Magnetic behavior of the novel pentagonal-bipyramidal erbium() complex (EtNH)[Er(HDAPS)Cl]: high-frequency EPR study and crystal-field analysis

We report the synthesis, crystal structure and magnetic properties of the new heptacoordinated mononuclear erbium( iii ) complex (Et 3 NH)[Er(H 2 DAPS)Cl 2 ] (H 4 DAPS = 2,6-diacetylpyridine bis-(salicylhydrazone)) ( 1 ). The coordination polyhedron around the Er( iii ) ion features a slightly distorted pentagonal bipyramid formed by the pentagonal N 3 O 2 chelate ring of the H 2 DAPS ligand in the equatorial plane and two apical chloride ligands. Detailed high-frequency/high-field electron paramagnetic resonance (HF-EPR) studies of 1 result in the precise determination of the crystal field (CF) splitting energies (0, 290 and 460 GHz) and effective g -values of the three lowest Kramers doublets (KDs) of the Er( iii ) ion. The obtained HF-EPR data are in good agreement with the results from CF analysis for the Er( iii ) ion based on the simulation of the dc magnetic data of 1 . The results from dynamic susceptibility measurements indicate that there is no slow relaxation of magnetisation behaviour. This observation is discussed in terms of the electronic structure of 1 obtained from experimental and theoretical results. We precisely quantified the zero field splittings of the lowest Kramers doublets for a novel Er( iii ) mononuclear complex by HF-EPR.