Bringing an important macrocycle into a polyoxometalate matrix: synthesis, crystal structure, spectroscopy and electrochemistry of [CoIII(transdiene)(Cl)2]2[Mo6O19], [NiII(transdiene)][W6O19]·DMSO·DCM and [ZnII(transdsiene)(Cl)]2[W6O19]

Abstract

Three polyoxometalate based ion pair solids (1–3), in which Co^III (d⁶), Ni^II (d⁸) and Zn^II (d¹⁰) complexes of a tetra-aza macrocycle, Me₆-trans-[14]-diene act as the cationic moieties, have been reported. The title complexes, formulated as [Co (C₁₆H₃₂N₄)(Cl)₂]₂[Mo₆O₁₉] (1), [Ni(C₁₆H₃₂N₄)][W₆O₁₉]·DMSO·DCM (2) and [Zn(C₁₆H₃₂N₄)(Cl)]₂[W₆O₁₉] (3) (C₁₆H₃₂N₄ = Me₆-trans-[14]-diene), are the first crystallographic paradigms where transition metal complexes of a Schiff condensed tetra-aza macrocycle have been associated with an isopolyanion, [M₆O₁₉]²⁻ (M = Mo(VI) and W(VI)). Compounds 1–3 have been characterized through routine spectroscopic analyses including elemental analysis and their structures have been unambiguously determined through single crystal X-ray crystallography. The molecules of compound 1 assemble obeying P (#2) space symmetry, whereas those of compounds 2 and 3 follow the higher symmetrical ensemble P2₁/c (#14). The ESR spectral studies of compounds 1–3 have revealed their diamagnetic (low-spin) nature. The last part of this article describes the electrochemical properties of the title compounds.