Solution Behaviour and Catalytic Potential towards Oxidation of Dopamine by Oxidovanadium(V) Complexes of Tripodal Tetradentate Ligands

Autor: Pedro Adão, Bhawna Uprety, J. Costa Pessoa, Mannar R. Maurya, Fernando Avecilla, Maxim L. Kuznetsov
Rok vydání: 2017
Předmět:
Zdroj: European Journal of Inorganic Chemistry. 2017:3087-3099
ISSN: 1099-0682
1434-1948
DOI: 10.1002/ejic.201700342
Popis: The reaction of dibasic tripodal tetradentate ligands H2L1-4 (I-IV) (prepared from the reaction of aminoethylmorpholine and 2,4-disubstituted phenols) with [VIVO(acac)2] or VIVOSO4*5H2O gave the corresponding mononuclear oxidoethoxidovanadium (V) complexes [VVO(OEt)(L1-4)] (1-4) in good yields. Similar reaction with H2L2 (II) and H2L4 (IV) in acetonitrile resulted in the formation of the corresponding dinuclear complexes [{VVO(L2)}2µ-O] (5) and [{VVO(L4)}2µ-O] (6). Single crystal X-ray diffraction analysis of 1, 2 and 4 confirmed the the distorted octahedral geometry. The molecular structures of 1, 2 and 5 were calculated by DFT, as well as the corresponding 51V NMR chemical shifts (in methanol and chloroform) and IR frequencies. The V-compounds depict time dependent solution behaviour which was studied and rationalized through the combined interpretation of data from spectroscopic techniques (mainly UV-Vis and 51V NMR), mass spectrometry and DFT calculations. They exhibit distinct speciation in different solvents and it was confirmed that in acetonitrile they form -O-oxido dinuclear species. The alkoxido ligand of complexes [VVO(OR)(L)] in CDCl3, are exchanged upon addition of alcohols; namely the 51V NMR chemical shift values of [VVO(OR)(L2)] depict an increasing shielding effect of the OR moiety in the order: OMe < OEt < OiPr < OtBu. Compounds 1-4 were employed as catalyst precursors in the oxidation of dopamine to aminochrome in MeOH using dioxygen as the oxidant.
Databáze: OpenAIRE
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