Synthesis and mesogenic behavior of metal-containing liquid crystalline networks

A new hydroxy functionalized liquid crystalline (LC) polyazomethine has been synthesized by the solution polycondensation of a dialdehyde with a diamine. The polymer was characterized by IR, H-1-, and C-13-NMR spectroscopy. Studies on the liquid crystalline properties reveal the nematic mesomorphic behavior. This polymer functions as a polymeric chelate and forms a three-dimensional network structure through the metal complexation. Influence of various metals and their concentration on the liquid crystalline behavior of the network has been studied. Networks up to 30 mol % of the metal show LC phase transitions; above this the transitions are suppressed and the network behaves like an LC thermoset. (C) 1996 John Wiley & Sons, Inc.

Synthesis, characterisation and superoxide dismutase activity of a manganese(II) complex

A potent superoxide dismutase mimic; Mn-II(HL)(2) [H(2)L = 2,6-bis(benzimidazol-2-yl)pyridine] has been synthesised and characterised by its crystal structure determination and EPR spectroscopy.

Synthesis of chiral bicyclo[2.2.2]oct-5-en-2-ones via an intramolecular alkylation reaction

Generation of the thermodynamic dienolate of 9-bromocarvone derivatives 5, 7 and 11 furnished the chiral bicycle[2.2.2] octenones 6, 8 and 9 and 12 and 13 containing a bridgehead methyl group via an intramolecular alkylation reaction. In an analogous manner intramolecular alkylation reaction of the bromo enones 15a-e, obtained from carvone 2 by 1,3-alkylative enone transposition (-->14) followed by a regiospecific bromoetherification reaction, furnished the bicyclo[2.2.2]oct-5-en-2-ones 16a-e and 17a-e.

Synthesis of DEF ring skeleton of naulafine alkaloid

6, 8-Dichloro-4, 5-dihydro-2-methyl-[2, 7]acenaphthyridin-1-one (5), obtained from the. reaction of 5-cyano-2, 6-dihydroxy-3, 4-cyclopentenopyridine with Vilsmeier reagent, has been transformed to the key synthon 4a in two steps.

Synthesis of epoxy-terminated polymers by radical polymerization using alpha-(t-butylperoxymethyl)styrene as chain transfer agent

Epoxy-terminated polystyrene has been synthesized by radical polymerization using alpha-(t-butylperoxymethyl) styrene (TPMS) as the chain transfer agent. The chain transfer constants were found to be 0.66 and 0.80 at 60 and 70 degrees C, respectively. The presence of epoxy end groups was confirmed by functional group modification of epoxide to aldehyde by treatment with BF3.Et(2)O. Thermal stability of TPMS was followed by differential scanning calorimetry and iodimetry. Thermal decomposition of TPMS in toluene follows first order kinetics with an activation energy of 23 kcal/mol. (C) 1996 John Wiley & Sons, Inc.

Synthesis of layered MoOPO4 center dot 2H(2)O and investigation of its intercalation chemistry

We describe in this paper the synthesis and characterization of a new layered phosphate, MoOPO4 . 2H(2)O (I), and its intercalation chemistry. The phosphate I, crystallizing in a tetragonal structure (a = 6.375(7), c = 7.80(1) Angstrom, and Z = 2) similar to that of VOPO4 . 2H(2)O, has been synthesized by the reduction of MoO2(HPO4). H2O (II) using ethylene glycol in an CH3CN medium at similar to 60 degrees C. Interestingly, I could be readily oxidized back to II using Br-2 in CH3CN at room temperature. Considering the close structural relationship existing between I and II, it is likely that the reduction and oxidation of the phosphates proceed by a topotactic mechanism. I is a novel layered host intercalating a variety of organic bases such as n-alkylamines, pyridine, and aniline, mainly through an acid-base interaction. Unlike VOPO4 . 2H(2)O, I does not exhibit reductive intercalation reactivity.

Synthesis of taxanes - The carvone approach; A simple, efficient stereo- and enantio-selective synthesis of the functionalised A ring

A highly stereo- and enantio-selective methodology for the construction of the chiral functionalised A-ring of taxanes, starting from (R)-carvone employing a short, simple and efficient sequence is described.

Synthesis, redox and electrochemical properties of new anthraquinone-attached micelle- and vesicle-forming cationic amphiphiles

Three new cationic amphiphiles bearing anthraquinone moieties at the polar headgroup region were synthesized, The single-chain amphiphile, N,N-dimethyl-N-octadecyl-N-(9,10-dihydro dioxoanthracen-2-ylmethyl)ammonium bromide 1, in the presence of cetyltrimethylammonium bromide upon dispersion in water gave co-micellar aggregates containing covalently attached anthraquinone residues at the polar aqueous interfaces. The other two double-chain amphiphiles, N,N-dioctadecyl-N-methyl-N-(9,10-dihydro-9,10-dioxoanthracen-2-ylmethyl)ammonium bromide 2 and N,N-dimethyl-N-(1,2-bispalmitoyloxypropanyl)-N-(9,10-dihydro-9,10-dioxanthracen-2-ylmethyl)ammonium bromide 3, however, on dispersion in aqueous media produced vesicular aggregates. The critical temperatures for the gel to liquid-crystalline-like phase transition processes for the vesicular systems were determined by following temperature-dependent changes in the ratios of keto-enol tautomeric forms of benzoylacetanilide doped within respective. vesicular assemblies. The redox chemistry of the these supramolecular assemblies was also studied by following the time-dependent changes in the ITV-VIS absorption spectroscopy in the presence of exogenous reducing or oxidizing agents, Electrochemical studies using glassy carbon electrodes reveal that redox-active amphiphiles adsorb on to the glassy carbon surfaces to form electroactive deposits when dipped into aqueous suspensions of either of these aggregates irrespective of the micellar or vesicular nature of the dispersions.