Structural and Aromaticity Control of [34]Octaphyrin(1.1.1.0.1.1.1.0) by Protonation and Deprotonation

Abstract

The structurala nd aromaticity control of hexakis(pentafluorophenyl) [34]octaphyrin(1.1.1.0.1.1.1.0) 1 was examined by protonation and deprotonation. Protonation of 1 with methanesulfonica cid (MSA) induced as tructural change from af igure-eightt oarectangular shape,a ccompanied by an aromaticity change from nonaromatict o strong Hückel aromatic. Deprotonation of 1 with tetrabutylammonium difluorotriphenylsilicate (TBAT) or fluoride (TBAF) produced amono-deprotonated specieswith asimilar figure-eight conformation andn onaromaticity.Recently,i ncreasing attention has been focused on expanded porphyrins in light of their fascinating properties such as large p-conjugations, conformationalf lexibilities, near-infrared (NIR) absorption, rich metal coordination,r adical-stabilizing abilities, and potential tos erve as platforms of Mçbius aromatic and antiaromatic molecules, which are not shared with porphyrin. [1] Since our serendipitousd iscoveryo faone-pot synthesis of meso-aryl-substituted expanded porphyrins, [2] we have actively exploredt heir properties. Sessler et al., [3] Latos-Grażyń ski et al., [4] Chandrashekar et al., [5] Anand et al., [6] and others [7] made continuous efforts to develop novel features of expanded porphyrins. Through these efforts, it is now clear that expanded porphyrins are an effectivea romaticity-switching motif.Naturally,t he aromaticity of expanded porphyrins is heavily dependentu pon their conformations,a nd therefore conformational control of expanded porphyrins is crucial in the exploration of aromaticity-switching expanded porphyrins. So far,p rotonation, [8] deprotonation, [9] metal coordination [10] and solvents [11] have been used for conformational control of expanded porphyrins. Among these means, protonation and deprotonation are expected to be quite effective, sincet he conformations of expanded porphyrins are usually held by intramolecular hydrogen bonding between the amine-and imine-type pyrroles. Actually,p rotonation and deprotonation of meso-hexakis(pentafluorophenyl)

Ag(III)···Ag(III) Argentophilic Interaction in a Cofacial Corrole Dyad

“…While the origin of this molecule is unclear, it is likely that the xanthene backbone templates the synthesis, enabling 6 to adopt this unique geometry. The absorption spectrum of 6 (Figure S9) exhibits a sharp feature at 715 nm and weaker transitions in the near-IR (900–1200 nm), similar to other derivatives of [34]­octaphyrin(1.1.1.0.1.1.1.0). , …”

Proton-Coupled Redox Switching in an Annulated π-Extended Core-Modified Octaphyrin

“…The seemingly unique proton-induced reduction seen in the case of naphthorosarin may reflect its relative rigidity. Most large porphyrin analogues, including a nonannulated version of rosarin, are characterized by their inherent flexibility. − This may allow alternative processes such as conformational changes to dominate over PCET in the presence of a putative reductant or a proton source. − To the extent this rationale is correct, large, highly rigid porphyrin analogues should favor PCET. To test this hypothesis, we have now prepared a new, highly rigidified expanded porphyrin, namely, an octaphyrin(1.0.1.0.1.0.1.0) analogue ( 1 ), containing both fused bipyrrole and fused bithiophene subunits .…”

Theoretical studies as a tool for understanding the aromatic character of porphyrinoid compounds

“…[209][210][211][212][213] Möbius twisted expanded porphyrins have been synthesized and characterized. [214][215][216][217][218][219][220][221][222][223][224][225][226] The molecular aromaticity and magnetically induced current densities of the expanded and twisted porphyrins have also been studied computationally. 116,[227][228][229][230] In 2008, a more general p electron count rule was proposed for various types of twisted molecules.…”