A polarization propagator analysis of through-space spin-spin coupling constants:19F-19F couplings

Abstract

The through-space transmission of I9F-I9F couplings is analyzed in a model compound employing inner projections of the polarization propagator, at the RPA and monoexcited CI levels, using an INDO ground state wave function. The emphasis of this work is (1) to study the dependence of the through-space transmitted component of such couplings on the interatomic F-F distance, and (2) to obtain an intuitive, although rigorous, model to describe the through-space transmission that could be used as a complementary tool in experimental measurements. In the first case an exponential decay is found and experimental data for different compounds are found to fit this curve fairly well. In the second case, localized molecular orbitals representing chemical functions are plotted, and the way in which they influence the through-space transmission is analyzed at the perturbator level as well as in inner projected polarization propagator terms. The important role played by the anti-bonding orbitals and the lone pairs of the F atoms is discussed.

C—H … O=C and C—H … H—C interactions in the side chains of 2-isopropylbenzaldehyde. A negative 5J(CHO,CH(CH3)2)

“…These shifts also imply that the side chains do not deviate from planarity by much more or Can = 5~p , gave rise to -0.30 Hz for 1 , in which the C-H bonds are proximate. Of course, 5~p is very sensitive to the interatomic distance (34,35), the contact contribution to the coupling constant depending on the overlap of orbitals o n the atoms or bonds carrying the coupled nuclei (36), s o that the present result is taken as confirmation of the proximate mechanism of 5~p , determined as -0.376(1) Hz in CS2/C6D12 and as -0.388(1) Hz in acetone-d6 solution. The slightly larger magnitude in the latter is consistent with the larger o-trans population in this solvent.…”

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants. Part 4: Bicycloalkanes

“…18,45 It was therefore a highly challenging task to find out whether the NBI effects would pronounce themselves at the SOPPA level. Further, it was of prime interest to test available additivity schemes of bridgehead-bridgehead carbon-carbon couplings along with other bridgehead carbon-proton and proton-proton couplings in bicycloalkanes derived in the paper by Della et al 46 on purely empirical grounds and in the two papers by Contreras and coworkers 45,47 based on the early IPPP (Inner Projections of Polarization Propagator 48 ) calculations. Accordingly, along with J(C,C), the corresponding J(C,H) and J(H,H) at bridgeheads were also calculated within the same approach, which beneficially provided an additional test of the reliability of SOPPA in reproducing experimental values of the different types of coupling constants in systems with marked deviations from the ordinary bonding environments.…”

Conformational dynamics of bis(BF2)‐2,2′‐bidipyrrins revealed by through‐space 13C19F and 19F19F couplings

“…Ruiz de Azua et al [16] used a method of polarization propagator analysis to calculate the through-space 19 F-19 F coupling and drew a similar relationship between the coupling constant and the internuclear distance in 1-fluoro-8-fluoromethyl-naphthalene, 1,12-difluorobenzo(c)-phenanthrene, and 4,5-difluorophenanthrene:…”