Use of the oxime–oximato binding mode to stabilise mixed valence copper iodide polymer networks using dipyridyl ketone oxime ligands

Abstract

Five complexes prepared from CuI and dipyridyl ketone oxime ligands were synthesised and structurally characterised, [Cu₂I₂(L²³)(L²³-H)]_∞, 1, [Cu(L²³-H)₂]_∞, 2, {[Cu₂(L²⁴)(L²⁴-H)I₂](CH₃CN)}_∞, 3, [Cu(L³³)I]_∞, 4, and {[Cu₈(L⁴⁴)₅I₈](CH₃CN)₄(C₄H₁₀O)₂(H₂O)₂}_∞, 5. The effect of the varying pyridyl substitution patterns of L²³, L²⁴, L³³ and L⁴⁴ was investigated, as well as the effect this had on forming mixed valence complexes. Complexes 1 and 3 formed mixed valence Cu(I)/Cu(II) polymer networks with Cu(II) stabilised by the formation of a pseudo tetradentate ligand through an oxime–oximato bridge. In comparison, the Cu(I) in complex 2 was completely oxidised to Cu(II), with the ligand fully deprotonating to act as a charge balance. Complex 4 formed a simple 1D Cu₂I₂ rhomboid dimer daisy chain, while 5 formed Cu₄I₄ cubane tetramer clusters, allowing four ligands to bind to one centre. Overall 5 existed as two interpenetrated hydrogen bonded 3D networks.