Ground state properties, stilbenes

Regarding the emission properties, AM I/Cl calculations, performed on a cluster containing three stilbene molecules separated by 4 A, show that the main lattice deformations take place on the central unit in the lowest excited state. It is therefore reasonable to assume that the wavefunction of the relaxed electron-hole pair extends at most over three interacting chains. The results further demonstrate that the weak coupling calculated between the ground state and the lowest excited state evolves in a way veiy similar to that reported for cofacial dimers. 

This paper summarizes the theoretical analysis of some new molecules with methylsulfonyl group as the electron acceptor group, describes the syntheses of new stilbene and azobenzene systems, and presents the measurements of their optical spectra, ground-state dipole-moments, and molecular hyperpolarizability coefficients, p. We compare theoretical and experimental results and comment on the potential usefulness of these chromophores as components for NLO materials. The incorporation of sulfonyl-containing chromophores into polymers, and the NLO properties of the resulting materials, will be discussed in our forthcoming paper (9). 

The effed of thienyl groups on the photoisomerization and rotamerism of symmetric and asymmetric stUbenes has been studied [73]. Stationary and pulsed fluorimetric techniques, laser flash photolysis, and conventional photochemical methods and theoretical calculations were used for investigating photochemistry of flve symmetric (bis-substituted) and asymmetric (mono-substituted) analogues of -stilbene, where one or both side aryls are 2 -thienyl or 3 -thienyl groups. It was shown that the presence of one or two thienyl groups and their positional isomerism afled the spectral behavior, the relaxation properties (radiative/reactive competition), the photoisomerization mechanism (singlet/triplet), and the ground-state rotamerism. 

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