Spectroscopic Studies of Metal Complexes with Large Magnetic Anisotropy

Single-molecule magnets are known for their high uniaxial anisotropy and slow magnetic relaxation. Trigonal bipyramidal Ni(II) complex [Ni(Me₆tren)Cl](ClO₄) (1, Me₆tren = tris[2-(dimethylamino)ethyl]amine) has recently been shown to possess large, uniaxial magnetic anisotropy. Direct observation of the transitions between Zeeman-split states in far-IR magnetospectrocopy (FIRMS) gives the axial ZFS parameter D = -110.7(3) cm⁻¹. Hirshfeld surface analysis of the crystal structure of 1 has been performed, revealing the interactions between the cation and anion in a molecule of 1 as well as among the molecules of 1 in crystals. Dy(acac)₃(H2O)₂ (2, acac = acetylacetonate) is a Dy(III) complex with distorted D₄̳d symmetry. It has a high barrier to magnetic relaxation due to its electron. A magnetic peak is identified at 175.5 cm⁻¹ and there is evidence of another peak observed in FIRMS. Multiple phonons are identified and avoided crossings that are characteristic of spin-phonon coupling are evident. Although inelastic neutron scattering (INS) alone cannot identify the magnetic peak in this case, the 0 K spectrum calculated with Vienna Ab-initio Simulation Package (VASP) does agree with experimental INS spectrum at 5 K. Furthermore, the irreducible representation of each phonon was identified. Yb(trensal) [3, H₃trensal = 2,2',2"-tris(salicylideneimino)trimethylamine] is a 7-coordinate, S = 1/2 Yb(III) complex with C₃̳v local symmetry. The far-IR spectrum shows a distinct repetitive pattern that needs further investigation and modelling to explain. If a magnetic peak could be identified via far-IR and/or INS spectroscopy would be helpful in confirming the magnetic peak, but INS cannot be used as a stand-alone identifier in this case. Furthermore, there is disagreement between the calculated and experimental spectra at low frequency and many of the irreducible representations cannot be computed based upon the complexity of the molecule and its interactions. Both 2 and 3 have complicated magnetic properties which are difficult to model and will require additional studies in the future.

Portions of this document were previously published in the Chinese Journal of Inorganic Chemistry.