Synthesis and Characterization of Conjugated Pyridine-(N-diphenylamino) Acrylonitrile Derivatives: Photophysical Properties

We have synthesized four novel highly conjugated and fluorescent compounds, 2-(phenyl)-3-(4-diphenylaminophenyl)acrylonitrile (I), 2-(2´-pyridyl)-3-(4-diphenylamino-phenyl)acrylonitrile (II), 2-(3´-pyridyl)-3-(4-diphenylaminophenyl)acrylonitrile III) and 2-(4´-pyridyl)-3-(4-diphenylaminophenyl)acrylonitrile (IV) by the Knoevenagel condensation.  In solution, the UV-vis spectra showed two maxima for each compound, one at ~296-300 nm and the other at ~403-428 nm. The compounds showed fluorescence emission in CHCl3 solution as well as in the state solid. The fluorescence quantum yield for the compounds in powder form showed values ranging from 0.07-0.11.  Structures were confirmed with IR, MS, and NMR spectroscopy. Molar coefficient absorption, absorbance, fluorescence emission spectra and fluorescence quantum yield (Ff) were compared to evaluate the effects of the diphenylamino-substituents and the position of nitrogen on the electronic properties of phenylpyridylacrylonitriles compounds