Structures, spectra and photophysics of new organic fluorophores: 2,3- and 2,5-di(phenylethenyl)furan

The rotational isomerism, electronic structure and photophysics of two new organic fluorophores, the 2,3- and 2,5-di(phenylethenyl)furan have been studied by a combined theoretical and experimental approach. The conformers of the ground electronic state have been investigated by Hartree-Fock ab initio methods and density functional theory. The electronic spectra have been calculated with the CS INDO S-CI and SDT-CI procedures. The spectral and photophysical behaviour was investigated by stationary and time-resolved techniques. The more stable conformer was found to be the A rotamer in planar or quasi planar form. DFT calculations gave more planar structure than those obtained using HF methodology. The UV-Vis absorption spectrum of 2,3-(PhE)2F is very similar to that of 3-cis-α,ω-diphenylhexatriene. The CS INDO CI analysis of the electronic spectra of all rotamers, with particular attention to the cis peak, shows coherence with the presence of A conformer. These very stable compounds show a strong and structured fluorescence indicating that the emitting state is the same as that implied in the absorption process, πHπL∗ singlet state. These new organic fluorophores may have very interesting applications as fluorescent probes, dye laser medium, scintillators and as π-core for new push-pull polyenes.