Anomalous line broadening in the ESR spectra of copper(II) dithizonate

The structure of the copper(II) complex with dithizone (H(2)Dz) was studied by ESR spectroscopy. The lines of the ESR spectra of the Cu(H Dz)(2) compl ex in solutions are so broad that the superhyperfine structure (SHFS) from the ligand atoms is unobservable and even the hyperfine structure (SHFS) fr om the copper nuclei is poorly resolved. In polycrystalline magnetically di lute powders with the ratio Ni(HDz)(2): Cu(HDz)(2)=60: 1, the SHFS from the N atoms is well resolved in both perpendicular and parallel Orientations. The copper(II) complex with dithizone has a square-planar structure in both liquid solutions and Ni(HDz)(2) matrix. Reasons for the unusual linewidths in the ESR spectra of Cu(HDz)(2) are discussed.