2-Aminoisobutyric Acid in Co(II) and Co(II)/Ln(III) Chemistry: Homometallic and Heterometallic Clusters

The synthesis and magnetic properties of 13 new homo- and heterometallic Co­(II) complexes containing the artificial amino acid 2-amino-isobutyric acid, aibH, are reported: [Co^II₄(aib)₃(aibH)₃(NO₃)]­(NO₃)₄·2.8CH₃OH·0.2H₂O (<b>1</b>·2.8CH₃OH·0.2H₂O), {Na₂[Co^II₂(aib)₂(N₃)₄(CH₃OH)₄]}_<i>n</i> (<b>2</b>), [Co^II₆La^III(aib)₆(OH)₃(NO₃)₂(H₂O)₄(CH₃CN)₂]·0.5­[La­(NO₃)₆]·0.75­(ClO₄)·1.75­(NO₃)·3.2CH₃CN·5.9H₂O (<b>3</b>·3.2CH₃CN·5.9H₂O), [Co^II₆Pr^III(aib)₆(OH)₃(NO₃)₃(CH₃CN)₆]·[Pr­(NO₃)₅]·0.41­[Pr­(NO₃)₃(ClO₄)_0.5(H₂O)_1.5]·0.59­[Co­(NO₃)₃(H₂O)]·0.2­(ClO₄)·0.25H₂O (<b>4</b>·0.25H₂O), [Co^II₆Nd^III(aib)₆(OH)₃(NO₃)_2.8(CH₃OH)_4.7(H₂O)_1.5]·2.7­(ClO₄)·0.5­(NO₃)·2.26CH₃OH·0.24H₂O (<b>5</b>·2.26CH₃OH·0.24H₂O), [Co^II₆Sm^III(aib)₆(OH)₃(NO₃)₃(CH₃CN)₆]·[Sm­(NO₃)₅]·0.44­[Sm­(NO₃)₃(ClO₄)_0.5(H₂O)_1.5]·0.56­[Co­(NO₃)₃(H₂O)]·0.22­(ClO₄)·0.3H₂O (<b>6</b>·0.3H₂O), [Co^II₆Eu^III(aib)₆(OH)₃(NO₃)₃(CH₃OH)_4.87(H₂O)_1.13]­(ClO₄)_2.5(NO₃)_0.5·2.43CH₃OH·0.92H₂O (<b>7</b>·2.43CH₃OH·0.92H₂O), [Co^II₆Gd^III(aib)₆(OH)₃(NO₃)_2.9(CH₃OH)_4.9(H₂O)_1.2]·2.6­(ClO₄)·0.5­(NO₃)·2.58CH₃OH·0.47H₂O (<b>8</b>·2.58CH₃OH·0.47H₂O), [Co^II₆Tb^III(aib)₆(OH)₃(NO₃)₃(CH₃CN)₆]·[Tb­(NO₃)₅]·0.034­[Tb­(NO₃)₃(ClO₄)_0.5(H₂O)_0.5]·0.656­[Co­(NO₃)₃(H₂O)]·0.343­(ClO₄)·0.3H₂O (<b>9</b>·0.3H₂O), [Co^II₆Dy^III(aib)₆(OH)₃(NO₃)_2.9(CH₃OH)_4.92(H₂O)_1.18]­(ClO₄)_2.6(NO₃)_0.5·2.5CH₃OH·0.5H₂O (<b>10</b>·2.5CH₃OH·0.5H₂O), [Co^II₆Ho^III(aib)₆(OH)₃(NO₃)₃(CH₃CN)₆]·0.27­[Ho­(NO₃)₃(ClO₄)_0.35(H₂O)_0.15]·0.656­[Co­(NO₃)₃(H₂O)]·0.171­(ClO₄) (<b>11</b>), [Co^II₆Er^III(aib)₆(OH)₄(NO₃)₂(CH₃CN)_2.5(H₂O)_3.5]­(ClO₄)₃·CH₃CN·0.75H₂O (<b>12</b>·CH₃CN·0.75H₂O), and [Co^II₆Tm^III(aib)₆(OH)₃(NO₃)₃(H₂O)₆]·1.48­(ClO₄)·1.52­(NO₃)·3H₂O (<b>13</b>·3H₂O). Complex <b>1</b> describes a distorted tetrahedral metallic cluster, while complex <b>2</b> can be considered to be a 2-D coordination polymer. Complexes <b>3</b>–<b>13</b> can all be regarded as metallo-cryptand encapsulated lanthanides in which the central lanthanide ion is captivated within a [Co^II₆] trigonal prism. dc and ac magnetic susceptibility studies have been carried out in the 2–300 K range for complexes <b>1</b>, <b>3</b>, <b>5</b>, <b>7</b>, <b>8</b>, <b>10</b>,<b> 12</b>, and <b>13</b>, revealing the possibility of single molecule magnetism behavior for complex <b>10