Improved correlation analysis of electron spin resonance spectra: pyridylmethyl radicals

Abstract

2-, 3-, and 4-Pyridylmethyl (picolyl) radicals have been prepared in fluid solution by hydrogen or halogen abstraction from the corresponding hydride or chloride. The weak e.s.r. spectra have been analysed by improved correlation methods: results agree with INDO calculations about as well as do those for benzyl radicals. All three radicals have higher spin density at the α-position than does benzyl: the order is 4 > 2 > 3 > benzyl. Improvements in correlation techniques required for this analysis include a method for finding the centre of a spectrum without prior determination of the coupling constants, and MULTIPEAK, a method of establishing new coupling constants, which uses the whole information available in the spectrum and which is particularly useful in the analysis of spectra with numerous doublet splittings.