Project

Vanadium compounds in catalysis and material chemistry: interaction of experiment and theory. 

Goal: VEGA Grant 1/0507/17:
The project covers the most actual topics in vanadium inorganic chemistry: catalytic oxidations and polyoxometalate chemistry in confrontation with quantum chemical calculations.

Date: 1 January 2017 - 31 December 2020

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Lukáš Krivosudský
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A new mononuclear vanadium peroxido complex [VO(O2)(phen)(quin)]·H2O (1) exhibiting an unprecedented isomerism of its ligands was isolated from a two-component water–acetonitrile solvent system. DFT computations aimed at inspecting the stability of all possible isomers of complexes [VO(O2)(L1)(L2)], where L1 and L2 are NN+ON, OO+ON, NN+OO, and ON+ON donor atom set ligands, suggested that every complex characterized so far was the one preferred thermodynamically. However, the particular case of complex [VO(O2)(phen)(quin)] reported herein poses a notable exception to this rule, as this complex yielded single crystals of the isomer with total energy above the anticipated isomer, although both of these isomers could be observed concurrently in solution and also in the solid state. 51V NMR spectroscopy suggested these isomers to be present both in the crystallization solution and in the acetonitrile solution of 1. The coexistence of two isomers is a consequence of their small computed energy difference of 2.68 kJ mol–1, while the preferential crystallization favoring the unexpected isomer is likely to be triggered by solvent effects and the effects of different solubility and/or crystal packing. The coordination geometry of the unusual isomer also manifests itself in FT-IR and Raman spectra, which were corroborated with DFT computations targeted at band assignments.
Lukáš Krivosudský
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PhD Student positions available 
The positions are suitable for students and researchers with a background in inorganic, organic, biological chemistry or biochemistry. Following topics may be covered in the dissertation project:
Interaction of vanadium-based polyoxometalates with biological systems
The aim of the work is the design, synthesis and characterization of vanadium polyoxometalates with structures enabling interaction with biomolecules and the study of the interaction using spectral methods.
Synthesis of fluorinated polyoxometalates
The goal is to develop methods for preparation of fluorinated polyoxometalates of vanadium, molybdenum and tungsten, the
study of their structures and properties applicable in materials chemistry.
Chiral oxido complexes of vanadium
The aim of the work is synthesis and characterization of oxido complexes of vanadium with potential use in catalysis or in
bioinorganic chemistry and the study of the structure and stereochemistry of such compounds focused on chirality.
We are looking for a dedicated and creative individual with a strong background in general chemistry knowledge and good written and spoken English. Preferred qualifications:
- MSc degree in chemistry or related fields (biochemistry, chemical biology, medicinal chemistry);
- Experience in chemical synthesis;
- Theoretical and practical experience in common spectral methods (infrared, uv-VIS and NMR spectroscopy).
 
Lukáš Krivosudský
added a research item
Two new 1D polymeric heterometallic copper–vanadium compounds were prepared. The polymers are constructed from [Cu(im)4]²⁺ cations that are coordinated to two terminal oxido ligands of [V2O4(mand)2]²⁻ anions. The stronger coordination in [Cu(im)4V2O4(mand)2]n (1) that contains the racemic mandelato ligand is manifested by a shorter Cu‒O bond distance 2.4095(12) Å, while the weaker interaction in [Cu(im)4(V2O4((S)-mand)2)]n·2nH2O (2) is exhibited by Cu‒O bond distances 2.4547(16) Å and 2.5413(16) Å. The vanadate anion in compound 2 carries only the (S)-enantiomer of the initial mandelic acid and differs from the anion in 1 in parallel cis orientation of the phenyl groups of the mandelato ligand. FT-IR spectroscopy was used for the confirmation of the coordination mode of mandelato ligand. Strong bands corresponding to the vibrations of carboxyl groups can be observed around 1650 and at 1344 cm⁻¹. The stretching vibration of deprotonated hydroxyl group in the mandelato ligand occurs at 1045 and 1065 cm⁻¹ for 1 and 2, respectively. In addition, the very strong, characteristic band corresponding to ν(V=O) vibration can be observed at 931 cm⁻¹ for 1 and 925 cm⁻¹ for 2, as well as in Raman spectrum. Graphic Abstract The polymeric structures of two new vanadium-copper heterometallic complexes are constructed from [Cu(imidazole)4]²⁺ cations that are coordinated to two terminal oxido ligands of [V2O4(mandelato)2]²⁻ anions with different orientation of the phenyl groups depending on the chirality of the mandelato ligand. Open image in new window
Lukáš Krivosudský
added a research item
A nickel‒vanadium metal–organic hybrid compound [Ni(phen)3]2[(V2O2(O2)2((S)-mand)2)][(V2O2(O2)2((R)-mand)2)]·18H2O (phen = 1,10-phenanthroline, mand²⁻ = mandelato(2−) ligand, C6H5–CO–COO²⁻) (1) was prepared and characterized by spectral methods, X-ray structure analysis and simultaneous DTA and TG measurements. The crystal structure of 1 contains both Δ and Λ enantiomers of the [Ni(phen)3]²⁺ cations that construct sandwich layers along the crystallographic axis c, in between which sit the vanadium(V) complex anions. These are present as ionic dimers in the form of a robust {[(V2O2(O2)2((S)-mand)2)][(V2O2(O2)2((R)-mand)2)]}⁴⁻ species. The two individual anions are coupled by a pair of weak, yet significant attractions between two vanadium atoms and two peroxido ligands of the adjacent anion at V‒O distances 2.660 Å. The ⁵¹V NMR spectrum of the compound in DMSO solution revealed a complicated course of decomposition reactions of the anion, which led to formation of the [(V2O4(S,R-mand)2]²⁻ anion as a single product. The metal–organic hybrid compound 1 is converted by thermal decomposition into a potential anode material for lithium-ion batteries Ni(VO3)2.
Lukáš Krivosudský
added a research item
New vanadium complexes of mandelic acid (NMe4)4[V2O4((R)-mand)2][V2O4((S)-mand)2] (1) (NMe4)2[V2O4((S)-mand)2]·H2O (2) (NEt4)2[V2O4((S)-mand)2]·H2O (3) (PPh4)2[V2O4((R)-mand)((S)-mand)]·2H3CCOCH3·2H2O (4), (NH4)2.5(NEt4)0.5[V3O7((R)-mand)((S)-mand)]·2H2O (5) (mand2− = mandelato ligand) have been synthesized and characterized by single crystal X-ray diffraction and FT-IR spectroscopy. The band assignment in IR spectra was corroborated by DFT calculations. While the structures of 1-4 comprise the expected dinuclear [V2O4(mand)2]2– (V2L2) anions, the structure of the [V3O7((R)-mand)((S)-mand)]3– (V3L2) in 5 is unique and represents a new structural type in vanadium(V) chemistry. Solution studies of vanadate with mandelic acid by 51V NMR revealed the presence of two dominant species V2L2 and V3L2 in aqueous solutions and increasing fraction of V3L2 species at slightly acidic pH (pH ≈ 6).
Lukáš Krivosudský
added a research item
Polyoxometalates (POMs) are promising inorganic inhibitors for P-type ATPases. The experimental models used to study the effects of POMs on these ATPases are usually in vitro models using vesicles from several membrane sources. Very recently, some polyoxotungstates, such as the Dawson anion [P2W18O62]6−, were shown to be potent P-type ATPase inhibitors; being active in vitro as well as in ex-vivo (N. I. Gumerova et al., Metallomics 10 (2018) 287–295). In the present study we broaden the spectrum of highly active inhibitors of Na+/K+-ATPase from basal membrane of epithelial skin to the bi-capped Keggin-type anion phosphotetradecavanadate Cs5.6H3.4PV14O42 (PV14) and we confront the data with activity of other commonly encountered polyoxovanadates, decavanadate (V10) and monovanadate (V1). The X-ray crystal structure of PV14 was solved and contains two trans-bicapped α-Keggin anions HxPV14O42(9-x)-. The anion is built up from the classical Keggin structure [(PO4)@(V12O36)] capped by two [VO] units. PV14 (10 μM) exhibited higher ex-vivo inhibitory effect on Na+/K+-ATPase (78%) than was observed at the same concentrations of V10 (66%) or V1 (33%). Moreover, PV14 is also a potent in vitro inhibitor of the Ca2+-ATPase activity (IC50 5 μM) exhibiting stronger inhibition than the previously reported activities for V10 (15 μM) and V1 (80 μM). Putting it all together, when compared both P-typye ATPases it is suggested that PV14 exibited a high potential to act as an in vivo inhibitor of the Na+/K+-ATPase associated with chloride secretion.
Lukáš Krivosudský
added a research item
Two novel heterometallic complexes [Cu(bpy) 2 V 2 O 2 (O 2 ) 2 (R-mand) 2 ][Cu(bpy) 2 V 2 O 2 (O 2 ) 2 (S-mand) 2 ]·2CH 3 CN·2H 2 O (1), and [Cu(phen) 2 V 2 O 2 (O 2 ) 2 (R-mand) 2 ][Cu(phen) 2 V 2 O 2 (O 2 ) 2 (S-mand) 2 ]·2CH 3 CN·2H 2 O (2), (mand = mandelato(2–) = C 6 H 5 CH(O)CO 22– ) were prepared and characterized by spectral methods. X-ray single-crystal analysis revealed the difference between both structures. While 1 contains a bonding copper(II) and vanadium(V) atoms through the bridging oxygen atom Cu–O–V, the metallic atoms are connected in 2 through the carboxylic group Cu[sbnd]O[sbnd]C[sbnd]O[sbnd]V. Complexes 1 and 2 are immediately decomposed in their aqueous solutions, but their integrity is preserved for some time in DMSO. ⁵¹ V NMR spectra of DMSO solutions of vanadates(V), peroxidovanadates(V) and vanadium(V) mandelato complexes are presented for the first time.
Lukáš Krivosudský
added a research item
Complex NH4[VO(O2)2(NH3)] (1) undergoes an order-disorder phase transition at Tc~258K. This transition is accompanied by change in the space group of the orthorhombic lattice and also by significant structural rearrangements of the constituent molecules, which are pertinent mostly to their NH4+ ions and their ammonia ligands. The low-temperature solid state IR and Raman spectra of 1 were corroborated by solid-state computations that employed Gaussian functions as the basis set. Results of these computations yielded excellent agreement with experimental data. On the curves of temperature dependence of vibrational modes, the phase transition is expressed by an abrupt change of the slope above Tc.
Lukáš Krivosudský
added an update
Complex NH4[VO(O2)2(NH3)] (1) undergoes an order-disorder phase transition at Tc ~ 258 K. This transition is accompanied by change in the space group of the orthorhombic lattice and also by significant structural rearrangements of the constituent molecules, which are pertinent mostly to their NH4+ ions and their ammonia ligands. The low-temperature solid state IR and Raman spectra of 1 were corroborated by solid-state computations that employed Gaussian functions as the basis set. Results of these computations yielded excellent agreement with experimental data. On the curves of temperature dependence of vibrational modes, the phase transition is expressed by an abrupt change of the slope above Tc.
 
Lukáš Krivosudský
added a project goal
VEGA Grant 1/0507/17:
The project covers the most actual topics in vanadium inorganic chemistry: catalytic oxidations and polyoxometalate chemistry in confrontation with quantum chemical calculations.