title: Quantum chemical characterization of the vertical electron affinities of didehydroquinolinium and didehydroisoquinolinium cations.
abstract: Vertical electron affinities (EA) are predicted for the lowest energy singlet states of the 21 didehydroquinolinium cation isomers and the 21 didehydroisoquinolinium cation isomers, as well as the doublet states of the seven dehydroquinolinium cation isomers, the seven dehydroisoquinolinium cation isomers, the seven N-methyldehydroquinolinium cations, and the seven N-methyldehydroisoquinolinium cations, by using density functional theory. For the monoradicals, the calculated EA of the radical site depends only on the distance from the (formally charged) nitrogen atom, and is reduced by 0.14-0.24 eV when the NH+ group is replaced with an NCH3+ group. Nearly all of the calculated EAs for the ortho biradicals are lower (by 0.04-0.72 eV) than those for either of the corresponding monoradicals. For the meta biradicals, the calculated EAs lie either between the EAs of the corresponding monoradicals or higher (by 0.07-0.58 eV), and they are extremely sensitive to the separation (distance) between the two dehydrocarbon atoms. For the biradicals that do not have either an ortho or meta relationship the calculated EAs are all higher (by 0.02-1.93 eV) than those for either of the corresponding monoradicals. The EAs are examined to gain insight into the nature of inductive/field and resonance effects that influence the electrophilicity of the radical site(s), which is a major factor controlling the reactivity of these types of (bi)radicals.
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA. jnash@purdue.edu
authors.forename: John J
authors.initials: JJ
authors.lastname: Nash
authors.forename: Hilkka I
authors.initials: HI
authors.lastname: Kenttämaa
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Cramer
mesh_terms: D002412:Cations / Q000737:chemistry; D003198:Computer Simulation; D004583:Electrons; D007546:Isoquinolines / Q000737:chemistry*; D008956:Models, Chemical; D015394:Molecular Structure; D011789:Quantum Theory; D011806:Quinolinium Compounds / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D002412:Cations; D007546:Isoquinolines; D011806:Quinolinium Compounds