Intramolekulare Übertragung von elektronischer Anregungsenergie in Spiroverbindungen

Abstract

It is shown that the observation of the degree of polarization of the fluorescence of 9,9′‐spirobifluorene VI and of 2,2′‐diamino‐7,7′‐dinitro‐9,9′‐spirobifluorene VII allows a determination of the rate constant for energy transfer from the initially excited to the unexcited part. The rate constants are of the order of 108 s−1 for VI and 3 · 109 s−1 for VII. The corresponding electronic matrix elements of interaction are evaluated. They are rather due to the Coulomb‐interaction of the transition densities than to spiroconjugation. In VI the coupling vanishes in the equilibrium conformation, vibronic effects must be evoked for explaining its existence.

Density Functional Theory Study of Vibrational Spectra of Fluorene

“…Also, the ultrafast dynamics of exciton transfer [8][9][10] and excimer formation 11 of fluorene derivatives has been studied by time-resolved fluorescence spectroscopy. Of particular importance is the determination of fundamental vibrational frequencies and modes in the ground state in order to provide insight into the vibronic spectra in the electronically excited state.…”

“…The electronic-vibrational structures of fluorene (FR) and its van der Waals complexes have been studied extensively by fluorescence excitation − and resonance two-photon ionization , spectroscopy since the FR molecule is well-known to fluoresce efficiently upon excitation of S 0 to S 1 . Also, the ultrafast dynamics of exciton transfer − and excimer formation of fluorene derivatives has been studied by time-resolved fluorescence spectroscopy. Of particular importance is the determination of fundamental vibrational frequencies and modes in the ground state in order to provide insight into the vibronic spectra in the electronically excited state.…”

Time-resolved fluorescence and fluorescence anisotropy of calix[4]arene: Elucidation of the excitation energies of various conformers

“…In recent years, there has been much effort to elucidate electronic energy transfers between chromophores in bichromophoric [22][23][24][25][26] and in polymer systems [27][28][29]. Recently, intramolecular energy transfer in bichromophoric systems such as 9,9'-bifluorene [23,24] and 2,2'-binaphthyl [23] have been investigated by using time-dependent fluorescence polarization measurements.…”