Application of excited-state intramolecular proton transfer (ESIPT) principle to functional polymeric materials

Abstract

Synthesis and properties of novel excited-state intramolecular proton transfer (ESIPT) materials, recently developed in our group, are described. Highly efficient ESIPT reaction, achieved in polyquinolines, polybenzoxazoles, and oxadiazole and imidazole derivatives possessing an intramolecular tautomerizable hydrogen bond, has been investigated theoretically and experimentally. It is demonstrated that unique properties arising from the ESIPT process (large Stokes' shift, no self-absorption, and easy population inversion, etc.) make it possible to produce advanced polymer devices for lasing, optical storage, and electroluminescence.

Advanced Organic Optoelectronic Materials: Harnessing Excited‐State Intramolecular Proton Transfer (ESIPT) Process

“…[ 30 ] Up to now, extensive spectroscopic and theoretical research works on the photophysical process of ESIPT molecules have been carried out and their molecular structure-property relationship has been well established. On the other hand, research works aiming at the practical application of them which harnesses their unique ESIPT process have been rather limited and often suffered from, for example, low emission effi ciency, concentration quenching of the keto emission and environmentsensitive spectral change.…”

25.1: Invited Paper: White‐emitting Molecule: ‘Molecular Pixel’ from Covalently Bonded Sub‐pixels

“…It has been the research subject intensively studied in photochemistry and photophysics. Representative molecular structure of highly fluorescent ESIPT molecules recently developed in our group is shown in Figure 2 [4]. As depicted in Figure 3, these ESIPT-exhibiting molecules exist exclusively as an enol (E) form in the ground state, while upon photoexcitation, undergo tautomerization into a keto form (E* → K*) via an extremely fast and irreversible ESIPT process occurring in the sub-picosecond time regime.…”

“…Moreover, different absorbing (E) and emitting (K*) species in the intrinsic four-level photocyclic scheme (E → E* → K* → K →···) give rise to a large Stokes'-shifted fluorescence without self-reabsorption as well as an easy population inversion of the proton transferred keto form in the lowest excited state facilitating stimulated emission. This peculiar characteristic has encouraged many novel applications including luminescent solar concentrators and proton transfer lasers [4]. Fluorescence probing is another promising application of ESIPT, due to its spectral sensitivity to environmental medium [4].…”

Excited State Intramolecular Proton Transfer of New Diphenyl‐ ethylene Derivatives Bearing Imino Group: A Combination of Experimental and Theoretical Investigation

“…[1][2][3][4][5][6][7][8][9][10] Normally, an ESIPT molecule is characterized with an exceptionally and anomalously large Stokes shift, which has been found in many varieties of applications including photochromic material, 11 laser dyes, 12 ultraviolet photostabilizers, 13 fluorescence probe, 14 electroluminescent materials 15 and so on. [16][17][18] This is achieved by an ultrafast photoinduced tautomerization process between enol form and keto form when the intramolecular H-bonded molecule is photoexcited, which is characterized with four-level cycle reaction occurring via five or six members ring. 19 The stable ground state in the enol form and the stable excited state in the keto form result in the absorption from E→E* and the emission from K*→K, causing an abnormally large Stokes shift without self-absorption.…”