Syntheses, structures, and anion-binding properties of two novel calix[2]benzo[4]pyrroles

Calix[2]benzo[4]pyrrole m-6 and p-6, each containing two dipyrromethane moieties and two m-phenylene or p-phenylene units, respectively, were readily synthesised from pyrrole, 1,3- and 1,4-bis(1,1'-dimethylhydroxymethyl)benzene, (m-4 and p-4, respectively) and acetone. Macrocycles m-6 and p-6 were tested as receptors for a selection of anions, such as acetate, dihydrogenphosphate and fluoride. The X-ray structures of m-6 and p-6 and those of the complexes m-6(.)F(-), m-6(.)Cl(-) and m-6(.)CH(3)COO(-) (with an nBu(4)N(+) counterion) were also determined.