Electronic Band Structure and UV-Visible Spectra

Optical Properties of Polythiophenes Electronic Band Structure and UV-Visible Spectra 

Recently, optically active polythiophenes, incorporating as ring substituents chiral selectors such as (R)-(-)- and CS )-(+)-/V-(3,5-dinitrobcnzoyl)-a-phcnylglycinc used in Pirkle-type stationary phases, have been synthesized.167 These may have potential in enantioselective analysis of chiral chemicals using high performance liquid chromatography (HPLC). 

The chiral polythiophene, poly(3- (.S )-5-amino-5-carboxyl-3-oxapcntyl -2,5-thiophenylene) hydrochloride, l-POWT, ring-functionalized with the amino acid L-serine, has been synthesized by Inganas and coworkers,69,168 and was found to exhibit pH-dependent UV-visible, fluorescence emission, and CD spectra. At a pH equal to the isoelectric point of the amino acid, the poly thiophene chains separate and adopt a nonplanar right-handed helical conformation. Increasing the pH leads to a more planar conformation of the backbone and aggregation of the polymer chains. 

Chiral disubstituted PEDOTs have recently been prepared for the first time via transetherification of 3,4-dimethoxythiophene monomers with chiral glycols followed by potentiodynamic oxidation.174 An alternative approach to optically active PEDOTs has also been recently described, which involves the electrochemical polymerization of the EDOT monomer in aqueous hydroxypropyl cellulose (HPC) as a polymer lyotropic liquid crystal to give a chiral PEDOT/HPC hybrid.175 The PEDOT prepared in this chiral nematic liquid crystal exhibited optically active electrochromism in that it could be electrochemically switched between a dark blue reduced state and a sky blue oxidized form that exhibited a different CD spectrum. 

Gningue-Sall, D. Fall, M. Dieng, M.M. Aaron, J.J. Lacaze, P.C. Phys. Chem. Chem. Phys. 1999, 1 1731. 

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