A Novel Synthesis of Soluble, Stable Derivatives of the Perchlorinated Trityl Radical

A new approach to the synthesis of derivatives of the perchlorinated tritryl radical is described. It relies on the fact that, under the conditions required to fully chlorinate the ortho positions of a triarylmethane, there is only minimal substitution of aryl fluorine by chlorine and then on the fact that, in the mixed Cl/F substituted triarylmethanes obtained, it is possible to selectively substitute the fluorine-bearing positions using the sodium salt of n-hexanol in n-hexanol/dimethylsulfoxide. The meta-hexyloxy derivatives obtained are much more soluble and photostable than the parent perchlorotrityl radical. For example, the introduction of four meta-hexyloxy substituents gives a radical where, under white light illumination, the lifetime is improved by a factor of almost 10⁴. The photostability of the radical, the lifetime of the excited state and the fluorescence all decrease as the number of meta-hexyloxy substituents is increased. The improvements in solubility and in photostability observed should help in creating a more diverse range of perchlorotrityl radical derivatives and in the development of new applications.