A new series of two-photon blue/violet fluorescent trans-alkenes: Green synthesis and optical properties.

A new series of trans-alkenes (3a-3e) containing different electron-donating groups were synthesized by the solvent-free Horner-Wadsworth-Emmons reaction, and characterized by infrared, hydrogen nuclear magnetic resonance, mass spectrometry and elemental analysis. Their UV-visible absorption, one-photon excited fluorescence, two-photon absorption, and two-photon excited fluorescence were systematically investigated in different solvents. Experimental results show different trends in linear and nonlinear optical properties with different donor units. 3a with triphenylamine donor exhibits the best optical properties. It emits strong blue up-converted fluorescence, and the two-photon absorption cross-section can be as large as 218 GM in DCM.