Determination of the anisotropy of rotational reorientation from ESR line width data

✍ Scribed by Jimmy S. Hwang; M. Habibur Rahman

• Publisher: Elsevier Science
• Year: 1992
• Tongue: English
• Weight: 453 KB
• Volume: 199
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(92)80120-z

✦ Synopsis

An ESR line width study of vanadyl acetylacetonate (abbreviated as VO(acac),) in toluene has been carried out as a function of temperature at 9.5 GHz. It was found that VO(acac), was undergoing anisotropic reorientation with N-2.8 in 1 along a symmetry axis I' = l', where N is the ratio ofR,/R, and R, is the rotational diffusion constant along the molecular Z axis and RL is the rotational dision constant perpendicular to tbe molecular Z axis. The N value obtained was found to be in agreement with N=3.0+ 1 obtained from the allowed-values equation withp,=O.634p,-0.910 withy,= 1 andp,=3.0 and is consistent, within experimental error, with N predicted from the Stokes-Einstein model (N= 2.1). The results of this study could be useful in simulating ESR spoctm of VO(acac)2 in the slow-tumbling region. It can also be used to determine the mtational hydrodynamic radius of the solvated vanadyl complex in neat solution.