Enantiopure Benzamidinate/Cyclooctatetraene Complexes of the Rare-Earth Elements: Synthesis, Structure, and Magnetism

摘要

Novel chiral rare-earth half sandwich complexes containing the chiral amidinate ligand, (S,S)-N,N'-bis(1-phenylethyl)benzamidinate ((S)-PEBA) or the tBu analogue (S,S)-N,N'-bis(1-phenylethyl) pivalamidinate ((S)-PETA) and the cyclooctatetraene dianion (C8H8)(2-) (COT) were synthesized. All complexes were fully characterized and the solid state structures were established by single-crystal crystallography. Magnetic property measurements indicated that the complex [{(S)PETA}Er(COT)(THF)] is a typical field-induced single-molecule magnet (SMM), of which the magnetic properties are in reasonable agreement with high-level quantum chemical calculations. Due to predominantly electrostatic ligand field effects, the relativistic J = 15/2 ground manifold of Er(III) is split into 8 Kramers doublets spanning a range of similar to 500 cm(-1), representable by means of higher order spin tensor operators. According to the quantum chemical calculations as well as from analysis of the experimental data, the magnetic relaxation pathways in these complexes are most likely to be of vibrational rather than electronic origin.