Structures of the yttrium complexes of 1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid (H₄dota) and N,N″-bis(benzylcarbamoylmethyl)diethylenetriamine-N,N′,N″-triacetic acid and the solution structure of a zirconium complex of H₄dota

Abstract

The solid-state crystal structure of Na[Y (dota) (H20)]*4H20 (H,dota = 1.4.7.1 O-tetraazacyclododecane-N,N'.N'',N"-tetraacetic acid) at 11 5 K has been obtained together with the solution structure of the neutral zirconium complex. The yttrium complex shows a mono-capped ( H 2 0 ) square-antiprismatic structure while the solution 'H N M R spectra of [Zr(dota) (H20)] suggest that a structure of lower symmetry is adopted and a minor isomer is observed. The crystal structure of the yttrium complex of N,N"-bis(benzylcarbarnoylmethyl)diethylenetriamine-N,N',N''-triacetic acid has revealed amide carbonyl ligation in a distorted mono-capped square-antiprismatic structure, with one metal-bound water molecule.The complexation chemistry of yttrium has been the subject of renewed interest in recent years because of the need to find yttrium complexes which are sufficiently stable in uiuo for radioimmunotherapy with "Y-labelled antibody conjugates. Following the work of Desreux and co-workers4 on stable lanthanide complexes of H,dota (1,4,7,1 O-tetraazacyclododecane-N,N',N",N"'-tetraacetic acid, H,L'), it was soon apparent that dota was a suitable ligand both for gadolinium

Gadolinium(III) Chelates as MRI Contrast Agents: Structure, Dynamics, and Applications

“…b Average of two independent molecules. 36 were reported (Chart 4). In all of these complexes, nonacoordinate metal ions were observed.…”

Evaluation of quinoline as a remote sensitiser for red and near-infrared emissive lanthanide(iii) ions in solution and the solid state

“…These results are consistent with the solution measurements of similar 8-coordinate DTPA-bis(amide) complexes from our group 15 as well as the crystal structures of DTPA-bis(amide) derivatives reported by other laboratories, where a single solvent molecule is observed to be directly coordinated to the lanthanide centre, occupying the ninth coordination site. 34,43 The lifetime of EuL in methanol is lower than that observed for the Eu-DTPA-bis(amidothiophenyl) system reported previously (0.8 ms) by our laboratories 15 and therefore we must conclude that the increase in the quantum yield by two orders of magnitude observed between the systems (0.04% in Lewis et al 15 vs. 4% for EuL) is caused primarily by an increase in the efficiency of the energy transfer from the quinoline antenna to the lanthanide centre, which contributes linearly to the overall quantum yield. Comparison of the quantum yield of EuL with other quinoline sensitized europium(III) complexes in the literature shows that our system exhibits sensitised emission efficiency within the same order of magnitude as the Eu-DOTA-quinoline complexes reported by Williams (6%, 0.2%) 44 and Botta (0.7%).…”

Luminescent lanthanide sensors for pH, pO2 and selected anions

“…In the complexes of dota 1 and the tetra-amides 8, the two major diastereoisomers in solution possess a mono-capped square-antiprismatic geometry (with a twist angle of the N 4 /O 4 planes of ca. 40°) and a twisted square-antiprismatic geometry (twist angle 29°) [39,40]. The relative proportion of these two isomers varies as a function of the nature of the substituents in the ligand [41], and of lanthanide size.…”