Critical analysis of the through‐space transmission of NMRJ_FHspin–spin coupling constants

Abstract

NMR JFH coupling constants transmitted through space are known to show several unusual peculiarities. The main three are (a) in many cases their experimental values are reported to be positive and in others, negative; (b) theoretical values show that in some cases they are substantially contributed not only from the Fermi contact (FC) term but also from the paramagnetic spin orbit (PSO) term, and their respective signs could be either like or unlike; (c) in many cases it can hardly be expected that the corresponding FH proximate interactions could be considered a “hydrogen bond,” whereas in other cases it is evident that they are. For discussing points (a) and (b), characteristics of both the FC and PSO terms are discussed performing qualitative analyses based on their expressions given in terms of the polarization propagator formalism. Point (c) is discussed in terms of the well‐known Bader's QTAIM method as well as recalling the known relationship between the transmissions of the Fermi hole and of the FC interaction of spin–spin coupling constants. © 2012 Wiley Periodicals, Inc.

Investigating Unusual Homonuclear Intermolecular “Through-Space” J Couplings in Organochalcogen Systems

“…In the solid state, however, it should, in principle, be possible to see intermolecular through-space J couplings, that is, between different molecules, if they are held in close proximity by the crystal packing. The existence of these interactions, and their relative magnitude in simple systems, has been studied computationally. ,− However, there remain relatively few experimental reports of any through-space J couplings in solids, either intermolecular or intramolecular, in the literature, − although some J couplings through intermolecular hydrogen bonding interactions have been observed . Examples of intramolecular through-space couplings observed in the solid state have included the observation of 77 Se– 125 Te and 31 P– 125 Te couplings in peri-substituted naphthalenes, , 11 B– 31 P interactions in frustrated Lewis pairs in alkenes, and 31 P– 31 P interactions in ferrocenes .…”

Latin American contributions to quantum chemical topology

“…These results indicate that ED, a property dependent on the pair density, carries information concerning the experimentally measurable NMR indirect coupling constants. Nevertheless, in an NMR study of how J FH indirect coupling constants transmit through space, Tormena et al found cases wherein the FC term can have negative values. However, as the contributions to the delocalization index are positive, the authors pointed out that the relation between the NMR indirect coupling constants and delocalization indexes should be taken with caution.…”

The electronic origin of unusually large nJFN coupling constants in some fluoroximes

“…The importance played by overlap interactions on the through‐space transmission of SSCCs is remarkable; thus, the overlap matrix (S) elements were evaluated using the natural bond orbital (NBO) analysis, implemented in the Gaussian 09 suite of programs. These calculations were performed with the B3LYP hybrid functional using the EPR‐III basis set.…”

“…Because in all cases, the FC contribution is the most significant one, special emphasis is put in rationalizing its transmission. It is important to recall that recently, it was found that the transmission of the coupling constant nTS J FH SSCCs originates in the competition between the overlaps of the X‐H bond with the C‐F bond and with the F non‐bonding electron pairs. In those cases, the proximity between fluorine lone pair LP 2 (F) and hydrogen atom increases the s % character of the LP 2 (F) playing an important contribution to the through‐space transmission of the FC term for some J FH SSCCs.…”