Excited-State Intramolecular Proton Transfer in a Dendritic Macromolecular System:  Poly(aryl ether) Dendrimers with Phototautomerizable Quinoline Core

Abstract

Poly(aryl ether) dendrimers of three different generations (n ) 1, 2, 3) that are cored with phototautomerizable quinoline (QGn) were synthesized to investigate the effect of dendritic architecture on the excited-state intramolecular proton transfer (ESIPT). It was deduced from the generation-dependent absorption spectra that the peripheral crowdedness arising from the dendritic structure not only decouples the ESIPT core from the molecular surrounding but also influences the core planarity. Static and picosecond kinetic studies on ESIPT emission provided further information that the ESIPT in the quinoline core is slowed down with increasing dendrimer generation via the reduced core planarity. However, it was also observed that the proton transfer is still so effective even in the highest generation dendrimer that the emission efficiency is largely increased with dendrimer generation through the enhanced isolation effect. Compared to the polystyrene blend film containing nondendritic model compound (MQ), the films of QGn were proven to be a truly single-component "solid solution" with better performances in terms of the emission efficiency and chromophore content.

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

“…[ 56 ] All dendrimers QG n were glassy and their glass Reproduced with permission. [ 54 ] Copyright 2007 American Chemical Society.…”

Molecular photonics materials with excited-state intramolecular proton transfer (ESIPT) activity

“…With an aim to obtain more effective solid medium of ESIPT, poly(aryl ether) dendrimers that are cored with phototautomerizable quinoline (QGn, n=1,2,3) were investigated since dendritic encapsulation strategy can isolate fluorophores from each other to depress concentration quenching. 6 The photo-tautomerizable quinoline core was prepared by Friedländer reaction between bis(aminoketone) monomer of PQDH and 2',4'-dihydroxyacetophenone and then coupled with Fréchet's archetypal poly(aryl ether) dendron to give QGn. nm are from the transition of conjugated core unit (2-quinolin-2-yl-phenol moiety), each denoted as S1 and S2, respectively.…”

“…Very recently, we reported highly concentrated but still ESIPT-active solid media, i.e., films of a semi-rigid polyquinoline and poly(aryl ether) dendrimers possessing a novel photo-tautomerizable quinoline as a repeating unit and core, respectively. [4][5][6][7] Here we describe the recent progress, i.e., theoretical design of a quinoline-based ESIPT chromophore and its optical properties in polymeric and dendritic systems including stimulated emission and amplified spontaneous emission.…”

Stilbene-cored poly(glutamate) dendrimers

“…In this area, the photoisomerization of dendrimers with photoresponsive cores-such as stilbene, [13][14][15][16][17][18][19][20][21] azobenzene, [22][23][24][25][26][27][28][29][30][31][32][33] diarylethene, [34][35][36][37][38] intramolecularly hydrogen-bonded chromophores, [39][40][41] and photolabile chromophores 42-44 -has been extensively investigated. We recently reported that stilbene dendrimers with benzyl ether-type dendrons exhibited a volume-conserving isomerization mechanism and a macromolecular effect (or generation effect) on energy transfer efficiency from the peripheral dendrons to the core stilbene in organic solvents [45][46][47] and aqueous solution.…”