Structural Diversity in Rubyrins: X-ray Structural Characterisation of Planar and Inverted Rubyrins

Abstract

Meso aryl rubyrins exhibit three different structures. A planar (7) and two unusual inverted structures [a]

Flexible Porphyrinoids

“…Some varieties of heterorubyrins obtained by Chandrashekar and co-workers have presented different conformational flexibility and dynamics in solution (Scheme ) (see refs , , , − ). It was found that the preferential conformation of the free base heterorubyrin strongly depends on the type of heteroatom and the type of meso -substituents.…”

“…At low-temperature limits, dithiarubyrin 53 - 2 and oxathiarubyrin 53 - 5 exist in solution in inverted conformations, while diselenarubyrin 53 - 3 and ditellurarubyrin 53 - 4 prefer a normal geometry with all the heteroatoms pointing into the cavity. Interestingly, tetramesityldioxarubyrin 53 - 6 adopts a conformation with two inverted pyrrole rings (Scheme ), as established by 1 H NMR at −50 °C.…”

Supramolecular Assemblies of Sulfur- and Selenium- Containing Expanded Porphyrins Mediated Through Noncovalent Interactions

“…1,2 From a structural perspective, expanded porphyrins with meso aryl substituents show a rich structural diversity where one or more heterocyclic rings exhibit an unusual 180 • ring flipping leading to partially inverted structures, including N-confused macrocycles. 9,10 Reactivity studies mostly have concentrated on studying the ability of these macrocycles to bind anions and cations. Expanded porphyrins in their free base form have affinity for transition metal cations 1,2 while in their protonated form they bind anions.…”

“…9 Three different types of structures have been observed for meso aryl rubyrins both in solution and in solid state. 10 …”

“…10 The rubyrin almost is planar with only small deviations from the mean plane. Specifically, 1 of the selenophene rings of the bisselenophene unit is deviated by 6.18 • , while the other deviates 1.45 • from the mean rubyrin plane.…”