complex 1(D+A ) and 3(D+A") , dissociation of which may lead to the formation of free charges D+ [214]. 

The mechanism of the photoarylation has been investigated <1995JPC5365>. The homolytic cleavage of the C-I bond probably occurs, not from an n,7t - but a higher excited state, perhaps cr,cr"-triplet state, localized mainly on C-I bond. 

For this complex cation the zero-phonon emission is peaked at 519.9 nm. The ODMR data showed that the emission is due to an excited triplet state localized on the thpy anion [65]. This anion is positioned at the same crystallographic site as the energy trapping site of Rh(TTB)+ [64,65]. The lifetimes and emissive properties of the triplet sublevels of the Rh(TPB)+ species are very similar to... 

If the cross-coupling is strong enough this may include a transition to a lower electronic level, such as an excited triplet state, a lower energy indirect conduction band, or a localized impurity level. A common occurrence in insulators and semiconductors is the formation of a bound state between an electron and a hole (called... 

The delocalization of excessive a- (or P-) spins and the bond polarization can take place among radical orbitals, p and q, and the central n (or o) and n (or o ) orbitals, resulting in the electron transferred configurations (T) and locally excited configurations (E), respectively (Fig. 5a). The delocalization-polarization mechanisms are different between singlet and triplet states, as addressed in the following subsections. 

Figure 4. Estimated transition energies of low-lying excited singlet and triplet states in the 5.35A MgP-P dimer. S1-S4 and T1-T9 correspond to localized states on the indicated monomers. 85 and Tio correspond...

Spectroscopic properties of [Ru(bpy)3] " ", and the effects of varying the diimine ligands in [Ru(bpy)3 L ] + (L = diimine) on the electronic spectra and redox properties of these complexes have been reviewed. The properties of the optical emission and excitation spectra of [Ru(bpy)3] +, [Ru(bpy)2(bpy-d )] + and [Ru(bpy-d )3] " " and of related Os, Rh , and Pt and Os species have been analyzed and trends arising from changes in the metal d or MLCT character in the lowest triplet states have been discussed. A study of the interligand electron transfer and transition state dynamics in [Ru(bpy)3] " " has been carried out. The results of X-ray excited optical luminescence and XANES studies on a fine powder film of [Ru(bpy)3][C104]2 show that C and Ru localized excitation enhances the photoluminescence yield, but that of N does not. 

Many spectroscopic methods have been employed for the investigation of such systems For example, wide-band, time-resolved, pulsed photoacoustic spectroscopy was employed to study the electron transfer reaction between a triplet magnesium porphyrin and various quinones in polar and nonpolar solvents. Likewise, ultrafast time-resolved anisotropy experiments with [5-(l,4-benzoquinonyl)-10,15,20-triphenylpor-phyrinato]magnesium 16 showed that the photoinduced electron transfer process involving the locally-excited MgP Q state is solvent-independent, while the thermal charge recombination reaction is solvent-dependent . Recently, several examples of quinone-phtha-locyanine systems have also been reported . 

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