Specific interactions in complexes formed by DNA and conducting polymer building blocks: Guanine and 3,4-(ethylenedioxy)thiophene

In the present paper we report direct experimental evidence of the existence of hydrogen bonds between poly(3,4-(ethylenedioxy)thiophene) (PEDOT) and DNA complexes and bring deeper knowledge about how such interactions can take place in such species. To this end, we used both experimental and theoretical methodologies to examine the interactions between the building blocks composing these two macromolecules. The specific interaction natures between 3,4-(ethylenedioxy)thiophene (EDOT, E) and doubly protonated guanine (GH ₂ ²⁺) monomers have been investigated using UV - vis spectroscopy. Quantum mechanical calculations in the density functional theory (DFT) and time-dependent density functional theory (TDDFT) frameworks have been used to identify the structures of the possible complexes. These differ in the interaction pattern, and it was possible to interpret the absorption spectra in terms of intermolecular interactions. Our results allow verification of the previous hypothesis about the formation of specific N - H·· ·O interactions between G-containing nucleotide sequences and PEDOT. Clearly, DFT calculations indicate that E:GH ₂ ²⁺ complexes are stabilized by N - H···O interactions, which involve an E oxygen and the - NH and - NH ₂ moieties of GH ₂ ²⁺. Furthermore, TDDFT calculations are able to reproduce the absorption spectra (both energy gaps and relative oscillator strength magnitudes) of E and GH ₂ ²⁺, as well as the complex.