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Synthesis, spectroscopy, and binding constants of ketocatechol-containing iminodiacetic acid and its Fe(iii), Cu(ii), and Zn(ii) complexes and reaction of Cu(ii) complex with H2O2 in aqueous solutionElectronic supplementary information (ESI) available: UV-vis spectra of different complexes at different reaction ratios and pHs; 1H NMR spectrum of H4L in DMSO and pH 8.0 D2O solution; 13C NMR of H4L in DMSO; IR spectra of HN(CH2CH3)3·H3L and Zn2L·4H2O (KBr disc); Crystal data and structure refineme
A new neuromelanin-like ketocatechol-containing iminodiacetic acid ligand, ( N -(3,4-dihydroxyl)phenacylimino)diacetic acid (H 4 L), which is also quite similar to compounds found in insect cuticle, has been synthesized and characterized. The X-ray crystal structure of H 4 L has been successfully de...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Online Access: | Get full text |
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| Summary: | A new neuromelanin-like ketocatechol-containing iminodiacetic acid ligand, (
N
-(3,4-dihydroxyl)phenacylimino)diacetic acid (H
4
L), which is also quite similar to compounds found in insect cuticle, has been synthesized and characterized. The X-ray crystal structure of H
4
L has been successfully determined. Proton binding and coordination with Fe(
iii
), Cu(
ii
), and Zn(
ii
) have been studied by potentiometric titrations and UV-vis spectrophotometry in aqueous solution. UV spectra of H
4
L in the absence and presence of different metal ions indicate complexes formed with the catechol moiety of H
4
L in aqueous solution. Visible spectra and NMR reveal that H
4
L with Fe(
iii
), Cu(
ii
), and Zn(
ii
) can all give stable mono-(ML) and dinuclear complexes [M(ML)]. Fe(
iii
) can also form {Fe(FeL)
2
} and {Fe(FeL)
3
} species with sufficient base. The process is accompanied by a drastic color change from light blue to deep-blue to wine-red. The Fe(
iii
)-Cu(
ii
) heteronuclear complex also exists in aqueous solution whose spectra are similar to the homonuclear Fe(
iii
) complex. However, the spectra of {Fe(CuL)} shifted to a longer wavelength and {Fe(CuL)
2
} and {Fe(CuL)
3
} shifted to a shorter wavelength. Keto-enol tautomerism was observed in weak basic aqueous solution as indicated by
1
H NMR spectra. The reaction products of Cu(
ii
) complex with H
2
O
2
depend on the H
2
O
2
concentration and pH value. Low concentrations of H
2
O
2
oxidize H
4
L to a series of semiquinone and quinone compounds with absorption maxima at 314-400 nm, while a high concentration of H
2
O
2
oxidizes H
4
L to colorless muconic acid derivatives. NaIO
4
gives different oxidase products, but no 2,4,5-trihydroxyphenylalanine quinone (TPQ)-like hydroxyquinone can be found.
A ketocatechol-containing iminodiacetic acid ligand can react with metal ions to form different colored species. Its copper(
ii
) complex reacts with H
2
O
2
to form different species depending on the H
2
O
2
concentration and pH. |
|---|---|
| ISSN: | 1477-9226 1477-9234 |
| DOI: | 10.1039/c4dt00118d |