Conformations and Photophysics of a Stilbene Dimer.

Photophysical studies of pseudo-p-distyryl[2.2]paracyclophane, a model molecule of a stilbene dimer arranged in a brick-wall geometry, in tetrahydrofurane solution indicate the existence of at least two conformers in the ground state. The conformer A with the smallest optical gap of 3 eV has a short radiative lifetime of 3.3 ns, while the conformer B with an optical gap about 0.3 eV larger is much more abundant in solution and its radiative lifetime is about 10 times longer. Ab initio calculations show that the ground-state energy has a shallow minimum with respect to the torsional angle between the styryl side group and the paracyclophane core around the zero position, with the lowest energy conformation at a torsional angle of -21. On this basis, A and B are assigned to flat and twisted conformations, respectively. Conformer B shows a partial decay of excited-state absorption and fluorescence with a time constant ranging from 5 to 30 ps, depending on excitation photon energy. We attribute this to isomerization of the stilbene moiety, which initially keeps conjugation in the ground state. The isomerization product is long-lived and tends to accumulate in solution.

Namdas, Ebinazar B (author)
Lee, J Y (author)
Mukamel, S (author)
Wang, S J (author)
Bazan, G C (author)
Sundström, VillyLund University,Lunds universitet,Kemisk fysik,Enheten för fysikalisk och teoretisk kemi,Kemiska institutionen,Institutioner vid LTH,Lunds Tekniska Högskola,Chemical Physics,Physical and theoretical chemistry,Department of Chemistry,Departments at LTH,Faculty of Engineering, LTH(Swepub:lu)chph-vs (author)
Kemisk fysikEnheten för fysikalisk och teoretisk kemi (creator_code:org_t)

In:The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory: American Chemical Society (ACS)107:40, s. 8029-80341520-5215
In:The Journal of Physical Chemistry A: American Chemical Society (ACS)107:40, s. 8029-80341089-5639

By the author/editor: Ruseckas, Arvyda ...; Namdas, Ebinazar ...; Lee, J Y; Mukamel, S; Wang, S J; Bazan, G C; show more...; Sundström, Villy; show less...

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