ansa-Ferrocene-Incorporated Calixpyrroles and Calixphyrins: Syntheses and Spectral/Structural Characterization

Abstract

The syntheses and spectral/structural characterization of ansa-ferrocene-incorporated normal calixphyrins and core-modified calixpyrroles and calixphyrins are reported. Acid-promoted dehydrative condensation of 1,1′-bis(dimethylpyrrolylmethyl)ferrocene and 2,5-bis(dimethylhydroxymethyl)thiophene/furan yielded ansa-ferrocene-based core-modified calixpyrroles, while acid-catalyzed dehydrative condensation of 1,1′-bis(diphenylpyrrolylmethyl)ferrocene with the aryl aldehydes and 2,5-bis(phenylhydroxymethyl)thiophene followed by DDQ oxidation resulted in the formation of ansa-ferrocene-appended normal and core-modified 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 ansa-type way. The core-modified calixpyrroles adopt a 1,3-alternate conformation, while the corresponding calixphyrins maintained partial planarity along the tripyrrin plane due to the presence of meso sp2 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.