Bathochromic Shift of Fluorescence Peak in Dipyrrolo[1,2-a:2′,1′-c]quinoxaline by Introducing Each of Electron-Donating and Electron-Withdrawing Substituent

Abstract

Development of organic fluorophore is an important theme. Especially, the fluorophores with longer fluorescence peaks are useful to biological probes. One of the methods to change the fluorescence peak is the introduction of substituents. However, opposing characteristics of the substituents lead to different changes in the fluorescence peaks. Furthermore, the introduction of the substituent also affects their electric properties. Thus, if the materials were developed with the substituent effect on the optical and electric properties separately, it will be useful to design the functional materials related to both optical and electric properties. Herein, we investigated the substituent effect of dipyrrolo[1,2-a:2′,1′-c]quinoxalines on fluorescence properties. We synthesized the compounds bearing electron-donating or electron-withdrawing substituents at the benzene ring on dipyrrolo[1,2-a:2′,1′-c]quinoxaline, which would have more direct influence on the optical properties. By introducing each substituent at the 6 position of dipyrrolo[1,2-a:2′,1′-c]quinoxaline, the bathochromic shift was observed in the fluorescence spectra. In the case of fluorine substituent, the change of the fluorescence peak reached was about 19 nm. Using a TDDFT calculation, we explained the reason for such a substituent effect that large on the increment of LUMO energy or decrement of HOMO energy occurred by introducing electron-withdrawing or electron-donating substituents at the 6 position, respectively. The substituent effect on the change of orbital energies is typical although the different characteristics of substituents resulted in the similar tendency about the change of fluorescence peak. Furthermore, with the introduction of phenyl substituents at the 3 and 10 positions, we achieved 40–50 nm longer fluorescence peaks compared with that of the original dipyrrolo[1,2-a:2′,1′-c]quinoxaline.

Self-assembled superstructures derived from suitably substituted phenanthro[9,10-d] imidazole-based Zn(ii)/Cd(ii) complexes for selective detection of acetone

“…Conversely, L3 metal complexes show a substantial bathochromic shift compared to L1 metal complexes (∼59–66 nm) due to the combined effects of solvent polarity enhanced ICT transitions. 67–69…”

Zinc (II) complexes with Schiff bases obtained from N‐[2‐(cyclohexyliminomethyl)‐ or 2‐(4‐cyclohexylphenyliminomethyl) phenyl]‐4‐methylbenzenesulfonamides and their application as highly luminescent blue emitters for OLEDs

“…The various electronic properties of substituents lead to various changes in the fluorescent peak, that is, a bathochromic shift is obtained by introducing the electron-withdrawing substituent in the case of a hypsochromic shift by the electron-donating substituent, and vice versa. [62][63][64][65] Upon excitation at 390-395 nm the complexes showed blue luminescence the Commission Internationale de T A B L E 4 Calculated wavelengths (λ), energies (E), oscillator strengths (f), involved molecular orbitals † and their contributions for different electronic transitions in complexes 2a and 2b according to TD-DFT calculations. I'Eclairage (CIE) coordinates of 0.15; 0.15 and 0.17; 0.21 with emission maxima centered at 468 and 467 nm and emission quantum yield of 29% and 20%, respectively.…”