Lanthanide(III) double-decker complexes with octaphenoxy- or octathiophenoxyphthalocyaninato ligands - Revealing the electron-withdrawing nature of the phenoxy and thiophenoxy groups in the double-decker complexes

A series of heteroleptic and homoleptic bis(phthalocyaninato) lanthanide(III) complexes, namely M(Pc)[Pc(OPh)₈], M[Pc(OPh) ₈]₂, Eu(Pc)[Pc(SPh)₈], and Eu[Pc(SPh) ₈]₂ [M = Eu, Ho, Lu; Pc = unsubstituted phthalocyaninate; Pc(OPh)₈ = 2,3,9,10,16,17,23,24-octaphenoxyphthalocyaninate; Pc(SPh)₈ = 2,3,9,10,16,17,23,24-octathiophenoxyphthalocyaninate] (1-8) have been prepared. The molecular structure of Eu-[Pc(OPh) ₈]₂ (4) has been determined by single-crystal X-ray diffraction analysis. All of the new sandwich compounds have been characterized with various spectroscopic methods. Their electrochemical characteristics show that the introduction of phenoxy or thiophenoxy groups onto the peripheral positions of the phthalocyaninato ligand makes the double-decker harder to oxidize and easier to reduce than the analogous compounds without the (thio)phenoxy group. Theoretical calculations, with the semi-empirical PM3 method, indicate that the change in the energy level of the frontier orbitals of these ligands induced by the electron-withdrawing substituents is responsible for these unusual electrochemical properties. © Wiley-VCH Verlag GmbH & Co. KGaA, 2006.