Axial coordination changes the morphology of porphyrin assemblies in an organogel system.
Axial coordination changes the morphology of porphyrin assemblies in an organogel system.
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DOI：
10.1039/b602025a
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发表时间：
2006-05
影响因子：
3.2
通讯作者：
Takanori Kishida;Norifumi Fujita;O. Hirata;S. Shinkai
中科院分区：
文献类型：
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作者：
Takanori Kishida;Norifumi Fujita;O. Hirata;S. Shinkai
在不存在和存在几种二胺的情况下，评价了含周围尿素基团（1 × Zn）的锌卟啉的凝胶性。在苯、甲苯和对二甲苯等芳香族溶剂中，1 × Zn只产生沉淀。相比之下，1 x Zn与0.5和1.0当量的哌嗪形成凝胶，并且含有0.5当量哌嗪的凝胶表现出独特的物理性质，称为“触变性”。另一方面，当加入类似的二胺如DABCO，乙二胺和N，N'-二甲基乙二胺时，1 × Zn不会使这些溶剂凝胶化。当临界胶凝浓度与哌嗪与1倍锌的比例成正比时，它的最小断点为0.5等，并且随着哌嗪比例的进一步增加，临界浓度也随之增加，这表明稳定凝胶是由1倍锌与哌嗪的2:1配合物形成的，随后转化为1:1配合物会使凝胶不稳定。非常有趣的是，通过SEM和TEM观察清楚地表明，哌嗪与1 x Zn的比例引起的这种单位复合物的结构变化可以导致逐渐的形态转变：另外，紫外可见光谱显示，1 × Zn本身呈j型聚集，而1 × Zn +哌嗪2:1和1:1配合物呈h型聚集。另一方面，当加入0.5等量的其他二胺时，1 × Zn +二胺配合物的形貌与一维纤维结构不同。为了探索这些结果的合理原理，我们进行了计算研究。结果发现，单位配合物的复对称性在决定最终有序结构中起着重要的作用。
The gelation properties of a zinc porphyrin bearing peripheral urea groups (1 x Zn) were evaluated in the absence and the presence of several diamines. In aromatic solvents such as benzene, toluene and p-xylene, 1 x Zn only provided the precipitate. In contrast, 1 x Zn with 0.5 and 1.0 equiv. of piperazine formed gels, and the gel with 0.5 equiv. of piperazine showed a unique physical property called 'thixotropy'. On the other hand, upon addition of similar diamines such as DABCO, ethylenediamine and N,N'-dimethylethylenediamine, 1 x Zn did not gelate these solvents. When the critical gelation concentration was plotted against the ratio of piperazine versus 1 x Zn, it afforded a minimum breakpoint at 0.5 equiv. and the critical concentration increased with further increase in the fraction of piperazine, indicating that the stable gel is formed from the 1 x Zn + piperazine 2:1 complex and the subsequent transformation to the 1:1 complex rather destabilizes the gel. Very interestingly, it was clearly shown by SEM and TEM observations that such structural changes of the unit complex induced by the ratio of piperazine versus 1 x Zn can lead to gradual morphological transitions: that is, spherical structure at 0 equiv., 1-D fibrous structure at 0.5 equiv. and 2-D sheet-like structure at 1.0 equiv. In addition, UV-VIS spectra revealed that 1 x Zn itself adopts a J-aggregation mode, whereas 1 x Zn + piperazine 2:1 and 1:1 complexes adopt an H-like aggregation mode. On the other hand, upon addition of 0.5 equiv. of other diamines, 1 x Zn + diamine complexes result in different morphologies other than the 1-D fibrous structure. To explore a reasonable rationale for these results, we conducted computational studies. As a result, we found that the complex symmetry of the unit complex plays an important role in determining the final ordered structure.