The ESIPT mechanism of dibenzimidazolo diimine sensor: a detailed TDDFT study

Abstract

Spectroscopic investigations on excited state proton transfer of a new dibenzimidazolo diimine sensor (DDS) were reported by Goswami et al. recently. In our present work, based on the time-dependent density functional theory (TDDFT), the excited-state intramolecular proton transfer (ESIPT) mechanism of DDS is studied theoretically. Our calculated results reproduced absorption and fluorescence emission spectra of the previous experiment, which verifies that the TDDFT method we adopted is reasonable and effective. The calculated dominating bond lengths and bond angles involved in hydrogen bond demonstrate that the intramolecular hydrogen bond is strengthened. In addition, the phenomenon of hydrogen bond reinforce has also been testified based on infrared vibrational spectra. Further, hydrogen bonding strengthening manifests the tendency of ESIPT process. The calculated frontier molecular orbitals further demonstrate that the excited state proton transfer is likely to occur. According to the calculated results of potential energy curves along O-H coordinate, the potential energy barrier of about 5.02 kcal/mol is discovered in the S 0 state. However, a lower potential energy barrier of 0.195 kcal/mol is found in the S 1 state, which demonstrates that the proton transfer process is more likely to happen in the S 1 state than the S 0 state. In other words, the proton transfer reaction can be facilitated based on the photo-excitation effectively. Moreover, the phenomenon of fluorescence quenching could be explained based on the ESIPT mechanism.

Hydrogen bonding interactions induced excited state proton transfer and fluoride anion sensing mechanism for 2‐(3,5‐dichloro‐2,6‐dihydroxy‐phenyl)‐benzoxazole‐5‐carboxylicacid

“…And the large Stokes shift could be attributed to the four energy level photophysical and photochemical behavior with the creation of photochromic tautomer in the ground state. [21][22][23][24][25][26][27][28][29][30] Independently of the application, the understanding of the dynamics between proton donor and acceptor sites in the electronic excited states is an important task. The model formulated by Weller is composed of a fourlevel photochemical cycle where the phototautomerization process happens.…”

A theoretical exploration and regulating about the excited state process for 2‐(4‐(diphenylamino)phenyl)‐3‐hydroxy‐4H‐chromen‐4‐one system

“…And this kind of process has been widely investigated in the past few years due to their significant characteristics in biological and chemical fields. In effect, these changes about properties have been extensively applied to fluorescent sensing technologies, fluorescence imaging, organic light‐emitting diodes (OLEDs), and so forth . However, some mechanisms of the ESPT reactions are complicated.…”

“…In effect, these changes about properties have been extensively applied to fluorescent sensing technologies, fluorescence imaging, organic lightemitting diodes (OLEDs), and so forth. [31][32][33][34][35][36][37][38][39][40] However, some mechanisms of the ESPT reactions are complicated. The mechanisms of PT, such as the sequence of PT in the dual-PT system as well as the mode of PT, and so forth, could not be obtained by spectra technologies.…”

Solvent controlling excited state proton transfer reaction in quinoline/isoquinoline‐pyrazole isomer QP‐I: A theoretical study

“…ESIPT process has been a popular research field since 1956, firstly reported by Weller and coworkers in experiment with methylsalicylate . In fact, the transferred tautomerization form (normally named keto in the S 0 state and keto* in the S 1 state) has charge redistribution characteristic, which are very fascinating towards the application of laser dyes, UV filters, fluorescence chemosensors, molecular switch, and so on . At experimental level, the excited state proton transfer processes can indeed be followed using ultrafast pump‐probe and time‐resolved emission experiments or coherent Raman methods.…”

“…[29,30] In fact, the transferred tautomerization form (normally named keto in the S 0 state and keto* in the S 1 state) has charge redistribution characteristic, which are very fascinating towards the application of laser dyes, UV filters, fluorescence chemosensors, molecular switch, and so on. [31][32][33][34][35][36][37][38][39][40] At experimental level, the excited state proton transfer processes can indeed be followed using ultrafast pumpprobe and time-resolved emission experiments or coherent Raman methods. Furthermore, some molecules are highly sensitive to the change in the microenvironments, based on which Sytnik et al reported how the ESIPT chromophores can be used in the study of protein conformations and binding site polarity.…”