Rotational spectroscopy of the gas phase complex of water and bromine monochloride in the microwave region: Geometry, binding strength and charge transfer

Density Functional Theory Studies of Bonding in Complexes H3N···XY of Ammonia and Dihalogen Molecules: A Comparison with Experimental Results from Rotational Spectroscopy

“…The dissociation energies, electron transfer (Fig. 3) and Wiberg indices of the complexes (Table 4) investigated here indicate that the relative acceptor strengths of the halogens have the same trend as shown by the NQCC of a given halogen and a similar trend as that described by the intermolecular stretching force constant [9]. The conclusions of the calculations reported here are consistent with a picture of the interaction in H 3 N XY that is predominantly electrostatic in origin and agree well with those derived experimentally from rotational spectroscopy.…”

“…This correlation between the fraction (N X) of an electronic charge donated from N to X and the calculated dissociation energies for halogen-bonded complexes contrasts with the different situation found for the main group and transition metal complexes [21]. The quantity (X-Y) has also been measured experimentally for several H 3 N XY complexes by a method based on the changes in the nuclear quadrupole coupling constants of the halogen molecules when subsumed into the complex and discussed in detail in [9]. The values are 0.009, 0.066, 0.069 and 0.15 for XY = Cl 2 , Br 2 , BrCl and ICl, respectively.…”

“…The values are 0.009, 0.066, 0.069 and 0.15 for XY = Cl 2 , Br 2 , BrCl and ICl, respectively. (The method described in [9] cannot be applied to H 3 N ClF because it depends on each halogen nucleus having a non-zero electric quadrupole moment and this is not the case for F). These val- ues of (X-Y) are all smaller than the corresponding quantities calculated here by the DFT approach, but by a nearly constant amount.…”

“…Analysis of hyperfine structure leads to the electric field gradient (EFG) at each halogen nucleus and, via a comparison of the EFG in the complex and the free halogen, to the changes in the extent of electric charge redistribution that accompanies complex formation. In fact, val- ues of the fractional intermolecular electron transfers (B X)e and (X Y)e have been obtained experimentally by application of the simple Townes-Dailey model to the observed nuclear quadrupole coupling constants (NQCC) [9]. A conclusion about the type of complex (inner or outer) is then possible once these quantities are known.…”

Halogen Bonding with Dihalogens and Interhalogens

“…Microwave studies of organohalogen complexes are also rare. Conversely, such studies are a powerful tool for examining gas phase bond energies and geometries of X 2 and XY complexes [13][14][15], and a chapter from A.C. Legon in this book specifically deals with this topic [16].…”