Hierarchical tandem assembly of planar 3×3 building units into {3×3×3} oligomers: mixed-valency electrical conductivity and magnetism

摘要

A hierarchical tandem assembly – coordination, oligomerisation and supramolecular organization – is identified using MALDI-TOF of the solid products of the solvothermal reaction of 5,5′-pyridyl-3,3′-bi-1H-pyrazole with CuSO4·5H2O in CH3OH–CH3CN. The initial coordination leads to a [3×3] [CuI4CuII5(L)6] (SO4)·2CH3OH (>Cu9) grid followed by oligomerisation to a 3×[3×3] [CuI6CuII21(L)18(CN)6(SO4)](SO4)2·8CH3CN (>Cu27) grid through bridging sulfate and in situ generated cyanide with time and subsequent supramolecular organization. The isolated silvery lustrous crystals, >Cu9 and >Cu₂₇, are good electrical conductors, with conductivities of 3.2 × 10^–2 and 5.4 × 10^–3 S cm^–1, respectively, due to the mixed valency. Their magnetic properties are dominated by antiferromagnetic interactions. DFT and band structure calculations confirm their valence distribution and semiconducting behavior. The planarity of the large 3×[3×3] >Cu₂₇ and its electro-activity renders it suitable for the development of large surface area molecular devices.