Two Vernier-Templated Routes to a 24-Porphyrin Nanoring
Two Vernier-Templated Routes to a 24-Porphyrin Nanoring
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DOI：
10.1002/anie.201202870
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发表时间：
2012-01-01
影响因子：
16.6
通讯作者：
Anderson, Harry L.
中科院分区：
文献类型：
--
作者：
Kondratuk, Dmitry V.;Perdigao, Luis M. A.;Anderson, Harry L.
巧妙的新模板导向策略使得合成越来越广泛的分子结构成为可能，否则这些分子结构是无法合成的。[1-12]最近，我们提出了Vernier模板的概念——使用模板和构件的非相称组合来指导环状低聚物的形成，使得产物中的结合位点数量是模板和起始材料中的位点数量的最小公倍数。[12d]这一原理允许小模板指导形成一个更大的大环。之前，我们通过从线性锌卟啉四聚体 l-P4 和六吡啶基模板 T6 合成 12-卟啉纳米环 c-P12 来说明这一想法。在这里，我们报道了通过两种 Vernier 模板路线合成 24-卟啉环 c-P24：a）在六吡啶基模板 T6 存在下偶联线性卟啉八聚体 l-P8，b）在八吡啶基模板 T8 存在下偶联线性卟啉六聚体 l-P6（方案 1）。 24-卟啉纳米环的制备收率高达25%。通过扫描隧道显微镜 (STM) 证实，它的直径为 10 nm，分子量为 26 kDa，因此处于典型蛋白质的大小范围内。这种柔性大环可以通过 2:24 双链复合物与线性二胺配体 1, 4-二氮杂双环的协同自组装锁定为平面 π 共轭构象 [2.2。 2]辛烷(DABCO)。方案 1 中对 c-P24 的两条路线的表示忽略了这样一个事实，即 (l-P8) 3·(T6) 4 和 c-P24·(T6) 4 等复合物具有许多可能的异构体，如图 1 所示。然而，这些异构体中间体的形成不应降低游标模板合成的效率，因为模板的去除会将所有这些异构体转化为相同的 c-P24 开环（打结结构除外，例如，图 1d [13]）。在六吡啶基模板 T6 [12b, c] 存在下，线性卟啉八聚体 l-P8 [12a] 的钯催化氧化偶联得到预期产物 c-P24，以及 16-卟啉环 c-P16 [14] 和线性聚合物，全部作为与 T6 的复合物。去除聚合物副产物
Ingenious new template-directed strategies make it possible to synthesize an increasingly wide range of molecular architectures, which would otherwise be inaccessible.[1–12] Recently, we developed the concept of Vernier templating—the use of noncommensurate combinations of templates and building blocks to direct the formation of cyclic oligomers, such that the number of binding sites in the product is the lowest common multiple of the numbers of sites in the template and the starting material.[12d] This principle allows a small template to direct the formation of a much larger macrocycle. Previously, we illustrated this idea with the synthesis of a 12-porphyrin nanoring, c-P12, from a linear zinc porphyrin tetramer, l-P4, and a hexapyridyl template, T6. Here we report the synthesis of a 24-porphyrin ring, c-P24, by two Vernier-templated routes: a) coupling the linear porphyrin octamer l-P8 in the presence of hexapyridyl template T6, and b) coupling the linear porphyrin hexamer l-P6 in the presence of the octapyridyl template T8 (Scheme 1). The 24-porphyrin nanoring can be prepared in yields of up to 25%. It has a diameter of 10 nm, as confirmed by scanning tunneling microscopy (STM), and a molecular weight of 26 kDa, thus placing it in the size range of a typical protein. This flexible macrocycle can be locked into a planar π-conjugated conformation by the cooperative self-assembly of a 2: 24 doublestrand complex with the linear diamine ligand 1, 4-diazabicyclo [2.2. 2] octane (DABCO). The representation of the two routes to c-P24 in Scheme 1 overlooks the fact that complexes such as (l-P8) 3·(T6) 4 and c-P24·(T6) 4 have many possible isomers, as illustrated in Figure1. However, the formation of these isomeric intermediates should not detract from the efficiency of the Vernier-templated synthesis, because removal of the template will convert all these isomers into the same c-P24 open ring (except for knotted structures, for example, Figure 1d [13]). Palladium-catalyzed oxidative coupling of the linear porphyrin octamer l-P8 [12a] in the presence of the hexapyridyl template T6 [12b, c] gave the expected product c-P24, together with the 16-porphyrin ring c-P16 [14] and linear polymers, all as complexes with T6. The polymeric by-products were removed