Substituent Effects on Fluorescent Properties of Imidazo[1,2-<b><i>a</i></b>]pyridine-Based Compounds
作者:Haruhiko Tomoda、Takafumi Hirano、Shojiro Saito、Toshiki Mutai、Koji Araki
DOI:10.1246/bcsj.72.1327
日期:1999.6
In order to search for novel fluorescent organic compounds, 20 derivatives of imidazo[1,2-a]pyridine (1) were synthesized, and their fluorescent properties were studied. Though the parent compound 1 (λfl = 370.5 nm, Φ = 0.57 in ethanol) was in the liquid state at ambient temperature, 2-phenylimidazo[1,2-a]pyridine (5), 2-(2-naphthyl)imidazo[1,2-a]pyridine (16), 7-methylimidazo[1,2-a]pyridine (3), 7-methyl-2-phenylimidazo[1,2-a]pyridine (12), and 7-methyl-2-(2-naphthyl)imidazo[1,2-a]pyridine (17) were found to give thermally stable solid compounds (mp 55—190 °C) without much affecting the fluorescent properties of the parent compound (λfl = 374—381 nm, Φ = 0.50—0.78 in ethanol). Among the 4′-substituted 2-phenyl derivatives, it was found that the introduction of the strong electron-donating amino and dimethylamino groups (2-(4-aminophenyl)imidazo[1,2-a]pyridine (7) and 2-[4-(dimethylamino)phenyl]imidazo[1,2-a]pyridine (8), respectively) caused marked red shift of their fluorescence (λfl = 445 and 446 nm, respectively, in ethanol), thus providing the way for tuning the fluorescence color of the IP derivatives. The observed red shift of the fluorescence of 7 and 8 was ascribed to the contribution of the excited intramolecular charge transfer state.
为了寻找新型荧光有机化合物,合成了20种咪唑并[1,2-a]吡啶(1)的衍生物,并研究了它们的荧光性质。尽管母体化合物1在室温下为液态(λfl = 370.5 nm,Φ = 0.57,在乙醇中),但2-苯基咪唑并[1,2-a]吡啶(5)、2-(2-萘基)咪唑并[1,2-a]吡啶(16)、7-甲基咪唑并[1,2-a]吡啶(3)、7-甲基-2-苯基咪唑并[1,2-a]吡啶(12)和7-甲基-2-(2-萘基)咪唑并[1,2-a]吡啶(17)被发现能形成热稳定的固态化合物(熔点55-190°C),且对母体化合物的荧光性质影响不大(λfl = 374-381 nm,Φ = 0.50-0.78,在乙醇中)。在4'-取代的2-苯基衍生物中,发现引入强电子供体的氨基和二甲氨基(分别为2-(4-氨基苯基)咪唑并[1,2-a]吡啶(7)和2-[4-(二甲氨基)苯基]咪唑并[1,2-a]吡啶(8))会导致它们的荧光显著红移(λfl = 445和446 nm,在乙醇中),从而提供了调节IP衍生物荧光颜色的途径。7和8荧光的红移归因于激发态分子内电荷转移态的贡献。