TICT化合物分子内电荷转移平衡及在生物大分子体系中的平衡转化

具有扭转的分子内电荷转移激发态（TICT）的化合物凭借其特别的光学敏感性识别生物大分子，实质是化合物激发态分子内电荷转移途径的改变。对化合物在生物大分子中的激发态分子内电荷转移平衡和转化进行科学的热力学评价对揭示TICT化合物特异性识别的机制至关重要。本项目在设计合成具有丰富D-A结构的TICT化合物基础上，系统测定化合物的光谱、波谱、电化学性质，结合理论化学手段，研究化合物在不同环境中的分子内电荷转移过程，确定电荷转移过程参数，实现化合物电荷转移过程的热力学评价，建立与TICT相关的热力学平衡；以蛋白质（以血清蛋白、球蛋白）、脂质（不同极性的脂质体、囊泡）为代表，评价化合物在生物大分子中的分子内电荷转移能力和途径，关注平衡转化方向和程度，结合TICT化合物与生物大分子的相互作用模型、驱动力和热力学参数等，揭示生物大分子体系对化合物分子内电荷转移平衡的调控机制。

Absorption of photons leads to the formation of excited state intramolecular charge transfer (ICT) in the molecules having both donor and acceptor moieties separated by a spacer triggers, whereas the emission takes place from the twisted ICT (TICT)state in a polar medium, caused by the electron donor twisting with respect to the rest of the molecule at an angle close to 90℃, exhibiting a highly Stokes-shifted and very weak fluorescence band. But the rotation of the molecule about this dihedral angle is also strongly affected by the micro-environment. The high sensitivity of TICT states and fluorescence properties towards the binding upon the macromolecules has been useful for biological probes. Some TICT compounds are therefore a promising candidate for investigating local protein or biomembrane conformational changes by reporting changes in microenvironmental polarity and solvation. The excited-state conversions from the LE state to the ICT state, and/or from the ICT to the TICT state, or the opposite conversions, is crucial in clarification of the recongnition mechanism for TICT probes. The estimation of thermodynamics of a possible ICT process on the basis of electrochemical and spectral data, in combination with DFT, TDDFT calculations, will gain some new insights into the conformational and photophysical behavior, correlation with the excited-state character in these D-A molecules. In this work, five kinds of D-A compounds with N-S conjugated system were synthesized for the study of ICT properties. The spectroscopy and electrochemical investigation combined with the theoretical calculation about structure and energy of ground and excited state of compounds of compounds will be performed. The thermodynamic evaluation of ICT ability for compounds and the equilibrium of in different media will be estabilished based on the measurement of various thermodynamic and kinetic constants, in order to answer the question regarding the specific factor that triggers the LE - TICT process. The effect of protein (serum albumin, or globulins), or liposomes/niosomes as two kinds of hosts on the LE or ICT (TICT) state of TICT compounds, as well as the thermodynamic equilibrium about charge transfer will be revealed in this project. It is a foundmental candidate for the mechanism of the recngnization of TICT compound to biomacramolecules.