paper

The Relevance of Non-axiality and Low-lying Excited States for Slow Magnetic Relaxation in Pentagonal-bipyramidal Erbium(III) Complexes Probed by High-frequency EPR

arXiv:2504.21170 · doi:10.1002/chem.202500369

Abstract

High-frequency/high-field electron paramagnetic resonance studies on a series of seven-coordinate pentagonal-bipyramidal (PBP) erbium(III) complexes Er(DAPMBH/H $_{2}$ DAPS)X (H $_{2}$ DAPMBH = 2,6-diacetylpyridine bis-4-methoxy benzoylhydrazone, H $_{4}$ DAPS = 2,6-diacetylpyridine bis-(salicylhydrazone)) demonstrate the effects of different apical ligands (X = (H $_{2}$ O)Cl (1), (CH $_{3}$ OH)N $_{3}$ (2), Cl $_{2}$ (3)) on the local magnetic anisotropy of the central Er(III) ions. In particular, we report direct experimental determination of the effective $g$ -values and zero field splittings of the energetically low-lying Kramers doublets. Our quantitative determination of the magnetic anisotropy highlights the relevance of an axial $g$ -tensor for SMM behaviour and suggests that fast magnetic relaxation is mainly driven by a thermally assisted quantum tunnelling process via low-lying excited states.

9 pages, 7 figures