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He I and He II UV photoelectron spectra (UPS) of isomeric thienylpyridines and thienylethynylpyridines have been recorded. Their electronic structures were analysed and spectra assigned on the basis of He II/He I intensity variations, comparison with UPS of pyridine, thiophene and ethyne and semiempirical MO calculations. The spectra indicate that there is considerable interaction between π orbitals of thiophene, pyridine and ethynyl moieties. The relationship between electronic structure and formation of novel polymer materials is discussed.

Poly(3,3′-dibromo-2,2′-bithiophene)(PBr2BT) and poly(3,3′-dichloro-2,2′-bithiophene)(PCl2BT) can be readily deposited on electrodes via electrochemical polymerization of the respective monomers. Visible cracks observed on the resulting PCl2BT and PBr2BT films were related to the steric influence of the substituents. The redox potentials of polymers were found to decrease in the order PBr2BT PCl2BT > poly(bithiophene)(PBT), suggesting that the steric hindrance and electronegative nature of the halogen groups impart a negative effect on the inculator-to-conductor transition in PBr2BT and PCl2BT. In addition, the less extended π-conjugation, together with the electrochemically unfavourable doped state and discontinuous macroscopic structure, prevent the solid-state PBr2BT and PCl2BT from achieving conductivity comparable to the parent PBT. However, the enhanced solubility with consequent improved processibility, coupled with the presence of reactive pendant halogens would make these systems useful as functional polymers for further modifications in the post-polymerization stage.

The selective functionalization of the 2,2'-bithiophene molecule is described. Selective alkyl substitution at the 3,3' positions was achieved by sequential bromination of the 3,3' and 5,5' positions followed by debromination at the 5,5' positions. The resultant 3,3'-dibromo-2,2'-bithiophene was transformed via a Grignard reaction to give a series of 3,3'-dialkyl-2,2'-bithiophenes. Finally, nitration of the active 5,5' positons gave the corresponding 3,3'-dialkyl-5,5'-dinitro-2,2'-bithiophenes

This communication reports the preparation of two new cyclodextrin (CD) chiral stationary phases (CSPs): heptakis(6-deoxy-6-azido)-β-CD and heptakis(6-deoxy-6-azido-phenylcarbamoylated)-β-CD CSPs that perform quite differently to our previously reported “click” immobilized CD-CSPs. These CSPs are sterically congested at the narrow mouth of the CD and exhibit chiral discrimination between over 40 pairs of enantiomers in high performance liquid chromatography. The free hydroxyl CSP afforded better separation of indoprofen, ketoprofen, Troger's base, hydroxyl, carboxylic and dansyl amino acids than did the phenylcarbamoylated CSP, while the latter was better at resolving aryl alcohols, flavonoids, β-blockers and β-agonists. The current work shows that enantiodiscrimination achieved with different CSPs for different classes of analyte may be correlated with CD accessibility and peripheral functionality.

published in Advance ACS Abstracts, April 15, 1994. 0022-3654/94/2098-5240$04.50/0 l2.P He 7 9 11 13 15 17 EileV Figure 1. He I and I1 photoelectron spectra of 22BSe 22FSe. selenophe0eyl)thiophene (22TSe), 3-( 2’-selenopheney1)thiophene (32TSe), 3-(2’-selenopheneyl)furan (32FSe), 5-chloro-2-( 5’- chloro-2’-selenopheneyl)thiophene (55C1), and 5-bromo-2-(5’- bromo-2’-selenopheneyl)thiophene (55Br) are shown in Figures 1-3. The ionization energies (Ei) quoted in Figures 1-3 and Table 1 refer to vertical energies. UV spectra were obtained in hexane solvent. Theoretical Calculations. MO eigenvalues and eigenvectors were calculated at the semiempirical level (PM3 Hamiltonian) with the MOPAC 6.0 packages running on a Silicon Graphics Iris platform. The selenium atom parametrization was only available with the PM3 method, and thus all calculations were performed at this level of theory. The experimental ring geometries for 0 1994 American Chemical Society

He I and He II photoelectron spectra of all isomeric mono- and diethynylthiophenes were recorded. The electronic structure was analyzed and spectra assigned on the basis of empirical considerations and semiempirical MO calculations. The spectra indicate various interactions taking place between thiophene π and ethynyl π orbitals. The relationship between deduced electronic structure and formation of novel polymer materials is discussed