Synthesis and crystal structure of 2,4,6,8-tetra-kis-(3,5-di--butyl-phen-oxy)pyrimido[5,4-]pyrimidine: expansion of the Piedfort concept.

The title host compound, CHNO, designed to self-assemble to form a new type of extended core Piedfort unit reminiscent of an eight-legged spider host, forms a number of crystalline inclusion compounds favouring oxygen-containing guest mol-ecules. We have established the presence of this unit in the unsolvated mol-ecular crystal at 100 K, which is monoclinic, space group 2/, with = 8. The new Piedfort unit is chiral and its core structure closely approximates to symmetry, with both enanti-omers present in the crystal.

The first spontaneous resolution of a sulfoxide: Dianin's compound analogue, ()-4-(4-hy-droxy-phen-yl)-2,2,4-tri-methyl-thia-chroman-1-oxide.

The title sulfoxide, CHOS, was prepared by controlled oxidation of -Dianin's compound using hydrogen peroxide in glacial acetic acid. On recrystallization from glacial acetic acid, it was found to form unsolvated, spontaneously resolved crystals, the initial crystal structure analysis revealing the presence of both sulfoxide epimers in the crystal. On multiple recrystallization a single epimer was observed, with crystallization occurring in the unchanged ortho-rhom-bic space group 222, with = 1.

Engineering robust polar chiral clathrate crystals.

The R-(+)-enantiomeric form of Dianin's compound and the S-(+)-enantiomeric form of its direct thiachroman analogue both obtained chromatographically employing a cellulose tris(3,5-dimethylphenylcarbamate) column, are shown to undergo supramolecular assembly to form a polar clathrate lattice which is stable even in the absence of a consolidating guest component.

1,2,4,5-Tetrakis(phenylsulfonyl)benzene: a novel quadruped host with D2 symmetry having ordered sulfolane and cycloheptanone guests.

The title tetrasulfone 1, in common with higher members of the multi-armed aromatic hosts, forms host-guest complexes with polar guest molecules. In the sulfolane and cycloheptanone complexes the host molecule possesses an abab conformation with exact C(2,) and approximate D(2) symmetry with deviations owing to crystal packing forces. The conformation of the well-ordered cycloheptanone molecule, which normally undergoes facile pseudorotation, is unambiguously defined in the voids of the crystalline inclusion compound.

The first members of the octasubstituted naphthalene spider-host series with type I (abababab) conformation: gateway to new nano-host gas storage materials.

Octakis(m-tolyloxymethyl)naphthalene, the first Type I spider host produced, crystallises from tetraglyme forming a novel channel structure with the host molecule attaining exact D(2) symmetry. The (flexible) channel structure is retained for guest CS(2), the host now only having exact C(2) symmetry. The octa-sulfone octakis(m-tolylsulfonylmethyl)naphthalene is also of Type I in its triclinic DMSO clathrate.