Synthesis and characterization of the yttrium(III) and lutetium(III) complexes of 1,4,7-tris(carbamoylmethyl)-1,4,7-triazacyclononane (TCMT). Crystal structure of [Y(TCMT)(CF3SO3)(2)(H2O)](CF3SO3)

The 1,4,7-tris(carbamoylmethyl)-1,4,7-triazacyclononane (TCMT) ligand and its complexes with yttrium(III) and lutetium(III) have been prepared. [Y(TCMT)(CF3SO3)(2)(H2O)](CF3SO3) crystallizes in the centrosymmetric triclinic space group P (1) over bar (No. 2) with a = 10.3660(14), b = 11.7663(15), c = 13.3008(20) Angstrom, alpha = 72.079(10), beta = 81.684(12), gamma = 78.401(11)degrees, V = 1506.1(4) and Z = 2. The structure was refined to R = 5.64% for those 1758 reflections with \F-0\ > 6 sigma(\F-0\). The nonacoordinate yttrium(III) ion has a bound water molecule, two bound triflate ions and a hexadentate TCMT ligand. The coordination geometry may be described as a 3:5:1 arrangement in which the C6N3 backbone occupies the '3' sites and H2O the unique '1' site, or alternatively as a capped square antiprism or as a distorted tricapped trigonal prism. The [Ln(TCMT)](3+) complexes dissociate completely in aqueous solution within 25 min at pH 6.0 and 37 degrees C in the presence of Cu2+ as a trapping agent. Molecular mechanics calculations have been used to investigate the strain energy of the TCMT and 1,4,7-triazacyclononane-1,4,7-triacetate (NOTA) ligands in complexes that are 6-, 7- or 9-coordinate.