Role of the Diamagnetic Zinc(II) Ion in Determining the Electronic Structure of Lanthanide Single-Ion Magnets.
Four complexes containing DyIIIand PrIIIions and their LnIII-ZnIIanalogs have been synthesized in order to study the influence that a diamagnetic ZnIIion has on the electronic structure and hence, the magnetic properties of the DyIIIand PrIIIsingle ions. Single-crystal X-ray diffraction revealed the molecular structures as [DyIII(HL)2(NO3)3] (1), [PrIII(HL)2(NO3)3] (2), [ZnIIDyIII(L)2(CH3CO2)(NO3)2] (3) and [ZnII2PrIII(L)2(CH3CO2)4(NO3)] (4) (where HL=2-methoxy-6-[(E)-phenyliminomethyl]phenol). The dc and ac magnetic data were collected for all four complexes. Compounds 1 and 3 display frequency dependent out-of-phase susceptibility signals (χM"), which is a characteristic signature for a single-molecule magnet (SMM). Although 1 and 3 are chemically similar, a fivefold increase in the anisotropic barrier (Ueff) is observed experimentally for 3 (83 cm-1), compared to 1 (16 cm-1). To rationalize the larger anisotropic barrier (1 vs. 3), detailed ab initio calculations were performed. Although the ground state Kramer's doublet in both 1 and 3 are axial in nature (gzz=19.443 for 1 and 18.82 for 3), a significant difference in the energy gap (Ueff) between the ground and first excited Kramer's doublet is calculated. This energy gap is governed by the electrostatic repulsion between the DyIIIion and the additional charge density found for the phenoxo bridging ligand in 3. This extra charge density was found to be a consequence of the presence of the diamagnetic ZnIIion present in the complex. To explore the influence of diamagnetic ions on the magnetic properties further, previously reported and structurally related Zn-DyIIIcomplexes were analyzed. These structurally analogous complexes unambiguously suggest that the electrostatic repulsion is found to be maximal when the Zn-O-Dy-O dihedral angle is small, which is an ideal condition to maximize the anisotropic barrier in DyIIIcomplexes.
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400076, India.
Apoorva
A
Upadhyay
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400076, India.
Chinmoy
C
Das
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400076, India.
Shefali
S
Vaidya
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400076, India.
Saurabh Kumar
SK
Singh
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400076, India.
Tulika
T
Gupta
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400076, India.
Ranajit
R
Mondol
School of Science and the Environment, Division of Chemistry, Manchester Metropolitan University, Manchester, M15 6BH, UK.
Stuart K
SK
Langley
School of Chemistry, Monash University, Clayton, 3800, Victoria, Australia.
Keith S
KS
Murray
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400076, India.
Gopalan
http://orcid.org/0000-0001-6133-3026
G
Rajaraman
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400076, India.
Maheswaran
http://orcid.org/0000-0002-9012-743X
M
Shanmugam
ab initio calculations; clusters; dysprosium; magnetic properties; praseodymium; single-ion magnets