Reversible cyanovinylcarbazole-based polymer gel via photo-cross-linking reaction

<p>A polymeric gel was prepared from a bis(3-cyanovinylcarbazole)-based derivative and a thymine-bearing calix[4]arene derivative via photo-cross-linking between 3-cyanovinylcarbazole and thymine groups by irradiation with 365 nm UV light, a novel and facile method to obtain a soft material. Values for storage and loss moduli of the bis(3-cyanovinylcarbazole)-based derivative and the thymine-bearing calix[4]arene derivative gradually increased during photoirradiation. This gel was transformed back to the solution state by decomposition of the polymer network to the monomers via irradiation with 312 nm UV light.</p

Metallogel of bis(tetrazole)-appended pyridine derivative with CoBr₂ as a chemoprobe for volatile gases containing chloride atom

<p>A bis(tetrazole)-appended ligand <b>1</b> formed the metallogel efficiently by mixing with Co²⁺ ion. Interestingly, the metallogel <b>1</b> with CoBr₂ showed the orange yellow colour, which has octahedral structure. The rheological properties of metallogel obtained with CoBr₂ were ca. 1.5-fold larger than that for the metallogel obtained with CoCl₂. Upon addition of HCl, SOCl₂, (COCl)₂ and COCl₂ containing chloride atoms in the metallogel <b>1</b> prepared with CoBr₂ changed from orange yellow to blue-green colour. These results indicate that the octahedral structure of metallogel was converted into the tetrahedral structure. On the other hand, no significant colour changes were observed in the presence of an excess of other anions, namely HF, HBr, HI, HNO₃ and H₂SO₄. These findings indicate that the metallogel <b>1</b> with CoBr₂ is useful as a chemoprobe for gases containing chloride atom.</p

Origin of Both Right- and Left-Handed Helicities in a Supramolecular Gel with and without Ni²⁺ at the Supramolecular Level

We demonstrate the different origins of helical directions in polymeric gels derived from a hydrazone reaction in the absence and presence of Ni²⁺. The right-handed helicity of polymeric gels without Ni²⁺ originates from the enantiomeric d-form alanine moiety embedded in the building block. However, the right-handed helicity is inverted to a left-handed helicity upon the addition of Ni²⁺, indicating that added Ni²⁺ greatly affects the conformation of the polymeric gel by overcoming the influence of the enantiomer embedded in the building block on the helicity at the supramolecular level. More interestingly, the ratio of the right-toleft-handed helical fibers varies with the concentration of Ni²⁺, which converts from 100% right-handed helical fiber to 90% left-handed helical fiber. In the presence of Ni²⁺, both right- and left-handed helical fibers coexist at the supramolecular level. Some fibers also exhibit both right- and left-handed helicities in a single fiber

Transfer and Dynamic Inversion of Coassembled Supramolecular Chirality through 2D-Sheet to Rolled-Up Tubular Structure

Transfer and inversion of supramolecular chirality from chiral calix[4]­arene analogs (<b>3D</b> and <b>3L</b>) with an alanine moiety to an achiral bipyridine derivative (<b>1</b>) with glycine moieties in a coassembled hydrogel are demonstrated. Molecular chirality of <b>3D</b> and <b>3L</b> could transfer supramolecular chirality to an achiral bipyridine derivative <b>1</b>. Moreover, addition of 0.6 equiv of <b>3D</b> or <b>3L</b> to <b>1</b> induced supramolecular chirality inversion of <b>1</b>. More interestingly, the 2D-sheet structure of the coassembled hydrogels formed with 0.2 equiv of <b>3D</b> or <b>3L</b> changed to a rolled-up tubular structure in the presence of 0.6 equiv of <b>3D</b> or <b>3L</b>. The chirality inversion and morphology change are mainly mediated by intermolecular hydrogen-bonding interactions between the achiral and chiral molecules, which might be induced by reorientations of the assembled molecules, confirmed by density functional theory calculations