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Blue‐to‐Green Delayed Fluorescence of 2‐Aminoisophthalic Acid Diesters Dispersed in Polymer Film
Author(s) -
Shimizu Masaki,
Nakatani Masaki
Publication year - 2017
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201700695
Subject(s) - intersystem crossing , luminescence , photochemistry , chemistry , fluorescence , intramolecular force , moiety , excited state , singlet state , microsecond , density functional theory , polymer , computational chemistry , materials science , organic chemistry , optoelectronics , atomic physics , physics , quantum mechanics , astronomy
We have synthesized ten 2‐aminoisophthalic acid diesters from commercially available dimethyl 2‐bromoisophthalate. The diesters in 2‐methyltetrahydrofuran were found to be non‐emissive or faintly fluorescent ( Φ = 0.04–0.08) at room temperature, whereas each ester in its powder form exhibits fluorescence in the blue to green spectral region with a luminescence efficiency superior to that in solution. DFT calculations revealed that luminescence occurs from the lowest singlet excited state generated by intramolecular charge transfer from the amino moiety to the isophthalate core. Time‐dependent DFT calculations suggest that the energy gap between the S 1 and T 1 states is very small, which allows reverse intersystem crossing leading to delayed fluorescence emission. Indeed, the diesters dispersed in poly(methyl methacrylate) (PMMA) films exhibit luminescence consisting of two components, the lifetimes of which are in the order of nano‐ and microseconds, respectively. The luminescence spectra of the PMMA films in air completely overlap with those recorded under vacuum, which indicates that the long‐lived emission can be assigned to delayed fluorescence.