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: [CoII4(aib)3(aibH)3(NO3)](NO3)4·2.8CH3OH·0.2H2O (1·2.8CH3OH·0.2H2O), {Na2[CoII2(aib)2(N3)4(CH3OH)4]}n (2), [CoII6LaIII(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 (3·3.2CH3CN·5.9H2O), [CoII6PrIII(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 (4·0.25H2O), [CoII6NdIII(aib)6(OH)3(NO3)2.8(CH3OH)4.7(H2O)1.5]·2.7(ClO4)·0.5(NO3)·2.26CH3OH·0.24H2O (5·2.26CH3OH·0.24H2O), [CoII6SmIII(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 (6·0.3H2O), [CoII6EuIII(aib)6(OH)3(NO3)3(CH3OH)4.87(H2O)1.13](ClO4)2.5(NO3)0.5·2.43CH3OH·0.92H2O (7·2.43CH3OH·0.92H2O), [CoII6GdIII(aib)6(OH)3(NO3)2.9(CH3OH)4.9(H2O)1.2]·2.6(ClO4)·0.5(NO3)·2.58CH3OH·0.47H2O (8·2.58CH3OH·0.47H2O), [CoII6TbIII(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 (9·0.3H2O), [CoII6DyIII(aib)6(OH)3(NO3)2.9(CH3OH)4.92(H2O)1.18](ClO4)2.6(NO3)0.5·2.5CH3OH·0.5H2O (10·2.5CH3OH·0.5H2O), [CoII6HoIII(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) (11), [CoII6ErIII(aib)6(OH)4(NO3)2(CH3CN)2.5(H2O)3.5](ClO4)3·CH3CN·0.75H2O (12·CH3CN·0.75H2O), and [CoII6TmIII(aib)6(OH)3(NO3)3(H2O)6]·1.48(ClO4)·1.52(NO3)·3H2O (13·3H2O). Complex 1 describes a distorted tetrahedral metallic cluster, while complex 2 can be considered to be a 2-D coordination polymer. Complexes 3–13 can all be regarded as metallo-cryptand encapsulated lanthanides in which the central lanthanide ion is captivated within a [CoII6] trigonal prism. dc and ac magnetic susceptibility studies have been carried out in the 2–300 K range for complexes 1, 3, 5, 7, 8, 10, 12, and 13, revealing the possibility of single molecule magnetism behavior for complex 10.