A double-tailed fluorescent surfactant with a hexavanadate cluster as the head group.
A double-tailed fluorescent surfactant with a hexavanadate cluster as the head group.
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DOI：
10.1002/anie.201006144
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发表时间：
2011-03
影响因子：
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通讯作者：
Panchao Yin;Pingfan Wu;Zicheng Xiao;D. Li;Emily Bitterlich;Jin Zhang;P. Cheng;D. Vezenov;
中科院分区：
文献类型：
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作者：
Panchao Yin;Pingfan Wu;Zicheng Xiao;D. Li;Emily Bitterlich;Jin Zhang;P. Cheng;D. Vezenov;
表面活性剂是常见的两亲性材料，通常含有小的极性头基和长的疏水性尾部。表面活性剂可以在极性和非极性介质中自组装成胶束或囊泡结构（在这种情况下，组装体被称为反胶束或反囊泡），从而创造微环境。 [1]最近，一些以大型无机金属氧化物簇作为极性头基的新型表面活性剂已被合成。[2-4]金属氧化物主要是多金属氧酸盐（POM），这是一类聚阴离子、相对亲水的簇，由最高氧化态的早期过渡金属（通常是Mo、W、V、Nb和Ta）和氧配体组成。[5, 6]将疏水性组分接枝到簇上可以为POM引入两亲性，增强了POM簇与非极性介质的兼容性，这将扩展这些簇的潜在应用。[1]例如，Cronin 及其同事成功地将两条烷基链共价连接到 Anderson 型 POM 的两侧，[2] 并且我们证明了在不同溶剂中形成规则囊泡和反向囊泡。 [7] Polarz 和同事用两条烷基链对 Keggin 型 POM 进行功能化，然后研究了所得化合物在溶液中的乳化特性和抗衡离子依赖性自组装行为。 [3]这些基于 POM 的表面活性剂之所以独特，是因为 1) 它们具有多功能 POM 极性头基，可应用于催化、医学和材料科学 [2-4] 和 2) POM 头基具有可调节的尺寸、形状和电荷，这可能导致可调节和可控的自组装，因为它们的堆积参数 PS 应与常见表面活性剂不同。[2-4] 在多氧钒酸盐 (POV) 中，六钒酸盐团簇近年来因其独特的性质而受到越来越多的关注。纳米级超八面体簇核结构、迷人的电子和磁性、各种热力学稳定的氧化还原异构体以及潜在的催化能力。 [8] Zubieta 及其同事借助三烷氧基 μ 桥联三足配体合成了 [V6O13Hx {(OCH2) 3CR} 2] nÀ (x, n= 0, 2; 2, 0; 4, 2; 6, 2; R= NO2, CH2OH, CH3)，并研究了其氧化还原性质，做出了早期贡献。 [9]这些化合物可以用羧基进行功能化，并通过与金属离子的配位键进一步开发金属有机框架（MOF）。 Hill 及其同事证实，具有 [V6O13Hx {(OCH2) 3CR} 2] nÀ 主链的 MOF 以其有序的纳米级多孔结构和大的内表面积而闻名，并表现出高异相催化活性。 [10]在此，我们报告了一种合成新型六钒酸盐有机杂化分子[V6O13-{(OCH2) 3CCH2OOC (CH2) 16CH3} 2] 2À (1)的方法，并利用其两亲特性来增强其在疏水相和亲水相中的相容性。通过硬脂酸和((C4H9) 4N) 2 [V6O13 {(OCH2) 3CCH2OH} 2]之间的酯化反应，将两条C18烷基链接枝到六钒酸盐簇的两侧（图1）。据我们所知，当四丁基铵 (TBA) 抗衡离子被质子取代时，无机簇发出意想不到的蓝色发光，从而产生了第一个具有抗衡离子依赖性荧光特性的 POM 化合物。更重要的是，溶剂极性和抗衡离子效应导向的适应性两性
Surfactants are common amphiphilic materials that usually contain small polar head groups and long hydrophobic tails. Surfactants can self-assemble into micellar or vesicular structures in both polar and nonpolar media (in this case the assemblies are referred as reverse micelles or reverse vesicles) and consequently create microenvironments.[1] Recently, some novel surfactants with large inorganic metal oxide clusters as polar head groups have been synthesized.[2–4] The metal oxides are mostly polyoxometalates (POMs), a large class of polyanionic, relatively hydrophilic clusters that consist of early transition metals (usually Mo, W, V, Nb, and Ta) in their highest oxidation states and oxo ligands.[5, 6] Grafting hydrophobic components to the clusters can introduce amphiphilic properties to the POMs and enhances the compatibility of POM clusters with nonpolar media, which will expand the potential applications of these clusters.[1] For example, Cronin and co-workers succeeded in covalently linking two alkyl chains to both sides of Anderson-type POMs,[2] and we have demonstrated the formation of regular vesicles and reverse vesicles in different solvents.[7] Polarz and co-workers functionalized Keggin-type POMs with two alkyl chains and then studied the emulsification properties and counterion-dependent self-assembly behavior of the resulting compounds in solution.[3] These POM-based surfactants are unique because 1) they have multifunctional POM polar head groups with applications in catalysis, medicine, and materials science [2–4] and 2) the POM head groups have adjustable size, shape, and charge, which might lead to adjustable and controllable self-assembly since their packing parameter PS should be different from those of common surfactants.[2–4] Among polyoxovanadates (POVs), hexavanadate clusters have gained increasing interest in recent years because of their nanoscale superoctahedral cluster–core structures, fascinating electronic and magnetic properties, various thermodynamically stable redox isomers, and potential catalytic capabilities.[8] Zubieta and co-workers made early contributions by synthesizing [V6O13Hx {(OCH2) 3CR} 2] nÀ (x, n= 0, 2; 2, 0; 4, 2; 6, 2; R= NO2, CH2OH, CH3) with the help of trisalkoxo μ-bridging tripodal ligands, and studied their redox properties.[9] These compounds can be functionalized with carboxylic groups and used to further develop metal–organic frameworks (MOFs) through coordination bonds with metal ions. The MOF with the [V6O13Hx {(OCH2) 3CR} 2] nÀ backbone is well known for its ordered nanoscale porous structure and large inner surface area, and displays high heterogeneous catalytic activity, as confirmed by Hill and co-workers.[10] Herein, we report an approach to synthesizing a novel hexavanadate–organic hybrid molecule,[V6O13-{(OCH2) 3CCH2OOC (CH2) 16CH3} 2] 2À (1), and use its amphiphilic properties to enhance their compatibility in both hydrophobic and hydrophilic phases. Two C18 alkyl chains were grafted onto two opposite sides of the hexavanadate cluster by the esterification reaction between stearic acid and ((C4H9) 4N) 2 [V6O13 {(OCH2) 3CCH2OH} 2](Figure 1). An unexpected blue luminescence from the inorganic clusters was observed when the tetrabutylammonium (TBA) counterions were replaced by protons to give, to the best of our knowledge, the first POM-based compound with counteriondependent fluorescent properties. More importantly, solvent polarity and the counterion-effect-directed adaptable amphi-