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The Quest for Optimal 3 d Orbital Splitting in Tetrahedral Cobalt Single‐Molecule Magnets Featuring Colossal Anisotropy and Hysteresis
Author(s) -
Legendre Christina M.,
DamgaardMøller Emil,
Overgaard Jacob,
Stalke Dietmar
Publication year - 2021
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.202100465
Subject(s) - magnetic anisotropy , chemistry , atomic orbital , anisotropy , condensed matter physics , magnet , magnetization , ab initio quantum chemistry methods , ab initio , tetrahedron , hysteresis , relaxation (psychology) , magnetic field , crystallography , molecule , physics , optics , quantum mechanics , organic chemistry , electron , psychology , social psychology
Abstract Only a few four‐coordinated Co 2+ ‐complexes show single‐molecule magnet (SMM) properties without an applied dc field. Common for those is a large magnetic anisotropy generated by the close proximity of the d x yand dx 2 - y 2orbitals. This type of magnetic anisotropy is strongly correlated with the extent of structural distortion from ideal tetrahedral towards linear coordination. Quantification of the governing magneto‐structural correlations is hence crucial for the development of better SMMs. For this purpose, we synthesized and analyzed four significantly distorted tetrahedral cobalt complexes that exhibit extremely large magnetic anisotropies and slow relaxation of magnetization in zero field. The N−Co−N bite angles vary from 70.8 to 72.7°, and magnetic measurements show strong anisotropy with D ‐values in the range from - 75 to - 114 cm −1 . Ab initio calculations supported the experimental results and highlighted a significant increase of D up to - 141 cm −1 , correlated with the reduction of the energy difference between the d x yand dx 2 - y 2orbitals. Based on these magneto‐structural correlations and in contrast to the current assumption that the smaller bite angle is the better, we predict that with an ideal bite angle in the range from 76–78° in distorted Co(N 2 R) 2 complexes, the energy difference between the two important d‐orbitals is at a minimum and hence the magnetic anisotropy is maximized.