Nuclear Scalar Spin-Spin Coupling Reveals Novel Properties of Low-Barrier Hydrogen Bonds in a Polar Environment

The quantum-chemical calculation of NMR indirect spin–spin coupling constants

“…This situation changed dramatically in the 1990s, with the first measurements of hydrogen-bond transmitted coupling constants [243][244][245][246][247][248][249]. Nowadays, much work is directed towards this particular aspect of spin-spin coupling constants, which has developed into a field of fruitful collaboration between experimental NMR spectroscopists and computational chemists.…”

A review with comprehensive data on experimental indirect scalar NMR spin–spin coupling constants across hydrogen bonds

“…• With HF [57,60,63,68] • With carboxylic acids [64,66] • With another pyridine (collidine/collidinium) [58] 3. Biological molecules and related compounds [59,61,67,69] …”

Characterizing Hydrogen Bonding and Proton Transfer in 2:1 FH:NH3 and FH:Collidine Complexes through One- and Two-Bond Spin−Spin Coupling Constants across Hydrogen Bonds

“…In a previous paper, we examined spin-spin coupling constants in 1:1 FH:NH 3 and FH:pyridine complexes as a function of proton position along the proton-transfer coordinate. 1 The computed one-bond F-H coupling constants ( 1 J F-H ) for these two complexes are large and positive at equilibrium, but become negative as the proton is transferred and hydrogenbonded ion-pairs F -: + HNH 3 and F -: + Hpyridine are formed.…”

“…Thus, the signs of these reduced coupling constants are consistent with generalizations made recently concerning the signs of reduced one-and two-bond spin-spin coupling constants across traditional X-H-Y hydrogen bonds. Moreover, 1 K F-H and 1h K H-N change sign as the proton is transferred from F to N. [4][5][6][7] The trimer FH:FH:NH 3 was included in a recent study of the effect of a third polar near-neighbor (AH) on one-and twobond spin-spin coupling constants across the X-H-Y hydrogen bond in trimers AH:XH:YH 3 , where A and X are 19 F and/ or 35 Cl, and Y is either 15 N or 31 P. 8 However, in that study, only X-H, X-Y, and H-Y coupling constants for equilibrium structures were examined. In the present work we expand the study of the F b H b :F a H a :NH 3 trimer by (1) investigating changes in F a -H a , H a -N, and F a -N coupling constants along the F a -H a -N proton-transfer coordinate, (2) presenting coupling constants for selected nonequilibrium transition and protontransferred structures on the trimer potential surface, (3) examining changes in coupling constants involving the F-H-F hydrogen bonds in these complexes, and (4) using coupling constants for 2:1 FH:NH 3 complexes computed at 2:1 FH:NH 3 , 2:1 FH:pyridine, and 2:1 FH:collidine geometries to provide…”