Design, Synthesis And Property Of Color-changing Indolo[2,1-b][1,3]Oxazine Molecules

Organic color-changing molecules have been given an in-depth study and wide applications in many fields, such as information memory and storage, color-change materials, display materials, due to their excellent properties. As an organic color-changing molecule, because of a special structure for its open form that the zwitterionic structure was not located in a same conjugated skeleton, indolo[2,1-b][1,3]oxazine molecules obviously display better stabilities and anti-fatigue properties than conventional spiropyran molecules, and are becoming a new research focus of color-changing molecules with a great application potential in the future. In this paper, basing on2,3,3-trimethyl-indolo[2,1-b][1,3]oxazine structure, we improve the preparation method and synthesize efficiently a series of new color-changing indolo[2,1-b][1,3]oxazine molecules, and the structures of all compounds have been determined by the various characterization methods. The solvent-induced switching characteristics and the electro-induced switching properties are investigated, respectively, and the application of ion detection under the condition of solvent-induced open-form was explored. In view of the disadvantages of low fluorescence quantum yield found during the research process for indolo[2,1-b][1,3]oxazine molecules, a biomimetic strategy to enhance the fluorescence quantum efficiency is explored.(1) Improved the preparation method of color-changing indolo[2,1-b][1,3]oxazine mole-cules and significantly improved the yield and the efficiency. We research the solvent-induced switching properties of P1and P2, and study the application in field of CN" detection. For the first time, we introduced UV-visible difference spectrum method and fingerprint peaks identification of test substance to the test system with indolo[2,1-b][1,3]oxazine as an anionic probe, and the accuracy and the sensitivity are significantly improved. The minimum detectable concentration of CN’reaches to0.4μM for P1.(2) Investigate the electro-induced switching properties of P1, P2for the first time. Comparing with the cyclic voltammograms of ring-close form and acid-induced open-forms for P1, P6, and P7, and the results of quantum chemical calculation, a new switchable mechanism was proposed. The microscopic dynamics of electrochromism for P1and P2are first studied in detail by the double-wavelength time-resolved spectroelectrochemistry in situ monitoring method in ITO device. And the research of microscopic dynamics indicates that the color reversibility and anti-fatigue property are improved by introducing a nitro group to the indole moiety of color-changing indolo[2,1-b][1,3]oxazine.(3) Achieved the fluorescence enhancement of color-changing indolo[2,1-b][1,3]oxazine molecules by the hyperconjugation effect and spatial coulomb force for the first time. Instead of the traditional fluorophores, a disulfide bond was introduced to P10by bionic space coulomb force inducing concept. Crystal structure and quantum chemical calculation indicate that the hyperconjugation and spatial coulomb force effect, which is present between disulfide bond and the adjacent nitrogen and aromatic ring, changes the molecular orbital energy and orbital distribution, and achieves the fluorescence enhancement by limiting the energy consumption of excited state.