Amputu Martha N, Naimhwaka Johannes, Uahengo Veikko
Department of Physics, Chemistry and Material Science, University of Namibia 340 Mandume Ndemufayo Avenue Windhoek 9000 Namibia
RSC Adv. 2022 Sep 21;12(41):27022-27043. doi: 10.1039/d2ra04568k. eCollection 2022 Sep 16.
A naphthylthioic-based emissive probe (M) bearing a hydroxyl and amine group was designed and synthesized a one-step Schiff base reaction process. The probe was characterized spectroscopically using H NMR, UV-Vis and fluorescence spectrophotometers. The probe turned out to be spectroscopically and colorimetrically selective and sensitive to multiple cations and anions. Interestingly, the probe displayed characteristics of excited-state intramolecular proton transfer (ESIPT)-driven dual emissive channels; experiencing fluorescence enhancement upon the molar additions of Al as well as the anions used, events presumably ascribed to chelation fluorescence enhancement (CHEF), hydrogen bonding and deprotonation effects. Moreover, the fluorometric titration with Hg resulted in ratiometric spectral behaviors of M, with the disappearance of the peak at 450 nm, concomitant with the appearance of a new peak at 520 nm, distinguished by a clear isosbestic point, the same behaviors exhibited by Sn and Ag analytes towards M. The introduction of all other cations used, resulted in fluorescence quenching, attributable to chelation enhanced fluorescence quenching (CHEQ), thereby inhibiting the ESIPT process. The experiments were all carried out in the aqueous environment medium of DMSO-HO (9 : 1) at ambient temperature. Theoretical density functional theory calculations were carried out to gain insight into the interaction of M with cations and anions, and their influence on the HOMO-LUMO energy gaps.
设计并合成了一种基于萘硫基的发光探针（M），其带有羟基和胺基，通过一步席夫碱反应过程制备。使用核磁共振氢谱、紫外可见分光光度计和荧光分光光度计对该探针进行了光谱表征。结果表明，该探针对多种阳离子和阴离子具有光谱和比色选择性及敏感性。有趣的是，该探针表现出激发态分子内质子转移（ESIPT）驱动的双发射通道特性；在加入铝以及所用阴离子后，荧光增强，这些现象可能归因于螯合荧光增强（CHEF）、氢键和去质子化效应。此外，用汞进行荧光滴定导致M呈现比率光谱行为，450nm处的峰消失，同时在520nm处出现一个新峰，有明显的等吸收点，锡和银分析物对M也表现出相同行为。加入所有其他所用阳离子会导致荧光猝灭，这归因于螯合增强荧光猝灭（CHEQ），从而抑制了ESIPT过程。所有实验均在室温下于二甲基亚砜 - 水（9∶1）的水性环境介质中进行。进行了理论密度泛函理论计算，以深入了解M与阳离子和阴离子的相互作用及其对最高占据分子轨道 - 最低未占据分子轨道（HOMO - LUMO）能隙的影响。
