Highly ordered LB films of DHAP : a donor acceptor substituted polyene

The donor acceptor substituted polyene 5-(4-dihexadecylaminophenyl)-2-methyl-2,4-pentadienal (DHAP) is - due to its amphiphilic nature - a promising candidate for the Langmuir-Blodgett (LB) technique. The molecule was studied as a monolayer on a pure water surface under argon atmosphere. Monolayers and multilayers were transfered onto solid support. The films showed a high degree of order in the monolayer as well as in thick multilayers. LB films were investigated with polarisation dependent UV/VIS absorption spectroscopy. The film spectra showed additional absorption peaks which were not present in the spectra of the molecules in solution. The relative peak intensities were highly dependent on the orientation of the electric field vector with respect to the substrate normal. To get a detailed picture of the arrangement of the films on the molecular level, we studied the polarisation dependence of the FTIR spectra in different experimental set-ups. The spectra showed a perpendicular orientation of the conjugated system with respect to the substrate, whereas the backbone of the saturated hydrocarbon chains showed a medium tilt angle of 20.0° with respect to the substrate normal. X-ray small angle diffraction measurements were applied to investigate the thickness of the LB layers. From the position of the Bragg peaks, a thickness of 5.45 nm per bilayer can be calculated, in agreement with a bilayer model showing different molecular alignment of the molecules transferred during upstroke and downstroke

Donor-acceptor substituted polyenes : orientation in mono- and multilayers

Large molecules containing different chemical units whose interactions within the molecule result in new macroscopically observable effects, have become increasingly important.The organization of molecules of this type in ordered structures leads to functional molecular materials.Their use in molecular electronics requires that the units exhibit specific electronic properties. Recently, we reported on the intramolecular energy transfer through terminally substituted conjugated polyenes. An intramolecular electron transfer within donor-acceptor substituted polyenes can be achieved by introducing suitable terminal groups

Preparation of conjugated polyenes with anthryl and N-nethylpyridinium terminal groups

The synthesis of terminally donor-acceptor substituted polyenes from the respective aldehydes via Horner reactions is described. As donor group the 9-anthryl and as acceptor moiety the 4-(N-methyl)pyridinium residue were chosen. A bicyclo[2.2.2]octane unit was incorporated into the chain to interrupt the conjugation. The separation and characterization of the mixtures of Z/E- isomers obtained in the syntheses was possible

A versatile synthesis of N-Carboxy-α,β-didehydro-α-amino acid anhydrides (4-Alkylidene-2,5-oxazolidinediones)

α-Azidocarboxylic acids 1 react with phosgene in the presence of catalytic amounts of sodium perrhenate in dimethoxyethane at 85°C to give N-carboxy-α,β-didehydroamino acid anhydrides (4-alkylidene-2.5-oxazolidinediones) 2 in good yields

Process for enantiomeric separation of racemic dihydro-1,3,5 triazines via preferential crystallization

A new process for the enantiomeric separation of racemic 3,6-dihydro-1,3,5-triazine derivatives for the treatment of disorders associated with insulin-resistance syndrome, by preferential crystallization