【作者】 曾毅；

【导师】 李嫕；

【作者基本信息】 中国科学院研究生院（理化技术研究所） ， 有机化学， 2009， 博士

【摘要】 树枝形聚合物是一类具有精确三维结构的树状大分子,在树枝形聚合物的核心或外围、或者支化单元上修饰光或电活性的官能团可以实现分子的功能化。树枝形聚合物的这种特殊结构可以用来模拟光合作用中的光捕获体系,如何改进光捕获树枝形聚合物的性能是目前相关研究工作的热点之一;树枝形聚合物还被广泛应用于离子传感器和金属纳米复合材料等领域,了解树枝形聚合物基团间相互作用以及金属离子与树枝形聚合物的结合过程,对扩展树枝形聚合物作为传感器或纳米材料模板的研究具有重要意义。本论文工作设计合成了0代到3代外围修饰了萘基团的聚酰胺-胺树枝形聚合物;研究了葫芦[7]脲与树枝形聚合物外围萘基团的自组装以及这种非共价修饰对光捕获树枝形聚合物性能的改进;通过稳态光物理方法研究了萘修饰的聚酰胺-胺树枝形聚合物分子内基团间相互作用以及树枝形聚合物与金属离子间的相互作用,得到了一系列有意义的研究结果,具体如下:1.化合物的合成:用发散合成法(Divergent approach)合成了0?3代以十二烷基二胺为核心、外围萘修饰的PAMAM树枝形聚合物(GnNap, n = 0?3);将GnNap骨架的胺基质子化得到一系列水溶性树枝形聚合物(GnNapH, n = 0?3);合成了主体分子葫芦[7]脲(CB[7])。所有化合物均通过了结构和纯度鉴定。2.非共价修饰对光捕获树枝形聚合物GnNapH (n = 0?3)性能的提高:葫芦[7]脲(CB[7])在缓冲溶液中与GnNapH外围萘基团自组装,得到结构完整的外围准轮烷修饰树枝形聚合物超分子GnNapH?xCB[7](n = 0?3,对应x = 4, 8, 16, 32),该组装是可逆过程。CB[7]与GnNapH外围萘包结复合物的形成抑制了体系的非辐射跃迁,大大提高了树枝形聚合物荧光量子产率,0?3代GnNapH荧光量子产率分别为0.12,0.097,0.065和0.062,而0?3代GnNapH?xCB[7]荧光量子产率分别增加至0.18,0.19,0.19和0.20。将能量受体9-蒽甲酸引入树枝形聚合物体系中,稳态光物理研究表明,CB[7]对外围的非共价修饰消除了官能团间相互作用导致的能量耗散,2代和3代光捕获体系GnNapH?xCB[7]中萘向蒽的能量传递效率比相应GnNapH体系分别提高了70%和100%。3.树枝形聚合物GnNap (n = 0?3)质子化过程的研究:稳态光物理研究表明,甲醇溶液中树枝形聚合物GnNap外围萘与骨架胺基发生光致电子转移,形成最大发射峰在450 nm的激基复合物,萘的荧光被猝灭;当GnNap骨架被质子化,分子内光致电子转移过程和萘与骨架胺基间激基复合物的形成被抑制,萘单体荧光发射大大增强;质子化后树枝形聚合物骨架趋于伸展构象,外围萘基团间相互作用增强而部分形成发射峰在400 nm的激基缔合物。4.树枝形聚合物GnNap (n = 0, 3)与金属离子相互作用研究:树枝形聚合物GnNap能有效络合多种金属离子,其中Hg2+与树枝形聚合物的结合具有特殊规律,荧光滴定结果表明,Hg2+先与最外围二级胺基以1:2的配比结合,抑制了萘和仲胺的光致电子转移使GnNap荧光增强,当外围二级胺与Hg2+完全结合后,Hg2+继续与GnNap骨架内部的三级胺以1:1配比结合并导致荧光猝灭。Fe2+,Co2+,Ni2+,Cu2+,Zn2+与树枝形聚合物有明显络合作用并对其光物理性质产生影响;树枝形聚合物与碱金属和碱土金属离子、Cd2+和Mn2+离子等没有明显作用。更多还原

【Abstract】 Dendrimers are well-defined and successively branched macromolecules with the possibility of modifying functional units in predetermined sites of their treelike structure. The unique structure of the dendrimer makes it a mimic of natural photosynthetic systems, which are surrounded by plentiful antenna chromophores. Improving light-harvesting dendrimers is an important research field of the artificial photosynthetic research. In addition, dendrimers are widely applied in the studies of ion senors and metallic nanocomposites. Understanding the relationship between photophysical properties and dendrimer structures and revealing the metal complexation processes with dendrimers are essential for those research fields.In this dissertation, light-harvesting poly(amidoamine) dendrimers with naphthyl decorated at periphery, generation 0?3, were synthesized. These light-harvesting dendrimers have been noncovalently modified by cucurbit[7]uril (CB[7]) through peripheral pesudorotaxane formation resulting in enhancement of energy utilization. The interactions among components of dendrimers and the metal complexation were investigated by steady-state spectroscopy.1. Synthesis of the target compounds. Naphthyl terminal-decorated poly(amidoamine) dendrimers, generation 0?3 (GnNap, n = 0?3), were synthesized divergently using diaminododecane as the core. Corresponding water-soluble light-harvesting dendrimers (GnNapH, n = 0?3) were obtained after the protonation of GnNap. Host molecule for noncovalent modification, cucurbit[7]uril (CB[7]), was also synthesized. Structures of all compounds were characterized. 2. Enhancement of energy utilization in light-harvesting dendrimers by noncovalent modification. Fluorescence studies reveal that strong interactions among peripheral chromophores occur in these dendrimers according to the intensive excimer emission and the low fluorescence quantum yields (Φf = 0.12, 0.097, 0.065 and 0.062 for G0–3NapH, respectively). Through assembly of dendrimers with cucurbit[7]uril (CB[7]), the well-defined pseudorotaxane assemblies GnNapH?xCB[7] (x = 4, 8, 16, 32 for n = 0–3, respectively) form and the energy dissipation is entirely suppressed resulting in a dramatic increase of the fluorescence quantum yield of dendrimers (Φf = 0.18, 0.19, 0.19 and 0.20 for 0–3 generations, respectively). The noncovalent modification is a reversible process and CB[7] can be unthreaded from the dendrimer periphery by adding 1-amimoadamantane (AD) which can form a more stable complex with CB[7]. Furthermore, 9-anthracenecarboxylic acid (AN), an energy acceptor, was introduced into the dendritic system to investigate the harvested energy utilization. Steady-state fluorescence investigations demonstrate that the energy transfer efficiencies from naphthyl to AN in G3NapH?32CB[7]–AN and G2NapH?16CB[7]–AN are enhanced 100% and 70% compared with those without CB[7] complexation.3. Protonation investigation of GnNap. Steady-state photophysical studies indicate that the fluorescence of naphthyl is quenched by the amine units of dendrimers GnNap via the intramolecular electron transfer, and a naphthyl-amine exciplex is formed with a structureless emission around 450 nm. The protonation of GnNap by addition of excess trifluoroacetic acid makes the fluorescence intensity of dendrimers increase dramatically due to suppression of the photoinduced electron transfer process and the exciplex formation, a weak naphthyl excimer emission with maximum at ca. 400 nm can be observed indicative of close-packed periphery and stretched conformation of protonated dendrimers.4. Investigation on the complexation of GnNap (n = 0, 3) with metal ions. GnNap show a special bingding behavior toward Hg2+. First, Hg2+ and peripheral secondary amine groups form a complex with an 1:2 binding mode resulting in an increase of the fluorescence of GnNap. After full complexation of peripheral secondary amine is reached, Hg2+ coordinates with tertiary amine units within dendrimer backbone in an 1:1 binding model and consequently quenched the emission of GnNap. Fe2+, Co2+, Ni2+, Cu2+ and Zn2+ can complex with GnNap and evidently affect the photophysical properties of dendrimers. Cd2+, Mn2+, alkali metal and alkaline-earth metal ions have no obvious effect on the photophysical properties of GnNap in methanol indicative of no obvious interactions between GnNap and those ions.更多还原