Lanthanide(III) complexes of 4,10-bis(phosphonomethyl)-1,4,7,10-tetraazacyclododecane-1,7-diacetic acid (trans-H6do2a2p) in solution and in the solid state: structural studies along the series.
Complexes of 4,10-bis(phosphonomethyl)-1,4,7,10-tetraazacyclododecane-1,7-diacetic acid (trans-H(6)do2a2p, H(6)L) with transition metal and lanthanide(III) ions were investigated. The stability constant values of the divalent and trivalent metal-ion complexes are between the corresponding values of H(4)dota and H(8)dotp complexes, as a consequence of the ligand basicity. The solid-state structures of the ligand and of nine lanthanide(III) complexes were determined by X-ray diffraction. All the complexes are present as twisted-square-antiprismatic isomers and their structures can be divided into two series. The first one involves nona-coordinated complexes of the large lanthanide(III) ions (Ce, Nd, Sm) with a coordinated water molecule. In the series of Sm, Eu, Tb, Dy, Er, Yb, the complexes are octa-coordinated only by the ligand donor atoms and their coordination cages are more irregular. The formation kinetics and the acid-assisted dissociation of several Ln(III)-H(6)L complexes were investigated at different temperatures and compared with analogous data for complexes of other dota-like ligands. The [Ce(L)(H(2)O)](3-) complex is the most kinetically inert among complexes of the investigated lanthanide(III) ions (Ce, Eu, Gd, Yb). Among mixed phosphonate-acetate dota analogues, kinetic inertness of the cerium(III) complexes is increased with a higher number of phosphonate arms in the ligand, whereas the opposite is true for europium(III) complexes. According to the (1)H NMR spectroscopic pseudo-contact shifts for the Ce-Eu and Tb-Yb series, the solution structures of the complexes reflect the structures of the [Ce(HL)(H(2)O)](2-) and [Yb(HL)](2-) anions, respectively, found in the solid state. However, these solution NMR spectroscopic studies showed that there is no unambiguous relation between (31)P/(1)H lanthanide-induced shift (LIS) values and coordination of water in the complexes; the values rather express a relative position of the central ions between the N(4) and O(4) planes.
Campello
M Paula C
MP
Departamento de Química, Instituto Tecnológico e Nuclear, Estrada Nacional 10, 2686-953 Sacavém, Portugal.
Lacerda
Sara
S
Santos
Isabel C
IC
Pereira
Giovannia A
GA
Geraldes
Carlos F G C
CF
Kotek
Jan
J
Hermann
Petr
P
Vanek
Jakub
J
Lubal
Premysl
P
Kubícek
Vojtech
V
Tóth
Eva
E
Santos
Isabel
I
D001372:Aza Compounds / Q000737:chemistry*; D043822:Cyclodecanes / Q000737:chemistry*; D007477:Ions / Q000737:chemistry*; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
C553652:4,10-bis(phosphonomethyl)-1,4,7,10-tetraazacyclododecane-1,7-diacetic acid; D001372:Aza Compounds; D043822:Cyclodecanes; D007477:Ions; D028581:Lanthanoid Series Elements; D009942:Organometallic Compounds; D012996:Solutions; D014867:Water