Electron Push–Pull Effects in 3,9-Bis(p-(R)-diphenylamino)perylene and Constraint on Emission Color Tuning

Abstract

A series of perylene-based donor–acceptor–donor (D–A–D) compounds, 3,9-bis­(p-(R)-diphenylamino)­perylene (R: CN (2a), F (2b), H (2c), Me (2d), and OMe (2e)), was synthesized using 3,9-dibromoperylene with p-(R)-diphenylamine, and the intramolecular charge transfer (ICT) on the D–A–D system with regard to the electron push–pull substituent effect was investigated. By introducing various p-(R)-diphenylamine derivatives with electron-donating or electron-withdrawing R groups, the energy band gaps of the D–A–D compounds were systematically controlled and the emission colors were efficiently tuned from green to red. As expected, the steady state emission spectra of all D–A–D compounds were observed, as well as the emission color controlled, depending on the Hammett substituent constants (σp). In the Lippert–Mataga plots, a different charge-transfer character was observed depending on the electron push–pull substitution, which showed gradually increased ICT characters from the electron-withdrawing to donating substitution. However, exceptionally, the strong electron-withdrawing group of CN-substituted 2a did not correlate with the other R group compounds. From the experimental data and density functional theory calculations, we assume that there is a constraint on emission color tuning to generate higher energy of blue emission in the D–A–D molecular system, due to the reverse charge-transfer property caused by the strong electron-withdrawing group.

Unsymmetrical 2,4,6‐Triarylpyridines as Versatile Scaffolds for Deep‐Blue and Dual‐Emission Fluorophores

“…The bathochromic shift of 5 d is related to the additional push-pull effect coming from the dimethylamino substituent. [39] For compounds 6 a-b, the optimized excited state geometries are similar for both tautomers, supporting the model of proton transfer in the excited state. The enol-imine tautomer presents a calculated emission transition around 380 nm, similar to fluorophores 5 a-b, corresponding to the push-pull effect from the anisole to the pyridine, and the keto-enamine tautomer presents an additional calculated emission transition around 460 nm.…”

“…In the case of 6 b , the presence of a strong intramolecular hydrogen bond constrains the phenol ring to be close to coplanar with the pyridine ring. This strong hydrogen bond increases the electro‐withdrawing character of the pyridine, and as a consequence the 4‐phenyl ring comes closer to coplanarity, increasing the conjugation of the backbone [39] …”

“…This strong hydrogen bond increases the electro-withdrawing character of the pyridine, and as a consequence the 4-phenyl ring comes closer to coplanarity, increasing the conjugation of the backbone. [39] Scheme 1. Synthesis of the triarylpyridine fluorophores.…”

“…Those gaps are similar for 5 a-c, smaller for 5 d, and much smaller for 5 e. This could rationalize the fact that 5 a-c have similar optoelectronic properties and that 5 d present a red shift in both absorption and emission. [39] The very small gap of 5 e could explain the absence of notable emission. The HOMO-LUMO gaps of the enol-imine tautomers of 6 a-e are in the same range as the corresponding 5 a-e. On the other hand, the gaps are much smaller for the keto-enamine tautomers, and this is usually observed for such tautomerism.…”

Visible light-induced cationic photopolymerization by diphenyliodonium hexafluorophosphate and benzothiadiazole dyes

“…The synthetic route of Y-1 and Y-2 is shown in Scheme 1. The intermediates 1 and 2 are prepared according to literatures [34][35][36][37].…”