Quantitative 2D EXSY and dynamic F-19-NMR studies of the dynamic behaviourof the bidentate chelate complex Ga(fox)(3) (fox=5-fluoro-8-hydroxyquinoline)

The rates of intramolecular rearrangement of the meridional isomer of the m etal tris-chelate complex [Ga(fox)(3), fox = 5-fluoro-8-hydroxyquinoline] i n DMF solution were measured using 1D NMR line shape analysis and 2D EXSY s pectra. The rates of exchange k(ab), k(bc) and k(ac) between the three none quivalent Ligands a, b and c were determined. The values of the activation parameters were obtained. Delta H-not equal was 70.6 kJ mol(-1) for all the rate constants. Delta S-not equal was different in each of the three cases : Delta S-ab(not equal), Delta S-bc(not equal) and Delta S-ac(not equal) we re 27.7, 28.5 and 34.6 J K-1 mol(-1) respectively. The interpretation of th ese data was related to the discrimination of different twist processes (Ba ilar and Ray-Dutt) for intramolecular rearrangement of the tris-chelate com plex.