Evidence for hydrogen-bonded ammonia wire influencing the ESMPT process of the 7-hydroxy-4-methylcoumarin·(NH₃)₃ cluster

Abstract

The excited-state multiple proton transfer (ESMPT) reaction has been investigated for tautomerization of the 7-hydroxy-4-methylcoumarinÁ(NH 3 ) 3 (7H4MCÁ(NH 3 ) 3 ) cluster by means of time-dependent density functional theory. In the 7H4MCÁ(NH 3 ) 3 cluster, our results have demonstrated that four intermolecular hydrogen bonds are strengthened in the first excited state upon photoexcitation. This mechanism can remarkably facilitate the releasing of the proton from the phenolic group of the 7H4MC moiety to the hydrogen-bonded ammonia wire (NH 3 Á Á ÁNH 3 Á Á ÁNH 3 ). Subsequently, an intermediate transition conformer (AÁ(NH 3 ) 3 H + ) appears on the excited-state proton-transfer energy curve. In the AÁ(NH 3 ) 3 H + conformer, the intramolecular charge transfer process is revealed due to the proton motion. This process is able to effectively trigger the subsequent ESMPT reaction. Therefore, the different types of excited-state hydrogen-bonded dynamics mechanisms orderly provide two driving forces for the ESMPT reaction in the 7H4MCÁ(NH 3 ) 3 cluster. In addition, the mechanism of the ESMPT processes in the 7H4MC molecule along different kinds of hydrogen-bonded wires (ammonia and water) has been elucidated, and the internal property of transformation is discussed in detail.

Theoretical insight into the excited‐state behavior of a novel Compound 1: A TDDFT investigation

“…While the investigations of ESIPT process are ambiguous due to the deficiency of specific excited state dynamical behavior. Moreover, to the best of our knowledge, experiments could just present some indirect information about the photo‐physical and photochemical characteristics . We deem that a detailed and straightforward excited state process could facilitate the understandings and applications of compound 1 in future.…”

Theoretical exploration about excited state proton transfer mechanism for a series of phenol–quinoline compounds

“…The excited‐state intramolecular proton transfer (ESIPT) reaction should be the initial event of numerous photochemical and photobiological processes. The basic principle of the ESIPT reaction refers to hydrogen transfer from the proton donor to the proton acceptor, which results in the corresponding balance between the initial (enol) form and the photo‐tautomer (keto) form, stimulating a dual emission and large Stokes shifts …”

“…The basic principle of the ESIPT reaction refers to hydrogen transfer from the proton donor to the proton acceptor, which results in the corresponding balance between the initial (enol) form and the photo-tautomer (keto) form, stimulating a dual emission and large Stokes shifts. [6][7][8][9][10][11][12] In general, on photoexcitation, the ground-state enol configuration can be excited to the excited state, forming an enol* structure. The ESIPT occurs along with the preexisting hydrogen bond, forming the tautomer form keto*.…”

A theoretical investigation about the excited state behavior for 2‐(6'‐hydroxy‐2'‐pyridyl)benzimidazole: The water‐assisted excited state proton transfer process

“…Further, different hydrogen-bonding patterns between the target molecule and the surrounding solvent have decisive influences on the ESPT process. The phototautomerization involved in solvent-assisted ESPT can be detected in different types of sensors, [27][28][29][30] which have attracted intense scientific interest from the viewpoints of both potential applications and theoretical investigations. [31][32][33] .…”