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

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.