Heptaphyrins: expanded porphyrins with seven heterocyclic rings

Expanded porphyrins containing seven pyrrole/heterocyclic rings linked in a cyclic fashion are termed heptaphyrins. The number of π-electrons in heptaphyrins depends on the number ofmeso carbon bridges used to link the heterocyclic rings, accordingly heptaphyrins with 28π-electrons and 30π-electrons are reported to date. Both condensation reactions of the appropriate precursors and acid-catalysed oxidative coupling reactions have been utilized to synthesise the heptaphyrins. The 30π heptaphyrins exhibit rich structural diversity where some of the heterocyclic rings in the macrocycle undergo a 180° ring flipping. An overview of the synthetic methods employed for the synthesis of heptaphyrins, their spectroscopic properties, structural behaviour and aromatic properties are highlighted in this paper

Core modified oxybenziporphyrins: new aromatic ligands for metalcarbon bond activation

Successful syntheses of two new aromatic core modified oxybenziporphyrins by a simple 3 + 1 methodology and the first aromatic core modified oxybenziporphyrin palladium complex are reported

Oxidative Transformation of a Tetrathia S‑Confused Isophlorin into Porphyrin Cation

The synthesis and redox properties of first generation S-confused isophlorins are described. Despite structural resemblance to a confused porphyrin, spectroscopic and computational studies reveal weak paratropic ring current effects in these 20π macrocycles. They display redox properties atypical of parent tetrathia isophlorins. Experimental evidence supports the oxidation of an unstable 19π neutral radical, as a transient intermediate, for the formation of a unique 18π aromatic monocationic species. Spectroscopic and structural characterization revealed the substituent dependent macrocycle oxidation unfamiliar to the chemistry of antiaromatic isophlorinoids

Cyclic Oligofurans: One-Pot Synthesis of 30\pi and 40\pi Expanded Porphyrinoids

Acid-catalyzed condensation of furan and pentafluorobenzaldehyde yielded conjugated macrocycles with six and eight furan rings. They represent systems similar to annulenes with 30\pi and 40\pi electrons. From their structural analyses, it was found that furan rings in both the molecules were inverted in an alternative fashion and displayed nontwisted conformations

meso-Substituted aromatic 34π core-modified octaphyrins: syntheses, characterization and anion binding properties

Modified octaphyrins with 34π electrons have been synthesized and characterized following a simple synthetic methodology. An acid-catalyzed α, α coupling of tetrapyrranes containing furan, thiophene and selenophene rings resulted in the formation of the respective octaphyrins in relatively good yield. Solution studies by 1H NMR and 2D NMR methods and single crystal Xray structural characterization reveal an almost flat structure with two heterocyclic rings inverted. Specifically, in 14 two selenophene rings (one on each biselenophene unit) are inverted while in 15 two furan rings (one on each bifuran unit) are inverted when the meso substituent are mesityl groups. On changing the mesityl substituent to m-xylyl group as in 19, the location of ring inversion shifts to pyrrole rings (one on each bipyrrole unit) indicating the dependence of structure on the meso substituents. UV/Vis studies, both in freebase and protonated forms reveal typical porphyrinic character and the aromatic nature of the octaphyrins. The Δδ values evaluated by 1H NMR spectroscopy also support their aromatic nature. The protonated forms of octaphyrins bind TFA anion in a 1:2 ratio. The TFA anions are located one above and below the plane of the octaphyrin macrocycle and they are held by weak electrostatic NH-O interactions similar to that observed for protonated rubyrins. However, in the present case, there is an additional non-electrostatic CH-O interaction involving β-CH of the inverted heterocyclic ring and the carbonyl oxygen of the TFA. Furthermore, inter molecular interactions between the CH of the meso-mesityl group and the fluorine of CF3 group of bound TFA leads to the formation of one-dimensional supramolecular arrays with interplanar distance of 13 Å between two octaphyrins

First structural characterization of core modified 10,15-meso aryl azuliporphyrins: observation of C-Hπ interaction between pyrrole β-CH and mesityl ring

First successful syntheses and structural characterization of new core modified meso aryl azuliporphyrins by a simple [3 + 1] methodology are reported

N-confused expanded porphyrin: first example of a modified sapphyrin with an inverted N-confused pyrrole ring

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