Cationic cyclopentadienyliron azo-complexes: Synthesis, spectroscopic characterization, and molecular structure

Two novel cationic cyclopentadienyliron azo-complexes (Azo-Fc) were synthesized by the SNAr reaction of (η6-chlorobenzene) (η5-cyclopentadienyl) iron hexafluorophosphate (Fc-Cl) with 1-phenylazo-2-naphthol and 4-(4-nitrophenylazo)carbazole. They were characterized by IR, 1H NMR, 13C NMR, and MS. The UV–vis spectral characteristics of the azo-complexes were investigated in four organic solvents of different degrees of polarity. These synthesized azo-complexes exhibited a bathochromic shift of the visible absorption maxima with the increase in conjugating skeleton. The study of photochemical properties reveals that the azo-complexes showed good photostability and that photolysis was difficult to realize. The geometric structures of the azo-complexes were optimized on the basis of density function theory at the B3PW91/Lanl2dz level. The energy levels of their frontier molecular orbitals were obtained.

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► Two cationic cyclopentadienyliron azo-complexes (Azo-Fcs) were synthesized.
► Theses two complexes showed good photostability and strong absorption.
► Electron transfer occurs from HOMO to LUMO in Azo-Fcs by calculation.