Syntheses, characterization, and magneto-structural analyses in 1,3-acetato-bridged tetracopper(ii) and mu(1,3)- and mu(1,1,3)-acetato-bridged pentanickel(ii) clusters

Abstract

Two pentanuclear NiII complexes, [Ni-5(L-1)(2)(CH3COO)(6)(OH)(2)(MeOH)(2)]- (1) and [Ni-5(L-2)(2)(CH3COO)(6)(OH)(2)(H2O)(2)] (2), and one tetranuclear CuII complex, [Cu-4(L-3)(2)(CH3COO)(4)(O)] (3), have been synthesized from phenol-based end-off compartmental ligands HL1 to HL3 {HL1 = 2,6-bis[ethyl(2-thienyl)iminomethyl]-4-tert-butylphenol; HL2 = 2,6-bis[ethyl(2-thienyl)iminomethyl]-4-chlorophenol and HL3 = 2,6-bis[ethyl(2-thienyl)iminomethyl]-4-methylphenol, respectively}. The complexes have been structurally characterized and their magnetic properties have been investigated within the temperature range 2.2-300 K. Complexes 1 and 2 comprise two dinuclear [Ni2L2] units linked to a central Ni ion by bridging 3-hydroxo groups. The cluster is stabilized by syn-syn-1,3-bridging and 1,1,3-bridging acetate anions. The structural analysis of 3 revealed two crystallographically independent complexes that consisted of a tetrahedron of CuII ions connected to a central 4-oxo species and further bridged by four acetate groups along four of the six edges of the Cu-4 core. The other two edges are occupied by -phenoxo bridges from the deprotonated L3 ligand. Magnetic investigations revealed both ferromagnetic and antiferromagnetic interactions in 1 and 2 with single-ion zero-field splitting of magnitude comparable to exchange interactions, and strong antiferromagnetic interactions in 3.