Fluorescence emission and conformational changes of 1,3,5,7-tetra-t-butyl-s-indacene (TTBI).

The electronic properties of 1,3,5,7-tetra-t-butyl-s-indacene (T TBI) in the second excited singlet state have been studied by absorption and fluorescence spectroscopy. Fluorescence from S2 may be related, as in the azulene case, to the large energy gap between S2 and S1 and to the high S0 - S2 oscillator strength. Absorption, fluorescence excitation, and fluorescence spectra have been measured on rigid TTBI solutions at 77 K. Several emissions have been observed which have been assigned to different conformers of TTBI. Photoselection data indicate that the symmetry of TTBI differs in the S2 state with respect to the ground state with minor structural changes.