INERT CARBON FREE-RADICALS .12. SYNTHESIS, ELECTRONIC-SPECTRA, AND MAGNETIC-PROPERTIES OF STABLE POLYMERIC POLYRADICALS WITH PERCHLOROTRIPHENYLMETHYL RADICAL UNITS

Taking steric hindrance as a guiding principle for the design of high- spin organic polymers, four stable polymeric polyradicals oro-(4,4'-di methyltriphenylmethyl)-alpha',alpha''- diylidene) (ERHP, 5), y(perchlo ro-(4,4'-dimethyltriphenylmethyl)-alpha', alpha''-diyidine) (ARHP, 4), e)tris(perchloro-p-xylene-alpha,alpha'-diylidene)] (ERCP, 10), and po ly[(perchloro-(4, idyne-alpha'-ylidene)bis(perchloro-p-xylene-alpha, a lpha'-diylidene)] (ARCP, 9)] with a polymerization degree of 13-28 and high radical purities (about 90%) have been synthesized and character ized. These polymers are highly colored substances, while ARHP and ARC P are dark green, ERHP and ERCP are dark red, depending on the presenc e of triple bonds in the connecting bridges. The electronic spectra of ERHP and ERCP show evidence of the presence of degenerate or nearly d egenerate states (SOMOs) caused by steric hindrance. The spin-spin int eractions in all these polyradicals are governed by the nature and len gth of the connecting bridges. Thus, while with long bridges (ARCP and ERCP) the interactions are negligible, with short ones (ARHP and ERHP ) stronger spin-spin interactions appear. While ARHP, with ethynylene bridges, shows strong intramolecular antiferromagnetic interactions, E RHP with vinylene ones, presents the characteristic magnetic behavior of a near degeneracy between its low- and high-spin states, as ascerta ined by SQUID magnetometry in the 4-300 K temperature range and ESR sp ectrometry in the 77-300 K temperature range. The magnetic behavior of these polyradicals agrees with their electronic spectral data.