137461-40-6Relevant academic research and scientific papers
Rapid Solution and Solid Phase Syntheses of Oligo(1,4-phenylene ethynylene)s with Thioester Termini: Molecular Scale Wires with Alligator Clips. Derivation of Iterative Reaction Efficiencies on a Polymer Support
Jones II, LeRoy,Schumm, Jeffry S.,Tour, James M.
, p. 1388 - 1410 (2007/10/03)
The syntheses of soluble oligo(2-alkyl-l,4-phenylene ethynylene)s via an iterative divergent/ convergent approach starting from 1-(diethyltriazyl)-3-alkyl-4-[(trimethylsilyl)ethynyl]benzenes are described. When the solublizing alkyl group is an ethyl substituent, the monomer, dimer, tetramer, and octamer can be synthesized. The octamer, however, is only minimally soluble. When the alkyl substituent is 3-ethylheptyl or dodecyl, the compounds are easily dissolved even at the 16-mer stage. The 16-mer is 128 A long in its near-linear extended conformation. At each stage in the iteration, the length of the framework doubles. Only three sets of reaction conditions are needed for the entire iterative synthetic sequence: an iodination, a protodesilylation, and a Pd/Cu-catalyzed cross coupling. Synthesis of the dodecyl-containing 16-mer was also achieved on Merrifield's resin using the iterative divergent/convergent approach. The oligomers were characterized spectroscopically and by mass spectrometry. The optical properties are presented which show that at the octamer stage, the optical absorbance maximum is nearly saturated. The size exclusion chromatography values for the number average weights, relative to polystyrene, illustrate the tremendous differences in the hydrodynamic volume of these rigid rod oligomers verses the random coils of polystyrene. These differences become quite apparent at the octamer stage. Equations were derived for assessing the efficiency of the polymer-supported reactions based on resin weight differences, molar concentration differences, and elemental analysis data. Each of these methods' limitations are discussed. Attachment of thiol end groups, protected as thioacetyl moieties, was achieved. These serve as binding sites for adhesion to gold surfaces. In some cases, one end of the oligomeric chains is capped with a thiol group so that the surface attachments to gold could be studied. In other cases, thiol groups are affixed to both ends of the molecular chains so that future conduction studies could be done between proximal metallic probes. The rigid rod conjugated oligomers may act as molecular wires in molecular scale electronic devices, and they also serve as useful models for understanding analogous bulk polymers.
Reaction of Azomethine Moiety Buried in Bilayer Membranes
Okahata, Yoshio,Ando, Reiko,Kunitake, Toyoki
, p. 802 - 808 (2007/10/02)
The reaction with water and amines of the azomethine moiety that is part of single-chain ammonium amphiphiles was examined.These amphiphiles form stable bilayer aggregates when they have the alkyl tail of C7 or C12.The reaction with water of the bilayer-forming amphiphiles ceases at the hydration stage and are 10-2000 times slower than those of the amphiphiles which do not form bilayers and undergo hydrolytic cleavage.The reactivity of the azomethine moiety in bilayers decreases with increasing distance from the membrane surface.The Arrhenius plots for the bilayer-forming amphiphiles show discontinuities at temperatures corresponding to phase transition of the respective bilayer (Tc).The apparent activation energy is larger at temperatures below Tc than at temperatures above Tc.This suggests that water penetration is facilitated in the fluid bilayer.The reaction with amines was affected by their solubility in the bilayer matrix, and poly(ethylenimine) gave a much reduced reaction rate when the azomethine moiety was buried deep in the bilayer matrix.
