Notes:
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Both the intermolecular interaction energies and the geometries for M ̄ thiophene, M ̄ pyrrole, M n+ ̄
thiophene, and M n+ ̄ pyrrole ͑with M = Li, Na, K, Ca, and Mg; and M n+ = Li+ , Na+ , K+ , Ca2+, and Mg2+͒
have been estimated using four commonly used density functional theory ͑DFT͒ 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 ̄ complexes. Regarding M n+ ̄ 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. |