Tripathi Alok Kumar, Mohapatra Monalisa, Mishra Ashok Kumar
Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, Tamil Nadu, India.
Phys Chem Chem Phys. 2015 Nov 28;17(44):29985-94. doi: 10.1039/c5cp04263a. Epub 2015 Oct 23.
The present work describes the synthesis and photophysical studies of two fluorescent dansylamide derivatives, in which the amine group is acylated by a long hydrophobic chain (a part of a biologically relevant palmitic acid) and by a short hydrophobic tail (a part of acetic acid). The long chain tethered dansyl analogue is successfully utilized in estimating critical micellar concentration (CMC) of bile salts (NaDC, NaC) as well as anionic and cationic surfactants (SDS, CTAB) with the help of enhanced fluorescence intensity facilitated by better solubilization of the molecule in microheterogeneous media. The long chain tethered dansylamide derivative shows significant fluorescence solvatochromism with a red shift (ca. 4000 cm(-1)) from hexane to water. In contrast, the solvatochromism exhibited by the parent/short acyl chain analogue is much less (ca. 2230 cm(-1) from hexane to water) and the fluorescence is not sensitive to micellization. Interestingly, the long chain tethered fluorescent probe shows high sensitivity towards premicellar aggregation of sodium deoxycholate (NaDC) bile salt, through a clear blue shift of emission maxima and concomitant enhancement of fluorescent intensity. Such an observation of fluorescence sensing of premicellar aggregation is unusual.
本工作描述了两种荧光丹磺酰胺衍生物的合成及光物理研究，其中胺基通过长疏水链（生物相关棕榈酸的一部分）和短疏水尾（乙酸的一部分）进行酰化。长链连接的丹磺类似物借助分子在微非均相介质中更好的增溶作用所促进的荧光强度增强，成功用于估算胆盐（脱氧胆酸钠、胆酸钠）以及阴离子和阳离子表面活性剂（十二烷基硫酸钠、十六烷基三甲基溴化铵）的临界胶束浓度（CMC）。长链连接的丹磺酰胺衍生物表现出显著的荧光溶剂化显色性，从己烷到水有红移（约4000 cm⁻¹）。相比之下，母体/短酰基链类似物表现出的溶剂化显色性要小得多（从己烷到水约2230 cm⁻¹），且荧光对胶束化不敏感。有趣的是，长链连接的荧光探针通过发射最大值的明显蓝移和荧光强度的相应增强，对脱氧胆酸钠（NaDC）胆盐的预胶束聚集表现出高灵敏度。这种对预胶束聚集的荧光传感观察是不寻常的。
