Investigate formation constant of some Amino Acids by p-sulphonato-calix (4) arene in Aqueous Solution

The formation constants (log K), of the complexes formed between a number of amino acids (glycine , L-valine and L-alanine) with p-sulfonatocalix [4] arene at varying temperatures (25± 0.1 to 65 ± 0.1 °C) in aqueous solutions and at natural pH of p-sulphonato-calix [4] arene (pH=3.2) by means of UV-Vis spectrophotometeric technique have been investigated. At this pH the guest molecule is in its cationic and zwitterionic forms. The results revealed that the host is q ui t e capable of complexing with the guest in 1:1 guest-to-host ratio. Regarding the formation constant values, the binding selectivity of the host towards the guests proves in the order (alanine > valine > glycine). The thermodynamic parameters have been assessed and interpreted in matters of the significance of the various interactions responsible for the complexation. A roughly linear relationship between BHo and TBSo has been observed for the studied complexes and it is discussed.