Synthesis and Physicochemical Characterization of Protonated and Deprotonated Forms in Heteroleptic Lanthanide(III) Porphyrinate Double-Deckers. X-ray Structure of Gd III H(oep)(tpp) at 298 and 21 K Georgios A. Spyroulias, † Catherine P. Raptopoulou, ‡ Dominique de Montauzon, § Alain Mari, § Rene ´ Poilblanc, § Aris Terzis, ‡ and Athanassios G. Coutsolelos* ,† Laboratory of Bioinorganic Coordination Chemistry, Department of Chemistry, School of Science, University of Crete, P.O. Box 1470, 714 09 Heraklion, Crete, Greece, Institute of Materials Science, NCSR “Demokritos”, 153 10 Aghia Paraskevi, Athens, Greece, and Laboratoire de Chimie de Coordination, CNRS, UPR 8241 lie ´e par convention a ` l’Universite ´ Paul Sabatier et a ` l’Institut Polytechnique de Toulouse, 205 Route de Narbonne, 31077 Toulouse Cedex, France ReceiVed July 18, 1997 The synthesis, spectroscopic characterization, and electrochemical study of eleven heteroleptic and their corresponding homoleptic lanthanide sandwiches are reported. Studies in solution have been carried out in solvents of different basicity, in order to elucidate the equilibrium between the protonated and deprotonated form of these complexes. The investigated compounds are represented by the formulas Ln III H(oep)(tpp) and [Ln III (oep)(tpp)] - corresponding to the protonated and deprotonated forms, respectively (in the case of heteroleptic), and the formulas Ln III H(tpp) 2 and [Ln III (tpp) 2 ] - (in the case of the homoleptic porphyrin double-deckers), where Ln Nd, ..., Lu (except Pm), oep ) 2,3,7,8,12,13,17,18-octaethylporphyrinate, and tpp ) 5,10,15,20-tetraphenylporphyrinate). Various spectroscopic methods are used for the physicochemical characterization of the title complexes. The electronic spectra of the complexes above present different features in CH 2 Cl 2 and in DMF. In the latter solvent they reveal features similar to those of the analogous actinide(IV) porphyrin double-decker. The electrochemical studies carried out in CH 2 Cl 2 and THF demonstrate clearly that the redox behavior of the double-deckers, heteroleptic or homoleptic, is strongly dependent on the proton on the porphyrinic core. In CH 2 Cl 2 , four reversible oxidation processes and two quasi-reversible waves are observed for the protonated species in both homo- and heteroleptic double-deckers. In contrast, two oxidations and two reductions are observed in THF for the homoleptic derivatives, while the corresponding heteroleptic ones undergo three oxidations and one reduction process. The structure of the new heteroleptic double-decker Gd III H(oep)(tpp) was determined by X-ray diffraction at 298 and 21 K. Both structures are compared with the first analogous structure of Sm III H(oep)(tpp). According to the spectroscopic and structural data reported for the heteroleptic protonated derivatives, the oep macrocycle is the favored binding site of the proton in solutions as well as in the solid state. 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