Quadruple bridged-carbonate supported dodecanuclear [Ni8Ca4] coordination cluster

Abstract

A dodecanuclear [Ni₈Ca₄] compound, [Ni₈(L)₈Ca₄(CO₃)₄(dmf)_5.5(H₂O)_6.5]·20H₂O (1) (dmf = dimethylformamide) has been prepared by the reaction of a polydentate ligand (E)-2-(2-hydroxy-3-methoxybenzylidene)amino-4-nitrophenol (H₂L) with NiCl₂·6H₂O, CaCl₂·2H₂O and Na₂CO₃ in dmf at room temperature. The solid-state molecular structure of compound 1 was determined by single crystal X-ray crystallography. Compound 1 consists of a [Ni₈Ca₄] coordination wheel with eight Ni^II ions and four Ca^II ions assembled by four carbonates and eight deprotonated L²⁻ ligands. The asymmetric unit of compound 1 contains two Ni^II ions, one Ca^II ion, two coordinated deprotonated Schiff base ligands (L²⁻), one coordinated carbonate ion, two coordinated dmf molecules (one with occupancy of 0.36), two coordinated water molecules (one with occupancy 0.64). Compound 1 is the largest coordination cluster containing Ni^II and Ca^II ions reported to date. The magnetic properties of 1 show the presence of predominant antiferromagnetic interactions. The magnetic susceptibility and isothermal magnetization data can be well reproduced with: g = 2.145(1), J₁ = 2.93(4) cm⁻¹, J₂ = −0.41(2) cm⁻¹ and J₃ = −5.66(4) cm⁻¹.