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Spectroscopic study of a series of fluorine-pyrrole oligomers using the density functional theory

Hossein Nikoofard

In one of the works previously reported by our research team [J. Fluor. Chem. 128 (2007)], we used a DFT-B3LYP method in order to study the structural and electronic properties of the oligomers including the dimer, trimer, and tetramer of fluoromethylpyrroles (FMPs), NC4H4-CX3 (where - CX3 stands for -CH2F, -CHF2 and -CF3), and their radical cations. In the work mentioned above, FMPs were proposed as candidate monomers for conducting polymers with modified characteristics compared to polypyrrole and polymethylpyrrole. In the present work, the method mentioned above is applied to predict the vibrational frequencies and NMR properties of FMPs and their corresponding oligomers. The optimized structural parameters of these compounds are used in the vibrational spectra and chemical shift calculations. Analysis of the vibrational frequencies and NMR chemical shifts for the mono-, di-, tri-, and tetramer of FMPs supports their structural and electronic properties. The results obtained from the computational studies carried out confirm that selectivity of the configuration of FMP oligomers in the polymerization process ismost affected by characteristics of the CX3-substitutedmonomer ring. The chemical shift data obtained show that the nucleation of FMP monomers occurs most probably at the áÂ’-position, far away from the group substituted on themonomer ring, while growth of the corresponding oligomers progresses more from the á–position of the oligomer chain, close to the substitution position. Also the results obtained from the spectroscopic studies carried out show that FMP oligomers consist of Py-CF3 compared with other FMP monomers, and that they have the most potential for electropolymerization.