Molecules (Jan 2014)

[15]aneN4S: Synthesis, Thermodynamic Studies and Potential Applications in Chelation Therapy

  • Nuno Torres,
  • Sandrina Gonçalves,
  • Ana S. Fernandes,
  • J. Franco Machado,
  • Maria J. Villa de Brito,
  • Nuno G. Oliveira,
  • Matilde Castro,
  • Judite Costa,
  • Maria F. Cabral

DOI
https://doi.org/10.3390/molecules19010550
Journal volume & issue
Vol. 19, no. 1
pp. 550 – 567

Abstract

Read online

The purpose of this work was to synthesize and characterize the thiatetraaza macrocycle 1-thia-4,7,10,13-tetraazacyclopentadecane ([15]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 [15]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