Jahn-Teller distortions of tris(ethylenediamine)copper(II) complexes

ESR spectra between room and liquid helium temperature of a number of Cu(en):+ complexes have been interpreted on the basis of dynamic-static Jahn-Teller distortions. On this very same idea assignment of the electronic spectra has also been suggested which can well be operative for all of the complexes with crystallographic D3 or Th symmetries reported to date. The possibility of observing the two types of distortions, Le., trans elongation or compression, has been discussed. From the temperature dependence of the ESR line width, the residence time of the complex in each potential well has been determined. Such a time has been found to be intermediate between the ESR and electronic time scales thus accounting for the experimental data