Directed Assembly of acac-Based Complexes by Deliberately Fine-Tuning Electrostatic Molecular-Recognition Events

A protocol for supramolecular synthesis of one-dimensional (1-D) chains comprising octahedral metal-complexes linked by predictable hydrogen bonds has been established. The synthetic process was refined by adjusting the reactants in an iterative manner to shift the magnitude of the electrostatic potential surfaces of competing hydrogen-bond acceptor sites thereby avoiding the formation of unwanted products. The synthetic space for this study was provided by a combination of reactants: Co­(II)/Ni­(II) cations and acac-based anions (dibenzoylmethanato, dbm/hexafluoracetylacetonato, hfac) combined with a series of pyridine-oxime ligands (4-pyridinealdoxime, 4-Hoxpy; methyl 4-pyridyl ketoxime, 4-Meoxpy; 3-pyridinealdoxime, 3-Hoxpy; methyl 3-pyridyl ketoxime, 3-Meoxpy). The initial self-assembly process did not produce the desired 1-D chains held together by oxime···oxime hydrogen bonds; however, through deliberate fine-tuning of the reactants, a robust synthetic protocol for the reproducible synthesis of the correct supramolecular products was obtained. The successful synthetic protocol was arrived at in much the same way as organic synthesis is systematically altered and refined in response to product yields.