title: Weak interactions as diagnostic tools for inductive effects.
abstract: No broadly applicable and well-defined measure for the inductive effects of substituents (outside of the context of substituted benzenes) exists. We assess the viability of two different forms of weak interactions as tools for this purpose. The responses of interatomic (I···N and Ge···N) separations in the halogen-bonded and dative covalent complexes F3CI···Y and FH3Ge···Y, where Y = NH2R, afford a direct ordering of a diverse set of substituents, R, according to their influence on the availability of the N lone pair in the base (NH2R) for bonding. Despite their structural and electronic differences, the two bonding modes that we consider show good qualitative agreement on the electron-withdrawing inductive tendencies of substituents because of their sensitivity to the electronic environment at the donor site (the N center, in this case) on the base. The choice of the monosubstituted (NH2R) base minimizes steric interactions, resonance, and other electronic effects that could interfere with the bonding between N and the I or Ge centers in the complexes. We find, moreover, that the inductive tendencies for substituents in these complexes are, in general, not additive. Depending on the identity of R, the trisubstituted base (NR3) may actually reverse rather than enhance changes in the acid-base interactions that are achieved going from NH3 to NH2R. These outcomes are observed at the MP2(full) and the M06-2X levels of theory, for both halogen and dative bonding interactions. A conservative ordering of substituents according to the observed inductive tendencies is presented.
authors: Department of Chemistry, Gottwald Center for the Sciences, University of Richmond, Richmond, Virginia 23173, United States.
authors: Kelling J
authors: KJ
authors: Donald
authors: Department of Chemistry, Gottwald Center for the Sciences, University of Richmond, Richmond, Virginia 23173, United States.
authors: Marina
authors: M
authors: Tawfik
authors: Department of Chemistry, Gottwald Center for the Sciences, University of Richmond, Richmond, Virginia 23173, United States.
authors: Brandon
authors: B
authors: Buncher