No abstract

Several new liquid-crystalline indene and pseudoazulene systems are reported. These molecules give rise to either columnar hexagonal mesophases and/or columnar plastic phases. The unique nature of these compounds stems from their non-classical discotic structure. Although the molecules have rigid aromatic cores, they lack terminal tails and instead the polarizable atoms (S, halogens) or polar groups (CN, CO) act as unusual soft parts. On the basis of many structurally related materials, we conclude that for this type of compound molecular stacking in the solid state is a prerequisite for the appearance of a columnar mesophase, although other intermolecular interactions within the layers are also important in establishing liquid-crystalline order. The behavior reported for these mesomorphic molecules opens up new possibilities in the search for related molecular interactions that might be useful for the construction of supramolecular architectures with particular properties.

New ferrocene derivatives bearing two donor-acceptor systems are capable of selectively sensing cations and anions by cooperative binding of the two alpha,alpha'-groups bonded to the ferrocene nucleus, thus permitting the naked-eye selective colorimetric detection of copper[II] cation and acetate, benzoate, or cyanide anions, which are ions of toxicological and biological relevance.

[structure: see text] A new sensory MCM-41-based material for the colorimetric sensing and discrimination of amines has been developed.

An organopalladium chemical dosimeter of Hg(2+) that methylates Hg(2+), undergoing a colour change in 1 : 1 ethanol-water with submicromolar sensitivity, gives rise to an aqua-palladium complex that is methylated by MeHg(+) in the presence of a dithiol compound, undergoing another colour change, thus making the system suitable for the naked-eye detection of Hg(2+) and MeHg(+), two environmentally important species of Hg(2+).

Cyclohexyl or benzyl isocyanide, benzoyl-, or 4-methoxybenzoylformic acid and semicarbazones underwent Ugi reactions in methanol for 3 days to give the Ugi adducts, which were then stirred with sodium ethoxide in ethanol for 12 h to give 3-hydroxy-6-oxo[1,2,4]triazin-1-yl alaninamides. The X-ray diffraction structure of the first example showed the tautomer having the proton in the O2 atom that was fixed in the crystal by packing in dimers with a H-bond distance of 1.9 A. Selected [1,2,4]triazines were treated with diazomethane for 12 h to get the O-methyl derivatives. Both hydroxy and O-methyl derivatives obtained by this method constitute a new class of pseudopeptidic [1,2,4]triazines composed of two different amino acids, arylglycine and alanine derivatives, in which the N-terminal arylglycine and the peptidic amide nitrogen atoms are bonded through a urea moiety.

Push-pull chromophores based on 1-dicyanomethylene-2-chloro-3-aminoindene are readily synthesized. These compounds undergo dramatic colour changes in the presence of metal cations as a result of the interaction of the amino substituent with the analytes. One of these compounds is a selective copper(ii) colorimetric probe in acetonitrile solution, displaying a dramatic colour change upon coordination of the amine group to the metal centre. These compounds are also selective cyanide sensors in acetonitrile solution because of the disruption of the intramolecular charge transfer process as the result of the nucleophilic addition of the anion to the indene moiety.

One-Pot Synthesis of Quinolin-2-(1H)-ones via Tandem Ugi-Knoevenagel Condensations. -An Ugi four-component reaction of aminoketones (I), aldehydes (II), cyclohexylisocyanide (III) and substituted acetic acids produces quinolin-2-one derivatives (V) via an intramolecular Knoevenagel cyclization of the primary Ugi products. In the case of arylsulfonic acids [cf. (VI)], the Ugi products can be isolated and independently cyclized. -(MARCACCINI, S.; PEPINO, R.; POZO, M. C.; BASURTO, S.; GARCIA-VALVERDE, M.; TORROBA*, T.; Tetrahedron Lett. 45 (2004) 21, 3999-4001; Dep. Quim., Fac. Cienc., Univ. Burgos, E-09001 Burgos, Spain; Eng.) -Mais 35-128