The First X‐ray Characterized Monosubstituted Ferrocenyl Azacrown Chalcone: Focus on Its Calcium Interaction/Electrochemical Detection Studies

Abstract The first X‐ray characterization of an azacrown ferrocenyl chalcone [(C 5 H 5 )Fe(C 5 H 4 COCH=CHC 6 H 4 ‐ p ‐aza‐15‐crown‐5)] ( 2 ) is reported. Its cation electrochemical detection capabilities have been evaluated and its behaviour towards protonation and calcium addition has been thoroughly examined. The uncommon ligand–Ca 2+ interaction process involves three species of different stoichiometry in equilibrium in solution. Their association constants have been calculated. These species are formed by interaction of calcium with both the azacrown and CO functions of compound 2 , as evidenced by NMR and IR spectroscopy. The theoretical MESP analysis also suggests that, contrary to its N ‐ethyl‐substituted homologue [(C 5 H 5 )Fe(C 5 H 4 COCH=CHC 6 H 4 NEt 2 )] ( 1a ), both coordination sites of 2 are involved in this interaction process. The study highlights that the CO group of 2 improves the selectivity of the cation electrochemical detection whencompared to the known compound [(C 5 H 5 )Fe(C 5 H 4 CH=CHC 6 H 4 ‐ p ‐aza‐15‐crown‐5)]. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)