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Synthesis of phenols with potential biological activities and crystallography and magnetism of nitroxides
A series of 2,6-di-tert-butylphenols with para aza-heterocyclic rings and fluorinated was synthesized. These phenols were oxidized to the corresponding persistent phenoxyl radicals and their EPR spectra (spin density distribution) and kinetic decay rates were studied. ^ The varying electron spin delocalizations in the phenoxyl radicals were studied using EPR spectroscopy and UB3LYP/6-31G* spin density computations. Kinetic studies showed that the attachment of different heterocyclic rings results in varying degrees of the persistence of the 2,6-di-tert-butylphenoxyl radicals. The phenolic compounds themselves were tested for antioxidant activity, and were sent to the National Cancer Institute for in-vitro cell culture assays of their anticancer effect. The crystal structures and IR spectra of the phenols revealed phenolic OH---N hydrogen-bonding pattern despite the steric hindrance caused by tert-butyl groups. ^ Conjugated nitroxide radicals have been widely used for molecular magnetism. The delocalization of the spin density over the entire molecule makes a larger variety of magnetic interactions possible. The way the spins interact with each other can lead to paramagnetic, antiferromagnetic or ferromagnetic interactions. By examining the crystal structures of a number of nitroxides and nitronyl nitroxides bearing heteroatom substituents the relationship can be studied between close crystallographic contact spin sites and the resulting magnetic behavior is investigated. 2-(4,5,6,7-Tetrafluorobenzimidazol-2-yl)-4,4,5,5-tetramethyl-4,5,dihydro- 1H-imidazole-3-oxide-1-oxyl (F4BImNN) was synthesized and shown to be the first ferromagnetically coupled purely organic radical synthesized in the Lahti group. 1-(4-(N-[para-Methoxyphenyl]- N-hydroxylaminoxyl) phenyl)pyrrole (MNPP) was made and found to be a very rare example of a stable diarylnitroxide. It shows two-dimensional square planar antiferromagnetic exchange behavior, which is very unusual in purely organic electronic materials. 1-(4-[N-tert-Butylaminoxyl]-2,3,5,6-tetrafluorophenyl)pyrrole (BNPPF4) was made as the first fluorinated nitroxide subjected to magnetostructural analysis to our knowledge. Its crystal structure suggests possible one-dimensional antiferromagnetic interactions. However it interestingly shows magnetic behavior that is more consistent with a spin-pairing model. ^
"Synthesis of phenols with potential biological activities and crystallography and magnetism of nitroxides"
(January 1, 2007).
Electronic Doctoral Dissertations for UMass Amherst.