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]

Three polyoxometalate based ion pair solids (1-3), in which Co-III (d(6)), NiII (d(8)) and Zn-II (d(10)) complexes of a tetra-aza macrocycle, Me-6-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]center dot DMSO center dot DCM (2) and [Zn(C16H32N4)(Cl)](2)[W6O19] (3) (C16H32N4 = Me-6-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 (1) over bar (#2) space symmetry, whereas those of compounds 2 and 3 follow the higher symmetrical ensemble P2(1)/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.