title: Ab initio study on anomalous structures of anionic [(N-heterocycle)-CO2]-complexes.
abstract: Several unusual anionic complexes between carbon dioxide (CO2) and N-heterocycles (NHCs) possessing a significantly positive adiabatic electron affinity over 0.7 eV were studied by density functional theory calculations (UB3LYP/6-311++g(d,p)). Unlike all previously reported [NHC-CO2]-anions with a coplanar structure that ensures full delocalization of the negative charge through extended π-conjugation, this new class of anionic [NHC-CO2]-complexes has a strongly non-coplanar geometry and no π-bond character between CO2and NHC. Despite the fundamental differences in chemical bonding between all prior cases and the new class of [NHC-CO2]-complexes, we found that the CO2moiety in the latter still has a large negative charge (∼0.4 e) and a strongly bent geometry (O-C-O angle of ∼140°) just like in the former. This seemingly anomalous case was explained by a simple model based on the torsional steric effect and the electron affinities of the constituent moieties.
authors.affiliation: Department of Chemistry, Seoul National University, Seoul 08826, South Korea.
authors.forename: Rena
authors.initials: R
authors.lastname: Oh
authors.affiliation: Department of Chemistry, Seoul National University, Seoul 08826, South Korea.
authors.forename: Eunhak
authors.initials: E
authors.lastname: Lim
authors.affiliation: Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA.
authors.forename: Xinxing
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Biomedical Technology, Sangmyung University, Seoul 31066, South Korea.
authors.forename: Jiyoung
authors.initials: J
authors.lastname: Heo
authors.affiliation: Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA.
authors.forename: Kit H
authors.initials: KH
authors.lastname: Bowen
authors.affiliation: Department of Chemistry, Seoul National University, Seoul 08826, South Korea.
authors.forename: Seong Keun
authors.initials: SK
authors.lastname: Kim