A 19F NMR study of C-I•••π halogen bonding

The formation of halogen bonded complexes between toluene-d(8) and the perfluoroiodopropanes 1-C3F7I and 2-C3F7I has been investigated using F-19 NMR spectroscopy. For both Lewis acids, evidence was found for the formation of a C-I center dot center dot center dot pi halogen bonded complex. The complex formed is a 1:1 type. Using spectra recorded at different temperatures, the complexation enthalpies and entropies for the complexes were determined to be -2.9(1) kJ mol (1) and -19.1(2) J K (1) mol (1) for the 2-C3F7I center dot toluene-d(8) complex and -2.7(1) kJ mol (1) and -16.0(4) K (1) mol (1) for the 1-C3F7I center dot toluene-d(8) complex. The experimental results are supported by ab initio calculations at the B3LYP-PCM/6-311++G(d, p) + LanL2DZ* level. (C) 2011 Elsevier B. V. All rights reserved.