title: Indirect nuclear 15N-15N scalar coupling through a hydrogen bond: dependence on structural parameters studied by quantum chemistry tools.
abstract: NMR spin-spin couplings through a hydrogen bond in the free-base and protonated forms of the complete series of [(15)N2]-N-methylated 1,8-diaminonaphthalenes have been analyzed using quantum chemistry tools. The dominating role of the overlap of the coupling pathway orbitals has been demonstrated. The correlation of the sum of the (13)C NMR shifts of the naphthalene ring C(1,8) carbons directly attached to the interacting nitrogens with the J(N-N) values and the degree of methylation found earlier by G. C. Lloyd-Jones et al. [Chem.-Eur. J. 2003, 9, 4523] have been reexamined. It has been found that the correlations of J(N-N) and [ΔΣC(1,8)] with the degree of methylation have different reasons. While the former is mostly connected with the structural changes due to the solvent effect, the latter is attributed to the changes in the paramagnetic contributions from the C-N and C-C bonds caused by the replacement of a hydrogen by a methyl group.
authors.affiliation: Institute of Inorganic Chemistry, Slovak Academy of Sciences , Dúbravská cesta 9, SK-84536 Bratislava, Slovakia.
authors.forename: Anežka
authors.initials: A
authors.lastname: Křístková
authors.forename: James R
authors.initials: JR
authors.lastname: Asher
authors.forename: Vladimir G
authors.initials: VG
authors.lastname: Malkin
authors.forename: Olga L
authors.initials: OL
authors.lastname: Malkina