Part I: Synthesis and Study of Excited-State Intermolecular Proton Transfer in 7-Aminoquinoline and its DerivativesPart II: Synthesis and Study of Planarized Intramolecular Charge Transfer in 1-Amino-7-azaindole and its Derivatives

• Main Authors: Ying-Hsuan Liu, 劉穎瑄
• Other Authors: Pi-Tai Chou
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/37v8w9

碩士 === 國立臺灣大學 === 化學研究所 === 106 === Part I 7-Aminoquinoline (7AQ) and its amino derivatives have been designed and synthesized to study their possible excited-state proton transfer (ESPT) reaction. Due to the far separation between the proton donor NR-H (D) and acceptor –N (A) sites, ESPT in 7AQ and analogues, if available, should proceed with solvent catalysis process. As a result, assisted by solvent molecules, TFA-7AQ, Ts-7AQ, Boc-7AQ and Ac-7AQ undergoes ESPT in alcohols such as methanol. Systematically probing ESPT spectroscopy and dynamics among all NR-H derivatives has been carried out in methanol. However, unlike the NR-H intramolecular system where the rate of excited-state intramolecular proton transfer (ESIPT) increases as increasing the NR-H acidity, the rate of solvent catalyzed ESPT was found to lack correlation with respect to the NR-H acidity among all NRH derivatives. The results are rationalized by the fact that increase of the NR-H acidity by the stronger electron withdrawing R group concurrently decreases the basicity of the quinolone nitrogen via resonance inductive effect. Part II In an aim to explore the mechanism of planarized intramolecular charge transfer (PLICT), we have synthesized 1-amino-7-azaindole (NH2-7AI) and N-amination derivatives, diMeN-7AI and AcNH-7AI. Because amino group is twisted in the ground states and becomes planarized in the excited states, this provides a powerful method to tune a very large Stokes shift and simultaneously emit high quantum yields in molecular spectroscopy. Measured in cyclohexane, apolar solvent, NH2-7AI and diMeN-7AI were investigated the large Stokes shifts amounting to about λ = 130 nm and 158 nm. This phenomenon can be rationally interpreted that in the excited states N-substituent molecules tend to delocalize electronic distribution via the lone pair electrons on nitrogen. Once the nitrogen lone pair electrons are coupled with aromatic π electrons through planarization, the molecules can potentially decrease excited-state energy. On the other hand, AcNH-7AI depicted a dual emission in cyclohexane at 323 nm and 380 nm, which could be implied as vertical state and planar state. In acetonitrile, polar solvent, AcNH-7AI was observed a large Stokes shift at 420 nm, progressing PLICT. Obviously, acetyl group is larger than dimethyl group, and the value of viscosity of cyclohexane is higher than that of acetonitrile, which results in the hinder of planarization. It is notable, consequently, that the size of substituent and viscosity of solvent are also the key elements of PLICT.