Dipartimento di Chimica G. Ciamician, Università di Bologna via Selmi 2, 40126 Bologna, Italy.
Chemistry. 2010 May 25;16(20):6048-55. doi: 10.1002/chem.200903117.
We have investigated the self-assembly of three luminescent species in CH(3)CN/CH(2)Cl(2), namely: 1) a polylysin dendrimer (D) composed of 21 aliphatic amide units and 24 green luminescent dansyl chromophores at the periphery, 2) a molecular clip (C) with two blue luminescent anthracene sidewalls and a benzene bridging unit that bears two sulfate groups in the para position, and 3) a near infrared (NIR)-emitting Nd(3+) ion. For purposes of comparison, analogous systems have also been investigated in which Gd(3+) replaced Nd(3+). The dendrimer and the clip can bind Nd(3+) ions with formation of [D.2Nd(3+)] and [C.Nd(3+)] complexes, in which energy transfer from dansyl and, respectively, anthracene to Nd(3+) ion takes place with 65 and 8% efficiency, in air-equilibrated solution. In the case of [C.Nd(3+)], the energy-transfer efficiency is quenched by dioxygen, thereby showing that the energy donor is the lowest triplet excited state of anthracene. In [D.2Nd(3+)] the intrinsic emission efficiency of Nd(3+) is much higher (ca. 5 times) than in [C.Nd(3+)] because of a better protection of the excited lanthanide ion towards nonradiative deactivation caused by interaction with solvent molecules. By mixing solutions of D, Nd(3+), and C with proper concentrations, a supramolecular structure with five components of three different species, [D.2Nd(3+).2C], is formed. The excitation light absorbed by the clips is transferred with 100% efficiency to the dansyl units of the dendrimer and then to the Nd(3+) ions with 65% efficiency either in the presence or absence of dioxygen. These results show that the [D.2Nd(3+).2C] complex is able to efficiently harvest UV light by the 24 dansyl units of the dendrimer and the four anthracene chromophores of the two clips, and efficiently transfer it to the encapsulated Nd(3+) ions that emit in the NIR spectral region.
我们研究了三种发光物种在 CH(3)CN/CH(2)Cl(2)中的自组装，分别为：1）一种由 21 个脂肪酰胺单元和 24 个绿色荧光丹磺酰基发色团组成的多聚赖氨酸树状大分子（D），2）一种具有两个蓝色荧光蒽侧壁和一个苯桥接单元的分子夹（C），该单元在对位带有两个硫酸盐基团，以及 3）一种近红外（NIR）发射 Nd(3+)离子。为了进行比较，还研究了类似的系统，其中 Gd(3+)取代了 Nd(3+)。树状大分子和夹子可以与 Nd(3+)离子形成[D.2Nd(3+)]和[C.Nd(3+)]配合物，在空气平衡溶液中，丹磺酰基和蒽分别向 Nd(3+)离子发生能量转移，效率为 65%和 8%。在[C.Nd(3+)]的情况下，能量转移效率被氧气猝灭，从而表明能量供体是蒽的最低三重态激发态。在[D.2Nd(3+)]中，Nd(3+)的固有发射效率（约高 5 倍）高于[C.Nd(3+)]，因为受激镧系离子受到更好的保护，免受与溶剂分子相互作用引起的非辐射失活。通过混合具有适当浓度的 D、Nd(3+)和 C 的溶液，形成了具有三种不同物种的五个成分的超分子结构[D.2Nd(3+).2C]。夹子吸收的激发光以 100%的效率转移到树状大分子的丹磺酰基单元，然后以 65%的效率转移到 Nd(3+)离子，无论是否存在氧气。这些结果表明，[D.2Nd(3+).2C]配合物能够通过树状大分子的 24 个丹磺酰基单元和两个夹子的四个蒽发色团有效地收集来自紫外光，并将其有效地转移到发射近红外光谱区域的封装 Nd(3+)离子。
