A New Family of SO₄^2--Templated 3d-4f High-Nuclearity Clusters: Syntheses, Structures, and Magnetic Properties

Abstract

The precise syntheses of transition–rare-earth metal clusters with desired structures remain a great challenge. Herein, by utilizing SO ₄ ^2- anion released by in-situ decomposition of sodium dodecyl sulfate (SDS) as a template, a series of novel high-nuclearity 3d-4f clusters, formulated as [Ni ₂₄Pr ₂₂(µ ₃-OH) ₃₁(pida) ₂₄(SO ₄) ₄(NO ₃) ₉(CH ₃COO) ₃]·Br ₄·(NO ₃) ₁₁·16H ₂O·25CH ₃OH ( 1, H ₂pida = N-phenyliminodiacetic acid), [Ni ₂₄Nd ₂₂(µ ₃-OH) ₃₁(pida) ₂₄(SO ₄) ₄(NO ₃) ₉(CH ₃COO) ₃]·Br ₄·(NO ₃) ₁₁·14H ₂O·24CH ₃OH ( 2) and [Ni ₂₄Gd ₂₂(µ ₃-OH) ₃₆(bida) ₂₄(SO ₄) ₇(NO ₃) ₃(CH ₃COO) ₃]·(SO ₄)·Br ₄·(NO ₃) ₄·31H ₂O·32CH ₃OH ( 3, H ₂bida = N-benzyliminodiacetic acid), have been successfully isolated. X-ray crystal structure analyses reveal that all the cationic {Ni ₂₄RE ₂₂} cores in 1— 3 possess a ball-like structure with C ₃ v symmetry, and can be viewed as consisting of an inner {RE ₂₂} core and an outer {Ni ₂₄} shell. From 1 and 2 to 3, due to the lanthanide contraction effect, the coordination numbers for rare-earth metal centers in {RE ₂₂} are different, resulting in different number of SO ₄ ^2- and NO ₃ ^- anions to support and stabilize the skeleton structures. Meanwhile, the magnetic properties of complexes 1— 3 were also studied. The result revealed that complexes 1— 3 show antiferromagnetic/ferrimagnetic interactions, and 3 exhibits magneto-caloric effect at ultralow temperatures with a maximum –Δ S _m (magnetic entropy change) value of 33.03 J·kg ⁻¹·K ⁻¹ at 3.0 K and 7 T.

Keywords

Transition−Rare-earth metal / Cluster / Anionic template / Magnetic exchange / Magnetic refrigeration

RIGHTS & PERMISSIONS

2024 SIOC, CAS, Shanghai, & WILEY-VCH GmbH.