Proton spin relaxation in solutions of the complex tris(acetylacetonato)chromium(III)
Resource
Journal of Magnetic Resonance (1969) 73 (2): 277-286
Journal
Journal of Magnetic Resonance (1969)
Pages
277-286
Date Issued
1987
Date
1987
Author(s)
Wang, Pei-Lein
Lee, Jing-Huei
Huang, Shiou-Mei
Hwang, Lian-Pin
Abstract
Field-dependent proton spin-lattice and spin-spin relaxation times have been measured for CH3 in dilute chloroform solutions of tris(acetylacetonato)chromium(III) (Cr(acac)3) complex over a temperature range of 253-323 K and a proton resonance frequency range of 10-90 MHz. The results have been interpreted in terms of scalar, dipolar, and scalar-dipolar cross relaxation. The effects of methyl group internal rotation are included. In particular, coupled modulation of ESR relaxation and electron-nuclear dipolar relaxation by reorientational motion of the complex is treated. The reorientational correlation times of the complex obtained are consistent with those measured from 13C T1 in the analogous diamagnetic Co(III) complex, but significant deviations from the Stokes-Einstein relation with the consideration of microviscosity are observed. Solvation of the complex with chloroform is further identified from chemical-shift measurements and is utilized to interpret the results. The proton T, data are discussed in terms of their relevance to the zero-field-splitting interaction and to the contribution of scalar-dipolar cross relaxation. © 1987.
Type
journal article
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