Abstract: The purpose of this work was to synthesize and characterize the thiatetraaza macrocycle 1-thia-4,7,10,13-tetraazacyclopentadecane (aneN4S). Its acid-base behaviour was studied by potentiometry at 25 °C and ionic strength 0.10 M in KNO3. The protonation sequence of this ligand was investigated by 1H-NMR titration that also allowed the determination of protonation constants in D2O. Binding studies of aneN4S with Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ metal ions were further performed under the same experimental conditions. The results demonstrated that this compound has a higher selectivity and thermodynamic stability for Hg2+ and Cu2+, followed by Ni2+. The UV-visible-near IR spectroscopies and magnetic moment data for the Co(II) and Ni(II) complexes indicated a tetragonal distorted coordination geometry for both metal centres. The value of magnetic moment and the X-band EPR spectra of the Cu(II) complex are consistent with a distorted square pyramidal geometry.
Keywords: macrocyclic compounds; thiatetraaza; stability constants; spectroscopic studies; chelation therapy; mercury(II) chelator; copper(II) chelator
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Torres, N.; Gonçalves, S.; Fernandes, A.S.; Machado, J.F.; de Brito, M.J.V.; Oliveira, N.G.; Castro, M.; Costa, J.; Cabral, M.F. aneN4S: Synthesis, Thermodynamic Studies and Potential Applications in Chelation Therapy. Molecules 2014, 19, 550-567.
Torres N, Gonçalves S, Fernandes AS, Machado JF, de Brito MJV, Oliveira NG, Castro M, Costa J, Cabral MF. aneN4S: Synthesis, Thermodynamic Studies and Potential Applications in Chelation Therapy. Molecules. 2014; 19(1):550-567.
Torres, Nuno; Gonçalves, Sandrina; Fernandes, Ana S.; Machado, J. F.; de Brito, Maria J.V.; Oliveira, Nuno G.; Castro, Matilde; Costa, Judite; Cabral, Maria F. 2014. "aneN4S: Synthesis, Thermodynamic Studies and Potential Applications in Chelation Therapy." Molecules 19, no. 1: 550-567.