Premium
Magnetic‐Field‐Dependent Electronic Relaxation of Gd 3+ in Aqueous Solutions of the Complexes [Gd(H 2 O) 8 ] 3+ , [Gd(propane‐1,3‐diamine‐ N , N , N ′, N ′‐tetraacetate)(H 2 O) 2 ] − , and [Gd( N , N ′‐bis[( N ‐methylcarbamoyl)methyl]‐3‐azapentane‐1,5‐diamine‐3, N , N ′‐triacetate)(H 2 O)] of interest in magnetic‐resonance imaging
Author(s) -
Powell D. Hugh,
Merbach André E.,
González Gabriel,
Brücher Ernö,
Micskei Károly,
Ottaviani M. Francesca,
Köhler Klaus,
Von Zelewsky Alex,
Grinberg Oleg Ya.,
Lebedev Yakob S.
Publication year - 1993
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19930760524
Subject(s) - chemistry , relaxation (psychology) , zero field splitting , field (mathematics) , magnetic field , condensed matter physics , nuclear magnetic resonance , atomic physics , physics , quantum mechanics , electron , psychology , social psychology , mathematics , pure mathematics , spin polarization
EPR Spectra have been measured for aqueous solutions of a series of Gd 3+ complexes at variable temperature and a range of magnetic fields; S‐band (0.14 T), X‐band (0.34 T), Q‐band (1.2 T), and 2‐mm‐band (5.0 T). The major contribution to the observed line widths is magnetic‐field‐dependent and is interpreted as being due to the modulation of the zero‐field splitting produced by distortion of the complexes from perfect symmetry. The transverse and longitudinal relaxation matrices for an 8 S ion with such an interaction have been calculated using Redfield theory with vector‐coupling methods, and diagonalised numerically to obtain relaxation rates and intensities for the degenerate transitions which contribute to the multiplet. The observed line width, which is inversely proportional to the magnetic field at low temperatures, is best described by the intensity‐weighted mean transverse relaxation time for the four transitions with non‐zero intensity. A least‐squares fit of the data yields the square of the zero‐field splitting tensor, Δ 2 , and a correlation time, τ v , with activation energy, E v . The physical significance of these parameters and the extent of validity of the theoretical approach are considered. The parameters are used to predict the magnetic‐field dependence of the longitudinal and transverse electronic relaxation times, which are discussed in the context of their relevance to 1 H‐NMR relaxivity.