Jiří Votinský

Intercalation of aliphatic amines into layered structure of vanadyl phosphate

Abstract Layered complexes VOPO 4 ·2RNH 2 (R means aliphatic unbranched chain C 1 -C 10 ) have been prepared and characterized by their basal spacings, DTA and IR spectra. The observed alternation of the basal spacing increments with the number of the carbon atoms of the chain indicates an oblique arrangement of these chains in the van der Waals gap.

Redox intercalation reaction of crystalline VOPO4 · 2H2O with NaI solution in acetone

Abstract Polycrystalline layered VOPO4·2H2O reacts very readily with NaI solution in acetone producing green solids and releasing molecular iodine. This redox intercalation is joined with NA+ ion insertion between layers of the host and with reduction of vanadium (VV to VIV). Three solid phases are created gradually with the compositions Na0.3VIV0.3VV0.7OPO4·2H2O, Na0.5VIV0.5OPO4·2H2O and NaVIVOPO4·H2O. These phases are stages 3, 2 and 1 and agree with situations in which the host is intercalated from 33, 50 and 100%. Basal spacings of all three stages were measured. Changes in phase ratio in the solid reaction products were determined by X-ray phase analysis for the reaction time 0–500 h and temperature range 20–40°C. Magnetic susceptibility (−170−30°C), a.c. conductivity and thermal properties (20–600°C) of these phases were investigated.

Layered compounds derived from vanadyl phosphate dihydrate

The layered crystalline solids stable in air with general formula [M(H{sub 2}O)]{sub x}(VO){sub 1{minus}x}PO{sub 4{sup {sm_bullet}}}2H{sub 2}O (M = Al, Cr, Fe, Ga; x = 0.15--0.20) were prepared by reaction of solid V{sub 2}O{sub 5} with a boiling aqueous solution of phosphoric acid and the corresponding metal salt. The elementary cells of these compounds are tetragonal (space symmetry group either P4/n or P4/nmm). The lattice parameters and densities were determined. The results of TG, DTA and magnetic susceptibility measurements are given.

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 aliphatic alcohol mixtures into the layered lattice of unhydrated vanadyl sulphate

Abstract The mixed intercalates of the type VOSO4·(2 − x)Cp·xCq have been prepared by reaction of unhydrated layered VOSO4 with liquid binary mixtures of the aliphatic alcohols. Symbols Cp and Cq mark two different unbranched primary aliphatic alcohols, p and q are numbers of carbon atoms in their molecules (p p + 2 these values range in intervals 〈0–0.05〉, 〈0.9–1.1〉 and (1.75−2). Relations between basal spacings of the formed layered complexes and their composition and the composition of the liquid alcohol (C2 to C7) mixtures were studied for fifteen systems. The schematic explanation of the arrangement of the alcohol molecules in van der Waals gap is proposed.

Possible Mechanisms of Intercalation

Recent knowledge of the kinetics and intercalation mechanisms are summarized and accompanied by examples of intercalation reactions of water and ethanol into anhydrous vanadyl phosphate and redox intercalation of alkali metal cations into vanadyl phosphate dihydrate. Three possible mechanisms of intercalation are presented which are based on: (i) a concept of exfoliation of layers; (ii) the formation of stages and randomly stacked layers; (iii) co-existence of intercalated and non-intercalated parts of crystals of the host separated by an advancing phase boundary. The corresponding kinetic curves are ascribed to mechanisms (ii) and (iii).

Synthesis and powder data for [Mn(H 2 O)] 0.25 (VO) 0.75 PO 4 ·2H 2 O

A new compound [Mn(H 2 O)] 0.25 (VO) 0.75 PO 4 ·2H 2 O was prepared by the reaction of V 2 O 5 with the boiling aqueous solution of H 3 PO 4 and KMnO 4 . The reaction product is a yellow-brown powder, stable in air. The tetragonal unit-cell parameters (298 K) are a = 6.2034(2)A, c = 13.814(1)A, V = 531.59A 3 , Z = 4, M r = 194.94, D x = 2.493 g/cm 3 , D exp = 2.52 g/cm 3 . X-ray (CoK α radiation) powder diffraction data (35 lines) are reported. The compounds structure is probably derived from the VOPO 4 ·2H 2 O layered lattice by substitution of [Mn(H 2 O)] 3+ ions for a quarter of the vanadyl groups VO 3+ . Practically the same powder data and unit-cell parameters were found for [Mn(H 2 O)] x (VO) 1−x PO4·2H 2 O, where x ranges from 0.185 to 0.25.

A kinetic study of the intercalation of ethanol into vanadyl phosphate

The course of intercalation of ethanol into VOPO4 has been studied by X-ray diffraction, thermomechanical analysis and a volumetric method. In all cases the kinetic curves were observed to have a sigmoidal shape. A model, based on the Avrami equation, has been proposed for description of the kinetic behavior. The activation energy of intercalation based on this model has been determined. The existence of the advancing phase boundary in the system during intercalation has been confirmed.

Intercalation of 1-Alkanol Binary Mixtures into the Layered Structure of Vanadyl Phosphate

Mixed intercalates VOPO4.C2H5 OH.C4 H9OH, VOPO4.C3H7 OH.C5H11OH, VOPO4.C3H7 OH.C6H13OH and VOPO4.C4H9 OH.C6H13OH have been prepared by reaction of polycrystalline vanadyl phosphate dihydrate with liquid mixtures of the 1-alkanols in a microwave field. The same mixed layer-type complexes were also obtained as intermediary products of exchange reactions consisting in substitution of one alkanol bound in the solid intercalate by another alkanol introduced in the form of vapour. The composition of products has been determined, and the basal spacing of all the mixed layer-type complexes prepared has been found by diffraction. A structural principle is suggested which governs the depositing of two kinds of 1-alkanol molecules (differing in the lengths of their aliphatic chains) while acting as guests in the layered structure of vanadyl phosphate.