Amending the Anisotropy Barrier and Luminescence Behavior of Heterometallic Trinuclear Linear [M^IILn^IIIM^II] (Ln^III=Gd, Tb, Dy; M^II=Mg/Zn) Complexes by Change from Divalent Paramagnetic to Diamagnetic Metal Ions

Abstract

The sequential reaction of a multisite coordinating compartmental ligand [2-(2-hydroxy-3-(hydroxymethyl)-5-methylbenzylideneamino)-2-methylpropane-1,3-diol] (LH4 ) with appropriate lanthanide salts followed by the addition of [Mg(NO3 )2 ]⋅6 H2 O or [Zn(NO3 )2 ]⋅6 H2 O in a 4:1:2 stoichiometric ratio in the presence of triethylamine affords a series of isostructural heterometallic trinuclear complexes containing [Mg2 Ln](3+) (Ln=Dy, Gd, and Tb) and [Zn2 Ln](3+) (Ln=Dy, Gd, and Tb) cores. The formation of these complexes is demonstrated by X-ray crystallography as well as ESI-MS spectra. All complexes are isostructural possessing a linear trimetallic core with a central lanthanide ion. The comprehensive studies discussed involve the synthesis, structure, magnetism, and photophysical properties on this family of trinuclear [Mg2 Ln](3+) and [Zn2 Ln](3+) heterometallic complexes. [Mg2 Dy](3+) and [Zn2 Dy](3+) show slow relaxation of the magnetization below 12 K under zero applied direct current (dc) field, but without reaching a neat maximum, which is due to the overlapping with a faster quantum tunneling relaxation mediated through dipole-dipole and hyperfine interactions. Under a small applied dc field of 1000 Oe, the quantum tunneling is almost suppressed and temperature and frequency dependent peaks are observed, thus confirming the single-molecule magnet behavior of complexes [Mg2 Dy](3+) and [Zn2 Dy](3+) .

Decanuclear Ln10 Wheels and Vertex‐Shared Spirocyclic Ln5 Cores: Synthesis, Structure, SMM Behavior, and MCE Properties

“…Recently, we have been experimenting with various types of ligands for the purpose of knowing their discriminatory capability in terms of directing homonuclear lanthanide assemblies versus heteronuclear 3d/4f complexes 11. Thus, the ligands, 2‐(hydroxymethyl)‐6‐carbaldehyde‐4‐methylphenol ( C2 ) and the Schiff base derivative (2‐(2‐hydroxy‐3‐(hydroxymethyl)‐5‐methylbenzylideneamino)‐2‐methylpropane1,3‐diol) afforded pentanuclear M 4 Ln11a, b and M 2 Ln11c, d, e derivatives respectively (Scheme ).…”

“… a) Pentanuclear M 4 Ln11a, b and b) trinuclear M 2 Ln11c, d, e derived from C2 and its Schiff base derivative, respectively. …”

Modelling spin Hamiltonian parameters of molecular nanomagnets

“…178 We have also performed extensive calculations on {Dy-OH} models with varying coordination number around Dy III and number of coordinated -OH ligands. 181 Experiments clearly revealed Zn II -Dy III -Zn II unit as an origin of magnetic relaxation rather than intermolecular interactions/long range ordering.…”

Heterometallic 3d–4f Complexes as Single‐Molecule Magnets

“…Counterintuitively, a diamagnetic metal ion linked to the lanthanide ion by a single atom bridge (such as oxide ion) seems to enhance the binding capacity of the oxide and help in increasing the energy gap between the ground the excited states of the lanthanide ions leading to more favorable magnetic properties –. Accordingly, isostructural, linear [Mg II 2 Ln III ] 3+ [Ln III =Gd III ( 167 ), Tb III ( 168 ) and Dy III ( 169 )] and [Zn II 2 Ln III ] 3+ (Ln III =Gd III ( 170 ), Tb III ( 171 ) and Dy III ( 172 )] complexes, analogous to the previously discussed systems, [Co II 2 Ln III ] 3+ and [Ni II 2 Ln III ] 3+ (vide supra) were synthesized by employing [2‐(2‐hydroxy‐3‐(hydroxymethyl)‐5‐methylbenzylideneamino)‐2‐methylpropane‐1,3‐diol] (L 16 H 4 ) . The Mg II or Zn II ions are present in the terminal positions and have a coordination environment comprising of four O atoms and two N atoms in a distorted octahedral geometry.…”