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Effect of co-ligands on photoredox pathways in Cr(III) oxalate complexes

Paper ID Volume ID Publish Year Pages File Format Full-Text
27866 44047 2012 7 PDF Available
Title
Effect of co-ligands on photoredox pathways in Cr(III) oxalate complexes
Abstract

The photochemical behaviour of some mixed ligand chromium(III) complexes with amino acids, [Cr(C2O4)2(Aa)]n− (where Aa = alanine, valine, serine, cysteine, asparagine, aspartic acid) was studied. The attention was focused on the photoredox mode, which proceeded via inner- or intramolecular pathway yielding Cr(II) species and hydrated electrons, respectively. The secondary thermal processes were dependent on the O2 presence and solution pH: (i) in oxygen-free media the regeneration of substrate and photoaquation induced by the Cr(III) → Cr(II) reduction were observed, (ii) in the presence of O2 both Cr(II) and ligands were oxidized and the former was transformed not only into Cr(III) but also to Cr(VI) (provided that pH > 7). Prolonged irradiation resulted in photoreduction of Cr(VI) accompanied by photodegradation of oxalate and/or amino-acid ligands. The photoreaction modes were independent of the co-ligand nature, but the secondary reaction rates and efficiencies were sensitive both to the co-ligand nature and its side substituent. Environmental consequences of the chromium photoreduction are discussed in the paper: the parameters affecting production and consumption of Cr(VI) are analysed, and the tools of controlling the photoredox behaviour of the Cr(III) and Cr(VI) compounds are suggested.

► Photoreduction of Cr(III) oxalate complexes with amino acids was studied. ► The mechanism relies on inner and intra paths yielding Cr(II) and eaq−, respectively. ► The mechanism depends on pH and O2 presence; is independent of the amino acid nature. ► The product yield depends on the ligand nature and its side substituents. ► Parameters controlling production and photoreduction of Cr(VI) are analyzed.

Keywords
Chromium(III) complexes; Chromate(VI); Oxalate; Amino acid; Photoreduction; Photoinduced electron transfer
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Effect of co-ligands on photoredox pathways in Cr(III) oxalate complexes
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 250, 15 December 2012, Pages 78–84
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us