STRUCTURAL CHARACTERIZATION OF 2 LIPOPHILIC TRIS(TROPOLONATO) GALLIUM(III) AND INDIUM(III) COMPLEXES OF RADIOPHARMACEUTICAL INTEREST

Tris(tropolonato)gallium(III), GaT3, and tris(tropolonato)indium(III), InT3, have been prepared in water from tropolone and the correspondin g metal(III) nitrate salt and structurally characterized. GaT, (1) cry stallizes in the monoclinic space group C2/c with a = 10.899(1), b = 1 0.282(1), c = 16.970(2) angstrom, beta = 103.721(8)-degrees and Z = 4. InT3 (2) crystallizes in the rhombohedral space group R3cBAR with a = 10.5349(5), b = 10.5349(5), c = 32.738(2) angstrom and Z = 6. The str uctures have been refined to an R factor of 0.027 for 1, based on 2171 observed reflections, and to an R factor of 0.030 for 2, based on 507 observed reflections. The octahedral coordination of the metal(III) i ons leads to an O-M-O' bond angle of 81.1(1)-degrees (mean value) in 1 and 75.3(1)-degrees in 2 and to an M-O bond length of 1.967(1) angstr om (mean value) in 1 and 2.134(3) angstrom in 2. Structural parameters are compared to AlT3 and FeT3 analogues and show the inflexibility of the tropolonato anion. The structural variations observed in the para meters external to the ring are consistent with the variation of the i onic radius in this series. The five signals observed on the C-13 NMR spectra are consistent with the C2nu symmetry of the tropolonato ligan d. A downfield shift for each carbon atom is observed upon complexatio n.