Experimental, SOPPA(CCSD), and DFT Analysis of Substitutent Effects on NMR (1)J(CF) Coupling Constants in Fluorobenzene Derivatives

Author(s)

Vilcachagua, Janaina Dantas ^[1] ; Ducati, Lucas C. ^[1] ; Rittner, Roberto ^[1] ; Contreras, Ruben H. ^{[2, 3]} ; Tormena, Claudio F. ^[1]

Affiliation

^[1] Univ Estadual Campinas, Inst Chem, BR-13084971 Campinas, SP - Brazil

^[2] Univ Buenos Aires, FCEyN, Dept Phys, Buenos Aires, DF - Argentina

^[3] IFIBA CONICET, Buenos Aires, DF - Argentina

• Document type: Journal article
• Source: Journal of Physical Chemistry A; v. 115, n. 7, p. 1272-1279, FEB 24 2011.
• Web of Science Citations: 26

Abstract

Interesting insight into the electronic molecular structure changes associated with substituent effects on the Fermi contact (FC) and paramagnetic spin-orbit (PSO) terms of (1)J(CF) NMR coupling constants (SSCCs) in o-X-, m-X-, and p-X-fluorobenzenes (X = NH(2); NO(2)) is presented. The formulation of this approach is based on the influence of different conjugative and hyperconjugative interactions on a second-order property, which can be qualitatively predicted if it is known how they affect the main virtual excitations entering into that second-order property. A set of consistent approximations are introduced in order to analyze the behavior of occupied and virtual orbitals, which define some experimental trends for (1)J(CF) spin-spin coupling constants. In addition, DFT hybrid functionals were used, and a similar degree of confidence to compute the (1)J(CF) with those observed for the SOPPA(CCSD) method was obtained. The (1)J(CF) SSCCs for ezetimibe, a commercially fluorinated drug used to reduce cholesterol levels, were measured and DFT-calculated, and the qualitative approach quoted above was applied. As a byproduct, a possible method to determine experimentally a significant PSO contribution to (1)J(CF) SSCCs is discussed. (AU)

• FAPESP's process: 05/59649-0 - Conformational equilibria studies by nuclear magnetic resonance spectroscopy, infrared spectroscopy and theoretical calculations
• Grantee: Roberto Rittner Neto
• Support Opportunities: Research Projects - Thematic Grants