Inclusion of organic molecule guests by sulfinyl bridged bis-salicylic acid-type open-chain host with flexible change of crystal structure

Abstract

To develop an open-chain host that can accommodate organic molecule guests via the formation of a recognition space, such as a pseudo-cyclic structure in the solid state, we designed and synthesized host molecules 4 and 5 comprising sulfur- and sulfinyl-bridged salicylic acids. X-ray structural analysis revealed that compound 5 affords the desired pseudo-cyclic structure in the solid state by the association of two of its molecules via syn-oriented salicylic acid units, presumably owing to the dipole repulsion against its sulfinyl group. Host 5 successfully formed inclusion crystals with specific organic molecules such as chloroform and 1,1,2,2-tetrachloroethane. We observed conformational and packing structure flexibility of host 5 based on the structure of guest molecules. 5·CHCl₃ and 5·[CHCl₂CHCl₂]₃ formed columnar and sheet structures, respectively, because of the differences in their host–guest interactions and the size of guest molecules.