Formation of mono- and di-nuclear complexes of Zn2+ from a 26 membered tetraester crown of 3,5-disubstituted pyrazole able to act as neutral and dianionic ligand

Article abstract of DOI:10.1016/S0040-4020(01)85015-8

A selective synthesis of bis(3,5-diketo-1H-pyrazole)-[26]crown- 12 (1, L₁) has been performed. Its deprotonation pK_a values, and those of the acyclic analogues (3-5) have been measured. The disodium dipyrazolate salt of 1 (2, [L₂]^2- 2Na⁺) has been isolated, and mono- and di- nuclear complexes of Zn²⁺ obtained from 1 ([L₁Zn]²⁺) and 2 ([L₂Zn₂]²⁺) have been studied by ¹³C NMR spectroscopy in DMSO-d₆ solution.