Synthesis and study of Cu II complex with nitroxide, a jumping crystal analog

摘要: We synthesized 1-ethylimidazolyl-substituted nitronyl nitroxides, i.e., 2-(1-ethylimidazol-4-yl)- (L4Et) and 2-(1-ethylimidazol-5-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole 3-oxide-1-oxyl (L5Et). The stable radical L5Et is an ethyl analog of 2-(1-methylimidazol-5-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole (L5Me) described earlier, the reaction which with Cu(hfac)2 (hfac 1,1,1,5,5,5-hexafluoropentane-2,4-dionate) leads to formation [Cu(hfac)2(L5Me)2] jumping crystals. reagent ratios 1: 2 1 yields heterospin complexes [Cu(hfac)2(L5Et)2] [Cu(hfac)2L5Et]2, respectively. X-ray diffraction study mononuclear complex determined that compound has a packing similar crystals studied only difference being O...O contacts between neigh- boring nitroxide groups were found be 0.3—0.5 A longer than in [Cu(hfac)2(L5Me)2]. As result lengthening these contacts, lack chemomechanical activi- ty. when cooling binuclear [Cu(hfac)2L5Et]2 below 50 K, antiferromagnetic exchange unpaired electrons >N—•O neighboring molecules full spin-pairing Cu2+ ions contributing residual paramagnetism compound.