Nuclear quadrupole resonance of charge-transfer complexes. II. The aminehalogen complexes

Abstract

Nuclear quadrupole resonance frequencies have been measured for some of the halogen nuclei in a number of crystalline charge-transfer complexes of amines with bromide, iodine, iodine monobromide, and iodine monochloride. From these measurements it has been possible to calculate approximate charge distributions for the bromine, iodine monobromide, and iodine monochloride complexes of 3,5-di-bromopyridine. The results correlate well with a three-centre delocalized LCAO-MO bonding theory. The correlation of this MO description with Mulliken's charge-transfer bonding scheme for n-σ complexes is discussed. This approach indicates the importance of considering an ?ionic? structure (which does not involve transfer of charge from the donor to the acceptor) in the electronic ground state of these complexes.