Spectral study on one-electron-oxidized di(phthalocyaninato)rare-earths(III)

Nine double-decker bis(phthalocyaninato)rare-earth(III) complexes, [M(pc) 2] (green radical species; M = Sc, Y, La, Pr, Sm, Eu, Tb, Ho, Yb) have been electrochemically and spectroelectrochemically investigated in CH2Cl2. All of them show one oxidation and three reduction waves, which involve phthalocyanine macrocycles. Apart from the lanthanum derivative, the first oxidation and reduction potentials show linear cathodic shift with an increase in ionic radius of the central metal (r(i)), whereas the second and third reduction little depend on r(i). Electrochemical oxidation (around the oxidation potential) and chemical oxidation produced the same red similar to orange species (depending on the central metal). Their optical absorption spectra show three characteristic bands in 400 similar to 600, 600 similar to 750, and 800 similar to 1200 nm in visible and near-infrared region and their peak positions (in cm(-1)) linearly depend on r(i) (except for La). Assignment of these bands has been done based on magnetic circular dichroism spectroscopy and the electrochemical data.