Periodicity of Single‐Molecule Magnet Behaviour of Heterotetranuclear Lanthanide Complexes across the Lanthanide Series: A Compendium

Abstract

Acetato-bridged palladium-lanthanide tetranuclear heterometallic complexes of the form [Pd₂ Ln₂ (H₂ O)₂ (CH₃ COO)₁₀ ]⋅2 CH₃ COOH [Ln₂ =Ce₂ (1), Pr₂ (2), Nd₂ (3), Sm₂ (4), Tb₂ (5), Dy₂ (6), Dy_0.2 Y_1.8 (6''), Ho₂ (7), Er₂ (8), Er_0.24 Y_1.7 (8''), Tm₂ (9), Yb₂ (10), Y₂ (11)] were synthesised and characterised by experimental and theoretical techniques. All complexes containing Kramers lanthanide ions [Ln³⁺ =Ce (1), Nd (3), Sm (4), Dy (6), DyY (6''), Er (8), ErY (8''), Yb (10)] showed field-induced slow magnetic relaxation, characteristic of single-molecule magnetism and purely of molecular origin. In contrast, all non-Kramers lanthanide ions [Ln³⁺ =Pr (2), Tb (5), Ho (7), Tm (9), Y³⁺ (11) is diamagnetic and non-lanthanide] did not show any slow magnetic relaxation. The variation in the electronic structure and accompanying consequences across the complexes representing all Kramers and non-Kramers lanthanide ions were investigated. The origin of the magnetic properties and the extent to which the axial donor-acceptor interaction involving the lanthanide ions and an electron-deficient <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>d</mml:mi> <mml:msup><mml:mi>z</mml:mi> <mml:mn>2</mml:mn></mml:msup> </mml:msub> </mml:math> orbital of palladium affects the observed magnetic and electronic properties across the lanthanide series are presented. Unique consistent electronic and magnetic properties of isostructural complexes spanning the lanthanide series with properties dependent on whether the ions are Kramers or non-Kramers are reported.