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5,12‐Diacetyl‐5,12‐dihydroquinoxalino[2,3‐ b ]quinoxalines: Solid‐State Fluorescence, AIE Properties, and Orbital Switching by Substituent Effect
Author(s) -
Miura Youhei,
Yoshioka Naoki
Publication year - 2018
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.201800502
Subject(s) - fluorescence , chemistry , quinoxaline , substituent , alkoxy group , crystallography , molecule , diacetyl , photochemistry , solid state , quenching (fluorescence) , absorption (acoustics) , stereochemistry , materials science , organic chemistry , alkyl , physics , quantum mechanics , composite material
The compound 5,12‐diacetyl‐5,12‐dihydroquinoxalino[2,3‐ b ]quinoxaline 1 a and its derivatives were prepared, and their solid‐ and solution‐state spectroscopic properties were studied; 1 a shows stronger fluorescence in solution than in the solid state due to aggregation caused by self‐quenching. Phenyl‐ or alkoxy‐substituted derivatives 1 b – d show solid‐state fluorescence with moderate quantum yields of about Φ =0.12–0.15, although the corresponding values are 0.01–0.07 in solution. The spectroscopic properties of alkoxy‐substituted derivatives were hardly changed compared to 1 a and 1 b , although 1 a and 1 b have similar absorption and fluorescence maxima in solution and in the solid state. DFT calculations indicate that orbital switching occurs between HOMO and HOMO‐1 and HOMO‐2 due to orbital interactions with introduced substituents. Crystal structure analysis revealed that the molecules have bent structures around tertiary nitrogen atoms and form a characteristic dimeric structure.