EVIDENCE OF MIXED-VALENCE IN COPPER-COMPLEXES USING X-RAY SPECTRAL STUDIES

X-ray K-absorption spectral studies have been carried out on five mixe d valence copper complexes using a 0.4m Cauchois type bent crystal spe ctrograph. The complexes studied are (chtsc)(2) Cu. CuI; (pptsc)(2) Cu . CuI; (aptsc)(2) Cu. CuI; (bmtsc)(2) Cu. CuI and (detsc)(2) Cu.CuI wh ere (tsc) represents thiosemicarbazone. In these complexes there are t wo copper centres available, one for Cu(I) and the other for Cu(II). T he K-absorption edge structures in all the five complexes show two dis tinct edges revealing the existence of mixed valencies in them. The ch emical shift values of the K-I and K-II edges corresponding to the cop per (I) and copper (II) sites, indicate that even if there is no chang e in the immediate neighbourhood of copper (I) centre, the effects of changes in the environment around copper (II) centre are transferred t o the copper (I) centres. A correlation has been reported between chem ical shifts and the effective magnetic moments of the complexes.