Synthesis, Photophysical and Electrochemical Properties of 1-, 2-, and 6-(2-Benzofuryl)azulenes

The synthesis of 2- and 6-(2-benzofuryl)azulenes was accomplished by the Sonogashira-Hagihara coupling reaction of the corresponding haloazulenes with 2-ethynylphenol. 1-(2-Benzofuryl)azulenes were prepared by the decarboxylation of the corresponding 3-methoxycarbonyl derivatives with 100% H3PO4, of which the synthesis has been reported by us, recently. The photophysical properties of the (2-benzofuryl)azulenes were investigated by UV/Vis and fluorescence spectroscopies that revealed their pronounced halochromic behavior and luminescent characteristics under the light-irradiation in acidic media. The electrochemical properties of (2-benzofuryl)azulenes were also evaluated by voltammetry experiments and spectroelectrochemistry measurements.