Summary
Iron(III) complexes of the formcis-[Fe(SB(X - K)] in whichSB 2− are open-chain tetradentateSchiff base N2O2-ligands ofacacen,benacen orsalen type, andX - K − are bidentate anions of kojic acid (5-hydroxy-2-hydroxymethyl-4H-pyran-4-one) or other γ-pyranones undergo photoredox transformations when being irradiated in methanol into intraligand orLMCT bands. The quantum yields of the photoredox reactions depend on the peripheral constitution of the N2O2 ligands, the substituentsA andB of the ligandsX - K −, and the wavelength of irradiation λirr. The proposed mechanism involves the population of photoredox reactiveLMCT states by photophysical deactivation steps, primary photoredox formation ofX - K radicals and Fe(II), and subsequent “dark” redox processes giving back the anionsX - K − and the final products Fe(II) and formaldehyde formed in the molar ratio 2:1.
Zusammenfassung
Eisen(III)-Komplexe der Formcis-[Fe(SB)(X - K)] mitSB 2−=offenkettige tetradentateSchiff-Basen-N2O2-Liganden undX - K −=bidentate Anionen von 5-Hydroxy 2-hydroxymethyl-4H-pyran-4-on oder andere β-Pyranone unterliegen bei Bestrahlung in Methanol Photoredoxumwandlungen, was durch Intraligand- oderLMCT-Banden belegt wird. Die Quantenausbeuten der Reaktionen hängen von der Konstitution der N2O2-Liganden, den SubstituentenA undB und dem LigandenX - K − sowie der Anregungswellenlänge λirr ab. Der vorgeschlagene Mechanismus beinhaltet die Population photoredoxreaktiverLMCT-Zustände durch photophysikalische Deaktivierungsschritte, die Bildung vonX - K*-Radikalen und Fe(II) und-Über Dunkelprozesse — die Rückbildung der AnionenX - K − sowie die Reaktion zu den Endprodukten Fe(II) und Formaldehyd im molaren Verhältnis 2:1.
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Šima, J., Makáňová, J. & Veverka, M. Photoredox properties of Kojic acid and its derivatives complexed to Iron(III). Monatsh Chem 126, 149–154 (1995). https://doi.org/10.1007/BF00812243
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DOI: https://doi.org/10.1007/BF00812243