Theoretical Insights into the Excited State Hydrogen Bond and ESIPT Reaction for 2-Amino-3-(2’-Benzoxazolyl)Quinoline and 2-Amino-3-(2’-Benzothiazolyl)-Quinoline

Abstract

Two N-H type excited state intramolecular proton transfer (ESIPT) systems (i.e., 2-amino-3-(2'benzoxazolyl)quinoline (ABO) and 2-amino-3-(2'-benzothiazolyl)-quinoline (ABT)) have been investigated. Adopting DFT and TDDFT methods coupling with B3LYP functional and TZVP basis set, our simulations about ABO and ABT molecules have successfully reappeared experimental results, based on which the rationality of our calculations is confirmed. Using Atoms in Molecules (AIM) analytical method, we firstly explore the interactions about chemical bond and verify the formation of hydrogen bond N-H•••N for ABO and ABT in the S 0 state. Investigating the primary geometrical parameters involved in N-H•••N, we find it should be strengthened in the S 1 state. Upon photoexcitation, charge transfer phenomenon is found via frontier molecular orbitals (MOs), and charge redistribution provides the tendency of ESIPT reaction for ABO and ABT. According to our constructed potential energy curves of both S 0 and S 1 states for ABO and ABT using two kinds of methods (i.e., the elongation of N-H single bond and the weakening of H•••N hydrogen bond), we clarify the ESIPT mechanisms and explain the recovery of four-level reaction cycle. Our searching transition state (TS) structures and simulated intrinsic reaction coordinate (IRC) path further confirm the ESIPT reaction.

Exploration and elaboration of photo-induced proton transfer dynamical mechanism for novel 2-[1,3]dithian-2-yl-6-(7aH-indol-2-yl)-phenol sensor*

“…In view of the differences between enol* configuration and keto* configuration, normally, keto* configuration emits a longer wavelength fluorescence. [31][32][33][34][35][36][37][38] Therefore, the dual emission band could be detected. It covers a broad region of steady-state emission by promoting ESIPT molecules to become suitable for cell images, UV filters, white emitting OLEDs, fluorescent probes, molecular switchers, etc.…”

“…It covers a broad region of steady-state emission by promoting ESIPT molecules to become suitable for cell images, UV filters, white emitting OLEDs, fluorescent probes, molecular switchers, etc. [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] Therefore, it cannot be denied that dynamics of ESIPT reaction is beneficial for more novel applications in future.…”

“…To the best of our knowledge, only spectroscopic techniques containing time-resolved as well as steady-state electronic spectra could just reveal oblique aspects about molecular photochemical properties. [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] Up to now, previous investigations and observed phenomenon of DIP system are limited except experiment study. In view of the significance of theoretical work, we adopt the quantum chemical computational manner to study photo-induced cases relevant to hydrogen bonding interactions as well as ESIPT reaction.…”