Spectral locations of low-energy electronic transitions in some fluorene derivatives

Abstract

Abstract The low energy singlet—singlet ( S-S ) and triplet—triplet ( TT ) absorption spectra of fluorene and 2-amino fluorene were measured. Also, the spectral locations of low-energy SS and TT intensity maxima of 2-methoxy, 2-hydroxy, 2,7-diamino, and 2-dimethylamino fluorene were recorded. When expressed in wavenumbers (energy) and within measurement accuracy, the following holds for the 2-position substituted fluorene: (a) the red shift caused by a certain substituent is about the same in both (singlet and triplet) manifolds; (b) the energy difference between SS and TT absorption maxima in fluorene as well as in all the substituted compounds is about the same and (c) the spectral red shifts observed in fluorene in the singlet and triplet manifold due to substitution by auxochromic groups can probably be used in fair approximation to estimate anticipated red shifts in other chromophores. For 2,7-diamino fluorene; p -terphenyl, p , p ′-diamino, p , p ′-diethylamino terphenyl, p -quaterphenyl; p , p ′-diamino, p , p −diethylamino quaterphenyl, spectral relations (a) to (c) also hold rather well.