Electrochemical and electrochromic properties of rare-earth metal diphthalocyanine complexes

The electrochemical and spectroelectrochemical properties of several new rare-earth metal diphthalocyanine complexes with different substituents containing both electron-withdrawing and -donating substituents in the phthalocyanine rings were studied. The influence of structural modification of the phthalocyanine complexes (viz., the nature of the central metal atom and substituents in the phthalocyanine rings and the number of phthalocyanine rings in the complexes) on the total number of redox transitions, their potentials, and spectral characteristics of anionic and cationic forms of the complexes was examined. The potentials of the first anodic and cathodic redox transitions of the diphthalocyanine complexes are in a good linear correlation with the ionic radii of lanthanides. The potentials of the observed redox transitions of the complexes under study correlate well with the sums of Hammett constants for the substituents and the minimum molecular electrostatic potential of the benzene rings in the phthalocyanine moiety, which serves as a measure of electron perturbations introduced by the substituents. The revealed regularities allow the prediction of the redox properties and structure of rare-earth element diphthalocyanine complexes, which are redox-active in a specified potential range.