Template Synthesis of Decaphyrin without Meso-Bridges: Cyclo[10]pyrrole

Abstract

An acenaphthylene-fused cyclo[10]pyrrole 1b was selectively synthesized via an oxidative coupling reaction of the corresponding 2,2'-bipyrrole with the appropriate dianion template, croconate anion. The structure of 1b as the isolated largest cyclo[n]pyrrole was elucidated by X-ray crystallographic analysis. The absorption spectrum exhibited a markedly red-shifted, intensified L band at 1982 nm, which was interpreted by application of Michl's perimeter and Gouterman's 4-orbital models, supported by magnetic circular dichroism (MCD) data and theoretical calculations.

Near-infrared dyes for two-photon absorption in the short-wavelength infrared: strategies towards optical power limiting

“…Second, increasing the number of delocalized π electrons by incorporating a higher number of pyrrolic heterocycles efficiently lowers the HLG, such as in sapphyrin (5 units), amethirine (6 units), NIR-absorbing cyclo [8]pyrrole, 185 or SWIR-absorbing cyclo [10]pyrrole. 186 Third, the further annellation of these extended porphyrin derivatives stiffens the structure and induces an additional bathochromic shift, as illustrated by cyclo [4]naphtoindole 56 absorbing ca. 1300 nm.…”

Cyclo[9]pyrrole: Selective Synthesis of [34]Nonaphyrin(0.0.0.0.0.0.0.0.0)

“…In contrast, a similar reaction using HCl resulted in low selectivity of the ring size to give a mixture of cyclo­[ n ]­pyrroles ( n = 6–8) . In 2016, we reported the selective synthesis of cyclo[10]­pyrrole using a croconate anion as an appropriate pentagonal template and a counter dianion . The size, charge, and geometry of the croconate anion are a perfect fit for the diprotonated decapyrrolic skeleton.…”

Functionalized 2,2’-Bipyrroles: Building Blocks for Pyrrolic Macrocycles

“…Kobayashi and co-workers have also synthesized a cyclo[10]pyrrole ( 158 ) derived only from 2,2’-bipyrrole 157 by using an oxidative cyclization with croconic acid as a template (Scheme 36). [109] This remains the largest cyclo[n] pyrrole prepared to date.…”