A self-regulatory host in an oscillatory guest motion: complexation of fullerenes with a short-spaced cyclic dimer of an organorhodium porphyrin.-猫眼课题宝

DOI：

10.1002/anie.200600478

发表时间：

2006-05

期刊：

Angewandte Chemie

影响因子：

通讯作者：

中科院分区：

文献类型：

作者：

Ayako Ouchi;Kentaro Tashiro;K. Yamaguchi;T. Tsuchiya;T. Akasaka;T. Aida

2005年。73 ppm（208 ℃）（图1b）。另一方面，在与上述相同的其他条件下以2：1的摩尔比混合1和C60导致主要形成12'C60，在δ= 0.05处观察到其MeCN Rh信号。80 ppm，在δ= 0.55处有次要信号。73 ppm，作为1 'C60的结果，并且δ= 0.66。06和06。49 ppm，这是无客体1的构象异构体的特征（图1 B）。[3b]在与较大的富勒烯C70和C76络合时，观察到1的类似趋势（图1 B）。对于1：1络合的C60与1，在208 ℃的甲苯中的吸光光谱滴定允许的缔合常数（Kaspersky）为2.1 × 105毫微克-1的评价。[7]另一方面，在[D8]甲苯中在208 C下的13 C NMR滴定实验表明，所得1 'C60与1结合，12'C60的Kasperton值为5.2 × 103 m3/1，[7]比1 'C60小两个数量级。还考虑到分子模型，1 'C60对1的亲和力比C60对1的亲和力小得多，这很可能是因为第一结合主体1的电子效应，而不是空间效应。如前所述，锌卟啉的[3b]环状二聚体对富勒烯的亲和力低于甲基铑卟啉类似物。当主体2 [7]（方案1）（这两种金属卟啉主体的混合形式）被允许与[D8]甲苯中的C60相互作用时，即使当存在相对于C60的两当量的2时，在宽的温度范围内（低至1080 ℃），通过13 C NMR光谱法仅检测到1：1络合物2 'C60（δ= 139.6ppm）。[7]因此，在电子上不太有利的12'富勒烯复合物的形成中，有机铑卟啉对富勒烯固有的大亲和力发挥着重要作用。1HNMR光谱也提供了有关1与富勒烯络合后金属卟啉单元的相对取向的信息。在络合前，1中的每个甲基铑卟啉单元具有一组两个当量的meso质子和两组四个当量的吡咯β质子。然而，通过在208 ℃下以2：1的比例混合1（5.0 × 10 - 3 m）和C60制备的12 ′ C60的1H NMR光谱分析显示出上述各组信号的分裂（图2a），而对于MeO 2 Rh质子信号没有显示出这种分裂。还考虑到与吸收和13 C NMR光谱的络合的化学计量，这样的1H NMR光谱图案表明主体1二聚形成包括一个C60分子的超分子胶囊，其中每个主体分子中的两个金属卟啉单元在NMR时间尺度上相对于彼此采用不平行的倾斜几何形状（图2a）。与12'C60相反，通过在[D8]甲苯中以1：2的比例混合1（5.0 × 10 ~ 4 m）和C60制备的1：1主体/客体络合物1' C60显示出普通的1H NMR光谱图，在1208 ℃没有任何特定的分裂（图2b）。然而，当进一步冷却至10908 ℃时，显示出分裂特征，如在109208 ℃下对12'C60所观察到的（图2a），其中内消旋和吡咯β质子都显示出两组信号，其积分比为1（图2b）。该光谱图与具有较长C6亚烷基间隔基的参比主体分子3（方案1）[7]形成鲜明对比，其中3 'C60在相同条件下对于每个相应质子仅表现出一组信号。[7]根据晶体学定义的6 'C60，[3b] 3' C60中的富勒烯客体最有可能位于平行取向的两个金属卟啉单元的中心。因此，对于1 'C60在908 C处的1H NMR谱图观察到的分裂特征（图2b.

À5. 73 ppm at À208C (Figure 1b). On the other hand, mixing of 1 and C60 at a molar ratio of 2: 1 under otherwise identical conditions to the above resulted in the predominant formation of 12'C60, whose MeÀRh signal was observed at δ= À5. 80 ppm, with minor signals at δ= À5. 73 ppm, as a result of 1'C60, and δ= À6. 06 and À6. 49 ppm, which are characteristic of conformational isomers of guest-free 1 (Figure 1 b).[3b] Similar trends were observed for 1 upon complexation with larger fullerenes C70 and C76 (Figure 1 b). For the 1: 1 complexation of C60 with 1, an absorptionspectral titration at 208C in toluene allowed the evaluation of the association constant (Kassoc) for 1'C60 as 2.1 105 mÀ1.[7] On the other hand, a 13C NMR titration experiment at À208C in [D8] toluene showed that resultant 1'C60 binds 1 with a Kassoc value of 5.2 103 mÀ1 for 12'C60,[7] which is two orders of magnitude smaller than that for 1'C60. Considering also the molecular models, the much smaller affinity of 1'C60 than C60 toward 1 is most likely because of an electronic effect, rather than a steric effect, of the first-bound host 1. As reported previously,[3b] cyclic dimers of zinc porphyrins have lower affinities than methylrhodium porphyrin analogues toward fullerenes. When host 2 [7](Scheme 1), a hybrid version of these two metalloporphyrin hosts, was allowed to interact with C60 in [D8] toluene, only 1: 1 complex 2'C60(δ= 139.6 ppm) was detected by 13C NMR spectroscopy over a wide temperature range (down to À808C), even when two equivalents of 2 with respect to C60 were present.[7] Therefore, in the formation of electronically less favored 12'fullerene complexes, the inherently large affinity of organorhodium porphyrins toward fullerenes plays a significant role. 1HNMR spectroscopy was also informative about the relative orientation of the metalloporphyrin units upon complexation of 1 with fullerenes. Before complexation, each methylrhodium porphyrin unit in 1 possesses one set of two equivalent meso protons and two sets of four equivalent pyrrole β protons. However, 1H NMR spectroscopic analysis of 12'C60, prepared by mixing 1 (5.0 10À3 m) and C60 in a 2: 1 ratio at À208C, showed splitting of each of the above sets of signals (Figure 2a), whereas no such splitting was displayed for the MeÀRh proton signal. Considering also the stoichiometry of the complexation with the absorption and 13C NMR spectra, such a 1H NMR spectral pattern indicates that host 1 dimerizes to form a supramolecular capsule which includes one C60 molecule, in which the two metalloporphyrin units in each host molecule adopt a nonparallel, tilted geometry with respect to one another on the NMR timescale (Figure 2a). In contrast with 12'C60, 1: 1 host/guest complex 1'C60, prepared by mixing 1 (5.0 10À4 m) and C60 in a 1: 2 ratio in [D8] toluene, showed an ordinary 1H NMR spectral profile without any particular splitting at À208C (Figure 2b). However, when cooled further to À908C, a splitting signature was displayed, as observed for 12'C60 at À208C (Figure 2a), in which the meso and pyrrole β protons both showed two sets of signals with an integral ratio of unity (Figure2b). This spectral profile is in sharp contrast with that of reference host molecule 3 with longer C6 alkylene spacers (Scheme 1),[7] in which 3'C60 exhibited only one set of signals for each of the corresponding protons under identical conditions.[7] By reference to crystallographically defined 6'C60,[3b] the fullerene guest in 3'C60 is most likely located in the center of the parallel-oriented two metalloporphyrin units. Therefore, the splitting signature, observed for the 1H NMR spectral profile of 1'C60 at À908C (Figure 2b …

A self-regulatory host in an oscillatory guest motion: complexation of fullerenes with a short-spaced cyclic dimer of an organorhodium porphyrin.

文献摘要

被引文献

相似文献