title: Photophysical behaviour of 1-(4-N,N-dimethylaminophenylethynyl)pyrene (DMAPEPy) in homogeneous media.
abstract: 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.
authors: Department of Chemistry, Indian Institute of Technology-Madras, Chennai, 36, India.
authors: Usharani
authors: U
authors: Subuddhi
authors: Sourav
authors: S
authors: Haldar
authors: S
authors: S
authors: Sankararaman
authors: Ashok K
authors: AK
authors: Mishra