Thiophenes excitation energies

Thus, the ease of desulfonylation of a l,3-dihydrobenzo[c]thiophene 2,2-dioxide and therefore the products obtained is dependent on the stability of the intermediate o-quinodimethane. The photochemical decomposition of l,3-dihydrobenzo[c]thiophene 2,2-dioxide probably involves an excitation energy of >74 kcal/mole and is not possible under the conditions already mentioned, whereas its 1,3-diphenyl derivative may be photochemically desulfonylated under these conditions because the intermediate o-quinodimethane derivative (96) is stabilized relative to o-quinodimethane itself (see also Cava and Shirley96).101... 

The PPP model with configuration interaction (PPP-CI) has been used to predict the long-wavelength excitation energies of thiophene and benzo[f]thiophene <1987MM2023>. 

Table 16 Excitation energies by TDDFT (eV) of bithiophene dimer 17 and siioie/thiophene dimer...

The oligothiophenes show within this series the strongest TPA, while oligofuranes are comparable with polyenes. Experiments confirmed the large TPA of several thiophene oligomers (29). These compounds have TPA cross sections greater than 1000 GM with an excitation energy of more than 4 eV for the optical TPA transition [407]. 

The occupied states are derived from energy distribution curves of the photoelectrons, excited by synchrotron illumination. We present XPS spectra at resonant excitation energies at the Cls (285 eV), and at the S2p (165 eV) ionisation thresholds. For the Cls threshold, we in addition show the spectrum taken off resonance. These valence band spectra are dominated by two broad features at -7 eV and -11.5 eV which are due to carbon-derived (//c) and sulfur-derived (//s) HOMOs of the thiophene monomer. These levels are pronounced in all data, as marked by the dashed lines. The weaker emission of the highest band at -3.1 eV is attributed to emission from electrons out of the 71-band, which is no longer assigned to individual monomers but is delocalised along the polymeric chain see also [33]. 

Fig. 1.4 Evolution with the inverse of the number of thiophene units ( /n) of the 5o 5i and 5o — T excitation energies, as calculated at the INDO/MRD-Cl level.

Table 1.3 VEH-Calculated Polaron Transition Energies Between the HOMO Level and the Lower Polaronic Level (H — POLl) and Between the Two Polaron Levels (POLl - P0L2) and Bipolaron Excitation Energies Between the HOMO Level and the Lower Bipolaronic Level (H -> BlPl) in Thiophene Oligomers Containing Three, Five, Seven, and Nine Rings ...

Figure 4. Evolution of the INDO/MRD-CI-calculated So— Si (open squares) and Sq— T4 (full circles) excitation energies as a function of the inverse number of thiophene rings (1/n).

Also in this case calculation results fit the experimental data (Fig. 7) [99H(50)1115]. In fact, the singlet excited state can evolve, giving the Dewar thiophene (and then isomeric thiophenes) or the corresponding excited triplet state. This triplet state cannot be converted into the biradical intermediate because this intermediate shows a higher energy than the triplet state, thus preventing the formation of the cyclopropenyl derivatives. 

FtG. 7. Relative energy of the excited states of thiophene and of some reactive intermediates. 

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