以吖啶酮为母体的双螺吡喃开关分子的设计、合成与性质研究

Design, Synthesis and Property Study of Bispiropyran Switchable Molecule Based on Acridone

设计了一个新型的以吖啶酮为母体的含有两个螺吡喃单元的双开关分子,通过路线优化最终以商业可得原料出发经过六步反应得到了目标化合物.该分子具有可逆的光致变色性质.另外,该分子的关环状态在甲醇和二氯甲烷溶液中显示出极强的对酸稳定性,在乙腈或乙腈/水混合溶液中则显示出酸致变色性能.但是通过对其变色过程的光谱研究发现在变色过程中并未出现由单开环到双开环状态的转变.通过理论计算模拟分析该双开关分子光致变色过程,表明该分子由双关环形式到单开环形式需要吸收7.2 kcal/mol的能量,要大于由单开环形式到双开环形式需要的能量(ΔG2=3.5 kcal/mol),因此该分子在外界刺激条件下更容易由双关环形式直接转变为双开环形式.

We designed a bispiropyran switchable molecule based on acridone. Using commercially available 3-bromoanisole and 2-amino-4-methoxybenzoic acid as starting materials, through a six-step synthetic route containing Ullmann biaryl amine condensation, Friedel-Crafts acylation, alkylation of the amine group in the resulting acridone core, regioselective double formylation at the ortho-position to the methoxy groups, demethylation of the two methoxy groups, double condensation with 1,2,3,3-tetramethyl-3H-indolium iodide, the target bispiropyran switchable molecule was successfully synthesized. The UV/Vis spectra and fluorescence spectra of the target dual-switch molecule were studied. It was demonstrated that the bispiropyran molecule had obvious reversible photochromic behavior in dichloromethane solution. For more detail, the spiropyran unit of the designed molecule could be changed to the open-ring form upon UV light irradiation, and the open-ring form of the molecule could be changed to its closed-ring form again when it was placed in the dark. The molecule showed a high stability to acid in Me OH and CH2Cl2, and it had a slow acidichromic behaviour in Me CN. In addition, the molecule showed an acidichromic behaviour in Me CN/H2 O solution only when the p H was below 4. However, in the above chromic process, through the UV/Vis spectra we have not found the two states containing single-ring-opened form followed by dual-ring-opened form of the designed molecule. Further study was performed through the computer simulation, and the optimal structures for the dual-ring-closed form（SP-Ac-SP）, single-ring-opened form（SP-Ac-MC） and dual-ring-opened form（MC-Ac-MC） of the target molecule in the photochromic process were calculated using B3LYP/6-31g（d） in vacuum. It was found that the SP-Ac-SP was more easily directly transformed to MC-Ac-MC, because the Gibbs free energy change（ΔG1=7.2 kcal/mol） from SP-Ac-SP to SP-Ac-MC was much higher than that（ΔG2=3.5 kcal/mol） from SP-Ac-MC to MC-Ac-MC. The relevant frontier molecular orbitals for the SP-Ac-SP and MC-Ac-MC of the designed molecule calculated using B3LYP/6-31g（d） in vacuum could further explain the detail of the chromic process. Our study will give inspiration to design new type of dual-switch molecules based on conjugate structure.