Charge-transfer character of halogen bonding: Molecular structures and electronic spectroscopy of carbon tetrabromide and bromoform complexes with organic σ- and π-donors

Abstract

Carbon tetrabromide and bromoform are employed as prototypical electron acceptors to demonstrate the charge-transfer nature of various intermolecular complexes with three different structural types of electron donors represented by (1) halide and pseudohalide anions, (2) aromatic (π-bonding) hydrocarbons, and (3) aromatics with (n-bonding) oxygen or nitrogen centers. UV–Vis spectroscopy identifies the electronic transition inherent to such [1:1] complexes; and their Mulliken correlation with the donor/acceptor strength verifies the relevant charge-transfer character. X-ray crystallography of CBr4/HCBr3 complexes with different types of donors establishes the principal structural features of halogen bonding. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:449–459, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20264