Vítězslav Zima

Direct-mixing assembly of a magnesium coordination complex as recyclable water adsorbent,

Direct-mixing: a new preparative method has been employed to synthesize a dinuclear magnesium coordination complex with highly recyclable water adsorption and luminescent property.

Synthesis, structures, and properties of alkali and alkaline earth coordination polymers based on V-shaped ligand

A series of metal coordination polymers, [Li2(OBA)] (1), [Na2(OBA)(H2O)] (2), [K(HOBA)] (3), [Rb(HOBA)] (4), [Cs(HOBA)] (5), [Mg(OBA)(H2O)2] (6), [Ca(OBA)(H2O)] (7), and [Sr(OBA)(H2O)] (8) (H2OBA = 4,4′-oxybisbenzoic acid), was synthesized from alkali and alkaline-earth metal salts and 4,4′-oxybisbenzoic acid by solvothermal reactions. Single crystal X-ray structure analysis revealed that compounds 1–5 and 7–8 are three-dimensional while complex 6 has a layered structure. The inorganic motifs, ranging from discrete octahedra (6), edge-sharing octahedral dimers (7), and straight one-dimensional inorganic chains (1 and 8) to two-dimensional inorganic layers (2–5), are connected through organic linkers and thus form neutral networks. High thermal stabilities were observed for compounds 1, 2, 6, 7, and 8 up to approximately 500 °C. Electrochemical measurements of 1 revealed a stabilized reversible capacity of approximately 100 mAh g−1 after more than 30 charge/discharge cycles.

Intercalation chemistry of layered vanadyl phosphate: a review

The intercalation chemistry of layered αI modification of vanadyl phosphate and vanadyl phosphate dihydrate is reviewed. The focus is on neutral molecular guests and on metal cations used as guest species. The basic condition for the ability of the neutral molecules to be intercalated into vanadyl phosphate is a presence of an electron donor atom in them. The most commonly used guest compounds are those containing oxygen, nitrogen or sulfur as electron donor atoms. Regarding the molecules containing oxygen, various compounds were used as molecular guests starting from water to alcohols, ethers, aldehydes, ketones, carboxylic acids, lactones, and esters. An arrangement of the guest molecules in the interlayer space is discussed in connection with the data obtained by powder X-ray diffraction, thermogravimetry, IR and Raman spectroscopies, and solid-state NMR. In some cases, the local structure was suggested on the basis of quantum chemical calculations. Besides of those O-donor guests, also N-donor guests such as amines, nitriles and nitrogenous heterocycles and S-donor guests such as tetrathiafulvalene were intercalated into VOPO4. Also intercalates of complexes like ferrocene were prepared. Intercalation of cations is accompanied by a reduction of vanadium(V) to vanadium(IV). In this kind of intercalation reactions, an iodide of the intercalated cation is often used as it serves both as a mild reduction agent and as a source of the intercalated species. Intercalates of alkali metals, hydronium and ammonium were prepared and characterized. In the case of lithium and sodium intercalates, a staging phenomenon was observed. These redox intercalated vanadyl phosphates undergo ion exchange reactions which are discussed from the point of the nature of cations involved in the exchange. Vanadyl phosphates in which a part of vanadium atom is replaced by other metals are also briefly reviewed.

Tg/dta, Xrd and NH3-TPD Characterization of Layered VOPO4·2H2O and its Fe3+-Substituted Compound

Iron(III)-substituted vanadyl phosphate, [Fe(H2O)]0.20VO0.80PO4·2.25H2O (FeVOP), has been prepared and characterized by XRD and TG/DTA analyses. The new compound is isomorphous with layered tetragonal VOPO4·2H2O (VOP), but it possesses a lower interlayer distance. Information on the reactivity and surface acidity of both VOP and FeVOP has been obtained by NH3-TPD experiments. The hydrated materials adsorb high amounts of NH3 (up to 2 mmol g-1). Different ammonia-containing phases are formed, characterized by lower interlayer distances in comparison with the NH3-free parent compounds. NH3 is intercalated between the layers without displacement of water. The materials dehydrated by heat treatment at 450°C retain the layered structure but adsorb NH3 only on the external surface. A wide variety of acid sites, from weak to strong, was observed. A mechanism is proposed for the NH3- acid sites interaction. SEM micrographs of VOP and FeVOP are shown.

Thermal, structural and acidic characterization of some vanadyl phosphate materials modified with trivalent metal cations

A set of new materials with general formula [M(H2O)]X(VO)1−XPO4·2H2O (M3+=Al, Cr, Ga, Mn), isomorphous with layered tetragonal VOPO4·2H2O and having potential catalytic properties, have been characterized by TG and DTA, X-ray diffraction and surface acid strength. During heating the compounds transform in the monohydrated and anhydrous phases, all maintaining a layered structure, with a proper interlayer spacing. Catalytic tests performed with 1-butene show that theM3+-vanadyl phosphates greatly improve the conversion of the olefine with respect to pure vanadyl phosphate.

Effect of intercalation and chromophore arrangement on the linear and nonlinear optical properties of model aminopyridine push–pull molecules

Three push–pull aminopyridine derivatives having D–π–A, D–(π–A)2, and D–(π–A)3 arrangements were examined as model organic chromophores capable of intercalation into inorganic layered materials (alpha modification of zirconium hydrogen phosphate, zirconium 4-sulfophenylphosphonate, and gamma modification of titanium hydrogen phosphate). The fundamental properties of these dyes, their methylated analogues as well as their intercalates were studied by X-ray analysis, electrochemistry, UV/Vis absorption spectra, TGA, IR spectra, SHG, and were completed by DFT calculations. The synthesis of tripodal tris(pyridin-4-yl)amine is given for the first time. The HOMO–LUMO gap, the position of the longest-wavelength absorption maxima, and the dipole moment of aminopyridines can easily be tuned by attaching/removing pyridin-4-yl electron withdrawing units and their quaternization (pyridine vs. pyridinium acceptors). Their intercalation proved to be feasible affording novel inorganic–organic hybrid materials. The intercalation is accompanied by protonation of the guest, which enhances its ICT and strongly anchors the aminopyridines into the confined space of the layered host. Moreover, this process results in ordering of the organic chromophores and also brings improved thermal and chemical robustness. As a result, the measured SHG efficiencies of the intercalates are larger than those observed for the pure organic push–pull chromophores. Hence, the methodology of intercalation turned out to be very useful strategy for property tuning of NLO-active organic molecules.

Glycine intercalated vanadyl and niobyl phosphates

Abstract Glycine intercalated vanadyl (VOPO4·NH2CH2COOH) and niobyl (NbOPO4·(NH2CH2COOH)0.85·0.45H2O) phosphates were prepared by shaking the reaction mixture at room temperature or by refluxing starting compounds respectively. The intercalates retain the layered structure of the parent phosphates with a basal spacing corresponding to a perpendicular arrangement of the glycine chains in the interlayer space. IR spectra confirm the presence of glycine molecules in the intercalates as zwitterionic species. Being similar to those observed for anhydrous VOPO4, impedance measurements of VOPO4·NH2CH2COOH support the idea that the conductivity in this intercalate is electronic and the glycine molecules in the interlayer space do not take part in the conductivity mechanism.

Intercalation of VOPO4 · 2H2O with hydronium and potassium ions

Abstract Intercalation compounds HxVOPO4 · yH2O (x = 0.3–1.0; y = 2.0–3.6) and KxVOPO4 · yH2O (x = 0.2–0.98; y = 1) were prepared by redox intercalation of VOPO4 · 2H2O with acetone solutions of hydroquinone and potassium iodide respectively. Time course of reactions, X-ray diffraction and ac conductivity of prepared compounds were studied. The decrease of conductivity with increasing content of guest was observed. The activation energy of conductivity of HxVOPO4 · yH2O was calculated from the Arrhenius plot. The content of interlayer water increases during intercalation of hydronium ions as it was determined by DTA.

Intercalation of Cyclic Ethers into Vanadyl Phosphate

Two cyclic ethers, tetrahydrofuran (THF) and tetrahydropyran (THP), were intercalated into vanadyl phosphate and characterized by X-ray powder diffraction, thermogravimetry, and IR and Raman spectroscopy. Both compounds contain one molecule of ether per formula unit of VOPO(4) and show high thermal stability in comparison with VOPO(4) intercalates with other organic guest molecules. Both ethers are anchored to the VOPO(4) host layers by their oxygen atoms, which are coordinated to the vanadium atoms of the host. The probable arrangement of the tetrahydropyran molecules in the host interlayer space is derived from molecular simulations by the Cerius(2) 4.5 program.

Intercalates of Vanadyl Phosphate with Branched Alcohols

Intercalates of VOPO4 with several branched alcohols (2-propanol, 2-methyl-1-propanol, 3-methyl-1-butanol, 4-methyl-1-pentanol, 2-methyl-2-propanol, 2,2-dimethyl-1-propanol, 3,3-dimethylbutanol, 3-methyl-1-pentanol, 2-methyl-1-pentanol, 2-hexanol, 2-ethyl-1-butanol, 2-propyl-1-pentanol) were prepared and characterized by powder X-ray diffractometry and thermogravimetry. Only 2-propanol, 2-methyl-1-propanol and 3-methyl-1-butanol were directly intercalated into vanadyl phosphate dihydrate. The other intercalates were prepared by the displacement of 2-propanol. Gas chromatography of the solid intercalates showed that no mixed intercalates still containing the starting alcohol are formed, except the 4-methyl-1-pentanol intercalate. The arrangement of the guest molecules in the interlayer space of the host is discussed. The alcohols are anchored to the host layers by donor-acceptor bonds between their oxygen atoms and the vanadium atoms of the host structure, and by hydrogen bonding.