Conjugated Materials: Problems and Prospects for Synthesis Using Carbohydrate Reagents

Abstract

C o n j u g a t e d M a t e r i a l s : P r o s p e c t s f o r S y n t h e s i s U s i n g C a r b o h y d r a t e R e a g e n t s Abstract: General considerations related to the use of sugars and closely related compounds as reagents for molecular and macromolecular synthesis are presented. For the first time, we have used unprotected carbohydrates to initiate polymerizations. A variety of dicyanoalkenes and -arenes react with sugars in the presence of alkali to give conjugated polymers. Both cyclopolymerization and polymerization at only one of two cyano groups are observed, and some qualitative mechanistic issues related to these observations are discussed. In some cases, a sugar alkoxide is the active initiating reagent. Characterization of the resulting polymers is reported. Alkaline sugar reagents have also been used in Knoevenagel reactions to synthesize CN-PPV oligomers and a related conjugated polymer in good yields. The use of the polysaccharide chitosan as a polycation allows the absorption spectrum of the polythiophene HPURET to shift to longer wavelengths than other polycations in electrostatically assembled films.

Sugar–Poly(para‐phenylene ethynylene) Conjugates as Sensory Materials: Efficient Quenching by Hg2+ and Pb2+ Ions

“…We suspect that the unusually high acidities of Hg 2+ and Pb 2+ 29 led to a higher than expected binding constant to alcohol functionalities. With the enhanced acidity of the OH groups in sugars (p K a =12.3–12.4)30 this binding should be somewhat more enhanced. We can speculate that a hexacoordinated Hg 2+ ion surrounded by three glucose molecules, of which two are mono‐deprotonated, is involved in these complexes (Figure 5).…”

Thermally Annealed Solid State Polymerization of 2,3-Dicyano-5,7-Dimethyl-6H-1,4-Diazepine: An NMR Study

“…Deuterium exchange occurs predominately at the methyl group via tautomeric form B. The reason why deuterium exchange favors the methyl group over the methylene group is due to the relative orientation of the CÀH bonds in A with the diazepine moiety [6], but could also be attributed to the 8p non-aromatic system of tautomeric form C [8]. Unfortunately, no chemical shifts in either the 1 H or 13 C NMR spectra characteristic of form B were found, which suggests that the tautomeric intermediate state is short lived with respect to the Larmor period of the NMR signal.…”