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Journal of Inorganic Biochemistry
Volume 101, Issue 1,
January 2007
, Pages 36-43
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Abstract
Using vanadate, poly(1H-pyrazol-1-yl)borate and pyrazole as starting materials, two new neutral peroxovanadium(V) complexes with poly(1H-pyrazol-1-yl)borate, VO(O2)(pzH)(HB(pz)3)(1) and VO(O2)(pzH)(B(pz)4)(2), were synthesized successfully. Both complexes were characterized by elemental analysis, IR, UV–vis and NMR spectra. And the structure of complex 1 was determined by X-ray diffraction, which is somewhat relevant for haloperoxidase enzymes. Cytotoxic effects also are discussed on 3T3 cell proliferation. In the concentration range (0.1–100μmol), both complexes have an inhibiting cellular proliferation effect. When the cells cultivated with the complexes at high dose, the toxicity effect of both complexes is more and more predominant.
Introduction
Vanadium haloperoxidases (VHPO) are enzymes catalyzing the oxidation of halides to corresponding hypohalous acids, which then readily undergo halogenation of organic substrates or conversion of hydrogen peroxide to singlet oxygen and generation of halides (Eq. (1)) [1]. Insight into the structural features of inorganic cofactor and its coordination environment were obtained by X-ray diffraction [2] of the VClPO (vanadium chlorinperxoxdases) from the pathogenic fungus Curvularia inaequalis. In the native state [3], the vanadium ion is characterized by a trigonal bipyramidal geometry, where three oxygen atoms belong to the equatorial plane and one oxygen atom occupies an axial position. The other apical ligand is His496, which links the metal ion to the protein, whereas Lys353, Arg360, His404, and Arg490 are involved in hydrogen bonds with the oxygen atoms of the cofactor. In the peroxo derivative of the enzyme [4], the cofactor is characterized by a strongly distorted trigonal bipyramidal geometry, with two oxo type oxygen atoms and one peroxo atom in the equatorial plane, while His496 and the other peroxo atom in the axial positions (Fig. 1). The catalytic properties of VHPOs have been extensively investigated in recent years [5], [6], [7], [8]. It has been observed that Lys353, which is the only amino acid interacting directly with the peroxo-bound moiety, might polarize the peroxo bond, making it more susceptible toward nucleophilic attack (Fig. 2):Hal−+H2O2+RH+H+→RHal+2H2O.
Recently, peroxovanadium(V) complexes have been also the objects of intense investigations, due to their biological relevance (insulinmimetic and antitumour activities [9], [10], [11], functional models for the haloperoxidase enzymes [12], [13], [14]). Some aminopolycarboxylic acid peroxovanadium complexes have been shown to be functional models of VHPO [8], [13], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24]. However, the synthesis of models characterized by the metal coordination environment observed in the enzyme has not yet been achieved, hindering direct comparison with the chemical properties of the cofactor within the enzyme active site. In this paper, we try to introduce a powerful ligand of poly(1H-pyrazol-1-yl)borate to synthesize peroxovanadium complexes. Poly(1H-pyrazol-1-yl)borates are a versatile class of anionic nitrogen-donor ligands. And the pyrazole of poly(1H-pyrazol-1-yl)borate can in many ways mimic histidine nitrogen ligation, so, it is possible to synthesize simple models for active sites of bio-organic macromolecules such as enzymes: for example the rigid N3 ligand framework of tris- and tetra(1H-pyrazol-1-yl)borate is able to mimic the spectroscopic behavior of the blue copper proteins [25], [26]. So we are now extending previous work carried out in this group on vanadium complexation with poly(1H-pyrazol-1-yl) borate to these systems involving hydrogen peroxide. To our knowledge no peroxovanadium complexes with poly(1H-pyrazol-1-yl)borate ligands have been reported, here, two new neutral peroxovanadium(V) complexes with poly(1H-pyrazol-1-yl)borate ligands, VO(O2)(pzH)(HB(pz)3) (1) and VO(O2)(pzH)(B(pz)4) (2) will be reported, which may help in driving the design of new functional model complexes.
Section snippets
General methods
All solvents were of analysis purity. All synthetic manipulations were carried out in the atmosphere at room temperature. Elemental analyses (C, H and N) were performed on a PE 240 C analyzer. Infrared spectra were recorded on a JASCO-FT/IR-480 spectrometer in the spectral range 4000–200cm−1 with the samples in the form of potassium bromide pellets. The UV–visible (UV–vis) spectra were recorded on JASCO V-570 spectrometer (200–1100nm, CH2Cl2 solution). The 1H, 13C and 51V NMR spectra were
Results and discussion
Base on the starting materials, the previous reaction routes of synthesizing the peroxovanadium complexes can be classified as two types: (1) using vanadate(V) as starting materials [29], [30], [31], [32], [33], [34], [35], [36], [37]; (2) using vanadium(IV) as starting materials [38]. In this paper complexes 1 and 2 were synthesized by the reaction of VOSO4, H2O2, potassium tris(1H-pyrazol-yl)borate(or potassium tetra(1H-pyrazol-yl)borate) and pyrazole in methanol/water solution. In the course
Conclusion
Using similar reaction routes, two new peroxovanadium(V) complexes were obtained. Comparing the data (elemental analyses, spectra of IR, UV–vis and NMR) of both complexes, it is concluded that complex 1 and 2 have similar structures. In the peroxovanadium complexes, peroxo-group and the hydrogen bonds present may play important role in the catalysis process of haloperoxidases (VHPO).
Acknowledgements
We wish to express our sincere thanks to National Natural Science Foundation of China (No. 20571036), and SRF for ROCS, SEM and Education Foundation of Liaoning Province (No. 05L212) for financial assistance.
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Recent development of biomimetic halogenation inspired by vanadium dependent haloperoxidase
2022, Coordination Chemistry Reviews
Organohalide is one of the most important and useful compounds in organic chemistry, broadly embodied in diverse bioactive molecules, organic materials and agrochemicals. Installation of halide to organic compound, in most cases, still relies on traditional electrophilic halogenation (e.g., utilizing Br2, I2 and Cl2), particularly in industrial production. Such process unavoidably generates undesired environmentally unfriendly by-products (e.g., HBr from Br2). By contrast, in nature the haloperoxidase produces organic halides under mild condition in atom economy. But they suffer from high cost, limited substrate scope and specific working condition. The biomimetic halogenation inspired by nature, in theory, provides a potential solution for these limitations, serving as an alternative green halogenation approach. In this review, the author summarized the recent development of biomimetic halogenation inspired by vanadium dependent haloperoxidase (VHPO). Evident progress has been achieved in its functional mimics utilizing transition metal (TM) catalysts, including vanadate (V5+), molybdate (Mo6+), tungstate (W6+), and rhenate (Re7+). These robust biomimetic catalysts work efficiently under mild condition with broad substrate scope, and even afforded drug molecules in preparative scale. The challenges and opportunities for further development in this field were also discussed, along with the elucidation of VHPO’s structure, functional mechanism and synthetic application.
Construction of five non-covalent-fabricated Zn<sup>2+</sup>/Cd<sup>2+</sup> supramolecules from 3,5-dimethylpyrazole: Their synthesis and features
2021, Journal of Molecular Structure
The present report pertains to the synthesis and characterization of 5 novel complexes of Zn2(Hdmpz)4(L1)2 (1) (L1=itaconate), Cd(Hdmpz)2(L2) (2) (L2=isophthalate), Cd(Hdmpz)2(L3) (3) (L3=5-amino-isophthalate), Zn(Hdmpz)2(L4)2 (4) (L4=3-(4‑bromo-phenylcarbamoyl)-acrylate) and [Cd(Hdmpz)2(L4)2]2 • 2H2O (5). These complexes were elaborated from EA, IR and SCXRD analysis and the TGA of all the complexes was also identified.
The X-ray studies told that these complexes display mononuclear to dinuclear structures with tetrahedral/octahedral arrangement around each Zn2+/Cd2+. The Hdmpzs in 1–5 are ligated only in monodentate fashion via its neutral N. The CO2− at 1 and 4 exhibits only unidentate coordination fashion, the CO2− in 2 and 3 show the chelating bidentate coordination mode. Compound 5 bear both unidentate bridging and bidentate chelating CO2−.
The uncoordinated O of the CO2− in 1 makes the intramolecular N
H•••O H-bond with NH of the Hdmpz. Compounds 2 and 3 bear the interchain NH•••O H-bonds from the Hdmpz and the coordinated O. The NH of one pyrazole at 4 made a bifurcated NH•••O H-bond with both O at the CONH and the uncoordinated O of the CO2−, the NH of the other pyrazole gave a single NH•••O H-bond to the CONH. At 5 the NH•••O H-bonds from the NH of the Hdmpz, the O at the CONH and the coordinated O of the CO2− were found. In the anions of 5 there also created the intramolecular NH•••O H-bond between the coordinated O and the CONH, building a S11(7) ring. The intricate intra- and intermolecular classical H-bonds, Br•••O, CHCH, CH3Cπ, CH-Br, CH•••O/CH2•••O/CH3•••O, CH•••π/CH2-π and CH3-π associations are elucidated by the X-ray crystallographic studies, which adhere the discrete units into high-dimensional ordered supramolecular structures.Synthesis and structural characterizations of nine non-covalent-bonded Zn<sup>2+</sup>, and Cd<sup>2+</sup> supramolecules based on 3,5-dimethylpyrazole and carboxylates
2019, Polyhedron
The present study pertains to the synthesis and characterizations of nine novel mixed-ligand complexes of [Zn(Hdmpz)2(L1)2] (1) (dmpz = 3,5-dimethylpyrazolate, L1 = 2-bromobenzoate), [Zn(Hdmpz)2(L2)2] (2) (L2 = 4-tert-butylbenzoate), Zn(Hdmpz)2(L3)2 (3) (L3 = 2-thiophenoate), [Zn(Hdmpz)2(L4)2] (4) (L4 = 4-methylsalicylate), [Cd(Hdmpz)2(L5)2]2 (5) (L5 = 2,6-dihydroxy benzoate), [Cd(Hdmpz)2(L6)2]2·2H2O (6) (L6 = 3-(4-methoxy-phenylcarbamoyl)-acrylate), [Zn(Hdmpz)2(L7)]2 (7) (L7 = acetylenedicarboxylate), [Zn(Hdmpz)2(L8)] (8) (L8 = 1,2-phenylenediacetate), and [Cd(Hdmpz)(L9)(H2O)2]·H2O (9) (L9 = 3-nitrophthalate). The resulting complexes were formulated via EA, IR, and SCXRD, and the TGA of all the complexes was also evaluated.
The X-ray studies reveal that these complexes present mononuclear to dinuclear structures with tetrahedral geometry around each Zn2+, and octahedral/pentagonal bipyramidal geometry for Cd2+. The Hdmpzs in all compounds are coordinated only in monodentate fashion with its neutral N. The carboxylates at 1–4 and 3–9 function only as unidentate coordination units, the CO2− in 5 has the chelating bidentate coordination mode. Compound 6 contains both unidentate bridging and bidentate chelating COO−.
The free carboxylate O at 2–4 and 7–8 accept the intramolecular N
H⋯O H-bonds, at 1 and 7 the uncoordinated O participate in the intermolecular NH⋯O H-bonds. For 6 there is intermolecular NH⋯O H-bond from the NHCO and H2O, and intramolecular NH⋯O H-bonds from the NH at Hdmpz, the NHCO (acceptor), and one O at the bismonodentate coordinated COO−. One anion at 6 also gives the intramolecular NH⋯O H-bonds from the NHCO(donor) and one O at the bismonodentate coordinated COO−. The intermolecular NH⋯O H-bonds are from the phenol at both 4 and 5, and from the H2O at 9. The CH3 at Hdmpz in all compounds are participated in the noncovalent bonds except 3.The intricate intra- and intermolecular N
H⋯O and OH⋯O H-bonds as well as CH⋯N, Cπ, O⋯O, Br⋯O, CH3⋯CH, CH2⋯C, CH3⋯C, CH⋯O, CH2⋯O, CH3⋯O, CH⋯S, CH⋯π, CH3⋯π, and π⋯π associations are elucidated by the X-ray crystallographic studies, which unite the discrete units into high-dimensional ordered supramolecular structures.Construction of nine non-covalently-bonded zinc(II) and cadmium(II) supramolecules containing the mixed-ligands of 3,5-dimethylpyrazole and carboxylates: Their synthesis and characterization
2018, Polyhedron
Citation Excerpt :
The location of the H2 and H4 atoms in 2, binding with the N atom not the O atom, is agreement with the different acidities between Hdmpz and HL2 [28], and is also verified by the difference electron density map from which the H atoms were deduced. The Cd–N bond lengths are 2.363(7) and 2.377(6) Å and the Cd–O bond distance is 2.286(7) Å, which are all within the bond length ranges of related published compounds [29]. The angles around the Cd2+ ion range from 85.8(2) to 180.0(3)°.
The present report pertains to the synthesis and characterization of nine novel mixed-ligand complexes, Zn(Hdmpz)2(L1)2 (1) (Hdmpz = 3,5-dimethylpyrazole, L1 = 2-furoate), Cd(Hdmpz)4(L2)2 (2) (L2 = 1-hydroxy-2-naphthoate), Zn(Hdmpz)2(L3)2 (3) (L3 = 5-bromosalicylate), Cd(Hdmpz)2(L4) (4) (L4 = 4-nitro-phthalate), Zn(Hdmpz)2(L5)2 (5) (L5 = 3-(2-chloro-phenylcarbamoyl)-acrylate), Zn(Hdmpz)2(L6)2 (6) (L6 = 3-m-tolylcarbamoyl-acrylate), Cd(Hdmpz)2(L6)2 (7), Zn(Hdmpz)2(L7)2 (8) (L7 = 3-p-tolylcarbamoyl-acrylate) and [Cd(Hdmpz)2(L7)2]2·2H2O (9). The resulting complexes were formulated from elemental analysis, IR spectra and single crystal X-ray diffraction analysis. The TGA of all the complexes was also evaluated.
The X-ray studies revealed that these complexes display mononuclear to binuclear structures with a tetrahedral geometry around each Zn atom and an octahedral geometry around each Cd atom. The Hdmpz ligands in all the compounds are coordinated only in a monodentate fashion through its neutral N atom. The carboxylate ligands in 1, 2, 3, 5, 6 and 8 act only as unidentate coordination ligands, while the carboxylate ligands in 4 and 7 have a chelating bidentate coordination mode. Compound 9 contains both unidentate bridging and chelating bidentate coordinated carboxylate groups.
The uncoordinated O atom of the COO− group in 1, 2 and 3 forms an intramolecular hydrogen bond with the N–H group of the Hdmpz, compound, 4 bears an intramolecular N–H⋯O hydrogen bond between the pyrazole ligand and the coordinated O atom. In 5, 6, 7 and 8, there are intramolecular N–H⋯O hydrogen bonds from the N–H unit of the Hdmpz ligand and the O atom of the CONH group. In 9, the N–H⋯O hydrogen bonds from the –H unit of the Hdmpz ligand, the O atom of the CONH group and the coordinated O atom of the COO− group were found. In addition, in the compound 9 there exists an intra-anion N–H⋯O hydrogen bond between the coordinated O atom and the CONH unit, displaying a S11(7) ring.
The intricate intra- and intermolecular classical hydrogen bonds, Br–Br, CH3–Br, CH–N, C–H⋯O, CH3⋯O, O⋯π(C), Cl–π, C–H⋯Cπ, C–H⋯π, CH3–π and π–π associations are elucidated from the X-ray crystallographic studies, which turn the discrete complexes into high-dimensional ordered supramolecular structures.
Peroxido complexes of vanadium
2016, Coordination Chemistry Reviews
Peroxido complexes represent an important group of vanadium compounds having practical applications in distinct areas of chemistry. They possess insulin mimetic properties, antitumor activity and stimulate or inhibit certain enzymes. The bioinorganic chemistry of peroxidovanadates studies also the role of vanadium in the active centers of vanadium dependent enzymes (haloperoxidases and nitrogenases). Peroxidovanadium compounds are intensively studied for their oxidative properties. They can act as catalysts or stoichiometric oxidants in oxidation reactions of organic compounds, e.g. in epoxidation, sulfoxidation, hydroxylation or bromination. This versatility of vanadium peroxido complexes necessitates a critical review of their molecular structure and properties both in solution and in solid state. In this inclusive review we present the complete set of peroxido complexes of vanadium heretofore characterized by X-ray diffraction analysis. Along with the molecular structures we present and discuss the solid state vibrational spectra and thermal decomposition data. Vibrational, UV–vis and 51V NMR spectraof complexes dissolved in various solvents are also discussed. We have extracted the data from several speciation studies in order to clarify the formation conditions for different types of peroxidovanadates and summarize their 51V NMR chemical shifts. We also refer to certain applications of peroxido complexes of vanadium and we place the emphasis on potential applications which have not yet been thoroughly examined but deserve more attention.
The first diperoxidovanadium complex with a monodentate amine ligand: Synthesis, characterization and crystal structure of methylbenzylammonium oxido-diperoxido-methylbenzylaminevanadate monohydrate
2015, Inorganic Chemistry Communications
The synthesis and structure of the first vanadium diperoxido complex carrying a monodentate amine ligand coordinated solely through its –NH2 group is reported herein. (S)-methylbenzylamine (mba) is acting as a ligand, while its protonated form is the cation in mbaH[VO(O2)2(mba)]∙H2O (1), which was isolated from a solution obtained by dissolving vanadium pentoxide in high excess of the amine and adding HCl and H2O2. [VO(O2)2(mba)]− is the dominating species in this solution and shows a resonance at −732ppm in 51V NMR spectrum. The anion exhibits in infrared and Raman spectra bands typical for pentagonal pyramidal diperoxido complexes of vanadium. The band assignment of the characteristic vibrations was confirmed by DFT calculations.
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