Tuning of the electronic and photophysical properties of ladder-type quaterphenyl by selective methylene-bridge fluorination

Abstract

The photophysics (spectral positions, band shapes, fluorescence quantum yields and lifetimes) of a series of fluorinated ladder type quaterphenyls L4P and L4P-F_n (n = 2, 4, 6) depend strongly on the degree and position of fluorine, despite the fact that substitution is not performed in the rings but only in methylene-bridges. This is driven by subtle differences in the molecular orbitals (MOs) participating in the electronic transitions, and in the vibronic pattern of the S₀ and S₁ electronic states as revealed by (TD)DFT calculations. Solid state spectra for n = 0, 2, 4 are similar to those of solution due to small intermolecular interactions as revealed by combined X-ray and (TD)DFT analysis.