Stability Constants of Ca²⁺, Cu²⁺, Zn²⁺, UO₂²⁺ , Mn²⁺, Co²⁺ and Ni²⁺ Complexes of Tetraethyl p-tert-Butylcalix[4]arene Tetraacetate in Nitrobenzene Saturated with Water

Emanuel Makrlík,^1,* Petr Vaňura² and Pavel Selucký²

¹ Faculty of Applied Sciences, University of West Bohemia, Husova 11, 306 14 Pilsen
² Institute of Chemical Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic
³ Nuclear Research Institute, 250 68 Řež, Czech Republic
* Corresponding author: E-mail: makrlik@centrum/sz

Abstract
From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M²⁺ (aq) + SrL²⁺ (nb) ↔ ML²⁺ (nb) + Sr²⁺ (aq) taking place in the two–phase water–nitrobenzene system (M²⁺ = Ca²⁺, Cu²⁺, Zn²⁺, UO₂²⁺  , Mn²⁺, Co²⁺, Ni²⁺; L = tetraethyl p-tert-butylcalix[4]arene tetraacetate; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Further, the stability constants of the ML²⁺ complexes in water saturated nitrobenzene were calculated; they were found to increase in the cation order Mn²⁺ < Co²⁺ < Cu²⁺ < Zn²⁺ < UO₂²⁺, Ni²⁺ < Ca²⁺.

Keywords: Divalent metal cations, calix[4]arene compound, strontium dicarbollylcobaltate, extraction and stability constants, water – nitrobenzene system