The behaviour of two tricyclic fused host systems in the presence of four saturated six-membered ring guest solvents, dioxane, morpholine, piperidine and tetrahydropyran

Abstract In this work, the behaviour of host compounds N , N’ -bis(9-phenyl-9 H -xanthen-9-yl)propane-1,3-diamine ( H1 ) and N , N’ -bis(9-phenyl-9 H -xanthen-9-yl)butane-1,4-diamine ( H2 ) was investigated in the presence of four saturated six-membered ring guest solvents, namely dioxane (DIO), morpholine (MOR), piperidine (PIP) and tetrahydropyran (THP). After crystallization experiments from each solvent, H1 was observed to only furnish a complex with DIO (the host: guest (H: G) ratio was 2:3), while H2 formed inclusion compounds with each one (H: G ratios were either 1:1 or 1:2). SCXRD analysis revealed that the guest molecules in complex H2 ·PIP occupied discrete cages, all other guests being located in channels of the inclusion compounds with H2 (in the THP b -containing complex with H2 , these channels were extremely constricted, THP b being a second polymorph identified in the H2 ·2(THP) complex). Competition experiments involving H2 revealed that DIO and MOR were, more usually, the favoured guest species. Guest competition experiments were not performed with H1 owing to extremely slow rates of crystallization. The relative thermal stabilities of the complexes of H2 were in agreement with the host selectivity behaviour: the complexes with DIO and MOR were the more stable ones (T on 56.7 and 48.2 °C) compared with those with PIP and THP. Finally, the lack of any host···guest interactions between H2 and PIP explained the observation that PIP was never a favoured guest species in the guest competition experiments.