ESR studies of free radicals derived from hydroxyquinones. Part I: Group 14 adducts of hydroxynaphthoquinones

The group 14 organometallic radical adducts of l&naphthoquinone, lawsone, juglone, plumbagin, and naphthazarin have been investigated by ESR spectroscopy. The results are discussed in terms of the regioselectivity of the addition reaction, the effects of hydroxyl substituent and intramolecular hydrogen bonding on the electron spin density distribution, and the effects of varying the group 14 metal from silicon to lead.