Metal Isotope Effects on the Vibrational Spectra of Polymeric Metal Complexes. V. Infrared Spectra of Bis (L-and DL-phenylalaninato) copper (II)

Abstract

The infrared spectra of bis (L-and DL-phenylalaninato) copper (II) and their N-deuterated analogues have been recorded in the region between 4000 and 200cm^-1. The vibrational assignments of the Cu-ligand stretching vibrations have been made by means of the metal isotope technique, ⁶³Cu and ⁶⁵Cu substitution. Three bands of trans-bis (L-phenylalaninato) copper at 400, 380, and 339cm^-1 shift appreciably on ⁶³Cu-⁶⁵Cu substitution. The blue isomer of bis (DL-phenylalaninato) copper also shows three copper isotope-sensitive bands at 380, 340, and 328cm^-1, analogous to those of trans-bis (D-alaninato)-and (L-phenylalaninato) copper. However, the blue-violet isomer of the DL complex shows only two sensitive bands at 370 and 322cm^-1, as in the case of cis-bis (D-alaninato) copper. Frequency shifts on N-deuteration suggest that one of the Cu-N stretching vibrations is at higher frequency than the Cu-O stretching vibrations for bis (L-phenylalaninato) copper, but this frequency order is reversed for the two isomers of bis (DL-phenylalaninato) copper, but this frequency order is reversed for the two isomers of bis (DL-phenylalaninato) copper.