Mechanically induced single-molecule white-light emission of excited-state intramolecular proton transfer (ESIPT) materials

Abstract

Described herein is the first example of mechanically induced single-molecule white-light emission based on excited-state intramolecular proton transfer (ESIPT) materials. Mechanism of mechanochromism is clearly disclosed by powder and single...

Correlation between Excited-State Intramolecular Proton Transfer and Electron Population on Proton Donor/Acceptor in 2-(2′-Hydroxyphenyl)oxazole Derivatives

“…14,15 Due to the presence of two excitedstate electronic configurations, the ESIPT molecules generally exhibit largely Stokes-shifted T* fluorescence or even dual fluorescence from both N* and T* states. 16,17 Modulating the ESIPT reaction for anticipant applications has been fascinating for material chemists. For instance, some near-infrared fluorescent materials are designed based on the occurrence of a highly exergonic ultrafast ESIPT reaction, 16,18,19 while some single-component white-light materials cover the entire visible region on account of the dual fluorescence originating from an ESIPT thermodynamic equilibrium, 17,20 and some deep-blue fluorescent materials are fabricated through prohibiting an undesired ESIPT reaction despite the preformation of intramolecular hydrogen bonds (intra-HB).…”

“…16,17 Modulating the ESIPT reaction for anticipant applications has been fascinating for material chemists. For instance, some near-infrared fluorescent materials are designed based on the occurrence of a highly exergonic ultrafast ESIPT reaction, 16,18,19 while some single-component white-light materials cover the entire visible region on account of the dual fluorescence originating from an ESIPT thermodynamic equilibrium, 17,20 and some deep-blue fluorescent materials are fabricated through prohibiting an undesired ESIPT reaction despite the preformation of intramolecular hydrogen bonds (intra-HB). 21 The strategies of modulating an ESIPT reaction could be mainly divided into extrinsic disturbance and intrinsic modification.…”

“…), − plays an important role in chemistry, biology, and material sciences. − As illustrated in Scheme , the ground-state molecules with enol-normal form (N) are populated to the excited state (N*) via photoexcitation. They subsequently transform into keto-tautomer (T*) through the ESIPT reaction, then deactivate to the ground-state tautomer (T) via radiative or nonradiative relaxation, and finally T state molecules transform back to the N state through ground-state intramolecular proton transfer (GSIPT) reaction. , Due to the presence of two excited-state electronic configurations, the ESIPT molecules generally exhibit largely Stokes-shifted T* fluorescence or even dual fluorescence from both N* and T* states. , …”

“…Fortunately, we learned about the synthesis of the deep-blue and white fluorescent materials with the substitution of different electron-donating/withdrawing groups on positions 5 and 5′ of the hydroxyl-type model ESIPT molecule 2-(2′-hydroxyphenyl)­oxazole (HPO) in You’s recent works. , The ESIPT reactions in these HPO derivatives are successfully modulated by the alteration of electron density distribution. It is known that the enhancement of excited-state acidity (proton donor) and basicity (proton acceptor) resulting from the redistribution of electron density through electronic excitation induces the occurrence of the ESIPT reaction .…”

Multistimulus Response of Two Tautomeric Zn(II) Complexes and Their White-Light Emission Based on Different Mechanisms

“…According to the colorimetric characteristics, white luminescence relies on a combination of blue, green, and red or blue and orange, covering the visible spectrum from 400 to 700 nm. − Compared to multicomponent materials, white-light-emitting single molecules have the advantages of highly stable and repeatable spectra and the simple reproducible preparation of devices . There are various mechanisms for white-light emission, including excited-state intramolecular proton transfer (ESIPT), − monomer and excimer fluorescence, − intramolecular energy transfer (IET), − charge transfer (CT), − thermally activated delayed fluorescence (TADF), − and fluorescence and phosphorescence dual emission. − ESIPT luminescence involves two molecules with different forms, normal (N) and tautomeric (T) forms, which have an intramolecular hydrogen bond, a large Stokes shift, and no self-absorption. The proton donor (−OH or −NH 2 ) and the proton acceptor (N– or −CO) groups are in the proximity of each other with an intramolecular hydrogen bond in the five- or six-membered ring. , The ESIPT process starts with a molecule (N) on the electronic ground state and goes to excited states (N*), producing a tautomeric species T* through electronic density rearrangement, providing dual emission from two excited states [N* (S 1 ) → N (S 0 ) and T* (S 1 ) → T (S 0 )].…”