Influence of intramolecular hydrogen bond formation sites on fluorescence mechanism

Abstract

The fluorescence mechanism of HBT-HBZ is investigated in this work. A fluorescent probe is used to detect HClO content in living cells and tap water, and its structure after oxidation by HClO (HBT-ClO) is discussed based on the density functional theory (DFT) and time-dependent density functional theory (TDDFT). At the same time, the influence of the probe conformation and the proton transfer site within the excited state molecule on the fluorescence mechanism are revealed. Combined with infrared vibrational spectra and atoms-in-molecules theory, the strength of intramolecular hydrogen bonds in HBT-HBZ and HBT-ClO and their isomers are demonstrated qualitatively. The relationship between the strength of intramolecular hydrogen bonds and dipole moments is discussed. The potential energy curves demonstrate the feasibility of intramolecular proton transfer. The weak fluorescence phenomenon of HBT-HBZ in solution is quantitatively explained by analyzing the frontier molecular orbital and hole electron caused by charge separation. Moreover, when strong cyan fluorescence occurs in solution, the corresponding molecular structure should be HBT-ClO(T). The influence of the intramolecular hydrogen bond formation site on the molecule as a whole is also investigated by electrostatic potential analysis.

A Simple and Rapid Quinoline Schiff Base as a Fluorescent Probe for Zn2+ and Its Application in Test Strips

“…In order to determine the reactive sites of the probe for metal ion recognition, electrostatic surface potential analysis was performed. When the ESP on a molecular surface is represented in blue, it indicates a negative charge distribution, favoring electrophilic reactions [67] . As represented in Figure 6, the ESP near the quinoline nitrogen and imine group is negative in probe L .…”

“…When the ESP on a molecular surface is represented in blue, it indicates a negative charge distribution, favoring electrophilic reactions. [67] As represented in Figure 6, the ESP near the quinoline nitrogen and imine group is negative in probe L. Therefore, the region containing the nitrogen atom of the quinoline and imine group is the most preferential binding site for Zn 2 + . In addition, the above region of LÀ Zn 2 + turned white, indicating that there is a robust binding interaction between the zinc ion and L. [68] In conclusion, the HOMO-LUMO and ESP maps of L and LÀ Zn 2 + showed the fluorescence enhancement of LÀ Zn 2 + owing to charge transfer interaction between L and Zn 2 + .…”

Unveiling the atomic‐electronegativity‐dependent ESIPT behavior for 4′‐dimethylamino‐flavonol chemosensor

“…As is known, the potential photo-induced molecular behaviors could be reflected via focusing on excitation process to a large extent [46][47][48][49][50]. Accordingly, herein, we mainly pay attention to probe into the vertical excitation behavior for 4DF-O, 4DF-S, and 4DF-Se.…”