Experimental and computational investigation of the substituent effects on the reduction of Fe³⁺by 1,2-dihydroxybenzenes

Abstract

This study reports on the kinetics of the early steps of the reactions between substituted 1,2-dihydroxybenzenes (1,2-DHB) and Fe3+.

Effect of aromatic ring substituents on the ability of catechol to produce brown carbon in iron(iii)-catalyzed reactions

“…The additional features are observed in the absorption spectrum during the reaction due to: (a) p to p* transition centered on the ligand in Fe-organics complex appearing in the near-UV and shied from the corresponding transition in the isolated ligand; (b) ligand-to-metal charge transfer (LMCT) transition in the bidentate iron-organic complexes appearing in the near-IR; (c) bands from soluble reaction products between Fe(III) and the organics reagents, including n to p* transition in the o-quinone species formed from oxidation of catechol-Fe complexes; (d) scattering and absorption by the insoluble suspended particles with a weak wavelength dependence. As demonstrated by Salgado et al, 23 the Fe-complex charge transfer appear quickly aer mixing, whereas absorption features of the reaction products take minutes or even hours to develop. In this study, the reaction was terminated aer two hours, and presence of particulate products was veried visually as well as by comparing absorption spectra before and aer ltering the solution.…”

Aging of atmospheric aerosols and the role of iron in catalyzing brown carbon formation

“…Scheme 1 shows a proposed mechanism for polycatechol formation based on the results from refs. [212][213][214][215][216] under dark conditions leading to the formation of oligomers and polymeric particles. Iron catalyzes the deprotonation of catechol and its derivatives below their first pK a 198 and forms strong bidentate complexes with stability constants that varies with iron species in solution.…”

Structures and Chromogenic Ion-Pair Recognition of a Catechol-Functionalized 1,8-Anthraquinone Macrocycle in Dimethyl Sulfoxide

“…36 There is a small amount of Fe(II) possibly due to electron transfer between catechol and Fe(III) at the very beginning, which has been mentioned in the literature. 37 TGA shows that crystalline water in FeCl S5). Many ammonium salts, such as hydroxypropyltrimethylammonium chloride/chitosan/Cd complexes, decompose at this temperature.…”

“…54 A recent investigation shows that an electrondonating substituent, such as a tert-butyl group, can obviously decrease the absorbance of catechole/Fe(III) by 600−700 nm, and the absorbance decreases with a time increase. 37 To further prove the existence of the 2:1 species in the absence of base, as well as to compare the function of the anthraquinone macrocycle, control experiments with TBC were performed. The absorption peak of 5.0 × 10 −4 M TBC in the presence of FeCl 3 (Figure S8) is consistent with those of 5.0 × 10 −4 M H 2 L and Fe 3+ because they have identical wavelengths as well as binding ratios (catechol:Fe = 2:1).…”

“…A monodentate catechol, as well as a partially deprotonated catechol/Fe(III) complex, has been reported. 56,57 In fact, the Fe(III) reaction with catechol is very complex, and many species can be characterized; 37 there are still some species that are not well characterized because of polymerization and oxidation, 7 as well as aggregation. 52,58 Our data show that nondeprotonated catechol/Fe(III) exists in an organic solvent, such as C 2 H 5 OH and DMSO.…”