E. Strandberg et Po. Westlund, Paramagnetic proton nuclear spin relaxation theory of low-symmetry complexes for electron spin quantum number S = 5/2, J MAGN RES, 137(2), 1999, pp. 333-344
A generalization of the modified Solomon-Bloembergen-Morgan (MSBM) equation
s has been derived in order to describe paramagnetic relaxation enhancement
(PRE) of paramagnetic complexes characterized by both a transient (Delta(t
)(ZFS)) and a static (Delta(s)(ZFS)) zero-field splitting (ZFS) interaction
. The new theory includes the effects of static ZFS, hyperfine coupling, an
d angular dependence and is presented for the case of electron spin quantum
number S = 5/2, for example, Mn(II) and Fe(III) complexes. The model gives
the difference from MSBM theory in terms of a correction term delta which
is given in closed analytical form. The theory may be important in analyzin
g the PRE of proton spin-lattice relaxation dispersion measurements (NMRD p
rofiles) of low-symmetry aqua-metal complexes which are likely to be formed
upon transition metal ions associated with charged molecular surfaces of b
iomacromolecules. The theory has been implemented with a computer program w
hich calculates solvent water proton T-1 NMRD profiles using both MSBM and
the new theory. (C) 1999 Academic Press.