✍ Scribed by Bernard Spiess; Françoise Arnaud-Neu; Marie-José Schwing-Weill
No coin nor oath required. For personal study only.
Complexation in anhydrous methanol of Cu (II) and Zn (II) with diaza‐polyoxamacrocyclic ligands
Protonation of five diaza‐polyoxamacrocyclic ligands, (L = [2.1], [2.2], [2.1.1.], [2.2.1], [2.2.2]), and their complexing properties towards Cu^2+^ and Zn^2+^ cations have been studied in anhydrous methanolic solutions.
Potentiometric measurements have been carried out at 25°, using 5 · 10^−2^MEt~4~N^+^ClO as support‐electrolyte, in order to determine the nature of the species formed upon complexation and their stability constants. The results were confirmed by spectrophotometry, for the cupric complexes of [2.1] and [2.2.2], and the electronic spectra of the different complexes were calculated.
Comparison between complexation in aqueous and methanolic solutions have been made: as in water, ML^2+^ species and sometimes protonated MHL^3+^ species, with higher stability constants, are present in methanol; but the main difference is the formation of dinuclear complexes M~2~L^4+^, between Cu^2+^ and all ligands except [2.1]. In these complexes the Cu^2+^ cations cannot be both ‘encaged’ in the ligand cavity because of its small size. The different possible structures are discussed in terms of the stability constants values. The protonation constants values and the existence of the binuclear complexes may indicate a possible conformational change in the complexing ligand on changing the solvent from water to methanol.
📜 SIMILAR VOLUMES