The Effect of Quinolyl Endgroups on Podand Fluctuations-1-DNMR and 2D-EXCSY-NMR of Co(II)-Complexes

Ligand fluctuations in complexes [Co(Kr5)]X (Kr 5 = 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane) with X = ClO , CF SO can be detected by NMR spectroscopy above room temperature in inert solvents such as nitromethane. This unusually slow ligand movement is due to the strong coordination of the quinolyl end groups to the Co(II) ion as demonstrated through measurements with oligo-ethylene-glycols. In contrast to the C spectra, the H 2 D EXCSY NMR spectra reveal cross peaks which are due to a magnetisation exchange between the chemically non-equivalent protons in the -CH - groups of the podand. This process is associated with a movement of the chain segments towards each other.