(I) 研究多環系統的逆磁環電流效應、酸值與動力學實驗. (II) 研究具有光感應雙三唑偶氮苯為橋聯的雙柱芳烴衍生物之動力學、主客化學與自主裝.

Abstract

第一部份研究，主要合成一系列多環化合物38、 39 與 41b 分別研究側翼苯環與相鄰的碳-氫、碳-氟與碳-甲基鍵結之間的逆磁效應，以及合成化合物 40 與 41b 用於探索在高度擁擠的多環系統Menschutkin reaction 之動力學。 令人驚訝的是化合物 39a 與 39b 的氟核磁共振光譜化學位移竟然為強烈的去遮蔽效應，並非如我們所預期的結果。 因而瞭解立體障礙效應為影響氟核磁共振光譜的主要因素，而非環電流效應。 另一方面，在化合物 40 的 X-ray 單晶結構中，氮原子與相鄰苯環的距離遠小於碳與氮原子之凡德瓦爾半徑之總和 (3.2 Å)，這說明化合物 40 的菲環與苯環之空間非常擁擠。 因此，化合物 49c 與 40 分別與碘甲烷高溫下的甲基化速率常數 (k’) 可以被量測為 2.22 × 10-4 以及 5.80 × 10-6 s-1mol-1L。 其共軛酸的 pKa 值分別為 4.65 與 5.07，這些實驗結果皆遠小於吡啶的 (k’ = 3.18 × 10-4 s-1mol-1L, pKa = 12.33)，可以說明化合物 49c 與 40 具有嚴重的分子內空間阻礙，會導致其鹼度、親核性與甲基化反應速率嚴重地降低。 有趣的是化合物 rac-41b 與 rac-78 為一類新穎的螺旋阻轉異構物，其阻轉活化能分別遠高於 18.1 與 15.9 仟卡/莫耳，而且化合物 (P/M) 41b 的氮-甲基鍵受到相鄰苯環的遮蔽效應，所以其氫核磁共振光譜化學位移有明顯地往高磁場位移 ( 1.0 ppm)，可以證實具有強烈的 CH- 作用力。 第二部份研究，主要合成雙柱芳烴之三唑偶氮苯的衍生物 trans-97 照光後由反式偶氮轉變成順式並探討熱誘導順反異構化的性質，但是動力學結果顯示此化合物的順反異構之活化能小於偶氮苯，並非我們所預期的結果。 這樣的現象可以證實取代基的組成大小不會影響活化能，反而是取代基之推拉電子效應降低順反異構的能障。 另一方面，利用 NMR 滴定、質譜與 DOSY NMR 等實驗可以證實 trans-97 與雙吡啶陽離子 95d 在不同濃度下的錯合比例以及錯合模式。 最後， trans-97 在三氯甲烷與甲醇混合溶液中有自主裝的囊泡結構，利用光與濃度的改變可以調控自主裝的形貌，並使用 SEM、 TEM、 FIB 與變溫核磁光譜儀可以探索囊泡的表面形貌、空心結構以及自主裝堆疊模型。

In part I, a series of polycyclic compounds 38, 39, and 41b were synthesized. Diatropic effects of a flanking phenyl rings by adjacent C-H, C-F, and N-Me bonds were studied, respectively. Furthermore, compounds 40 and 41 were designed to probing the limit of the Menschutkin reaction and kinetic studies in highly congested polycyclic systems. Surprisingly, the strong deshielding effect of the 19F NMR of 39a and 39b were opposite to what we originally expected, the results are fully explainable by “steric effect” instead of “ring-current effect”on the fluorine NMR. On the other hand, the distances between N atoms and nearby flanking phenyl rings of 40 in X-ray single-crystal structure are significantly smaller than the sum of van der Waals radii of C and N atoms (3.2 Å), which implies that the molecular spaces between the phenanthroline and the phenyl group in 40 are very congested. Hence, the methylation rate constants (k’) of 49c and 40 with MeI were found to be 2.22 × 10-4 and 5.80 × 10-6 s-1mol-1L, respectively, and the pKa values of the conjugate acids of 49c and 40 in acetonitrile were determined to be 4.65 and 5.07, respectively, which are much smaller compared to that of pyridine (k’ = 3.18 × 10-4 s-1mol-1L and pKa = 12.33), implying that the basicity, nucleophilicity, and amine alkylation rates of 49c and 40 are remarkably decreased by the severe steric hindrance of the flanking phenyl rings in the polyheterocycles. Interestingly, the rotational barriers of the phenyl ring nearby the N-methyl group in rac-41b and rac-78 were estimated to be >>18.1 kcal/mol from VT-NMR experiments making them a new type of helical atropisomers. Compared to those without a nearby phenyl, the N-methyl protons in (P/M) 41b exhibit a significant upfield shift ( 1.0 ppm) in its 1H-NMR, indicating a strong CH- interaction is involved. In part II, the triazole-azobenzene bridged bispillar[5]arene 97 was synthesized and used to study the photochemical transformation of trans to cis azo followed by thermally induced cis-trans isomerization. However, the energy barrier of the isomerization of cis-97 is smaller compared to that of azobenzene. The result implies that the electronic effect rather than the size of the substituent decreases the energy barrier of the thermally induced cis-trans isomerization of the azobenzene. On the other hand, trans-97 and dipyridinium 95d at different concentration exhibit different complexation ratios and models by NMR-titration, Mass, and DOSY-NMR experiments. In mixed solvent of CHCl3, compound trans-97 showed a self-assemble vesicular structure by SEM, TEM, and FIB. Furthermore, VT NMR was applied to explore the morphology.