Accessing a Diverse Set of Functional Red-Light Photoswitches by Selective Copper-Catalyzed Indigo N-Arylation

ChemRxiv, vol. 146, pp. 21367–21376

Abstract

The ability to correlate the structure of a molecule to its properties is the key to a rational and accelerated design of new functional compounds and materials. Taking photoswitches as an example, the thermal stability of meta-stable state is a crucial property that dictates their application in molecular systems. Indigos have recently emerged as an attractive motif for designing photoswitchable molecules due to their red-light addressability, which can be advantageous in biomedical and material applications. The absence of comprehensive synthetic techniques and a thorough understanding of the impact of structural factors on the photochemical and thermal properties of this widely available dye hinders its broad application. Herein, we report an efficient copper-catalyzed indigo N-arylation that enables the installation of a wide variety of aryl moieties carrying useful functional groups. The exclusive selectivity for mono-arylation likely originates from a bimetallic cooperative mechanism through a binuclear copper-indigo intermediate. Functional N-aryl-N′-alkylindigos were prepared and shown to photoisomerize efficiently under red light. Moreover, this design allows for the modulation of thermal half-lives through N-aryl substituents, while the N′-alkyl groups enable the independent attach-ment of functional moieties without affecting the photochromic properties. Strong correlation between the structure of N-aryl moiety and the thermal stability of the photogenerated Z-isomers was achieved by multivariate linear regression models obtained through a straightforward data-science workflow. This work thus builds an avenue leading to versatile red-light photoswitches and a general method for structure-property correlation that is expected to be broadly applicable to the design of photoresponsive molecules.

Authors 8

1. Amit Kumar Jaiswal

   Hokkaido University

   Affiliation as printed

   Hokkaido University

2. Julong Jiang

   Hokkaido University

   Affiliation as printed

   Hokkaido University

3. Kimichi Suzuki

   Hokkaido University

   Affiliation as printed

   Hokkaido University

4. Anna Jasny Aachen

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen University

5. Bernd M. Schmidt

   Heinrich Heine University Düsseldorf

   Affiliation as printed

   Heinrich-Heine-Universität Düsseldorf

6. Satoshi Maeda

   Hokkaido University

   Affiliation as printed

   Hokkaido University

7. Stefan Hecht Aachen

   RWTH Aachen University · Humboldt-Universität zu Berlin

   Affiliation as printed

   Humboldt-Universität zu Berlin

   RWTH Aachen University

8. Chung-Yang Dennis Huang

   Hokkaido University

   Affiliation as printed

   Hokkaido University