Tetra-2,3-pyrazinoporphyrazines with peripherally appended pyridine rings. 21. Mono- and pentanuclear FeII complexes: Solid state and solution studies

Abstract

New Fe[Formula: see text] complexes of formula [Py8TPyzPzFe] · xH2O, its bis-pyridine adduct [Py8TPyzPzFe(py)2] · xH2O, the pentanuclear species [(MCl[Formula: see text]Py8TPyzPzFe] · xH2O (M [Formula: see text] Pd[Formula: see text], Pt[Formula: see text] and the bis-DABCO adducts [Py8TPyzPzFe(DABCO)2] · 11H2O and [(PdCl[Formula: see text]Py8TPyzPzFe(DABCO)2] · H2O (Py8TPyzPz [Formula: see text] octapyridino-tetrapyrazinoporphyrazinato dianion; DABCO [Formula: see text] 1,4-diazabiciclo[2.2.2]octane) were synthesized and characterized by elemental and thermogravimetric analysis, IR and UV-vis spectroscopy, with added studies on the starting complex [Py8TPyzPzFe] · xH2O regarding magnetic and electrochemical behavior. Clathrated water molecules are present in all compounds and have little to no effect on their physicochemical behavior as was observed for all previously reported analogs. UV-vis spectra of the mononuclear [Py8PyzPzFe] · xH2O complex in DMSO and pyridine are indicative of aggregation immediately after dissolving the compound. However, the spectra change slowly over time leading to formation of a porphyrazine species having spectral features typical of a monomer. UV-vis spectra of the parent pentanuclear [(MCl[Formula: see text]Py8TPyzPzFe] · xH2O (M [Formula: see text] Pd[Formula: see text], Pt[Formula: see text] complexes show a smaller degree of aggregation upon dissolution in DMSO or pyridine and the spectra of these solutions also change over time to those of a monomer. The presence of aggregation, spectral evolution with time and final species formed from the N-base adducts [Py8TPyzPzFe(DABCO)2] · 11H2O and [(PdCl[Formula: see text]Py8TPyzPzFe(DABCO)2] · H2O are reported and discussed.