STABLE POLYRADICALS WITH HIGH-SPIN GROUND-STATES .2. SYNTHESIS AND CHARACTERIZATION OF A COMPLETE SERIES OF POLYRADICALS DERIVED FROM 2,4,6-TRICHLORO-ALPHA,ALPHA,ALPHA',ALPHA',ALPHA'',ALPHA''-HEXAKIS(PENTACHLOROPHENYL)MESITYLENE WITH S = 1/2, 1, AND 3/2 GROUND-STATES

The series of stable polyradicals 2-4 was synthesized via the title mesitylene hydrocarbon. Cyclic voltammetry of radicals 2-4 revealed, in accordance with the number of radical centers and their topologies, several reversible one-electron reduction processes. Reduction potentials of the radicals clearly show the existence of mutual electronic interactions between their redox centers. ESR spectra obtained in glassy toluene at low temperature were consistent with 2, 3, and 4 in doublet, triplet, and quartet states, respectively. The high-spin states of radicals 3 and 4 were shown to be the ground states by magnetic (susceptibility, magnetization, and ESR) measurements. In addition, such measurements showed that their nearby low-spin states are thermally unaccessible. Polyradicals 3 and 4 exist in several interconvertible stereoisomeric forms. Zero field splitting (zfs) parameters and anisotropic g components of such stereoisomeric forms are given. On the basis of the relative values of these magnetic parameters, structural assignations to each one of these stereoisomers have been made. In the case of triradical 4, its stereoisomeric forms have C2 and D3 symmetries and are isolable (HPLC) as solids showing outstanding stabilities (stable in air up to 250-degrees-C).