Branchi Barbara, Ceroni Paola, Bergamini Giacomo, Balzani Vincenzo, Maestri Mauro, van Heyst Jeroen, Lee Sang-Kyu, Luppertz Friedhelm, Vögtle Fritz
Dipartimento di Chimica G. Ciamician, Università di Bologna, via Selmi 2, 40126 Bologna, Italy.
Chemistry. 2006 Dec 4;12(35):8926-34. doi: 10.1002/chem.200601129.
We have synthesized a dendrimer (1) consisting of a 1,4,8,11-tetraazacyclotetradecane (cyclam) core, appended with four benzyl substituents that carry, in the 3- and 5-positions, a dansyl amide derivative (of type 2), in which the amide hydrogen is replaced by a benzyl unit that carries an oligoethylene glycol chain in the 3- and 5-positions. All together, the dendrimer contains 16 potentially luminescent moieties (eight dansyl- and eight dimethoxybenzene-type units) and three distinct types of multivalent sites that, in principle, can be protonated or coordinated to metal ions (the cyclam nitrogen atoms, the amine moieties of the eight dansyl units, and the 16 oligoethylene glycol chains). We have studied the absorption and luminescence properties of 1, 2, and 3 in acetonitrile and the changes taking place upon titration with acid and a variety of divalent (Co2+, Ni2+, Cu2+, Zn2+), and trivalent (Nd3+, Eu3+, Gd3+) metal ions as triflate and/or nitrate salts. The results obtained show that: 1) double protonation of the cyclam ring takes place before protonation of the dansyl units; 2) the oligoethylene glycol chains do not interfere with protonation of the cyclam core and the dansyl units in the ground state, but affect the luminescence of the protonated dansyl units; 3) the first equivalent of metal ion is coordinated by the cyclam core; 4) the interaction of the resulting cyclam complex with the appended dansyl units depends on the nature of the metal ion; 5) coordination of metal ions by the dansyl units follows at high metal-ion concentrations; 6) the effect of the metal ion depends on the nature of the counterion. This example demonstrates that dendrimers may exhibit complete functionality resulting from the integration of the specific properties of their component units.
我们合成了一种树枝状大分子（1），其核心为1,4,8,11-四氮杂环十四烷（环胺），带有四个苄基取代基，这些取代基在3位和5位带有一个丹磺酰胺衍生物（2型），其中酰胺氢被一个苄基单元取代，该苄基单元在3位和5位带有一个聚乙二醇链。总的来说，该树枝状大分子包含16个潜在的发光基团（八个丹磺酰基和八个二甲氧基苯型单元）以及三种不同类型的多价位点，原则上这些位点可以被质子化或与金属离子配位（环胺氮原子、八个丹磺酰单元的胺基以及16个聚乙二醇链）。我们研究了1、2和3在乙腈中的吸收和发光特性，以及用酸和各种二价（Co2+、Ni2+、Cu2+、Zn2+）和三价（Nd3+、Eu3+、Gd3+）金属离子作为三氟甲磺酸盐和/或硝酸盐进行滴定时发生的变化。所得结果表明：1）环胺环的双质子化在丹磺酰单元质子化之前发生；2）聚乙二醇链在基态下不干扰环胺核心和丹磺酰单元的质子化，但会影响质子化丹磺酰单元的发光；3）第一个当量的金属离子由环胺核心配位；4）所得环胺配合物与连接的丹磺酰单元的相互作用取决于金属离子的性质；5）在高金属离子浓度下，丹磺酰单元会与金属离子配位；6）金属离子的作用取决于抗衡离子的性质。这个例子表明，树枝状大分子可能会由于其组成单元的特定性质的整合而展现出完整的功能。
