Employment of a New Tripodal Ligand for the Synthesis of Cobalt(II/III), Nickel(II), and Copper(II) Clusters: Magnetic, Optical, and Thermal Properties
2012-10-01T00:00:00Z (GMT) by
The employment of 2-(β-naphthalideneamino)-2-(hydroxymethyl)-1-propanol (LH3) in cobalt, nickel, and copper chemistry has led to the isolation of five new metallic complexes with interesting magnetic properties. More specifically, the reaction of Co(OAc)2·4H2O with LH3 in MeOH in the presence of NEt3 under solvothermal conditions forms the complex [CoIII2CoII3(L)2(LH)2(L′)(OAc)]·8.5MeOH (1·8.5MeOH; L′ = monoanion of 2-hydroxy-1-naphthaldehyde), while in nickel chemistry, a similar reaction of Ni(OAc)2·6H2O with LH3 in MeCN in the presence of NEt3 under high pressure/temperature forms the complex [NiII(LH2)2]·2MeCN (2·2MeCN). Repeating the same reaction in MeOH and switching from Ni(OAc)2·4H2O to NiSO4·4H2O produces the complex [NiII4(HL)3(OMe)(MeOH)3](SO4)0.5·2MeOH (3·2MeOH) under solvothermal conditions. Furthermore, in copper chemistry, the reaction of Cu2(OAc)4·2H2O with LH3 in the presence of NEt3 in MeOH under solvothermal conditions affords the complex [CuII4(LH)4] (4), while the same reaction under ambient temperature and pressure conditions forms [CuII4(LH)4] ·3.5MeOH·2.25H2O (5·3.5MeOH·2.25H2O). Complex 1 is a mixed-valent [CoIII2CoII3] complex, consisting of three edge-sharing [Co3] triangles. Complex 2 is a nickel(II) monomer in which the central metal is found in an octahedral geometry, while complex 3 describes a [NiII4] cubane. Complexes 4 and 5 may be considered as structural isomers because they possess the same formulas but different topologies: 4 describes a highly distorted [CuII4(OR)4]4+ eight-membered ring, while 5 consists of a distorted [CuII4(μ3-OR)4]4+ cubane. In addition, 5 can be converted to 4 in excellent yield under solvothermal conditions. Direct-current magnetic susceptibility studies have been carried out in the 5–300 K range for complexes 1 and 3–5, revealing the possibility of a high-spin ground state for 1, an S = 4 ground state for 2, and diamagnetic ground states for 4 and 5.