Oxidation Products of Doubly Trimethylene-Bridged Tetrabenzyl p-Phenylenediamine Paracyclophane

Formation of persistent organic diradicals from N,N'-diphenyl-3,7-diazacyclooctanes

ABSTRACT

N,N'-Diphenyl-3,7-diazacyclooctane and structurally related N,N'-diphenylbispidine derivatives react with silver(I) ions in a high-yielding C-C coupling reaction to produce dication-diradical species, with the silver ions serving a double function both as template and as an oxidant. The resulting bis(benzidino)phane derivatives are persistent organic radicals, stable for several months in solution as well as in the solid state, at room temperature and above, as well as being exposed to the atmosphere. The molecular structure features a double-decker cyclophane motif, stabilized by intramolecular π-dimerization of two delocalized benzidinium radical segments. Intermolecular π-dimers are formed in the solid state.

GRAPHICAL ABSTRACT

Carboranes in the chemist's toolbox

Once seldom encountered outside of a few laboratories, carboranes are now everywhere, playing a role in the development of a broad range of technologies encompassing organic synthesis, radionuclide handling, drug design, heat-resistant polymers, cancer therapy, nanomaterials, catalysis, metal-organic frameworks, molecular machines, batteries, electronic devices, and more. This perspective highlights selected examples in which the special attributes of carboranes and metallacarboranes are being exploited for targeted purposes in the laboratory and in the wider world.