Electrochemistry of homoleptic bis[3(4),12(13),21(22),30(31)-tetra(tert-butyl)-naphthalocyaninato] rare earth(III) complexes

Abstract

The electrochemistry of homoleptic bis(naphthalocyaninato) double-decker complexes for the whole series of tervalent rare earths M ( TBNc )2 ( M = Y , La … Lu except Ce and Pm ; H 2 TBNc = 3(4),12(13),21(22),30(31)-tetra(tert-butyl)naphthalocyanine) has been systematically studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Up to three quasi-reversible one-electron oxidations and four quasi-reversible one-electron reductions have been revealed for these double-deckers.The half-wave potentials of all oxidations and the first reduction for double-decker complexes are dependent on the size of the metal center. The difference between the redox potentials of the first and second reductions for M III( TBNc )2, which represents the potential difference between the first oxidation and first reduction of [ M III( TBNc )2]−, lies in the range 1.09-0.95 V and gradually diminishes along with the lanthanide contraction, indicating increased π-π interaction in the double-deckers in the same order. Comparison of electrochemical characteristics between M ( TBNc )2 and M ( TBPc )2 ( H 2 TBPc = 2(3),9(10),16(17),24(25)-tetra(tert-butyl)-phthalocyanine) reveals that extension of the ligand conjugated system upon going from phthalocyanine to naphthalocyanine attenuates the ring-to-ring separation effect on the redox potentials of the double-deckers of the whole series of tervalent lanthanides.