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<i>ansa</i>-Ferrocene-Incorporated Calixpyrroles and Calixphyrins: Syntheses and Spectral/Structural Characterization
The syntheses and spectral/structural characterization
of <i>ansa</i>-ferrocene-incorporated <i>normal</i> calixphyrins
and <i>core-modified</i> calixpyrroles and calixphyrins
are reported. Acid-promoted dehydrative condensation of 1,1′-bisÂ(dimethylpyrrolylmethyl)Âferrocene
and 2,5-bisÂ(dimethylhydroxymethyl)Âthiophene/furan yielded <i>ansa</i>-ferrocene-based <i>core-modified</i> calixpyrroles,
while acid-catalyzed dehydrative condensation of 1,1′-bisÂ(diphenylpyrrolylmethyl)Âferrocene
with the aryl aldehydes and 2,5-bisÂ(phenylhydroxymethyl)Âthiophene
followed by DDQ oxidation resulted in the formation of <i>ansa</i>-ferrocene-appended <i>normal</i> and <i>core-modified</i> calixphyrins, respectively. The newly synthesized macrocycles were
characterized by FAB-MS, NMR, and UV–vis spectral analyses
and finally confirmed by single-crystal X-ray structural analysis.
All these studies clearly revealed the introduction of ferrocene in
the main framework of the corresponding macrocycles in an <i>ansa</i>-type way. The <i>core-modified</i> calixpyrroles
adopt a 1,3-alternate conformation, while the corresponding calixphyrins
maintained partial planarity along the tripyrrin plane due to the
presence of <i>meso</i> sp<sup>2</sup> carbon and generated
curved staircase conformation. In addition to the intramolecular hydrogen-bonding
interactions, calixphyrins generate self-assembled dimers, one- and
two-dimensional supramolecular assemblies
through intermolecular hydrogen bonding in the solid state