Kuchlyan Jagannath, Banik Debasis, Roy Arpita, Kundu Niloy, Sarkar Nilmoni
Department of Chemistry, Indian Institute of Technology , Kharagpur 721302, West Bengal, India.
J Phys Chem B. 2014 Dec 4;118(48):13946-53. doi: 10.1021/jp510389d. Epub 2014 Nov 21.
In this article we have investigated intermolecular excited-state proton transfer (ESPT) of firefly's chromophore D-luciferin in DMSO-water binary mixtures using steady-state and time-resolved fluorescence spectroscopy. The unusual behavior of DMSO-water binary mixture as reported by Bagchi et al. (J. Phys. Chem. B 2010, 114, 12875-12882) was also found using D-luciferin as intermolecular ESPT probe. The binary mixture has given evidence of its anomalous nature at low mole fractions of DMSO (below XD = 0.4) in our systematic investigation. Upon excitation of neutral D-luciferin molecule, dual fluorescence emissions (protonated and deprotonated form) are observed in DMSO-water binary mixture. A clear isoemissive point in the time-resolved area normalized emission spectra further indicates two emissive species in the excited state of D-luciferin in DMSO-water binary mixture. DMSO-water binary mixtures of different compositions are fascinating hydrogen bonding systems. Therefore, we have observed unusual changes in the fluorescence emission intensity, fluorescence quantum yield, and fluorescence lifetime of more hydrogen bonding sensitive anionic form of D-luciferin in low DMSO content of DMSO-water binary mixture.
在本文中，我们使用稳态和时间分辨荧光光谱法研究了萤火虫发色团D - 荧光素在二甲基亚砜 - 水二元混合物中的分子间激发态质子转移（ESPT）。以D - 荧光素作为分子间ESPT探针时，我们也发现了Bagchi等人（《物理化学杂志B》2010年，第114卷，12875 - 12882页）所报道的二甲基亚砜 - 水二元混合物的异常行为。在我们的系统研究中，该二元混合物在二甲基亚砜低摩尔分数（低于XD = 0.4）时显示出其异常性质。在中性D - 荧光素分子被激发后，在二甲基亚砜 - 水二元混合物中观察到双重荧光发射（质子化和去质子化形式）。时间分辨区域归一化发射光谱中的一个清晰的等发射点进一步表明，在二甲基亚砜 - 水二元混合物中，D - 荧光素激发态存在两种发射物种。不同组成的二甲基亚砜 - 水二元混合物是迷人的氢键体系。因此，我们观察到在二甲基亚砜 - 水二元混合物中低二甲基亚砜含量下，对氢键更敏感的阴离子形式的D - 荧光素的荧光发射强度、荧光量子产率和荧光寿命发生了异常变化。
