Artificial Amino Acids in Nickel(II) and Nickel(II)/Lanthanide(III) Chemistry

The synthesis and magnetic properties of five new homo- and heterometallic nickel(II) complexes containing artificial amino acids are reported: [Ni4(aib)3(aibH)3(NO3)](NO3)4·3.05MeOH (1·3.05MeOH), [Ni6La(aib)12](NO3)3·5.5H2O (2·5.5H2O), [Ni6Pr(aib)12](NO3)3·5.5H2O (3·5.5H2O), [Ni5(OH)2(l-aba)4(OAc)4]·0.4EtOH·0.3H2O 6(4·0.4EtOH·0.3H2O), and [Ni6La(l-aba)12][La2(NO3)9] (5; aibH = 2-aminoisobutyric acid; l-abaH = l-2-aminobutyric acid). Complexes 1 and 4 describe trigonal-pyramidal and square-based pyramidal metallic clusters, respectively, while complexes 2, 3, and 5 can be considered to be metallocryptand-encapsulated lanthanides. Complexes 4 and 5 are chiral and crystallize in the space groups I222 and P213, respectively. Direct-current magnetic susceptibility studies in the 2–300 K range for all complexes reveal the presence of dominant antiferromagnetic exchange interactions, leading to small or diamagnetic ground states