Magnetic Interactions in a Series of Homodinuclear Lanthanide Complexes

A series
of seven isostructural homodinuclear lanthanide complexes are reported.
The magnetic properties (ac and dc SQUID measurements) are discussed
on the basis of the X-ray structural properties which show that the
two lanthanide sites are structurally different. MCD spectroscopy
of the dysprosium­(III) and neodymium­(III) complexes ([DyIII2(L)­(OAc)4]+ and [NdIII2(L)­(OAc)4]+) allowed us to thoroughly
analyze the ligand field, and high-frequency EPR spectroscopy of the
gadolinium­(III) species ([GdIII2(L)­(OAc)4]+) showed the importance of dipolar coupling in
these systems. An extensive quantum-chemical analysis of the dysprosium­(III)
complex ([DyIII2(L)­(OAc)4]+), involving an ab initio (CASSCF) wave function, explicit spin–orbit
coupling (RASSI-SO), and a ligand field analysis (Lines model and
Stevens operators), is in full agreement with all experimental data
(SQUID, HF-EPR, MCD) and specifically allowed us to accurately simulate
the experimental χT versus T data, which therefore allowed us to establish a qualitative model
for all relaxation pathways.