Tuning the redox potentials of ternary cobalt(III) complexes containing various hydroxamates

P. Buglyó, István Kacsir, Máté Kozsup, Imre Nagy, Sándor Nagy, A. Bényei, Éva Kováts, E. Farkas

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Abstract

Sixteen cobalt(III) complexes incorporating one of the investigated 4N donor tripodal amines in the presence or absence of differently substituted hydroxamates have been synthesized and the effect of the nature of the N-donor, size of the chelates formed and the effect of the type of the substituent(s) at the hydroxamate moiety on the redox properties of the complexes have been studied. The crystal and molecular structures of the new complexes, [Co(uns-penp)(H2O)Cl]Cl2·H2O (4), [Co(tren)(phebha)](ClO4)2 (11), [Co(tpa)(bha)](ClO4)2·C2H5OH·H2O (15) and [Co(tpa)(phebha)](ClO4)2 (16) have also been determined by single crystal X-ray diffraction method. Cyclic voltammetric (CV) results indicated the irreversible reduction of Co(III) in all the investigated complexes. Out of the four studied tripodal amines, abap was found to decrease the Co(III/II) reduction potential far below the region of bioreductants. Decreasing of two of the chains by one CH2 in tren compared to abap resulted in less negative reduction potential of the corresponding complex. Further positive shift was observed by introducing two (uns-penp), and especially three (tpa) π-back-bonding pyridyl rings into the chains of tetramines. In agreement with literature results, the 3+ oxidation state of the central cobalt ion was found to be extremely stabilized in the ternary complexes containing the doubly deprotonated benzohydroximate, but the metal ion is significantly more reducible in the ternary complexes with mono-deprotonated benzohydroxamate/derivative ligands. Measurable effect was not found on the redox potential via introduction of chloro or nitro substituents in para position into the phenyl moiety of bha (Cl-bha and NO2-bha). Significant positive shift (ca. 200 mV) was obtained, however, when RN = H was replaced by a phenyl ring in phebha therefore complexes with this latter ligand can be likely candidates for the in vitro releasing of hydroxamates with proven biological activity.

Original languageEnglish
Pages (from-to)234-242
Number of pages9
JournalInorganica Chimica Acta
Volume472
DOIs
Publication statusPublished - Mar 1 2018

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Cobalt
tetramethylenedisulfotetramine
cobalt
Tuning
tuning
Amines
Ligands
amines
Bioactivity
Molecular structure
ligands
Metal ions
rings
shift
releasing
activity (biology)
Crystal structure
chelates
Single crystals
Ions

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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Tuning the redox potentials of ternary cobalt(III) complexes containing various hydroxamates. / Buglyó, P.; Kacsir, István; Kozsup, Máté; Nagy, Imre; Nagy, Sándor; Bényei, A.; Kováts, Éva; Farkas, E.

In: Inorganica Chimica Acta, Vol. 472, 01.03.2018, p. 234-242.

Research output: Contribution to journalArticle

Buglyó, P. ; Kacsir, István ; Kozsup, Máté ; Nagy, Imre ; Nagy, Sándor ; Bényei, A. ; Kováts, Éva ; Farkas, E. / Tuning the redox potentials of ternary cobalt(III) complexes containing various hydroxamates. In: Inorganica Chimica Acta. 2018 ; Vol. 472. pp. 234-242.
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AU - Kacsir, István

AU - Kozsup, Máté

AU - Nagy, Imre

AU - Nagy, Sándor

AU - Bényei, A.

AU - Kováts, Éva

AU - Farkas, E.

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N2 - Sixteen cobalt(III) complexes incorporating one of the investigated 4N donor tripodal amines in the presence or absence of differently substituted hydroxamates have been synthesized and the effect of the nature of the N-donor, size of the chelates formed and the effect of the type of the substituent(s) at the hydroxamate moiety on the redox properties of the complexes have been studied. The crystal and molecular structures of the new complexes, [Co(uns-penp)(H2O)Cl]Cl2·H2O (4), [Co(tren)(phebha)](ClO4)2 (11), [Co(tpa)(bha)](ClO4)2·C2H5OH·H2O (15) and [Co(tpa)(phebha)](ClO4)2 (16) have also been determined by single crystal X-ray diffraction method. Cyclic voltammetric (CV) results indicated the irreversible reduction of Co(III) in all the investigated complexes. Out of the four studied tripodal amines, abap was found to decrease the Co(III/II) reduction potential far below the region of bioreductants. Decreasing of two of the chains by one CH2 in tren compared to abap resulted in less negative reduction potential of the corresponding complex. Further positive shift was observed by introducing two (uns-penp), and especially three (tpa) π-back-bonding pyridyl rings into the chains of tetramines. In agreement with literature results, the 3+ oxidation state of the central cobalt ion was found to be extremely stabilized in the ternary complexes containing the doubly deprotonated benzohydroximate, but the metal ion is significantly more reducible in the ternary complexes with mono-deprotonated benzohydroxamate/derivative ligands. Measurable effect was not found on the redox potential via introduction of chloro or nitro substituents in para position into the phenyl moiety of bha− (Cl-bha− and NO2-bha−). Significant positive shift (ca. 200 mV) was obtained, however, when RN = H was replaced by a phenyl ring in phebha− therefore complexes with this latter ligand can be likely candidates for the in vitro releasing of hydroxamates with proven biological activity.

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