ESR measurements of the partitioning of some new spin probes in n-octanol-water

The stable free radical 1,1,3,3-tetramethylisoindolin-2-yloxyl (TMIO) has p roved to be very suitable for use as a spin probe for a number of applicati ons. Because it is soluble mainly in non-polar liquids, there is a need for new derivatives that can be used in a variety of environments. This has be en done by introducing substituents in the 5-position of the aromatic ring, namely carboxyl (CTMIO), trimethylamino (TMTMIOI) and sodium sulphonate (N aTMIOS). An accurate ESR method was developed for the measurement of partit ion coefficients in n-octanol-water. For comparison purposes the method was also applied to some Tempo derivatives. The effect of temperature on the r otational correlation times and the nitrogen-14 hyperfine coupling constant of some of the spin probes was investigated. There is evidence for dimeriz ation of CTMIO to form a biradical. Copyright (C) 1999 John Wiley & Sons, L td.