ESR study on some copper(II) complexes of bis(4′‐benzo‐15‐crown‐5)

ESR measurements have been carried out for some copper(II) complexes of bis(4′‐benzo‐15‐crown‐5) at 77 K. The results of ESR spectrometric titration indicated that the binuclear complexes were prepared in the present system. The binuclear complexes revealed characteristic ESR g‐anisotropies (gZ<gX, gY) which are typical of the copper(II) complexes with a 3d z 2 ground state doublet. However, in this case, the innermolecular copper(II)‐copper(II) spin interaction was not observed. ESR measurements also showed that a small amount of the sandwich type copper(II) complexes were formed in the presence of excess bis (4′‐benzo‐15‐crown‐5). A reasonable explanation was given for the ESR results.