Issue 20, 2024

Photochromism of phenazine-2,3-diol derivatives through excited state intermolecular proton transfer based on keto–enol tautomerization

Abstract

Photochromism through excited-state intermolecular proton transfer (ESInterPT) processes based on keto–enol tautomerization was found in phenazine-2,3-diol PD1 and its monoalkoxy derivative PD2 in a glassy matrix at 77 K: the colorless solutions of enol forms PD1-E and PD2-E at 298 K transformed into orange-colored solutions of keto forms PD1-K and PD2-K upon photoirradiation (λ = 385 nm) at 77 K. Furthermore, this report is the first to achieve the single-crystal X-ray structural analyses of phenazine-2,3-diol PD1 and its monoalkoxy derivative PD2, since the report on the synthesis of PD1 70 years ago. Indeed, it was found that PD1 and PD2 molecules exist in the keto form (PD1-K) and the enol form (PD2-E), respectively, in the crystal, and the neighboring PD1-K and PD2-E molecules are linked by one-dimensional intermolecular NH⋯O and OH⋯N hydrogen bonding, respectively. The fact suggests strongly that for PD1 and PD2, the formation of continuous intermolecular hydrogen bonding in aggregates such as in a glassy matrix at 77 K is involved in the keto–enol tautomerization of phenazine-2,3-diol derivatives based on ESInterPT. More interestingly, the color and the photoabsorption spectrum of the solids obtained by sublimation of crystals of PD2-E are similar to those for the crystals of PD1-K, indicating that the PD2 molecule exists in the keto form (PD2-K) in the solid of the sublimate. Therefore, this study provides a valuable insight for a greater understanding of the keto–enol tautomerization of diazaacene-diol derivatives and their photophysical properties in the solution and in the solid state.

Graphical abstract: Photochromism of phenazine-2,3-diol derivatives through excited state intermolecular proton transfer based on keto–enol tautomerization

Supplementary files

Article information

Article type
Paper
Submitted
09 Mar 2024
Accepted
10 Apr 2024
First published
11 Apr 2024
This article is Open Access
Creative Commons BY license

Org. Biomol. Chem., 2024,22, 4077-4088

Photochromism of phenazine-2,3-diol derivatives through excited state intermolecular proton transfer based on keto–enol tautomerization

K. Ohira, K. Kozuka, N. Kaneda, M. Yamamoto, K. Imato and Y. Ooyama, Org. Biomol. Chem., 2024, 22, 4077 DOI: 10.1039/D4OB00387J

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements