Thermodynamic and kinetic study of palladium(II) complexation with 1-methyl-2-mercaptoimidazole (methimazole) and their importance for structural design of metallodrugs
(2025) In Journal of Inorganic Biochemistry 262.- Abstract
The acidobasic and complexing properties of 1-methyl-2-mercaptoimidazole (Methimazole, an anti-thyroid drug) were investigated. The pKa 11.49 ± 0.03 was estimated by molecular absorption spectroscopy (I = 0.10 M NaCl, t = 25.0 ± 0.1 °C). This value is in good agreement with the value 11.58 ± 0.05, obtained using the solvent-extraction technique. Theoretical (LFER and quantum chemical calculations) and experimental (1H/13C NMR spectroscopy) methods confirmed that the ligand prefers to be in the thion form, and the proton dissociation takes place on the nitrogen atom. Using glass electrode potentiometry, the complexation of the Pd(II) ion by the methimazole ligand occurs without the participation of... (More)
The acidobasic and complexing properties of 1-methyl-2-mercaptoimidazole (Methimazole, an anti-thyroid drug) were investigated. The pKa 11.49 ± 0.03 was estimated by molecular absorption spectroscopy (I = 0.10 M NaCl, t = 25.0 ± 0.1 °C). This value is in good agreement with the value 11.58 ± 0.05, obtained using the solvent-extraction technique. Theoretical (LFER and quantum chemical calculations) and experimental (1H/13C NMR spectroscopy) methods confirmed that the ligand prefers to be in the thion form, and the proton dissociation takes place on the nitrogen atom. Using glass electrode potentiometry, the complexation of the Pd(II) ion by the methimazole ligand occurs without the participation of protons. The best chemical model considers the [Pd(HL)]2+, [Pd(HL)2]2+ and [Pd(HL)3]2+ complex species, whose stability constants were also determined using spectroscopy and capillary zone electrophoretic (CZE) measurements. The metal complexes dissociate at –log [H+] > 7, where an uncharged palladium(II) hydroxide is formed. The formation kinetics of the palladium(II) complex with methimazole were studied in perchloric and hydrochloric acids (I = 1.00 M, t = 15–40 °C) and the determined rate constants and activation parameters are consistent with literature values determined for the reactions of the Pd(II) ion with thiourea derivatives. The rate constants decrease by two orders of magnitude in both media, which can be assigned to a lower tendency of the chloride ion to dissociate from the [PdCl4]2− complex species than the water molecule from the [Pd(H2O)4]2+ ion. The presented results can be utilized for the design of new Pd and Pt metallodrugs.
(Less)
- author
- Širůčková, Viktorie ; Lubal, Přemysl ; Hamacek, Josef ; Kapička, Libor and Elding, Lars Ivar LU
- organization
- publishing date
- 2025-01
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Anti-thyroid drug (methimazol, tapazol): 1-methyl-2-mercaptoimidazole, Complexation properties, Equilibria/kinetics, Metallodrug, Pd(II) ion, Protonation
- in
- Journal of Inorganic Biochemistry
- volume
- 262
- article number
- 112722
- publisher
- Elsevier
- external identifiers
-
- pmid:39326300
- scopus:85204802971
- ISSN
- 0162-0134
- DOI
- 10.1016/j.jinorgbio.2024.112722
- language
- English
- LU publication?
- yes
- id
- 49d17b76-8150-4ad4-926d-7180121220ea
- date added to LUP
- 2024-11-12 16:48:04
- date last changed
- 2025-07-09 12:48:02
@article{49d17b76-8150-4ad4-926d-7180121220ea,
abstract = {{<p>The acidobasic and complexing properties of 1-methyl-2-mercaptoimidazole (Methimazole, an anti-thyroid drug) were investigated. The pK<sub>a</sub> 11.49 ± 0.03 was estimated by molecular absorption spectroscopy (I = 0.10 M NaCl, t = 25.0 ± 0.1 °C). This value is in good agreement with the value 11.58 ± 0.05, obtained using the solvent-extraction technique. Theoretical (LFER and quantum chemical calculations) and experimental (<sup>1</sup>H/<sup>13</sup>C NMR spectroscopy) methods confirmed that the ligand prefers to be in the thion form, and the proton dissociation takes place on the nitrogen atom. Using glass electrode potentiometry, the complexation of the Pd(II) ion by the methimazole ligand occurs without the participation of protons. The best chemical model considers the [Pd(HL)]<sup>2+</sup>, [Pd(HL)<sub>2</sub>]<sup>2+</sup> and [Pd(HL)<sub>3</sub>]<sup>2+</sup> complex species, whose stability constants were also determined using spectroscopy and capillary zone electrophoretic (CZE) measurements. The metal complexes dissociate at –log [H<sup>+</sup>] > 7, where an uncharged palladium(II) hydroxide is formed. The formation kinetics of the palladium(II) complex with methimazole were studied in perchloric and hydrochloric acids (I = 1.00 M, t = 15–40 °C) and the determined rate constants and activation parameters are consistent with literature values determined for the reactions of the Pd(II) ion with thiourea derivatives. The rate constants decrease by two orders of magnitude in both media, which can be assigned to a lower tendency of the chloride ion to dissociate from the [PdCl<sub>4</sub>]<sup>2−</sup> complex species than the water molecule from the [Pd(H<sub>2</sub>O)<sub>4</sub>]<sup>2+</sup> ion. The presented results can be utilized for the design of new Pd and Pt metallodrugs.</p>}},
author = {{Širůčková, Viktorie and Lubal, Přemysl and Hamacek, Josef and Kapička, Libor and Elding, Lars Ivar}},
issn = {{0162-0134}},
keywords = {{Anti-thyroid drug (methimazol, tapazol): 1-methyl-2-mercaptoimidazole; Complexation properties; Equilibria/kinetics; Metallodrug; Pd(II) ion; Protonation}},
language = {{eng}},
publisher = {{Elsevier}},
series = {{Journal of Inorganic Biochemistry}},
title = {{Thermodynamic and kinetic study of palladium(II) complexation with 1-methyl-2-mercaptoimidazole (methimazole) and their importance for structural design of metallodrugs}},
url = {{http://dx.doi.org/10.1016/j.jinorgbio.2024.112722}},
doi = {{10.1016/j.jinorgbio.2024.112722}},
volume = {{262}},
year = {{2025}},
}