Synthesis, spectroscopic characterization and photophysics of new functionalized 2,3-distyrylfurans: Substituent and solvent effects on their photobehavior

Two new groups of p-chloro-, p-methoxy- and p-nitro-substituted derivatives of the trans,trans-isomers of 2,3-distyrylfuran have been synthesized by a sequence of reactions according to known methods. These new conjugated heterocyclic compounds along with the parent one and its methyl-derivative have been characterized spectrally, photophysically and photochemically. These compounds, except for the nitro-derivatives, display high fluorescence quantum yields in the non-polar n-hexane (ΦF = 0.76–0.98). In ethanol of high polarity, the lifetime of their singlet excited state increases from 1.31–2.59 ns to 2.01–4.77 ns, significantly enhancing the quantum yield of their photochemical reaction from 0.02–0.24 to 0.25–0.46, and diminishing their fluorescence efficiency (ΦF = 0.26–0.64). Deviating from the other compounds studied, the quantum yields for both the fluorescence and the photolysis of the nitro-derivatives are rather low (ΦF < 10−4, Φ = 0.025–0.042 in ethanol), probably due to an efficient intersystem crossing leading to a non-reactive triplet state. Accordingly, their singlet-state lifetime is also relatively short (τF < 0.3 ns).