Stilbene resonance energy

The quantum-mechanical treatment previously applied to benzene, naphthalene, and the hydrocarbon free radicals is used in the calculation of extra resonance energy of conjugation in systems of double bonds, the dihydro-naphthalenes and dihydroanthracenes, phenylethylene, stilbene, isostilbene, triphenylethylene, tetraphenylethyl-... 

In conclusion, we present a spectroscopic study of nn excitation in trans-Stilbene in a molecular beam experiment. The excitation involves a 1+1 REMPI scheme following the interaction of the molecule with femtosecond UV laser pulses. When the excitation is resonant with the origin of the intermediate Si state, the measured photoelectron distribution reveals a maximum probability for the 0-0 transition. For higher photon energies (266nm) the photoelectron spectrum exhibits a rather complex distribution, due to the excitation of an alternate (C-C) stretching mode. 

With stilbene and azobenzene there are two isomers. In these cases a plane structure is realized for the //mf-isomers, in contrast to the cis forms where this is impossible on spatial grounds. The stability of the trans forms is a consequence of the extra resonance (extra R.E. /z -stilbene 7.0 kcal energy content of frmy-azobenzene 10 kcal lower than the cis form). This resonance also appears from the distances, stilbene, trans C—C 1.445 A, C=C 1.33 A azobenzene, trans C—N 1.415 A, cis C—N 1.46 A (sum of atomic distances 1.54 A and 1.47 A, respectively) in this latter compound the planes of the rings make an angle of 50°. 

Bredas et al. studied theoretical TPA properties of the 4-dimethylamino-4 -formylstilbene (DAFS) with the degree of tt bond-order alternation (BOA) by the application of an external field [54]. This work shows two possible strategies to optimize TPA response in stilbenic molecules, as shown in Fig. 5 (1) In the case of TPA resonance in the lowest excited state at oi energy, the D term of Eq. 5 presents the main contribution and ajpA varies in the same way as and Afioi as a function of BOA, with a maximum for an intermediate regime between the neutral Brl and the cyanine Br2 Umits. (2) For a TPA resonance in the specific two-photon state S2, the structure presents huge ajpA values for the cyanine structure near the double resonance at Eoi =. ... 

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