Relationship between Antioxidant Activity and Ligand Basicity in the Dipicolinate Series of Oxovanadium(IV) and Dioxovanadium(V) Complexes

Abstract

Oxidative stress plays an important role in the pathogenesis of many serious diseases, including cancer, atherosclerosis, coronary artery disease, Parkinson’s disease, Alzheimer’s disease, stroke and myocardial infarction. In the body’s natural biochemical processes, harmful free radicals are formed, which can be removed with the help of appropriate enzymes, a balanced diet or the supply of synthetic antioxidant substances such as flavonoids, vitamins or anthocyanins to the body. Due to the growing demand for antioxidant substances, new complex compounds of transition metal ions with potential antioxidant activity are constantly being sought. In this study, four oxovanadium(IV) and dioxovanadium(V) dipicolinate (dipic) complexes with 1,10-phenanthroline (phen), 2,2′-bipyridyl (bipy) and the protonated form of 2-phenylpyridine (2-phephyH): (1) [VO(dipic)(H2O)2] · 2 H2O, (2) [VO(dipic)(phen)] · 3 H2O, (3) [VO(dipic)(bipy)] · H2O and (4) [VOO(dipic)](2-phepyH) · H2O were synthesized including one new complex, so far unknown and not described in the literature, i.e., [VOO(dipic)](2-phepyH) · H2O. The oxovanadium(IV) dipicolinate complexes with 1,10-phenanthroline and 2,2′-bipyridyl have been characterized by several physicochemical methods: NMR, MALDI-TOF-MS, IR, but new complex [VOO(dipic)](2-phepyH) · H2O has been examined by XRD to confirm its structure. The antioxidant activities of four complexes have been examined by the nitrotetrazolium blue (NBT) method towards superoxide anion. All complexes exhibit high reactivity with superoxide anion and [VOO(dipic)](2-phepyH) · H2O has higher antioxidant activity than L-ascorbic acid. Our studies confirmed that high basicity of the auxiliary ligand increases the reactivity of the complex with the superoxide radical.

Preparation of Allyl Alcohol Oligomers Using Dipicolinate Oxovanadium(IV) Coordination Compound

“…In order to confirm the structure of the synthesized crystal of complex compound, we described the IR spectrum of the dipicolinate oxovanadium(IV) complex (Figure 3) [41]. The characterization results presented in Tables 1 and 2 and their validation with theoretical calculations and literature data indicate that the vanadium complex synthesis was correct [41,42]. The synthesized complex was used for 2-propen-1-ol oligomerization.…”

Dipicolinate Complexes of Oxovanadium(IV) and Dioxovanadium(V) with 2-Phenylpyridine and 4,4′-Dimethoxy-2,2′-bipyridyl as New Precatalysts for Olefin Oligomerization

“…The compound [VOO(dipic)](2-phepyH) • H 2 O was obtained as crystals, while compound [VO(dipic)(dmbipy)] • 2 H 2 O was obtained as a powder. All crystal parameters of the complex have been published in the literature [34]. In [VOO(dipic)](2-phepyH) • H 2 O crystal structure, the lengths and angles of bonds characterizing the geometry of the dioxo-(pyridine-2,6-dicarboxylate)-vanadium(V) cation have values similar to other crystal structures containing this oxovanadium cation(V) [34].…”

“…All crystal parameters of the complex have been published in the literature [34]. In [VOO(dipic)](2-phepyH) • H 2 O crystal structure, the lengths and angles of bonds characterizing the geometry of the dioxo-(pyridine-2,6-dicarboxylate)-vanadium(V) cation have values similar to other crystal structures containing this oxovanadium cation(V) [34]. XRD studies of the crystals of the synthesized compound, [VOO(dipic)](2-phepyH) • H 2 O, confirmed that this complex compound crystallizes in the monoclinic P21/c space group.…”

“…An asymmetric unit consists of one 2-phenylpyridine cation, one dioxo (pyridine-2,6-dicarboxylate)anion)-vanadium(V), and one water molecule. The crystal structure [VOO(dipic)](2-phepyH) • H 2 O contains ions and water molecules bound by hydrogen bonds [34].…”

Synthesis, In Vitro, and Computational Studies of PTP1B Phosphatase Inhibitors Based on Oxovanadium(IV) and Dioxovanadium(V) Complexes

“…The polycarboxylate oxovanadium(IV) and dioxovanadium(V) complex compounds (Figure 1) were synthesized according to the procedures described in the literature: [22,23] for [24] for [VO(ida)(bipy)]•2 H 2 O (Com-pound 3), [25] [VO(dipic)(dmbipy)]•2 H 2 O (Compound 4). The complex compound [VOO(dipic)](2-phepyH)•H 2 O was synthesized in crystalline form and all data specifying the XRD analysis of this complex have been described in the publication [22].…”