- 學位論文
7號位胺取代喹啉於激發態的質子轉移反應與控制氮呯衍生物動力學與熱力學於激發態下平面化: 擴展Bell–Evans–Polanyi Principle 於激發態化學構型轉變與光致變色
Catalytic Type Excited-State N-H Proton Transfer Reaction in 7-Aminoquinoline and Its Derivatives and Controlling Kinetics and Thermodynamics for Excited-State Planarization of Dibenzazepines: A New Scope of Bell–Evans–Polanyi Principle in Chemical Transformatio and A Photochromism
摘要
摘要(Topic 1):以7-Aminoquinoline (7AQ)為核心結構挑戰設計一系列7-Aminoquinoline的胺類與醯胺化合物，研究其在質子溶劑(甲醇)中的激發態質子轉移反應 (Eexcited State Proton-Transfer, ESPT)。因為其質子的給予端(Donor site)與受體端(Acceptor site)有很大的距離，因此無法進行分子內的質子轉移反應，但是可以透過質子溶劑達到激發態質子轉移的現象，其中醯胺類的7AQ衍生物基表現出兩包螢光光譜譜帶。經過pH滴定實驗與光譜動力學實驗，我們發現這系列化合物其Acceptor site的鹼性主導了這系列分子的質子轉移速度，鹼性越大速度越快。另外我們發現2,2,2-Trifluoro-N-(quinolin-7-yl)acetamide (TFA-7AQ)在激發態下，由於強的拉電子效應，使其在激發態時的amide bond性質較接近單鍵，使其在進行激發態質子轉移反應時，必須考慮單鍵旋轉的效應。 摘要(Topic 2):我們發現了一個非常有趣的化學的動力學與熱力學的關係。長久以來，我們使用Bell–Evans–Polanyi principle 於 A-B + C to A + B-C 化學鍵的斷裂與鍵結，在依同一系列的類似結構的化合物，也就是沿著其反應座標的過度態的frequency 通常有相近的值的化合物們 (同一家族)，其反應熱力學與動力學將會存在正比關係。擴展 Bell–Evans–Polanyi principle 至其他的類型在化學上具有重要意義。我們是第一次嘗試將 Bell–Evans–Polanyi principle 擴展至激發態的分子變形上。在這次的應用上，我們設計與合成了 N-phenyl derivatives of dibenz[b,f]azepine (DBA) ，其以8pi-electron的七元環的azepine 作為核心結構。以X-ray 觀察結晶構造，DBA與其N-phenyl 衍伸物們其DBA核心結構部分在基態為彎曲狀態，在激發態時將有雙螢光出現 (Dual fluorescence)，依取代基不同有不同比例的雙螢光。我們透過動力學建立了在激發態下的構造變形的轉換機制 (R* to P*)，其依賴DBA核心部分的平面化，與 N-phenyl 取代基的旋轉。其轉換過程涉及N-phenyl旋轉，因為charge transfer 性質的導致激發態下 N-phenyl 碳-氮鍵有接近雙鍵的鍵級，引導出構型轉換時必須越過一個能障 (barrier)。增加拉電子性質的官能團在 N-pheny 的para- 位上，將使扭轉能障 (twisting barrier) 下降並使分子更容易在激發態下轉換結構。最重要的，從Bell–Evans–Polanyi principle 去解釋在此激發態下，構型轉換能障 (barrier) 與轉換焓 (enthalpy) 的關係， 在此的體現為越小的反應能障的分子其有越大的反應放熱，也因此證明此分子在激發態的行為涉及鍵的生成與斷裂。 摘要(Topic 3):我們發現了一個可逆的光化學反應。我們發現1, 8-Naphyridine的衍伸物 NaPicoAm (A form) 在甲苯中會有可逆的光化學反應，此類反應稱之為光致變色，尚未有人提起1, 8-Naphyridine衍生物能夠以光化學方式進行可逆的轉變。NaPicoAm在光照下，能與溶劑分子進行反應，因為在激發態下產生的radical能與多數溶劑分子發生化學反應，例如，環己烷、甲苯、四氫咈喃…等等。然而我們不知道其可逆之生成的產物 (B form) 結構為何，本研究使用有機化學方式分析鑑定其結構，我們得知NaPicoAm光反應後得到了一個不穩定的結構 (B form)，是因加成一個溶劑分子並破壞了一個本身的芳香環結構所導致，因此產物在常溫是不穩定的，然而它可以保存在稀薄溶液中，如果在高濃度下，推測是自身碰撞催化了脫除氫氣的反應而使結構回復為兩個穩定芳香環。然而單獨對該不穩定結構 (B form) 進行照光，如其結合之溶劑分子為甲苯，由於radical在甲苯的甲基上是穩定的，因此從該處進行化學鍵的斷裂而發生脫除反應 (與N上的氫一併脫除)，使B form回復為原本的NaPicoAm (A form) ，但是如果是與環己烷反應，則會走脫除氫的反應形成一個不可逆穩定產物。
並列摘要
TOPIC 1: 7-Aminoquinoline (7AQ) and various amino derivatives thereof (-NHR) have been strategically designed and synthesized to study their excited-state proton-transfer (ESPT) properties. Due to the large separation between the proton donor -NHR and the acceptor -N- site, ESPT in 7AQ derivatives, if available, should proceed under protic solvent catalysis. ESPT is found to be influenced by the acidity of -NHR and the basicity of the proton-acceptor -N- in the quinoline moiety. The latter is varied by the resonance effect at the quinoline -N- site induced by the -NHR substituent. For those 7AQ derivatives undergoing ESPT, increased quinoline basicity results in a faster rate of ESPT, implying that proton donation from methanol to the quinoline moiety may serve as a key step in the process. Our studies also indicate the existence of an equilibrium between cis and trans arrangements of -NHR in terms of its hydrogen-bond (H-bond) configuration with methanol, whereby only the cis-H-bonded form undergoes methanol-assisted ESPT. With one exception, the interconversion between cis and trans configurations is much faster than the rate of ESPT, yielding amino-type (normal form) and imine-type (proton-transfer tautomer) emissions with distinct relaxation dynamics. TOPIC 2:One of paramount interests in chemistry is to find correlation between reaction kinetics and thermodynamics. In this context, the long-standing Bell-Evans-Polanyi principle states that in an A-B + C → A + B-C bond breakage-formation reaction, if the position and the frequency of the transition state along the reaction coordinate is similar within a family of reactants, the activation energy is then proportional to the enthalpy of the reaction. Extending the Bell–Evans–Polanyi principle to other types of chemistry is of great fundamental importance. Here, we demonstrate for the first time the application of Bell–Evans–Polanyi principle to the excited-state structural transformation. In this approach, we have designed and synthesized a series of N-phenyl derivatives of dibenz[b,f]azepine (DBA) that possess an 8-pi-electron, seven-membered ring azepine moiety. Supported by X-ray and computational analyses, DBA and the N-phenyl derivatives, i.e. PDBAs, revealed bending structures at the core azepine moiety. Upon electronic excitation, remarkably, the titled compounds exhibit dual emission, for which intensity ratiometry depends on the substitution of the N-phenyl ring. Comprehensive spectroscopic and dynamic analyses established the mechanism of the excited-state structural R* → P* transformation, which undergoes planarization of the core azepine accompanied by rotation of the N-phenyl moiety. The latter involves twisting around the N-C(phenyl) bond possessing partial double bond character resulting from the charge transfer and hence introduces a barrier amid structural transformation. Increasing electron-withdrawing substituent at the para-substituted N-phenyl moiety reduces the twisting barrier and hence facilitates the structural reorganization. Importantly, the Bell–Evans–Polanyi principle effectively explains the relationship between the reaction barrier and enthalpy where the smaller reaction barrier leads to the larger exothermicity of the planarization, extending its scope to structure transformation involving virtually no bond breakage and reformation. TOPIC 3: We find a reversible photochemical reaction. We found the reversible chemical reaction can be done in 1,8-Naphyridine derivative, NaPicoAm (A form), by irradiative, which reaction is so called photochromism. Yet, never reach was reported in reversible transformation in 1,8-naphyridine derivatives. Under UV radiative, NaPicoAm can be reacted with solvent molecule, because the radical generated by bond cleavage in excited state can react with most of solvent molecule, e.g., cyclohexane, toluene and tetrahydrofuran. However, we don’t know the product structure (B form), in this research, the B form was identified and it is unstable in high concentration solution at room temperature, because it may do a base and catalyst eliminated reaction itself and then transform B form into C form (this C form core is two aromatic rings and similar to A form core) by eliminating a H2. If we irradiate the unstable B form, and the structure was generated from NaPicoAm with toluene, the covalent bond combined 1,8-Naphyridine and toluene can be cleaved homogeneously and carried the radical, because the benzoic radical is very stable. Therefore, B form generated from toluene can do a reversible reaction and transform into A form by irradiating UV light, but that generated from cyclohexane (B’ form) can’t. Radical is not stable on cyclohexane, radiating B’ form will only go to C’ form (generated from B’ form eliminates the H2.).