Synthesis of a Fourfold Enlarged Porphyrin with an Extremely Large, Diamagnetic Ring‐Current Effect

Abstract

A solution of 3a (0.9 g, 6.1 mmol) in toluene (40 mL) was treated at -50°C with 4 m L of a solution of tris(ethene)nickel in toluene (2.0 mmol Ni(C2H4)?; titer determined by reaction with P(OCH,), and 1,5-cyclooctadiene). The stirred mixture was allowed to warm to room temperature in 30 min and the solvent was then removed under vacuum. At 45OC/IO-' torr, light green 4a sublimed, which is colorless in thin layers (75 mg, 0.19 mmol, 12.5%). MS: m / z 403

Furan-Based Porphyrins: Tetraoxa[4n+2]porphyrin Dications with 18π-, 22π-, or 26π-Electron Systems

“…The D 4h -symmetric tetraoxa [18]porphyrin dication 1, [1] which is isoelectronic with diprotonated porphyrin, and the N,N',N'',N'''-tetramethyl [26]porphyrin- (3.3.3.3) dication (3 with NCH 3 instead of O; as the octaethyl derivative) described by Franck et al [2] are prototypes of chalcogenaporphyrins [3] and symmetrically expanded porphyrins, respectively. [4] These dicationic porphyrin variants should be viewed as resonance hybrids (carbenium and onium ion structures) in which special importance is attributed to carbenium ion structures with 4n2 p electrons on the 4(n1) carbon perimeterÐin agreement with both experiment and theory.…”

“…Our interest in 2 and 3 was stimulated by the exceptional spectroscopic properties of the N,N',N'',N'''-tetramethyl[26]-porphyrin dication from Franck et al, which prompted the authors to call the compound a super arene. [2] . If 2 and 3Ðlike 1Ðwere to exist as D 4h -symmetric molecules, the triad 1 ± 3 would be ideally suited to provide meaningful spectroscopic correlations between the three members.…”

“…[14] For the synthesis of the tetraoxa [26]porphyrin-(3.3.3.3) dication, as the octaethyl derivative 13 for reasons of solubility, we followed the route illustrated in Scheme 2, which was based on porphyrin chemistry methodology. [2] The starting aldehyde 10 was obtained by vinylogous Vilsmeier formylation of 3,4-diethylfuran with 3-(N,N-dimethylami- no)acrolein and phosphorus oxychloride in dichloromethane at 0 8C (pale yellow crystals; m.p. 53 ± 54 8C; yield 65 %).…”

“…[2] As with its NCH 3 analogue, 13 is characterized by an unusually strong diamagnetic ring current which is manifested in the position of the signals of the outer-and inner-perimeter protons at extremely low and high field: C NMR spectra (six signals) and the finding that the structure of 13 exhibits a planar ring framework (see the following communication [19] ). A comparison of the UV/Vis spectrum of 13 with those of the octaethyl derivatives 1 a [15] and 8 a [13] of 1 and 8 is particularly informative.…”

Bis-vinylogous Corrole: The First Expanded Corrole

“…[8] The relationship between porphyrin and corrole led us to explore the existence of a bis-vinylogous system 4 similar to 2. Our target macrocycle 5, according to the nomenclature suggested by Franck, [6,9] would be called [22]porphyrin(3.1.3.0). Herein we describe the synthesis and characterization of 5, a bisvinylogous corrole.…”