Rotational Correlation Times of Tris(acetylacetonato)cobalt(III) in Various Organic Solvents by NMR Relaxation Measurements

NMR relaxation times of the dual-specific nuclei of metal cobalt-59 and ligand methine carbon-13 for tris(2,4-pentanedionato)cobalt(III), which is commonly named as tris(acetylacetonato)cobalt(III), [Co(acac) 3 ], in four organic solvents, acetonitrile, dichloromethane, chloroform, and benzene, have been measured at several temperatures. The rotational correlation times of complex molecules in different solvents, obtained from the NMR relaxation times, can be semi-quantitatively described by the hydrodynamic Debye–Einstein–Stokes (DES) model. However, the slight deviations from the DES model were observed dependent on the kind of solvents, where the effective rotational volume increased in the order of C 6 H 6 ~ CH 3 CN