Twisted-Planar-Twisted expanded porphyrinoid dimer as a rudimentary reaction-based methanol indicator

Abstract

Directly linked porphyrin dimers have attracted considerable attention because of their intriguing electronic features. Most emphasis has been placed on either dimers with large dihedral angles between the constituent planar monomeric subunits or those with overall planarity, referred to as “Planar-Twisted-Planar” and “Planar-Planar-Planar”, respectively. Herein, we report a “Twisted-Planar-Twisted” framework, the hexaphyrin dimer D that exists in a trans configuration. Treatment of D with MeOH affords two isomeric dimers, MD1 and MD2, both of which incorporate a methoxy moiety and exist in cis orientations with respect to the tethering linkage. The methanol-promoted conversion is accompanied by a readily discernible color change from green to brown and is not induced to an appreciable level by other alcohols. Dimer D thus acts as a rudimentary, albeit highly selective, reaction-based methanol indicator. This work provides a promising approach for constructing reaction-based chemosensors using porphyrinoid dimers of nonplanar subunits with biased reactivity.

Loading Phlorins with Fullerenes by a [4 + 2]-Cycloaddition Reaction: Regulation of the Regioselectivity by Pyrrole Linkage Modes

“…Thus, the sulfolenopyrrole-based phlorins are promising candidates to develop the functionalized phlorins. The structure–reactivity relationship of the sulfolenophlorins in [4 + 2]-cycloaddition reaction has also attracted our interest, in that the handful examples on the cycloaddition reaction of sulfolenopyrrole-based porphyrins commonly exhibited no regio-selectivity toward annulation and afforded statistic cycloaddition products. − In the early works, changing the pyrrole linkage mode (e.g., α,α and α,β in Figure ) effectively regulates the resulting reactivity toward chemical transformation. − Hence, in this work, the normal (α,α) sulfolenophlorin 1 and N-confused (α,β) sulfolenophlorin 2 have been prepared to study the functionalization of phlorin with fullerene and explore the effect of pyrrole linkage on the [4 + 2]-cycloaddition reaction of masked phlorindienes. As a result, phlorin 1 contains two sufolenopyrrole units with identical reactivity upon tautomerization and undergoes stepwise [4 + 2]-cycloaddition with fullerenes, giving the mono and bis-fullerene adducts at 140 °C.…”

Confusion Approach Modulated Syntheses of Corrorin Parasitized Hexaphyrins(1.1.1.1.1.0) and the Oxidative Ring Cleavage Behavior

“…In continuation of porphyrin chemistry, porphyrinoids like expanded porphyrins have attracted extensive research interest because of their conformational flexibility, multimetal coordination, near-infrared absorption, and extraordinary reactivity . In this respect, hexaphyrins composed of six pyrrolic units have been developed as a class of the most intensively investigated expanded porphyrins (Figure a) . In recent years, the internally bridged expanded porphyrinoids with dual conjugation frameworks, like tetraphyrin- and hexaphyrin-based edge-sharing macrocycles with two cavities (Figure b, c), have received considerable interest in light of their intriguing photophysical and aromatic properties and multiple π-electronic conjugation pathways …”

Creation from Confusion and Fusion in the Porphyrin World─The Last Three Decades of N-Confused Porphyrinoid Chemistry

“…In addition, oxidative dimerization of 452 afforded the dimer 454 in 65% yield, which had a unique twisted-planar-twisted type structure (Scheme 177). 426 The dimer 454 selectively reacted with methanol over other alcohols to give 455 and 456 in the presence of a base (56% and 41% yields, respectively) or acid (63% and 15% yields, respectively), where considerable color changes were observed. Similar to the reaction of α,ω-doubly N-confused hexapyrrane, oxidation of α,ω-doubly N-confused octapyrrane 457 caused N−C bond formation between the terminal pyrrole rings, affording neo-confused octaphyrin 458 in 31% yield (Scheme 178).…”

“…In addition, oxidative dimerization of 452 afforded the dimer 454 in 65% yield, which had a unique twisted-planar-twisted type structure (Scheme ). The dimer 454 selectively reacted with methanol over other alcohols to give 455 and 456 in the presence of a base (56% and 41% yields, respectively) or acid (63% and 15% yields, respectively), where considerable color changes were observed.…”