Interaction between closed and open-shell molecules. V. 13C contact shift and molecular orbital studies on the interaction between halogenated molecules and nitroxide radical

Abstract

13C NMR contact shifts induced by the addition of the di- tert-butyl nitroxide (DTBN) radical were observed for halomethanes, haloethanes, haloethylenes and halobenzenes. The sensitively induced downfield 13C contact shifts for the carbon bonded directly to halogen were of the order of 1 /s > Br /s > Cl. These results were interpreted in terms of electron donor-acceptor interaction of halides with the DTBN radical with the aid of INDO MO calculations of electron spin density on the carbon atoms of halide molecules.