Licentiate Thesis: Zero-Field Splitting in Gd(III) complexes
Thursday 07 January 2016
to 12:00 at
Shehryar Khan (Stockholm University, Department of Physics)
The prime objective of contrast agents in Magnetic Resonance Imaging(MRI) is to accelerate
the relaxation rate of the solvent water protons in the surrounding tissue. Paramagnetic
relaxation originates from dipole-dipole interactions between the nuclear spins and the
fluctuating magnetic field induced by unpaired electrons. Currently, Gadolinium(III) chelates
are the most widely used contrast agents in MRI, and therefore it is incumbent to extend the
fundamental theoretical understanding of parameters that drive the relaxation mechanism in
these complexes. Traditionally, the Solomon-Bloembergen-Morgan equations have been
utilized to describe relaxation times in terms, primarily of the Zeeman interaction, which is
the splitting of degenerate energy levels due to an applied magnetic field. However, in
compounds such as Gadolinium(III) complexes with total electron spins higher than 1 (in this
case S=7/2) other interactions such as the Zero-Field Splitting(ZFS) play a significant role.
ZFS is the splitting of degenerate energy levels in the absence of an external magnetic field.
For this purpose, the current research delves into an understanding of the relaxation process,
focusing on ZFS in various complexes of interest, using quantum chemical methods as well as
molecular dynamic simulations.