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π‐Extended Push‐Pull‐Type Bicyclic Fluorophores Based on Quinoline and Naphthyridine Frameworks with an Iminophosphorane Fragment
Author(s) -
Umeno Tomohiro,
Usui Kazuteru,
Karasawa Satoru
Publication year - 2021
Publication title -
asian journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.846
H-Index - 44
eISSN - 2193-5815
pISSN - 2193-5807
DOI - 10.1002/ajoc.202100015
Subject(s) - chemistry , bicyclic molecule , quinoline , steric effects , moiety , photochemistry , molecule , polar effect , crystallinity , fluorescence , trifluoromethyl , stereochemistry , crystallography , organic chemistry , alkyl , physics , quantum mechanics
Emissive quinoline and naphthyridine derivatives, bearing an iminophosphorane (IPP) fragment as an electron‐donating group and two trifluoromethyl groups as electron‐withdrawing groups, were prepared as electron push‐pull‐type bicyclic fluorophores: quinoline‐IPP ( 1 ) and naphthyridine‐IPP ( 2 ). Compared to those of the precursor bicyclic amines without the IPP moiety, the fluorescence quantum yields (Φ f ) of 1 and 2 were considerably higher, not only in low polarity solvents but also polar solvents. Moreover, the molar absorption coefficients (ϵ) were enhanced; thus, 1 and 2 are fluorophores with relatively high brightness (Φ f ×ϵ). Using density functional theory calculations, the t indices were calculated, and these reveal that locally excited character is dominant in both molecules. Because of the sterically bulky IPP fragments, 1 and 2 emitted with moderate Φ f values, even in the solid state. Further, by exploiting the low crystallinity of 1 and 2 , emissive amorphous thin films were prepared.