Super Extended Calix[4]Pyrroles as Candidate for Binding Mercury

Abstract

The binding of mercury Hg (II) by calix[4]pyrrole derivative; 2 has been much less discovered than anion complexation. The presence of hydroxyl group in the structure of meso-tetramethyl-tetrakis-[2(4-hydroxyphenyl)ethylcalix[4]pyrrole is important for further modifications in the next steps. The modification of the hydroxyl group by the substitution of ester group was carried out to produce the ester derivative for the modified calix[4]pyrrole 2. The ester group would be expected to deliver high electronic contributions in the complexation processes with the guests as well as to increase the solubility of the receptor in different organic solvents. 1H NMR and isothermal titration calorimetric studies revealed that the receptors exhibited strong interaction with mercury cation and the complexation process was driven enthalpically and entropically. Conductance measurements in acetonitrile were carried out to identify the composition of the formed complex. From Nano Isothermal Titration Calorimetric studies, the thermodynamic parameters for the complexation processes were calculated.