Inverse halogen dependence in anion C-13 NMR

Autor(es)

Viesser, Renan V. ^[1] ; Tormena, Claudio F. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Campinas UNICAMP, Inst Chem, POB 6154, BR-13083970 Campinas, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Physical Chemistry Chemical Physics; v. 23, n. 4, p. 3019-3030, JAN 28 2021.
• Citações Web of Science: 0

Resumo

Halogens cause pronounced and systematic effects on the C-13 NMR chemical shift (delta C-13) of an adjacent carbon nucleus, usually leading to a decrease in the values across the halogen series. Although this normal halogen dependence (NHD) is known in organic and inorganic compounds containing the carbon atom in its neutral and cationic forms, information about carbanions is scarce. To understand how delta C-13 changes in molecules with different charges, the shielding mechanisms of CHX3, CX3+, and CX3- (X = Cl, Br, or I) systems are investigated via density functional theory calculations and further analyzed by decomposition into contributions of natural localized molecular orbitals. An inverse halogen dependence (IHD) is determined for the anion series as a result of the negative spin-orbit contribution instead of scalar paramagnetic effects. The presence of a carbon nonbonding orbital in anions allows magnetic couplings that generate a deshielding effect on the nucleus and contradicts the classical association between delta C-13 and atomic charge. (AU)

• Processo FAPESP: 17/20890-1 - Avaliação dos mecanismos de blindagem e de transmissão dos acoplamentos em RMN de 1H, 13C e 19F
• Beneficiário: Renan Vidal Viesser
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 15/08541-6 - Ressonância magnética nuclear: além da determinação estrutural
• Beneficiário: Claudio Francisco Tormena
• Modalidade de apoio: Auxílio à Pesquisa - Temático