A Simple and Convenient Synthesis of a Multifunctional Spin Probe, Phosphonate Derivative of a Persistent Radical of the Triarylmethyl Series

The reaction of tris(8-carboxy-2,2,6,6-tetramethylbenzo[1,2-d;4,5-d′]bis[1,3]dithiol-4-yl)methanol, diamagnetic precursor of Finland trityl radical} with trifluoroacetic acid gave the corresponding triarylmethyl cation. Nucleophilic quenching of this cation with triethyl phosphite generated trityl radical containing a diethyl phosphonate moiety, and hydrolysis of the latter to phosphonic acid afforded a multifunctional oxygen- and pH-sensitive spin probe.