In a previous paper in this series, we discussed the formation of recoupled pair bonds in the aΣ states of CF and SF in which the recoupling process was essentially complete at the equilibrium geometry of the molecule. In this paper, we examine the Σ state of oxygen monofluoride (OF), which could also have a recoupled pair bond. Unlike the other two molecules, generalized valence bond calculations predict that the recoupling in OF is woefully incomplete at R and the resulting potential energy curve for the OF(aΣ) state is purely repulsive; the binding energy, ≈11 kcal/mol, is entirely due to dynamical correlation. A number of factors account for these differences, but the nature of the dominant correlation effect in the oxygen 2p lone pair as well as the spatial extent of the 2p orbital are paramount.
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Chemical shift tensors (CSTs) are sensitive probes of structure and dynamics. R-symmetry pulse sequences (RNCSA) can efficiently recouple CSTs of varying magnitudes in magic angle spinning (MAS) NMR experiments, for a broad range of conditions and MAS frequencies. Herein, we introduce dual-channel R-symmetry pulse sequences for simultaneously recording CSTs of two different nuclei in a single experiment (DORNE-CSA).
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