Preparation of the copper(II) complex of the binucleating hexaaza macrocycle 2,5,8,17,20,23-hexaaza[9.9]paracyclophane and its solution chemistry, hydrolytic activity and acid dissociation kinetics

Abstract

The binucleating hexaaza macrocycle 2,5,8,17,20,23-hexaaza[9.9]paracyclophane (PEA) and its N-permethylated derivative 2,5,8,17,20,23-hexamethyl-2,5,8,17,20,23-hexaaza[9.9]paracyclophane (Me₆PEA) have been prepared. The copper(II) complex of PEA has been prepared and the stability constants of the copper complexes determined in aqueous solution by potentiometric and spectrophotometric methods. The protonation sites of PEA have been identified by NMR titration. The crystal structure of the complex [Cu₂(PEA)Cl₃]⁺Cl⁻·2.6MeCN·2.9H₂O has been determined. The copper centres have an N₃Cl₂ donor set with a square pyramidal geometry. The Cu ⋯ Cu distance is 7.02 Å. The copper complex catalyses hydrolysis of the phosphotriester 2,4-dinitrophenyl diethyl phosphate (DNPDEP) and the [Cu₂(PEA)(OH)₂]²⁺ and [Cu₂(PEA)(OH)]³⁺ complexes have been identified as the active species. The acid catalysed dissociation of the copper complex has been studied by stopped-flow methods. The reaction is monophasic and displays saturation kinetics at high acidities.