Carbazole-disulfonamide-containing macrocycles as powerful anion receptors with tunable selectivity

The design of synthetic anion receptors with potent anion binding and customizable anion selectivity under competitive solvent conditions remains challenging. Herein, we report easily-synthesized 1,8-disulfonamidocarbazole- and 3,5-diamidopyridine-based hybrid macrocycles 1-3 and reveal their strong anion recognition properties as determined by 1H NMR/UV-vis titration studies, X-ray diffraction measurements, and DFT calculations. While the dithioamidopyridine-based macrocycle 2 displayed strong and selective binding of AcO- in DMSO, modification of the selectivity pattern towards the more basic F- anion was achieved by replacing the thioamides moieties to amides (macrocycle 1). For macrocycle 3 (bearing pyridine N-oxide core), no selectivity was observed among F-, AcO-, and H2PO4- ions. The demonstration of tunable anion selectivity by slight structural modifications in our macrocycles is informative for developing structurally simple anion receptors with the desired selectivity for transmembrane anion transport, anion sensing, and anion sequestration applications.

Cubane-1,3-dicarboxamides as structural isosteres for isophthalamides in hydrogen bond templated interlocked molecules

The synthesis and characterization of the first examples of cubane containing interlocked molecules are reported. Catenanes and rotaxanes have been prepared by hydrogen bond templation with cubane-1,3-dicarboxamides replacing isophthalamide motifs.

A pyridine-N-oxide catenane for cation recognition

The rapid preparation of a pyridine-N-oxide containing [2]catenane is described. The [2]catenane was characterized by NMR spectroscopy, mass spectrometry and X-ray single crystal structure determination. 1H NMR titration experiments reveal the [2]catenane may be reversibly protonated, as well as an ability to bind lithium cations more strongly than sodium cations.

Hydrogen bond templated synthesis of catenanes and rotaxanes from a single isophthalic acid derivative

Hydrogen bond templated [2]catenanes and [2]rotaxanes have been synthesized using azide precursors derived from a single isophthalic acid derivative precursor. The interlocked molecules were prepared using either stoichiometric or near stoichiometric amounts of macrocycle and CuAAC "click" precursors, with yields of up to 70% for the mechanical bond formation step. Successful preparation of the interlocked structures was confirmed by NMR spectroscopy and mass spectrometry, with detail of co-conformational behaviour being elucidated by a range of ¹H NMR spectroscopic experiments.

An Adjustable Cleft Based on an 8-sulfonamide-2-naphthoic Acid with Oxyanion Hole Geometry

Cleft type receptors showing the oxyanion hole motif have been prepared in a straightforward synthesis starting from the commercial 3,7-dihidroxy-2-naphthoic acid. The double H-bond donor pattern is achieved by the introduction of a sulfonamide group in the C-8 position of naphthalene and a carboxamide at the C-2 position. This cleft, whose geometry resembles that of an oxyanion hole, is able to adjust to different guests, as shown by the analysis of the X- ray crystal structures of associates with methanol or acetic acid. Combination of hydrogen bonds and charge-transfer interactions led to further stabilization of the complexes, in which the electron-rich aromatic ring of the receptor was close in space to the electron-deficient dinitroaromatic guests. Modelling studies and bidimensional NMR experiments have been carried out to provide additional information.

A Mechanochromic Hydrogen-Bonded Rotaxane

Tensile forces influence a variety of important biological processes and force sensors are required to study these processes in vivo. Current force sensors are often tailor-made for a specific application, or activate at much higher forces than those observed at the cellular or tissue level. A versatile force sensor, with tunable mechanical and optical properties, activated at low pN forces will be ideal. In this communication, a new mechanoresponsive fluorescent hydrogen-bonded rotaxane, built around a maleimide dye, is reported. Its force-sensing properties are demonstrated in a polyacrylamide gel, a synthetic model of living tissue.

Modulating the expression of chirality in a mechanically chiral rotaxane

Expression of mechanical chirality by a rotaxane may be modulated by affecting the co-conformational behaviour through varying solvent or by addition of acid and base.

Rapidly accessible “click” rotaxanes utilizing a single amide hydrogen bond templating motif

The rapid synthesis (in yields of up to 47%) and co-conformational study of hydrogen bond templated rotaxanes are presented.