1,4-Phenylene-bis(di-p-fluorophenylmethanol): a highly efficient wheel-and-axle host compound for organic heterocyclic solvents

Abstract In the present investigation, the wheel-and-axle host compound, 1,4-phenylene-bis(di- p -fluorophenylmethanol) ( H1 ), was revealed to have inclusion ability for three saturated heterocyclic organic solvents, namely DIO, MOR and PIP, in addition to the previously reported complex with PYR. Guest competition experiments demonstrated H1 to possess an affinity for PIP and PYR while, in 20:80 PYR/DIO, 40:60 PYR/DIO and 20:80 PIP/DIO binary solutions, the host affinity for PYR, PYR and PIP, respectively, was overwhelming (K > 10). Crystal structure analysis of the complexes showed that favoured PYR was held in the crystals of its complex by means of a much shorter (guest)N‒H···O(host) hydrogen bond compared with the other nitrogen-containing guest solvents (DIO was also retained in its complex by means of a classical hydrogen bond). Plausibly as a result of this observation, the PYR-containing complex had the higher crystal density and was thermally more stable than the other complexes, explaining the affinity of H1 for PYR. The reasons for the host selectivity for PIP was less clear.