Reliability of the density functional approximation to describe the charge transfer and electrostatic complexes involved in the modeling of organic conducting polymers -: art. no. 026704

Both the intermolecular interaction energies and the geometries for M center dot center dot center dot thiophene, M center dot center dot center dot pyrrole, Mn+center dot center dot center dot thiophene, and Mn+center dot center dot center dot pyrrole (with M=Li, Na, K, Ca, and Mg; and Mn+=Li+, Na+, K+, Ca2+, and Mg2+) have been estimated using four commonly used density functional theory (DFT) methods: B3LYP, B3PW91, PBE, and MPW1PW91. Results have been compared to those provided by HF, MP2, and MP4 conventional ab initio methods. The PBE and MPW1PW91 are the only DFT methods able to provide a reasonable description of the M center dot center dot center dot pi complexes. Regarding Mn+center dot center dot center dot pi complexes, the four DFT methods have been proven to be adequate in the prediction of these electrostatically stabilized systems, even though they tend to overestimate the interaction energies.