Infrared spectra of cupferron and some rare earth cupferrates

Infrared spectra of cupferron and some rare earth cupferrates have been obtained in the region of 4000-650 cm−1. Assignments of the various absorption bands are given. It is shown that on complex formation NO stretching frequencies are lowered and the deformation frequencies increased while the CN and NN stretching frequencies are not very much altered, indicating that the complex formation takes place through the oxygen of the NO groups. Comparison of the spectra of various rare earth cupferrates and the sodium salt shows that there is a change in covalency from sodium cupferrate to lanthanum cupferrate while amongst the various rare earth cupferrates there is not much change in covalency.