Subuddhi Usharani, Haldar Sourav, Sankararaman S, Mishra Ashok K
Department of Chemistry, Indian Institute of Technology-Madras, Chennai, 36, India.
Photochem Photobiol Sci. 2006 May;5(5):459-66. doi: 10.1039/b600009f. Epub 2006 Apr 18.
The photophysical behaviour of a new pyrene derivative, 1-(4-N,N-dimethylaminophenylethynyl)pyrene (DMAPEPy), in various solvents has been studied. Due to the presence of an ethynyl link with a cylindrical pi cloud between the donor (N,N-dimethyl group) and the acceptor (pyrene), the molecule shows efficient intramolecular charge transfer, with a high extinction coefficient in all the solvents. There is significant solvatochromism in the fluorescence with a large increase in the Stokes' shift of around 125 nm between n-hexane and acetonitrile. The solvent-dependent spectral data show a good correlation with the Kamlet-Taft solvent polarity parameter (pi*). The plots of Stokes' shifts with E(T)(30) are linear for non-protic solvents and for protic solvents but with different slopes. The fluorescence quantum yields are high for non-polar solvents and decrease as the solvent polarity increases. Unlike the parent molecule pyrene, DMAPEPy shows a short lifetime, which is fairly insensitive to oxygen-induced quenching and is dependent on solvent polarity. The molecule shows high steady-state fluorescence anisotropy, which is very sensitive to the viscosity change of the medium.
研究了一种新型芘衍生物1-(4-N,N-二甲基氨基苯乙炔基)芘(DMAPEPy)在各种溶剂中的光物理行为。由于在供体(N,N-二甲基基团)和受体(芘)之间存在带有圆柱形π云的乙炔键，该分子表现出有效的分子内电荷转移，在所有溶剂中都具有高消光系数。荧光中存在显著的溶剂化显色现象，在正己烷和乙腈之间斯托克斯位移大幅增加约125nm。溶剂依赖的光谱数据与Kamlet-Taft溶剂极性参数(π*)具有良好的相关性。对于非质子溶剂和质子溶剂，斯托克斯位移与E(T)(30)的关系图是线性的，但斜率不同。非极性溶剂的荧光量子产率较高，且随着溶剂极性的增加而降低。与母体分子芘不同，DMAPEPy的寿命较短，对氧诱导猝灭相当不敏感，且依赖于溶剂极性。该分子表现出高稳态荧光各向异性，对介质的粘度变化非常敏感。
