Photochemistry of anthrylethene derivatives containing heteroaromatic ring: Thiophene, furan, and their fused ring derivatives

Four 1-(9-anthryl)-2-heteroarylethene derivatives containing sulfur or oxygen atom such as 1-(9-anthryl)-2-(2-thiophenyl)ethene (ATE), 1-(9-anthryl)-2-(2-benzo[b]thiophenyl)ethene (ABTE), 1-(9-anthryl)-2-(2-furanyl)ethene (AFE), and 1-(9-anthryl)-2-(2-benzofuranyl)ethene (ABFE) have been prepared and their excited state properties have been investigated in cyclohexane, acetonitrile, and methanol. These sulfur- or oxygen-heteroaromatic ring derivatives show solvent-dependent fluorescence and photoisomerization behavior, due to the intramolecular charge-transfer character of the lowest S1 state. Substituent effect on fluorescence and photoisomerization of ATE further supports the contribution of the intramolecular charge-transfer character to the lowest S1 state, which is more increased by the introduction of electron-withdrawing substituent into anthracene ring.