Photoredox Properties of Iron(III) Fluoro Complexes Containing Tetradentate Open‐Chain N₂O₂Ligands

Abstract

Tetradentate open-chain Schiff base N,02-ligands of acacen, benacen or salen type and fluoride anions Fcoordinate to the iron(II1) cenual atom in methanol forming the complexes [Fe(N202)(CH30H)FJ. The complexes do not undergo spontaneous redox changes when kept in Lhe dark. Their irradiation into inmligand or ligand-to-metal charge transfer bands causes the photoreduction of Fe(III) to Fe(Il) associated with oxidation of metanol to its radical CH,OH. The final products of the primary photoredox and secondary dark redox processes, Fe(i1) and CH'O, are formed in a 2: 1 molar ratio, The efficiency of the axial methanol ligand photooxidation is strongly wavelength dependent and influenced by the peripheral groups R of the tetradentate ligands.

Mechanism of deactivation processes of excited iron(III) thiocyanato complexes with benacen‐type ligands

“…Based on previously published data [14][15][16], bands in the visible region can be attributed to ligand-to-metal chargetransfer (LMCT) transitions O2p or N(2p) → Fe3d, the ultraviolet bands in the regions of 210-280 nm and 300-360 nm to the intraligand transitions IL(π → π * ) localized predominantly on the phenyl rings and on C=N fragments of the N 2 O 2 -ligands, respectively. Due to their spin-forbidden nature, ligand-field (LF) bands were not observed in solution spectra.…”

“…A low-pressure germicidal lamp G8T5 or a high-pressure 150 W Hg-lamp (applied photophysics) were used as radiation sources. Radiation of the high-pressure lamp was monochromatized passing through solution filters [16].…”

“…The total amount of photolysis was limited to less than 5% to avoid an inner filter effect. Details on the photolysis, analytical procedures, and experimental data processing are described elsewhere [14][15][16].…”

Solution properties of iron(III) complexes with 5-fluorosalicylic acid — spectra, speciation, and redox stability

“…Radical formation was monitored by spin-trapping EPR technique using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and nitrosodurene (ND) as spin-traps. The course of the photoredox change was monitored by electronic absorption spectroscopy as time evolution of c(Fe II ), details are described in our previous papers (Šima et al, 1999;Renz et al, 1995).…”