Rigid duplex alpha-cyclodextrin reversibly connected with disulfide bonds. Synthesis and inclusion complexes.

The rigid duplex cyclodextrin 6 composed of two alpha-cyclodextrin macrocycles connected with two disulfide bonds in "transannular" (C6(I), C6(IV)) positions was prepared from partially debenzylated alpha-cyclodextrin 1 in four steps in 73% overall yield. In the last key step involving oxidative coupling of the thiol 5, predominance of the target duplex 6 can be attained under conditions of thermodynamic control. The structure of duplex cyclodextrin was established by MS as well as 2-D NMR methods and confirmed by a single-crystal X-ray analysis.

Role of anions on the crystal structures of copper(II) and zinc(II) complexes of a tunable butterfly cyclophane macrocycle.

Three crystal structures of a ditopic cyclophane ligand (L) in which two 1,5,8,12-tetraamine molecules have been attached through methylene spacers to the ortho positions of a benzene ring are reported. The first one (1) corresponds to the tetraprotonated free macrocycle (H4L4+) having two tetrachlorozincate(II) counteranions (C24H54O2N8Cl8Zn2, a = 9.1890(2) A, b = 14.

Shape-complementarity in the recognition of tricarboxylic acids by a [3+3] polyazacyclophane receptor.

[structure: see text] The interaction of a macrocycle containing three trans-(1R,2R)-diaminocyclohexane units connected by p-xylene spacers with the isomers 1,3,5-benzenetricarboxylic (1,3,5-BTC), 1,2,4-benzenetricarboxylic (1,2,4-BTC), and 1,2,3-benzenetricarboxylic (1,2,3-BTC) acids and their relevant anions is studied by means of potentiometric and NMR analysis. The interaction is highest for the isomer 1,3,5-BTC, which perfectly fits within the macrocyclic cavity of the host species. The studies have been extended to the triacid 1,3,5-benzenetriacetic observing in this case the effect of a size mismatch between host and guest species.

Self-Assembly of 1,1'-Biphenyl-2,2',6,6'-tetracarboxylic Acid: Formation of an Achiral Grid with Chiral Compartments.

D -symmetric chiral hydrogen-bonded cyclotetramers (see the structure in the picture) are present in the self-assembled achiral title compound in the solid state. The unilayered network set up from the chiral "square" blocks is achiral as a consequence of the crystal symmetry.