Department of Chemistry, Indian Institute of Technology , Powai, Mumbai 400076, India.
School of Chemical Sciences, National Institute of Science Education and Research , Bhubaneswar 752050, Odisha, India.
Chem Rev. 2017 Feb 22;117(4):3329-3376. doi: 10.1021/acs.chemrev.6b00507. Epub 2016 Dec 29.
Porphyrins and expanded porphyrins have attracted the attention of chemists for a long time in view of their diverse applications in catalysis; as anion, cation, and neutral substrate receptors; as ligands to coordinate large metal ions; as nonlinear optical materials, MRI contrasting agents, and sensitizers for photodynamic therapy (PDT); and more recently as models for aromaticity (both Hückel and Möbius). A diverse range of synthetic expanded porphyrins containing up to 96π electrons have been reported, and their properties have been exploited for various applications. The present Review is only confined to 22π electron expanded porphyrins containing five pyrrole/heterocyclic rings such as sapphyrins and smaragdyrins. Even though these two macrocycles contain 22π electrons and five pyrrole/heterocyclic rings, they are structurally different. In sapphyrins, the five pyrrole/heterocyclic rings are connected through four meso-carbon bridges and one direct pyrrole-pyrrole bond, whereas in smaragdyrins, the five pyrrole/heterocyclic rings are connected through three meso-carbon bridges and two direct pyrrole-pyrrole bonds. The chemistry of sapphyrins has been well-established in recent years due to the availability of easy and efficient synthetic methods. On the other hand, smaragdyrins are not explored significantly because of their unstable nature. However, recently it was shown that smaragdyrins can be stabilized if one of the pyrrole rings is replaced with a furan ring to afford stable oxasmaragdyrin. The availability of oxasmaragdyrin allowed the exploration of smaragdyrin in recent years. Thus, an attempt has been made in this Review to describe the chemistry of both sapphyrins and smaragdyrins in terms of their synthesis, characterization, metal ion coordination, and anion-recognition properties.
卟啉和扩展卟啉因其在催化方面的多种应用、作为阴离子、阳离子和中性底物受体、作为配位大金属离子的配体、作为非线性光学材料、磁共振对比剂和光动力治疗（PDT）的敏化剂等方面的多样性，长期以来一直引起化学家的关注。已经报道了含有多达 96π 电子的各种合成扩展卟啉，并且已经开发了它们的性质用于各种应用。本综述仅限于含有五个吡咯/杂环的 22π 电子扩展卟啉，如 sapphyrins 和 smaragdyrins。尽管这两个大环含有 22π 电子和五个吡咯/杂环，但它们的结构不同。在 sapphyrins 中，五个吡咯/杂环通过四个中位碳桥和一个直接吡咯-吡咯键连接，而在 smaragdyrins 中，五个吡咯/杂环通过三个中位碳桥和两个直接吡咯-吡咯键连接。由于易于合成且效率高的合成方法，近年来 sapphyrins 的化学性质已得到很好的确立。另一方面，sma-ragdyrins 由于其不稳定的性质尚未得到充分探索。然而，最近表明，如果一个吡咯环被呋喃环取代，则可以稳定 smaragdyrins 以得到稳定的 oxasmaragdyrin。oxasmaragdyrin 的可用性使得近年来对 smaragdyrin 进行了探索。因此，本综述试图从合成、表征、金属离子配位和阴离子识别特性等方面描述 sapphyrins 和 smaragdyrins 的化学性质。
