Supramolecular aggregation in diimine adducts of zinc(II) 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-(HO)-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.