Synthetic Expanded Porphyrin Chemistry

Abstract

Expanded porphyrins are synthetic analogues of the porphyrins, and differ from these and other naturally occurring tetrapyrrolic macrocycles by containing a larger central core with a minimum of 17 atoms, while retaining the extended conjugation features that are a hallmark of these quintessential biological pigments. The result of core expansion is to produce systems with novel spectral and electronic features, interesting and, often unprecedented, cation-coordination properties, and, in many cases, an ability to bind anions in certain protonation states. Also adding to the appeal of expanded porphyrins is their central role in addressing issues of aromaticity. In many cases, they also display structural features, such as decidedly nonplanar "figure-eight" motifs, that have no antecedents in the chemistry of porphyrins or related macrocyclic compounds. In this Review, the various synthetic approaches now being employed to produce expanded porphyrins as well as their various applications-related aspects are discussed.

Thiadiazole-Сontaining Macrocycles as Core-Modified Analogues of Phthalocyanine

“…[12] The application of 2,5-diamino-1,3,4-thiadiazole for these purposes unexpectedly led to a new type of Mc with expended inner cavity (ABABAB) for instance, 3a-c. [13,14] They are representatives of a new class of porphyrinoids Thiadiazole Containing Macrocycles having expanded coordination cavity and can be considered as heteroanalogues of hexaphyrins. [15] For a long period its structure was under discussion [16][17][18] and numerous efforts were made to solve the task. C NMR, infrared and UVvis spectroscopy, and elemental analysis.…”

“To Twist or Not to Twist”: Figure‐of‐Eight and Planar Structures of Octaphyrins

“…However,i ts eems to be an impossible task to interconvert structures 64 a and 65 through ar edox mechanism. As tructurally similaro ctaphyrin dianaion, [3] 2À ,r epresents as ystem that is very close to octaphyrin 64 a; however, neither structures 64 a or 65 have been realized as discreeta nd neutralo ctaphyrins. The furan derivative (64 b)i s the only neutral and planar 40 p antiaromatico ctaphyrint hat has been identified to date.…”

Functionalization of dipyrromethanes via hetero-Diels–Alder reaction with azo- and nitrosoalkenes

“…1 are of wide interest as building blocks in organic synthesis, namely in the synthesis of porphyrins 2 and porphyrin analogues such as mesosubstituted corroles, 3 chlorins, 4 expanded porphyrins, 5 and calix [4]pyrroles. 6 On the other hand, dipyrromethanes are the precursors of BODIPY dyes (4,4-difluoro-4-bora3a,4a-diaza-s-indacenes) whose photophysical properties make them the ideal fluorescent scaffold for the development of high performance imaging probes.…”