Zhu Weihong, Professor of East China University of science and technology, made a new breakthrough in the field of all visible light driven photochromic dyes

Recently, Professor Zhu Weihong's research group of School of chemistry and molecular engineering of East China University of science and technology has made a breakthrough in the development of a new type of all visible light driven thiophene ethylene photochromic dye system The relevant research results were published in Journal of the American under the title of "all visible light activated dichienylethenes induced by internal proton transfer" Chemical Society （ DOI: 10.1021/jacs.9b07357 ） 。 Molecular photoswitch is a kind of functional molecule with reversible structure change under the action of two different wavelengths of light It has an important and extensive application in the research field of light regulation Among them, the photochromic dye system based on Photocyclization of dithienylethene (DTE) has attracted much attention due to its good thermal stability, excellent fatigue resistance and fast response However, the opening ring of ethylene dithiophene usually needs to be controlled by ultraviolet light, while the short wavelength and high energy ultraviolet light has the disadvantages of high damage and low penetration, which hinders the rapid development of molecular optical switch in biological applications Therefore, it is very important to study and develop the photochromic dye system of ethylene dithiophene under the action of all visible light It is of great significance to use more moderate visible light instead of ultraviolet light to stimulate its photoisomerization process and broaden its application field In the development and application of thiophene ethylene photochromic dye system, all visible light regulation has always been a research hotspot, but the existing strategies often lose the excellent performance of thiophene ethylene itself, which will lead to a sharp reduction in the efficiency of Photocyclization, or even a complete loss of the photoregulation performance At the molecular structure level, there is a lack of a general and reliable structure module to guide the development of all visible light driven thiophene ethylene Based on the energy level regulation related to IPT strategy, the mechanism related to the visible light driving of ethylene dithiophene (source: Journal of the American Chemical Society) is realized, IPT) is a common phenomenon in the hydrogen bonding system For example, in salicylidene amines, there is a dynamic transfer equilibrium process between the proton donor phenolic hydroxyl and the proton acceptor imine bond When the active hydrogen is transferred from the oxygen atom to the nitrogen atom, it is transferred from the oh configuration to the NH configuration Compared with the oh configuration, the team innovated to utilize the NH configuration absorption red shift generated by IPT, so as to take the lead in realizing all visible light triggered photochromism At the same time, it also took into account its excellent light regulation efficiency, good thermal stability, excellent fatigue resistance and other properties As a general design strategy, the introduction of the molecular endoplasmic transfer unit (IPT) has developed into a reliable module design for all visible light driven thiophene vinyl dye system for the first time It can effectively avoid the short wavelength ultraviolet light, and finally use the milder visible light instead of the ultraviolet light to excite its photoisomerization process, and successfully expand its application field, which provides a simple, effective and direct new idea for the design of all visible light controlled thiophene ethylene photochromic dye and optical switch Due to the universality of IPT effect, the target system based on IPT mechanism can be used as a module to design more excellent visible light thiophene ethylene optical switches Furthermore, the proton acceptor part of IPT functional group, i.e imine bond, was further developed into aromatic imines, thiazoles, quinazolinones and other structures, all of which have the characteristics of IPTS They can give a new absorption band in the visible light region to the thiophene vinyl dye system, thus producing excellent all visible driven photochromic performance Quantitative analysis of this kind of all visible light driven thiophene vinyl compounds based on IPT mechanism shows that the quantum efficiency of Photocyclization at 450 nm is greatly improved (up to 31.9%) compared with the traditional visible light thiophene vinyl system, and the conversion rate of photoreaction is excellent (up to 94.9%) At the same time, this kind of system can effectively reduce the occurrence of side reactions in the process of all visible light regulation, so it has better anti fatigue performance than the traditional UV control system In addition, the excellent thermal stability of ethylene dithiophene was also maintained These results fully prove that the IPT mechanism based on intramolecular proton transfer proposed by our group is indeed a new strategy for the development of all visible light driven thiophene ethylene optical switches with high efficiency and reliability The work was completed by Xi Hancheng, a doctoral student, and Zhang Weiwei, a postdoctoral student, under the guidance of Professor Zhu Weihong and Professor Zhang Zhipeng, and under the guidance of academician Tian He The research results are supported by Feringa Nobel Prize center, NSFC basic science center project and key projects, Shanghai major special project, Shanghai innovation plan, "111" talent introduction plan and China Postdoctoral Science Foundation.