Conformational control of the self-assembly of triple helicates and [2 × 2]-grids from zinc(II) and 3,6-di(2-pyridyl)pyridazine based ligands.

The reaction of symmetrical ligands based on 3,6-di(2-pyridyl)pyridazine () with carbocyclic rings fused to the pyridazine ring; 7,10-di(2-pyridyl)-8,9-diazafluoranthene (), 1,4-di(2-pyridyl)-6,7-dihydro-5H-cyclopenta[d]pyridazine (), 1,4-di(2-pyridyl)-5,6,7,8-tetrahydrophthalazine (), 1,4-di(2-pyridyl)-6,7,8,9-tetrahydro-5H-cyclohepta[d]pyridazine () in reactions with zinc perchlorate gave a series of complexes (). Characterisation of these using single crystal X-ray structure determination showed that less sterically hindered and gave saturated triple helicates ( and , respectively), while [2 × 2]-grids were formed with more sterically hindered ligands ( from and from ), or if methanol (rather than acetonitrile) was used as the reaction solvent with (). The most sterically-hindered ligand formed a mononuclear complex (). The structures of these complexes in solution was determined by (1)H-NMR, and found to match their solid-state structures. The [2 × 2]-grids are effective molecular clips able to hold solvent and anions between their arms via hydrogen bonding to a Zn4(H2O)2(OH)2 core.