Synthesis and Study of Molecular Switchable Mechanically Interlocked Rotaxane and Polyrotaxane as Novel Chemosensor Materials
|摘要:||這篇論文所描述的工作涉及rotaxane和 polyrotaxane結構中內含兩個不同的栓子去探討氫鍵分子的互鎖機制並藉由有機溶劑和水溶液中酸鹼刺激調控陽離子感測去探討分子穿透的過程。先前我們已經在博士論文的介紹部份描述了連鎖分子互鎖機制(MIMs),如 rotaxanes和 catenanes 以及他們的聚合物對應物的和成過程。此外，透過刺激(酸-鹼或離子)調控的MIMs藉由最新的分子穿梭穩定的例子和模板也在這裡提出一部份。 首先，在博士論文中簡要的介紹主客的感應或鍵結機制。
分子互鎖機制主體rotaxane的形成是利用tetraphenylethylene(TPE)和phenanthroimidazole (PIZ)分子放射顯著的發射帶，通過主客分子拓樸受限展示交互作用,因此誘導顯著並有選擇性螢光對鐵離子(Fe3+)的螢光猝滅。 研究具有鐵離子（Fe3+）和生物分子Hemin（含鐵離子）的的淬滅效率，以比較鐵離子和生物分子血紅素的敏感性。此研究可探測rotaxane和鐵離子Fe3和血紅素的主客相互作用和調控抗壞血酸鈉(作為還原劑)存在下監測血紅素至血紅蛋白的生物轉換，其中減少的無毒血紅素可以是 產生自血紅素的毒性形式。
為了研究互鎖機制的rotaxane與兩個相當的共軛聚合物的主鏈的超分子相互作用，透過氟基單體F與phenanthroimidazole（PIZ）的單體A和rotaxane單體R的共聚來合成軸聚合物P1和P2。與其他類似的聚合物P1相比，polyrotaxane P2的1H NMR，UV-vis和PL輪廓顯示出敏感和可逆的酸 - 鹼分子轉換性能，通過分子間相互作用。 分子轉換的能力也透過理論計算證實。顯然，P2的可控納米自組裝過程是通過可逆的酸基分子開關方法實現的，其中正交的H鍵合的polyrotaxane單元在膨脹形式上從質子化轉化為薄片形式。我們透過自分選方法與正交自組裝的組合產生具有優異複雜性的多組分超分子系統（MSS，其產生星形rotaxaneR4。 透過高選擇性方式將三種類型的簡單組分成功地自組裝成一鍋（即鑑擊反應），然後通過1H NMR光譜和ESI-TOF-MS光譜進行定量。 星形rotaxane R4顯示出對通過主體 - 客體相互作用的酸鹼處理明顯的和可逆的響應，透過UV-vis，PL和NMR滴定來確認。 理論計算（DFT計算）還揭示了分子轉換的性質和R4的星形吸引力變為具有可相互轉化的H鍵，π-陰離子相互作用，疏水相互作用和π-π堆積的奈米結構。
The work described in this thesis concerns the synthesis of novel mechanically H-bonded interlocked rotaxane and polyrotaxane architectures with two different stoppers and to study their molecular shuttling process via acid-base control stimuli, cation sensing under organic and aqueous solution. We have described early synthetic procedure to create mechanically interlocked molecules (MIMs) such as rotaxanes and catenanes as well as their polymeric counterparts in the introduction section of the doctoral thesis. Moreover the latest well stabilized examples of MIMs based molecular shuttles via stimuli (acid-base or ions based) control, and templating methodology were also presented in this part. Primarily, the mechanisms involved to the sensing or binding with guest were presented briefly in the doctoral thesis. Second chapter: A mechanically interlocked host rotaxane (R1) was synthesized by incorporation of tetraphenylethylene (TPE) and phenanthroimidazole (PIZ) units in the axle to exhibit significant emission bands and demonstrate host-guest interactions via its topologically constrained cavity, and thus to induce a significant and selective fluorescence quenching of rotaxane towards ferric ion (Fe3+). The quenching efficiencies of rotaxane with both ferric ion (Fe3+) and bio-molecular Hemin (containing ferric ion) were investigated to compare the sensitivities of rotaxane for ferric ion and bio-molecular Hemin. The present study could probe host guest interactions of rotaxane with ferric ion (Fe3+) and Hemin as well as monitoring the biological conversion of Hemin to Heme in presence of sodium ascorbate (as a reducing agent), where the reduced non-toxic Heme could be generated from the toxic form of Hemin. Third chapter: To study the supramolecular interactions of the mechanically interlocked rotaxane pendants with the backbone of two comparable conjugated polymers, axle polymer P1 and polyrotaxane P2 were synthesized by copolymerization of fluorine-based monomer F with phenanthroimidazole (PIZ)-based axle monomer A and rotaxane monomer R, respectively. Prevailing1H NMR, UV-vis and PL profiles revealed that polyrotaxane P2 showed sensitive and reversible acid-base molecular switching properties viasupramolecular interactions in contrast to the other analogous polymer P1. The capability of molecular switching is also proven by computational study. Apparently, the controllable nano self-assembly process of P2 was fulfilled by reversible acid-base molecular switch approaches, where the orthogonal H-bonded polyrotaxane units were converted from bloated form into flake form on protonation. Forth Chapter: we have constructed the multicomponent supramolecular systems (MSSs) with superior complexity through the self-sorting approach with the combination of orthogonal self-assembly that resulted in star shaped rotaxane R4. The three types of simple components were successfully self-assembled into one pot (i.e. click reaction) through a highly selective manner, which were then quantified by 1H NMR spectroscopy and ESI-TOF-MS spectroscopy. The star shaped rotaxane R4 displayed an intriguing sensible and reversible response towards acid-base treatment via host–guest interactions, which were confirmed by UV-vis, PL, and NMR titrations. The computation study (DFT calculation) also revealed the property of molecular switching and the staric appeal of R4 allowed to morph into nanostructure with the interconvertable H-bond, π-anion interactions, hydrophobic interaction, and π-π stacking. Thus in conclusion, a novel archetype PIZ and TPE based rotaxane was synthesized. The remarkable stimulated responses towards the Ferric (Fe3+) ion and Hemin were discussed. Moreover, the extended efforts of this current design into polyrotaxane architectures along with their acid-base controllable nanostructure assembly formations via reversible optical molecular switch approaches coupled with various non-covalent interactions were discussed. Furthermore the acid-base controllable star shaped branched rotaxane was synthesized via click reaction.
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