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VIVO versus VIV complex formation by tridentate (O, Narom, O) ligands: prediction of geometry, EPR 51V hyperfine coupling constants, and UV–Vis spectra

Pisano, Luisa and Várnagy, Katalin and Timári, Sarolta and Hegetschweiler, Kaspar and Micera, Giovanni and Garribba, Eugenio (2013) VIVO versus VIV complex formation by tridentate (O, Narom, O) ligands: prediction of geometry, EPR 51V hyperfine coupling constants, and UV–Vis spectra. Inorganic Chemistry, Vol. 52 (9), p. 5260-5272. eISSN 1520-510X. Article.

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DOI: 10.1021/ic400186x

Abstract

Systems formed using the VIVO2+ ion with tridentate ligands containing a (O, Narom, O) donor set were described. Examined ligands were 3,5-bis(2-hydroxyphenyl)-1-phenyl-1H-1,2,4-triazole (H2hyphPh), 4-[3,5-bis(2-hydroxyphenyl)-1H-1,2,4-triazol-1-yl]benzoic acid (H3hyphC), 4-[3,5-bis(2-hydroxyphenyl)-1H-1,2,4-triazol-1-yl]benzenesulfonic acid (H3hyphS), and 2,6-bis(2-hydroxyphenyl)pyridine (H2bhpp), with H3hyphC being an orally active iron chelator that is commercially available under the name Exjade (Novartis) for treatment of chronic iron overload arising from blood transfusions. The systems were studied using EPR, UV–Vis, and IR spectroscopies, pH potentiometry, and DFT methods. The ligands bind vanadium with the two terminal deprotonated phenol groups and the central aromatic nitrogen to give six-membered chelate rings. In aqueous solution the main species were the mono- and bis-chelated VIVO complexes, whereas in the solid state neutral non-oxido VIV compounds were formed. [V(hyphPh)2] and [V(bhpp)2] are hexacoordinated, with a geometry close to the octahedral and a meridional arrangement of the ligands. DFT calculations allow distinguishing VIVO and VIV species and predicting their structure, the 51V hyperfine coupling constant tensor A, and the electronic absorption spectra. Finally, EPR spectra of several non-oxido VIV species were compared using relevant geometrical parameters to demonstrate that in the case of tridentate ligands the 51V hyperfine coupling constant is related to the geometric isomerism (meridional or facial) rather than the twist angle Φ, which measures the distortion of the hexacoordinated structure toward a trigonal prism.

Item Type:Article
ID Code:9920
Status:Published
Refereed:Yes
Uncontrolled Keywords:EPR, UV–Vis, IR spectroscopies, pH potentiometry, DFT methods, VIVO, VIV complex, tridentate ligands
Subjects:Area 03 - Scienze chimiche > CHIM/06 Chimica organica
Area 03 - Scienze chimiche > CHIM/03 Chimica generale e inorganica
Divisions:001 Università di Sassari > 01-a Nuovi Dipartimenti dal 2012 > Chimica e Farmacia
Publisher:American Chemical Society
eISSN:1520-510X
Deposited On:27 Jun 2014 10:25

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