Influence of Tuned Linker Functionality on Modulation
of Magnetic Properties and Relaxation Dynamics in a Family of Six
Isotypic Ln2 (Ln = Dy and Gd) Complexes
posted on 2016-10-11, 14:18authored bySoumya Mukherjee, Jingjing Lu, Gunasekaran Velmurugan, Shweta Singh, Gopalan Rajaraman, Jinkui Tang, Sujit K. Ghosh
A coordination
complex family comprising of six new dinuclear symmetric lanthanide
complexes, namely, [Ln2(Lx)2(L′)2(CH3OH)2]·yG (H2Lx: three related
yet distinct Schiff-base linkers; x = 1–3,
according to the nomenclature of the Schiff-base linker employed herein.
HL′: 2,6-dimethoxyphenol. yG refers to crystallographically
assigned guest solvent species in the respective complexes; y = number of solvent molecules; LnIII = Dy/Gd)
were isolated employing a mixed-ligand strategy stemming out of a
strategic variation of the functionalities introduced among the constituent
Schiff-base linkers. The purposeful introduction of three diverse
auxiliary groups with delicate differences in their electrostatic
natures affects the local anisotropy and magnetic coupling of LnIII ion-environment in the ensuing Ln2 dinuclear
complexes, consequentially resulting into distinctly dynamical magnetic
behaviors among the investigated new-fangled family of isotypic Ln2 complexes. Among the entire family, subtle alterations in
the chemical moieties render two of the Dy2 analogues to
behave as single molecule magnets, while the other Dy2 congener
merely exhibits slow relaxation of the magnetization. The current
observation marks one of the rare paradigms, wherein magnetic behavior
modulation was achieved by virtue of the omnipresent influence of
subtly tuned linker functionalities among the constituent motifs of
the lanthanide nanomagnets. To rationalize the observed difference
in the magnetic coupling, density functional theory and ab initio
calculations (CASSCF/RASSI-SO/POLY_ANISO) were performed on all six
complexes. Subtle difference in the bond angles leads to difference
in the J values observed for Gd2 complexes,
while difference in the tunnel splitting associated with the structural
alterations lead to variation in the magnetization blockade in the
Dy2 complexes.