Lanthanide Triangles Sandwiched by Tetranuclear Copper Complexes Afford a Family of Hendecanuclear Heterometallic Complexes [Ln^III₃Cu^II₈] (Ln = La–Lu): Synthesis and Magnetostructural Studies

Abstract

Reaction in ethanol of 3-hydroxymethylen-5-methylsalicylaldoxime (<b>H</b>_<b>3</b><b>L</b>) with CuCl₂·2H₂O and LnCl₃·<i>x</i>H₂O [Ln = La (<b>1</b>), Ce (<b>2</b>), Pr (<b>3</b>), Nd (<b>4</b>), Eu (<b>5</b>), Gd (<b>6</b>), Tb (<b>7</b>), Dy (<b>8</b>), Er (<b>9</b>), Yb (<b>10</b>), Lu (<b>11</b>), Ho (<b>12</b>)] allowed the synthesis of a family of hendecanuclear heterometallic copper­(II)–lanthanide­(III) clusters with general formula [Ln^III₃Cu^II₈(<b>HL</b>)₆(μ₄-O)₂Cl₆(H₂O)₈]­Cl₃ (<b>1</b>–<b>12</b>). According to the single-crystal X-ray diffraction investigation, the complexes are isomorphous and crystallize in the trigonal <i>R</i>32 group. The hendecanuclear cluster is formed by two tetrahedral μ₄-oxo {Cu₄} clusters assembled by three lanthanide ions sandwiched in between. Along the family, the separation between the {Cu₄} moieties increases linearly from Lu to La in good correlation with ionic radius of the lanthanide ions. A comparative analysis of the magnetic data for the lanthanum (<b>1</b>) and lutetium (<b>11</b>) compounds shows the presence of ferromagnetic and antiferromagnetic interactions within the μ₄-oxo {Cu₄} moieties. For the gadolinium (<b>6</b>) and terbium (<b>7</b>) compounds, the magnetic interactions between the lanthanide and the copper ions are found to be ferromagnetic. The dysprosium (<b>8</b>) compound exhibits single-molecule magnet behavior