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Building Molecular Complexity from Quinizarin: Conjoined Coumarins and Coronene Analogs
Author(s) -
Węcławski Marek K.,
Deperasińska Irena,
Banasiewicz Marzena,
Young David C.,
Leniak Arkadiusz,
Gryko Daniel T.
Publication year - 2019
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201800757
Subject(s) - bathochromic shift , chemistry , coronene , homo/lumo , photochemistry , quantum yield , excited state , solvatochromism , pyrene , fluorescence , stokes shift , aryl , molecule , organic chemistry , alkyl , physics , quantum mechanics , nuclear physics
Abstract The double Knoevenagel condensation of 1,4‐dibenzoyloxyanthraquinone with methyl esters of arylacetic acids affords a series of compounds based upon a previously unknown 1,8‐dioxa‐benzo[ e ]pyrene‐2,7‐dione heterocyclic core. The aryl groups incorporated in the 3‐ and 6‐positions can be oxidatively coupled to the π‐expanded backbone to produce a further new heterocyclic core: 1,10‐dioxa‐dibenzo[ dj ]coronene‐2,9‐dione. The intriguing optical properties of these π‐expanded coumarin derivatives are discussed and rationalized through quantum chemical calculations. The broad absorption bands of 1,8‐dioxa‐benzo[ e ]pyrene‐2,7‐dione‐based dyes are attributed to both HOMO−1→LUMO and HOMO→LUMO transitions, which have a similar energy. Weakly coupled electron‐donating aryl substituents result in a moderate bathochromic shift of both the absorption and emission by 30–60 nm in toluene. The emissive properties of these compounds are in part determined by the oscillator strength of the main transition, lifetimes of the excited state, and by the energy match of the excited state with a triplet state of a similar energy. The 1,10‐dioxa‐dibenzo[ dj ]coronene‐2,9‐dione displays a much smaller Stokes shift, yet a markedly increased fluorescence quantum yield of 90 % owing to the increased rigidity compared with the 1,8‐dioxa‐benzo[ e ]pyrene‐2,7‐dione core.