A comparative study of the metal binding behavior of alanine based bis-thiourea isomers

Two new symmetrical bis-thiourea, 2,2'-[{(terephthaloylbis(azanediyl)bis(carbonothioyl) bis(azanediyl)}dipropanoic acid] (1A) and 3,3'-[{(terephthaloylbis(azanediyl)bis (carbonothioyl)bis(azanediyl)} dipropanoic acid] (1B) were synthesized by the reaction of terephthaloyl chloride with α- and β-alanine in good yields. Their binding properties were investigated with various metal cations using UV-Vis titration experiments. Both isomers exhibited effective binding with Ag(+), Cu(2+), Hg(2+), Pb(2+), Fe(2+) and Fe(3+) cations. However, in the presence of other cations, such as Na(+), Ni(2+), Co(2+), Cd(2+), Zn(2+), Mn(2+), Mg(2+), Ca(2+), Sn(2+), Al(3+), and anions tetrabutylammonium Cl(-) and H2PO4(-), no interaction occurred. Both isomers displayed similar trends towards binding with metal cations.