A Versatile Tripodal Host with Cylindrical Conformation: Solvatomorphism, Inclusion Behavior and Separation of Guests - 主-客体和超分子化学

A new tripodal host molecule 2,4,6-tris(1-phenyl-1H-tetrazol -sulfanylmethyl) mesitylene (TPTM) has been synthesized through a facile procedure. As expected, this molecule adopts an all-syn cylindrical configuration, thereby delimiting an inner cavity. To explore the solvatomorphism chemistry and inclusion behavior of TPTM, a series of organic and inorganic species have been employed as guests to afford 17 inclusion compounds (1, 2, 3a-3f, 4a-4i), which can be classified into four distinct forms (Form I-IV) under similar conditions. These compounds have been characterized by single-crystal and powder X-ray diffraction methods, and 1H NMR studies. In compound 1 with Form I, one foot of a TPTM molecule inserts into the cavity of the other TPTM in the opposite to form a dimeric “hand-shake” motif with one acetonitrile molecule occupying the void. Compound 2 with Form II contains three types of capsule-shaped dimers each holding a CH2Cl2 molecule as guest. In compounds 3a-3f with Form III, each pair of TPTM molecules interdigitate to form a capsule-shaped dimeric unit accommodating a guest molecule in endo-cavity. In compounds 4a-4i with Form IV, each TPTM makes contact with three nearby TPTM molecules in a “self-including” manner to generate a graphite-like organic layer, and through further superposition to form open hexagonal channels. From experimental and theoretical results, the intrinsic properties of guest molecules such as size, shape and self-interaction can be regarded as the main factors leading to these solvatomorphism phenomena and the subtle inclusion behavior of TPTM. Thermogravimetric analyses show that the encapsulated guest molecules in these compounds can be evacuated at relatively high temperatures, which demonstrates an outstanding inclusion capability of TPTM. In addition, based on compound 4a with benzenes in channels, reversible exchange of toluene and separation of xylene isomers on single crystals have been observed.