Weaker Bonds with Shorter Bond Lengths
نویسندگان
چکیده
One of the paradigms of chemistry predicts that the shorter the bond of a given type is always the stronger bond. Although this qualitatively holds for many compounds, there exists no general proof that this is always correct. Here, we discuss molecules, for which longer bonds lead to stronger rather than weaker bonds. This is possible by introducing the local mode stretching force constants as reliable bond strength descriptors. For the fl uoroamines NH2F (1), NHF2 (2), and NF3 (3), the NF bond length decreases whereas the NF bond strength decreases. Similar effects are found for bonds involving a heavy element with a distinct relativistic effect. A rational for these fi ndings will be given.
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