TY - JOUR
T1 - Tris(phosphonomethyl) Cyclen Derivatives: Synthesis, Acid-Base Properties and Complexation Studies with Cu2+ and Zn2+ Ions
AU - Lima, Luís
PY - 2012/1/1
Y1 - 2012/1/1
N2 - Three compounds that are based on cyclen and contain three methylphosphonate pendant arms ? (1,4,7,10-tetraazacyclododecane-1,4,7-triyl)tris(methylene)triphosphonic acid (H6do3p), 3-{4,7,10-tris[(dihydroxyphosphoryl)methyl]-1,4,7,10-tetraazacyclododecan-1-yl}propanoic acid (H7do3p1pr) and [10-(3-hydroxypropyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]tris(methylene)triphosphonic acid (H6do3p1ol) ? were synthesized and characterized. X-ray crystal structures were determined for H6do3p and for the complex [Cu(H2O)6]2+[Cu(H2O)(H4dotp)]2 of a related ligand H8dotp [H8dotp = (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetrakis(methylene)tetraphosphonic acid]. They show the copper(II) centre coordinated only to the four amines of the macrocycle and one water molecule in the apical position. The acidbase properties of the three compounds were studied in aqueous solution by potentiometry and 31P NMR spectroscopy. All ligands exhibit very high basicity and their protonation schemes are dominated by proton relocations between the basic sites and intramolecular hydrogen bonding. The thermodynamic stability constants for complexes of the three ligands with Cu2+ and Zn2+ metal ions were determined by potentiometry and exhibit very high values for the complexes of Cu2+. UV/Vis spectroscopy was used to assess the acid-assisted dissociation of the Cu2+ complexes and showed that the dissociation rates are faster than for the corresponding complex of H8dotp, whereas the [Cu(do3p1ol)]4 complex is the most inert one in this series.
AB - Three compounds that are based on cyclen and contain three methylphosphonate pendant arms ? (1,4,7,10-tetraazacyclododecane-1,4,7-triyl)tris(methylene)triphosphonic acid (H6do3p), 3-{4,7,10-tris[(dihydroxyphosphoryl)methyl]-1,4,7,10-tetraazacyclododecan-1-yl}propanoic acid (H7do3p1pr) and [10-(3-hydroxypropyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl]tris(methylene)triphosphonic acid (H6do3p1ol) ? were synthesized and characterized. X-ray crystal structures were determined for H6do3p and for the complex [Cu(H2O)6]2+[Cu(H2O)(H4dotp)]2 of a related ligand H8dotp [H8dotp = (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetrakis(methylene)tetraphosphonic acid]. They show the copper(II) centre coordinated only to the four amines of the macrocycle and one water molecule in the apical position. The acidbase properties of the three compounds were studied in aqueous solution by potentiometry and 31P NMR spectroscopy. All ligands exhibit very high basicity and their protonation schemes are dominated by proton relocations between the basic sites and intramolecular hydrogen bonding. The thermodynamic stability constants for complexes of the three ligands with Cu2+ and Zn2+ metal ions were determined by potentiometry and exhibit very high values for the complexes of Cu2+. UV/Vis spectroscopy was used to assess the acid-assisted dissociation of the Cu2+ complexes and showed that the dissociation rates are faster than for the corresponding complex of H8dotp, whereas the [Cu(do3p1ol)]4 complex is the most inert one in this series.
KW - Phosphonate complexes
KW - Thermodynamics
KW - Kinetics
KW - Copper
KW - Macrocyclic ligands
U2 - 10.1002/ejic.201101334
DO - 10.1002/ejic.201101334
M3 - Article
VL - 2012
SP - 2533
EP - 2547
JO - European Journal of Inorganic Chemistry
JF - European Journal of Inorganic Chemistry
SN - 1434-1948
IS - 15
ER -