Hetero trinuclear oxo-bridged complexes of ruthenium porphyrin and iron phthalocyanine

Abstract

New diamagnetic hetero bi- and trinuclear oxo-bridged metal complexes of formula (L)(Pc)Fe-O-Ru(TPP')(O) and (L)(Pc)Fe-O-Ru(TPP')-O-Fe(Pc)(L) have been prepared from Ru(TPP')(O)2 and Fe(Pc)(L)2 (TPP' = tetrakis(4-methoxyphenyl)porphyrinate, Pc = phthalocyanate ion, L = monodentate ligand). The trinuclear complex binds a variety of ligands (4,4'-bipy, 4-MePy, P(OEt)3, pip, NH3, 1-MeIm, P(Me)2Ph) trans to the oxo-bridge. 1H NMR spectra are characterized by large ring current shifts (rcs) due to the TPP' and Pc ions. The complexes show an unusually weak Pc Q band in their visible spectra at 700 nm and two CT bands in the near-IR region from 1000 to 1500 nm, which are sensitive to the trans ligand. The trinuclear complex can be reversibly oxidized to the +1 and +2 ions, formally Fe(IV)-O-Ru(IV)-O-Fe(III) and Fe(IV)-O-Ru(IV)-O-Fe(IV) at 0.4 and 0.76 V. The +1 ion is chemically obtained by reaction of the neutral species with (Cp)2Fe+ for L = 4-MePy and this reaction is reversed upon addition of L' = P(Me)2Ph. Reductive cleavage by hydroquinone, phosphines and phosphites are the slowest of all RuTPP[O(FeN4)]2 systems studied to date (t1/2 = 8 h at 40°C).Key words: ruthenium, iron, porphyrin, phthalocyanine, oxo.