Electronic structure of hydrogen-bonded imidazole chains. Influence of the proton position

We present Hartree-Fock ab initio STO-3G and 4-31G calculations on imidazole monomer and dimer, and STO-3G and pseudopotential band structure calculations on the imidazole hydrogen-bonded infinite chain. The band structure calculations are performed for three different positions of the proton in the hydrogen bond. In this way, we address the problem of the influence of the proton position on the electronic properties of the chain, in particular the band gap. It is shown that the band gap is very large, of the order of 9 eV, and does not depend on the proton position. It is concluded that the conductivity observed along the hydrogen-bonded chains in the imidazole single crystals is protonic in nature and a soliton model for proton transfer along the chains is put forward.