Hydrogen-Bonded Inclusion Compounds with Reversed Polarity: Anionic Metal-Complexes and Cationic Organic Linkers

Synthesized and structurally characterized is a new series of soft-host frameworks assembled by charge-assisted hydrogen bonds between an anionic metal complex (MC) and cationic organic linkers (OL), specifically [Co­(en)­(ox)2]− and diprotonated 4,4′-bipyridinium (H2bpy) or 1,2-bis­(4-pyridinium)­ethylene (H2bpye). While frameworks built of cationic complexes and anionic organic linkers are already well-known, the seven new compounds described here represent the first series of frameworks with reversed polarity, that is, made of anionic complexes and cationic organic linkers. The compounds have a general formula [OL]­[MC]2·n(guest), where the guest molecules 4,4′-biphenol (bp), 4-methoxyphenol (mp), 1,4-dimethoxybenzene (dmb), 1,6-dimethoxynaphtalene (dmn), and 4-nitroanisole (na). Structurally the compounds can be described as pillared-layer frameworks with layers constructed of MC anions and linked together by hydrogen-bonded cationic OL pillars. The guest molecules occupy the galleries between the pillars while their steric, electronic, and π–π and hydrogen-bonding capabilities influence the overall structure of the soft frameworks.