Ferrocene-substituted calix[4]pyrrole: a new electrochemical sensor for anions involving CH center dot center dot center dot anion hydrogen bonds

A new calix[4]pyrrole 1 containing a ferrocene moiety attached to one of th e meso-positions has been synthesised by co-condensation of pyrrole, cycloh exanone and acetylferrocene. The crystal structure of 1 has been elucidated whilst H-1 NMR titration studies in acetonitrile-d(3)/DMSO-d(6) 9:1 v/v ha ve revealed that 1 binds fluoride, chloride, and dihydrogen phosphate in th is solvent mixture. Electrochemical studies using cyclic voltammetric and s quare-wave voltammetric techniques show cathodic shifts of up to 100 mV (ap prox.) with dihydrogen phosphate anions. (C) 2001 Elsevier Science Ltd. All rights reserved.