TOWARD ORGANIC-SYNTHESIS OF A MAGNETIC PARTICLE - DENDRITIC POLYRADICALS WITH 15 AND 31 CENTERS FOR UNPAIRED ELECTRONS

Starting from a bromo triether derivative 1, we prepared a homologous pentadecaether, which is a precursor for the title pentadecaradical, b y repeating twice the following two-step procedure (total of four step s): (1) Br/Li exchange followed by the addition of the organolithium t o a benzoic acid ester derivative and (2) conversion of the triarylmet hyl alcohol to methyl ether. Similarly, a 31-ether precursor was prepa red by repeating three times the above sequence (total of six steps). The polyethers were converted with lithium metal in THF to the corresp onding carbopolyanions and, subsequently, oxidized with iodine at 180 K to give the polyradicals. The polyradicals were studied in frozen TH F and 2-MeTHF solutions by SQUID magnetometry in the 2-80 K temperatur e range and the 0-5.5-T magnetic field range; spin values, which are l ower than expected for strong ferromagnetic coupling, were obtained. O ne of the possible explanations is the presence of defects, which disr upt ferromagnetic coupling between the triarylmethyl sites in these si ngle-path pi-conjugated systems; relationship of the current work to t he percolation problem is discussed.