Supramolecular aggregation in diimine adducts of zinc(ii) dithiophosphates: controlling the formation of monomeric, dimeric, polymeric (zig-zag and helical), and 2-D motifs

Abstract

The interplay between steric demands of dithiophosphate-bound R groups in Zn(S₂P(OR)₂)₂ on the one hand and the coordination requirements of a variety of di-pyridyl-type bases on the other, is shown to be pivotal in determining supramolecular aggregation patterns in a series of their adducts. Thus, the combination of sterically demanding cyclohexyl groups and the congested trans-1,2-bis(2-pyridyl)ethylene ligand leads to a mononuclear species, but replacing the cyclohexyl by the less bulky isopropyl group allows for dimer formation in the structure of [Zn(S₂P(OiPr)₂)₂(2-NC₅H₄C(H)C(H)C₅H₄N-2)_0.5]₂; a similar motif is found when pyrazine is the bridging ligand. These molecules aggregate in the solid-state to form chains via C–H⋯O interactions. Zig-zag polymers are found when the somewhat less congested 2,2′-dithiopyridine and bis(4-pyridyl)amine ligands are used as the bridges; the hydrogen-bonding functionality in the latter leads to a 2-D motif. Finally, exploiting the curved nature of the 1,3-bis(4-pyridyl)propane ligand leads to the formation of helical chains.