title: Intriguing Electrostatic Potential of CO: Negative Bond-ends and Positive Bond-cylindrical-surface.
abstract: The strong electronegativity of O dictates that the ground state of singlet CO has positively charged C and negatively charged O, in agreement with ab initio charge analysis, but in disagreement with the dipole direction. Though this unusual phenomenon has been fairly studied, the study of electrostatic potential (EP) for noncovalent interactions of CO is essential for better understanding. Here we illustrate that both C and O atom-ends show negative EP (where the C end gives more negative EP), favoring positively charged species, whereas the cylindrical surface of the CO bond shows positive EP, favoring negatively charged ones. This is demonstrated from the interactions of CO with Na(+), Cl(-), H2O, CO and benzene. It can be explained by the quadrupole driven electrostatic nature of CO (like N2) with very weak dipole moment. The EP is properly described by the tripole model taking into account the electrostatic multipole moments, which has a large negative charge at a certain distance protruded from C, a large positive charge on C, and a small negative charge on O. We also discuss the EP of the first excited triplet CO.
authors.affiliation: Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea.
authors.forename: Hahn
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Chemistry, School of Natural Science, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Korea.
authors.forename: Van Dung
authors.initials: VD
authors.lastname: Doan
authors.affiliation: Department of Chemistry, School of Natural Science, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Korea.
authors.forename: Woo Jong
authors.initials: WJ
authors.lastname: Cho
authors.affiliation: Department of Chemistry, School of Natural Science, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Korea.
authors.forename: Rosendo
authors.initials: R
authors.lastname: Valero
authors.affiliation: Department of Chemistry, School of Natural Science, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Korea.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Aliakbar Tehrani
authors.affiliation: Department of Chemistry, School of Natural Science, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Korea.
authors.forename: Jenica Marie L
authors.initials: JM
authors.lastname: Madridejos
authors.affiliation: Department of Chemistry, School of Natural Science, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Korea.
authors.forename: Kwang S
authors.initials: KS
authors.lastname: Kim