Anodic stripping voltammetric determination of thallium as [TlBr4]-rhodamine B complex

The anodic stripping voltammetric behaviour of the [TlBr₄]-rhodamine B complex is described and compared with that of thallium(I) and thallium(III) ions. The electrolyte composition, the best potential for the deposition of thallium from the complex in the selected electrolyte, the duration of the electrolysis, and the possibility of reduction of thallium in the [TlBr₄]-rhodamine B complex before the electrolysis with ascorbic acid were investigated. The results showed good reproducibility of the measurements of thallium as [TlBr₄]-rhodamine B complex and are similar to those obtained for thallium as Tl(I) and Tl(III) ions. As the [TlBr₄]-rhodamine B complex is strongly adsorbed on polyethylene, a previous preconcentration step on a column, packed with polyethylene powder, allowed the voltammetric determination of thallium as [TlBr₄]-rhodamine B complex in samples of KCl and NaCl as solid salts after the separation of the matrix. With this procedure it was possible to reach enrichment factors of 25 with recoveries from 96.7 to 107.9% for thallium concentrations from 5 to 40 μg L^–1 and RSD between 4.2 and 9.2%. The procedure was used to determine thallium traces in KCl and in sea salt. The results of these determinations were compared with the results obtained by graphite furnace atomic absorption spectrometry. Received: 5 February 1998 / Revised: 19 May 1998 / Accepted: 29 May 1998     

Structural Diversity in Thallium Chemistry. Part V

From thallium(III) bromide solution, the unsubstituted pyridinium cation yields a complex ( 1 ) with the [Tl₂Br₉]^3? anionic stoichiometry. The Raman spectrum and single‐crystal X‐ray crystallographic analysis showed that the salt contains independent [TlBr₄]^? and bromide anions. A variety of mono‐ and disubstituted pyridinium cations were also employed in similar syntheses. The 2‐bromopyridinium cation gave a salt 2 with [TlBr₅]^2? stoichiometry, but the crystal structure revealed very weakly interacting [TlBr₄]^? and bromide anions with a Tl ???Br^? distance of 4.1545(6) Å. The 2‐(ammoniomethyl)pyridinium and 2‐amino‐4‐methylpyridinium cations yielded complexes containing [TlBr₅]^2? ( 3 ) and [TlBr₄]^? ( 4 ) species, respectively, which were confirmed by Raman spectroscopy and X‐ray crystallographic analyses. For 3 , the [TlBr₅]^2? anion has a highly distorted trigonal bipyramidal conformation with one long axial Tl ???Br bond of 3.400(2) Å. Microanalytical results in conjunction with Raman spectra from a further five salts confirmed that they all contain the simple [TlBr₄]^? anion. N? H ???Br Hydrogen bonds clearly influence the nature of the anionic species obtained in these systems.     

Die Schichtstruktur von Tl[CuAsO4] und Tl[CuPO4] mit Zwischenschichten aus Thallium(I) mit stereoaktivem Elektronenpaar

The Layer Structure of Tl[CuAsO₄] and Tl[CuPO₄] with Layers of Thallium(I) with Stereoactive Lone Pair Single crystals of Tl[CuAsO₄] and Tl[CuPO₄] were prepared by reaction of oxygen with Tl/Cu/As and Tl/Cu/P alloys, respectively. The new isotypic compounds crystallize in spacegroup C2/c with Z = 8 and lattice constants a = 684.70(7) pm, b = 712.64(5) pm, c = 1822.4(2) pm, β = 92.76(1)° for Tl[CuAsO₄] and a = 671.57(8) pm, b = 697.09(6) pm, c = 1789.1(2) pm, β = 93.12(1)° for Tl[CuPO₄]. Square planar [CuO₄]-units are connected by common corners to form undulated [CuO₃]₂-chains running along [010]. Interconnection of the chains by arsenate or phosphate groups results in the formation of anionic cuprate-arsenate- and cuprate-phosphate-slabs, respectively. Along [001] these slabs are alternating with double layers of thallium(I) ions in which the stereochemical activity of the Tl⁺ lone pair is apparent from an hemispheric coordination of thallium by oxygen. The structure is related to that of the orthorhombic form of KCuPO₄.     

Syntheses and characterization of thallium(I) complexes with 3-nitrophenoxide [Tl(3-np)], 4-nitrobenzoate [Tl(4-nb)] and 2,4-dinitrophenoxide [Tl(2,4-dnp)]: X-ray crystal structures of [Tl(3-np)]n and Tl(2,4-dnp) (two new polymeric compounds)

Complexes thallium(I)3-nitrophenoxide [Tl(3-np)], thallium(I)2,4-dinitrophenoxide [Tl(2,4-dnp)] and thallium(I)4-nitrobenzoate [Tl(4-nb)] have been synthesized using a direct reaction between TlNO₃ and the appropriate ligand. The complexes have been isolated and characterized by IR spectra and CHN elemental analyses. The structures of [Tl(3-np)]_n and [Tl(2,4-dnp)] have been confirmed by X-ray crystallography. The single crystal X-ray crystallography of [Tl(3-np)]_n shows the complex to be a one-dimensional polymer as a result of bridging 3-nitrophenoxide ligands. The Tl atoms have an unsymmetrical three-coordinate, O₃ geometry (three oxygen atoms of the 3-nitrophenoxide ligand). The crystal structure of [Tl(2,4-dnp)] shows the complex to be a three-dimensional polymer as a result of bridging 2,4-dinitrophenoxide ligands. The Tl atoms have an unsymmetrical two-coordinate, O₂ geometry (two oxygen atoms of the 2,4-dinitrophenoxide ligand). The arrangement of the 3-nitrophenoxide and 2,4-dinitrophenoxide ligands suggests a gap in coordination geometry around the Tl(I) ions, occupied possibly by a stereoactive lone pair of electrons on Tl(I). There is a π–π stacking interaction between the parallel aromatic rings belonging to adjacent chains in the compounds that may help to increase the ‘gap’ in coordination geometry around the Tl(I) ions.     

Mixed‐Valence Thallium(I,III) Bromides The Crystal Structure of α—Tl2Br3

Thallium sesquibromide Tl₂Br₃ is dimorphic. Scarlet coloured crystals of α‐Tl₂Br₃ were obtained by reactions of aqueous solutions of TlBr₃ and Tl₂SO₄ in agarose gel. In case of rapid crystallisation of hydrous TlBr₃/TlBr solutions and from TlBr/TlBr₂ melts ß‐Tl₂Br₃ is formed as scarlet coloured, extremely thin lamellae. The crystal structures of both forms are very similar and can be described as mixed‐valence thallium(I)‐hexabromothallates(III) Tl₃[TlBr₆]. In the monoclinic unit cell of α‐Tl₃[TlBr₆] (a = 26.763(7) Å; b = 15.311(6) Å; c = 27.375(6) Å; β = 108.63(2)°, Z = 32, space gr. C2/c) the 32 Tl^III‐cations are found in strongly distorted octahedral TlBr₆ groups. The 96 Tl^I cations are surrounded either by four or six TlBr₆ groups with contacts to 8 or 9 Br neighbors. Crystals of β‐Tl₃[TlBr₆] by contrast show almost hexagonal metrics (a = 13.124(4) Å, b = 13.130(4) Å, c = 25.550(7) Å, γ = 119.91(9)°, Z = 12, P2₁/m). Refinements of the parameters revealed structural disorder of TlBr₆ units, possibly resulting from multiple twinning. Both structures are composed of Tl₂[TlBr₆]^— and Tl₄[TlBr₆]⁺ multilayers, which alternate parallel (001). The structural relationships of the complicated structures of α‐ and β‐Tl₃[TlBr₆] to the three polymorphous forms of Tl₂Cl₃ as well as to the structures of monoclinic hexachlorothallates M₃TlCl₆ (M = K, Rb) and the cubic elpasolites are discussed.     

Solubility, complex formation, and redox reactions in the Tl2O3-HCN/CN(-)-H2O system. Crystal structures of the cyano compounds Tl(CN)3.H2O, Na[Tl(CN)4].3H2O, K[Tl(CN)4], and Tl(I)[Tl(III)(CN)4] and of Tl(I)2C2O4

Thallium(III) oxide can be dissolved in water in the presence of strongly complexing cyanide ions. Tl(III) is leached from its oxide both by aqueous solutions of hydrogen cyanide and by alkali-metal cyanides. The dominating cyano complex of thallium(III) obtained by dissolution of Tl2O3 in HCN is [Tl(CN)3(aq)] as shown by 205Tl NMR. The Tl(CN)3 species has been selectively extracted into diethyl ether from aqueous solution with the ratio CN-/Tl(III) = 3. When aqueous solutions of the MCN (M = Na+, K+) salts are used to dissolve thallium(III) oxide, the equilibrium in liquid phase is fully shifted to the [Tl(CN)4]- complex. The Tl(CN)3 and Tl(CN)4- species have for the first time been synthesized in the solid state as Tl(CN)3.H2O (1), M[Tl(CN)4] (M = Tl (2) and K (3)), and Na[Tl(CN)4].3H2O (4) salts, and their structures have been determined by single-crystal X-ray diffraction. In the crystal structure of 1, the thallium(III) ion has a trigonal bipyramidal coordination with three cyanide ions in the equatorial plane, while an oxygen atom of the water molecule and a nitrogen atom from a cyanide ligand, attached to a neighboring thallium complex, form a linear O-Tl-N fragment. In the three compounds of the tetracyano-thallium(III) complex, 2-4, the [Tl(CN)4]- unit has a distorted tetrahedral geometry. Along with the acidic leaching (enhanced by Tl(III)-CN- complex formation), an effective reductive dissolution of the thallium(III) oxide can also take place in the Tl2O3-HCN-H2O system yielding thallium(I), while hydrogen cyanide is oxidized to cyanogen. The latter is hydrolyzed in aqueous solution giving rise to a number of products including (CONH2)2, NCO-, and NH4+ detected by 14N NMR. The crystalline compounds, Tl(I)[Tl(III)(CN)4], Tl(I)2C2O4, and (CONH2)2, have been obtained as products of the redox reactions in the system.     

Thermal Decomposition of Thallium(I) Bis-oxalatodiaquaindate(III) Monohydrate

Thallium(I) bis-oxalatodiaquaindate(III) monohydrate was obtained by precipitation of indium(III) withoxalic acid from slightly acidic solution in the presence of thallium(I). The complex was subjected to chemical analysis. The thermal decomposition behavior of the complex was studied using TG, DTA and DTG techniques. The solid complex salt and the intermediate product of its thermal decomposition were characterized using IR absorption and X-ray diffraction spectra. Based on data from these physicochemical investigations the structural formula of the complex was proposed as Tl[In (C₂O₄)₂ (H₂O)₂]⋅H₂O. This revised version was published online in August 2006 with corrections to the Cover Date.     

Studies with dithizone : Part 26. The interaction of thallium(III) with solutions of dithizone in organic solvents

The strong oxidising capacity of thallium(III) dominates its reaction with solutions of dithizone (H₂Dz) in organic solvents. When carbon tetrachloride is used as solvent, the unstable thallium(III) complex Tl(HDz)³ is found in the organic phase but it very quickly disproportionates to the thallium(I) complex [Tl(HDz)], and bis-1,5-diphenylformazan-3-yl-disulphide. This reaction is notably faster in chloroform, in which thallium(I) dithizonate is the first identifiable product. In contact with an acidic aqueous phase, thallium(I) dithizonate is reverted to regenerate dithizone in the organic phase and Tl⁺ ions appear in the aqueous phase. Organic solutions of the disulphide disproportionate spontaneously by first-order kinetics to give an equimolar mixture of dithizone and the mesoionic compound, 2,3-diphenyl-2,3-dihydrotetrazolium-5-thiolate: this change is much slower in carbon tetrachloride than in the more polar chloroform and is catalysed by both Tl⁺ and Tl³⁺. If thallium(III) is present in excess, the mesoionic compound is the principal oxidation product of the dithizone although a dication may also be formed. The mesoionic compound does not react with thallium(I) but forms a water-soluble 2:1 complex with thallium(III); partition of this complex into the organic phase is uninfluenced by chloride ions. Because of the large number of competing reactions, the composition of the reaction mixture at any stage of the reaction between thallium(III) and dithizone depends on the relative concentrations of the components, the order in which they are brought together, the time elapsed after mixing, the pH of the aqueous phase, and the nature of the organic solvent.     

Polyethylene powder as an absorbent for preconcentration of aluminium, beryllium and thallium

Polyethylene powder has been shown to function effectively as an adsorbent for the preconcentration of complexing agents and their metal complexes. The adsorbed trace compound can easily be eluted from the polyethylene by use of polar organic solvents and subsequently be determined by AAS or spectrophotometry. In this paper, the adsorptivity of chrome azurol S and rhodamine B and their complexes with aluminium, beryllium and thallium (as [Tl Br₄]^–) on polyethylene was investigated. The influence of the pH and the effect of the saline concentration of the solution were studied. From the preconcentration of aluminium and beryllium with chrome azurol S, enrichment factors up to 10 and 20, respectively, could be achieved. For thallium with rhodamine B the factor was 50. With this analytical procedure, recoveries of 92–110%, 94–103% and 96–104% with relative standard deviations of 3.4–5.4%, 2.6–5.3 and 1.6–7.2% for aluminium, beryllium and thallium respectively, were achieved. The method was used for the preconcentration of trace amounts of the metals from tap water, dialysis solutions and solid salts.     

Extrahierte Verbindungen von Gallium, Indium und Thallium in Verteilungssystemen mit Tributylphosphat, Cyclohexanon und Isobutylmethylketon

Zusammenfassung Das Verteilungsverhalten der Halogenide und Halogenometallate von Gallium, Indium und Thallium mit den drei Solventien (S) Tributylphosphat (TBP), Cyclohexanon (Cyclo) und Isobutylmethylketon (IBMK) wurde untersucht. Die extrahierten Verbindungen wurden nach der Geradenmethode nach Asmus, der logarithmischen Methode nach McKay, der Methode der kontinuierlichen Variation, durch Analyse der beiden Phasen und durch konduktometrische Extraktionstitration nachgewiesen. Identifiziert wurden folgende Verbindungen: [GaCl₄]^–·2 S, Ga-(SCN) ₃·3 TBP, [Ga(SCN)₄]^–·2 TBP, [InCl₄]^–·2 TBP, [InBr₄]^–·2TBP, [InBr₄]·x Cyclo, [InBr₄]^–·x IBMK, [InJ₄]^–·2 S, In(SCN)₃·3 TBP, [In(SCN)₄]^–·2 TBP, TlCl₃·1 TBP, [TlCl₄]^–·2 S, TlBr₃·1 TBP, [Tl-Br₄] ^–·2 S, TlJ₃·x TBP und [TlJ₄]^–·xS. Wegen der nicht eindeutig definierten Oxydationsstufe von Thalliumjodiden ergaben sich bei den Versuchen experimentelle Schwierigkeiten. Daher wurde in diesem System zusätzlich das radioaktive Isotop ²⁰⁴Thallium verwendet.

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Extracted compounds of gallium, indium and thallium in distribution systems with tributyl phosphate, cyclohexanone and isobutylmethylketone

The behaviour of distribution of the halides and halogenometallates of gallium, indium and thallium with the three solvents (S) tributylphosphate (TBP), cyclohexanone (Cyclo) and isobutylmethylketone (IBMK) are investigated. The extracted compounds are detected with the straight-line method of Asmus, the logarithmic method of McKay, the method of continuous variation, by analysis of the two phases, and with the conductometric extraction-titration. The following compounds were identified: [GaCl₄]^–·2S, Ga(SCN)₃·3TBP, [Ga(SCN)₄]^–·2TBP, [InCl₄]^–·2TBP, [InBr₄]^–·2TBP, [InBr₄]·x Cyclo, [InBr₄]^–·x IBMK, [InJ₄]^– ·2S, In(SCN)₃·3TBP, [In(SCN)₄]^–·2TBP, TlCl₃·1TBP, [TlCl₄]^–·2S, TlBr₃ ·1TBP, [TlBr₄]^–·2S, TlJ₃·x TBP and [TlJ₄]^–·x S. The not unequivocally defined stage of oxidation of thallium iodides resulted in experimental difficulties. Thus, in this system the radioactive isotope ²⁰⁴thallium was additionally used.

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Herrn Professor Dr. E. Asmus zum 60. Geburtstag gewidmet.

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Wie danken Herrn Priv.-Doz. Dr. H. Nickel für die freundliche Unterstützung bei den in der KFA Jülich durchgeführten radioaktiven Messungen.     

Hg(II), Tl(III), Cu(I), and Pd(II) Complexes with 2,2'-Diphenyl-4,4'-Bithiazole (DPBTZ), Syntheses and X-Ray Crystal Structure of [Hg(DPBTZ)(SCN)2]

Reaction of the ligand 2,2′-diphenyl-4,4′-bithiazole (DPBTZ) with Hg(SCN)₂, Tl(NO₃)₃, CuCl, and PdCl₂ gives complexes with stoichiometry [Hg(DPBTZ)(SCN)₂], [Tl(DPBTZ)(NO₃)₃], [Cu(DPBTZ)(H₂O)Cl]_, and [Pd(DPBTZ)Cl₂]. The new complexes were characterized by elemental analyses and infrared spectroscopy. The crystal structure of [Hg(DPBTZ)(SCN)₂] determined by X-ray crystallography. The Hg atom in the title monomeric complex, (2,2′-diphenyl-4,4′-bithiazole)mercury(II)bisthiocyanate, [Hg(C₁₈H₁₂N₂S₂)(SCN)₂], is four-coordinate having an irregular tetrahedral geometry composed of two S atoms of thiocyanate ions [Hg-S 2.4025(15) and 2.4073(15) Å] and two N atoms of 2,2′-diphenyl-4,4′-bithiazole ligand [Hg-N 2.411(4) and 2.459(4) Å]. The bond angle S(3)-Hg(1)-S(4) of 147.46(5)° has the greatest derivation from ideal tetrahedral geometry. Intermolecular interaction between Hg(1) and two S atoms of two neighboring molecules, 3.9318(15) and 3.9640(18) Å, make the Hg(1) distort from a tetrahedron to a disordered octahedron. The attempts for preparation complexes of Tl(I), Pb(II), Bi(III), Cd(II) ions with 2,2′-diphenyl-4,4′-bithiazole ligand were not successful and also the attempts for preparation complexes of 4,4′,5,5′-tetraphenyl-2,2′-bithizole ligand with Cu(II), Ni(II), Co(II), Co(III), Mn(II), Mn(III), Fe(II), Fe(III), Cr(III), Zn(II), Tl(III), Pb(II), Hg(II), Cu(I), Pd(II) were not successful. This point can be regarded as the initial electron withdrawing of phenyl rings and also their spatial steric effects.     

1H NMR Spectra of Phenylthallium (III) Crown-Ether Complexes, [C6H5Tl (III)(Crown)X]n(ClO4) (n=1 OR 2); Trans Influence of The X Groups

Abstract

Trans influence of the X groups on the spin-pin coupling constants between the thallium nucleus and the meta protons of the phenyl group attached to the thallium atom, J(Tl-H^m), were studied for a number of phenylthallium (III) crown-ether complexes, [C₆H₅Tl (III) (crown)X]n(ClO₄) (n=1 or 2).     

Two-dimensional thallium(I) supramolecular polymer constructed from Tl?π interactions: A new precursor for the preparation of thallium(III) oxide with a nano-structural surface

A new two-dimensional thallium(I) supramolecular polymer, [Tl₂(μ₃-9-Ac)(μ₄-9-Ac)(H₂O)]_n (1) [9-HAc = 9-anthracene carboxylic acid]_, has been synthesized and characterized. The single-crystal X-ray data of compound 1 shows two types of Tl^I ions with coordination numbers of four and five. The thallium atoms have irregular coordination spheres, containing a stereo-chemically active lone pair with η⁵ Tl?C interactions in the vacant coordination sphere of the Tl^I ions, thus attaining total hapticities of 9 and 10 with O₅Tl1?C₅ and O₄Tl2?C₅ environments and Tl?π_(centroid) distances of 3.308 and 3.251 Å, respectively. The thermal stability of 1 was studied by thermo gravimetric (TG) and differential thermal analyses (DTA). Different morphologies of thallium(III) oxide with a nano-structural surface were prepared from compound 1 powders and compound 1 micro-rods. These nano-structures were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM).     

Aerobic and Electrochemical Oxidative Cross‐Dehydrogenative‐Coupling (CDC) Reaction in an Imidazolium‐Based Ionic Liquid

The ionic liquid 1‐butyl‐3‐methylimidazolium tetrafluoroborate [BMIm][BF₄] has demonstrated high efficiency when applied as a solvent in the oxidative nitro‐Mannich carbon? carbon bond formation. The copper‐catalyzed cross‐dehydrogenative coupling (CDC) between N‐phenyltetrahydroisoquinoline and nitromethane in [BMIm][BF₄] occurred with high yield under the described reaction conditions. Both the ionic liquid and copper catalyst were recycled nine times with almost no lost of activity. The electrochemical behavior of the tertiary amine substrate and β‐nitroamine product was investigated employing [BMIm][BF₄] as electrolyte solvent. The potentiostatic electrolysis in ionic liquid afforded the desired product with a high yield. This result and the cyclic voltammetric investigation provide a better understanding of the reaction mechanism, which involves radical and iminium cation intermediates.     

Thallium(I), Silver(I), and Mixed Thallium(I)/Copper(I) Clusters with Bridging {Me2Si(N‐C6H4‐2‐SPh)2}2– Ligands

The S‐functionalized aminosilane Me₂Si(NH‐C₆H₄‐2‐SPh)₂ (H₂L) ( 1 ) was prepared from dichlorodimethylsilane and lithiated 2‐(phenylthio)aniline. Treatment of compound 1 with two equivalents of n‐butyllithium led to the dilithium derivative Li₂L, which was used in subsequent reactions with MCl (M = Tl, Cu, Ag) to prepare the complexes [Tl₂L] ( 2 ), [Cu₂Tl₂L₂] · 2THF ( 3a ), [Cu₂Tl₂L₂(THF)₂] ( 3b ), and [Ag₄L₂(THT)₂] ( 4 ) (THT = tetrahydrothiophene). Compound 2 consists of two thallium atoms, which are connected by a L^2– ligand to give a puckered Tl₂N₂ ring with Tl–N distances of 255(1)–268(1) pm. Compounds 3a and 3b are heterobimetallic complexes, which are based on [Cu₂L₂]^2– cores featuring a Cu₂N₄Si₂ ring with linearly coordinated copper atoms [Cu–N: 190.7(3)–192.5(3) pm] and two peripherally attached Tl atoms [Tl–N: 272.7(3)–281.9(3) pm]. The molecular structure of the tetranuclear silver(I) complex 4 is closely related to the structure of compounds 3a and 3b by replacement of the Cu and Tl atoms with Ag atoms. The Ag–N distances are 217.5(3)–245.7(3) pm.     

Tl2CuAsO4 – ein Zwischenprodukt bei der Oxidation von Tl/Cu/As-Legierungen im Sauerstoffstrom

Tl₂CuAsO₄ – an Intermediate Phase in the Oxidation of Tl/Cu/As Alloys with Oxygen Waxy, honey-jellow single crystals of the new compound Tl₂CuAsO₄ (monoclinic, P2₁/c, a = 860.1(1) pm, b = 533.94(7) pm, c = 1200.1(2) pm, β = 98.10(1)°, Z = 4) were prepared as an intermediate product of the oxidation process in the reaction of Tl/Cu/As-alloys with oxygen. Their structure was determined from IPDS data (w2R = 0.071 for 1271 F² values and 74 parameters). The structure contains an isolated [Cu₂As₂O₈]^4– group consisting of two AsO₄-tetrahedra connected by two Cu⁺ ions with an approximately linear O–Cu–O coordination. The [Cu₂As₂O₈]^4– groups are linked to a threedimensional framework by thallium(I) ions which show an hemispheric coordination sphere of oxygen ions indicating the stereochemical activity of the Tl⁺ lone pair.     

The trigonal–bipyramidal triiodo­thallium(III) complex [TlI3{(CH3)2SO}2]

The title compound, bis(dimethyl sulfoxide)triiodo­thallium(III), [TlI₃(C₂H₆OS)₂], was crystallized from equimolar amounts of Tl^II and I₂ in a dimethyl sulfoxide (DMSO) solution. After the initial redox reaction, the thallium(III)–iodo complex forms and precipitates as a DMSO solvate. In the crystal structure, Tl is surrounded by three iodide ligands in the equatorial plane and two O‐coordinated DMSO mol­ecules in the axial positions, forming a slightly distorted trigonal bipyramid. The complex lies on a twofold rotation axis, making the DMSO mol­ecules and two of the I atoms crystallographically equivalent.     

A thallium(I) tetranuclear cubic cage unit in an interpenetrated supramolecular polymer: A new precursor for the preparation of Tl2O3 nanostructures

A new thallium(I) supramolecular polymer, [Tl₄(μ₃-4-BN)₄]_n (1) [9-HBN = 4-hydroxy benzonitrile], with a disordered cubic cage structural unit has been synthesized and characterized. The single-crystal X-ray data of compound 1 shows one type of Tl^I ion in the tetranuclear cubic cage structure with a coordination number of three. In addition to two intra cage thallophilic interactions in 1, each thallium(I) atom has a weak Tl?N secondary interaction with the nitrile group of the 4-BN⁻ ligand. Finally the Tl-ions attain the O₃Tl?NTl₂ coordination sphere with a stereo-chemically ‘active’ electron lone pair on the metal. The self assembly between the benzonitrile groups of one cubic cage structure with an adjacent one with a Tl?N short contact, by π-π stacking and weak hydrogen bonding interactions, results in the formation of a new interpenetrating thallium(I) supramolecular polymer. The thermal stability of 1 was studied by thermo gravimetric (TG) and differential thermal analyses (DTA). Nanostructures of thallium(III) oxide were prepared from a calcination process of compound 1 fine powder at 743 K. These nanostructures were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM).     

Electrochemical studies with dissolved and surface-confined forms of neo-pentyl-ferrocene-based polyesters utilising [NBu4][B(C6F5)4] and other electrolytes

The voltammetric oxidation at a glassy carbon electrode of a series of ferrocenyl polyesters PmF{X}, (X=T, terephthalate; N, 2,6-naphthalene dicarboxylate; B, 4,4′-biphenyl dicarboxylate) is reported in the weakly donating and low-polarity CH₂Cl₂ solvent containing [NBu₄][PF₆], [NBu₄][B(C₆F₅)₄], or 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([bmpyr][TFSA]) as the supporting electrolyte. The one electron oxidation of the ferrocenyl groups is strongly influenced by the nature of the supporting electrolyte anion. Use of the conventional [PF₆]⁻ anion or the room temperature ionic liquid (RTIL), [bmpyr][TFSA] as the supporting electrolyte, gives rise to significant oxidation product interaction (precipitation and/or adsorption) with the electrode surface. In marked contrast, diffusion-controlled, chemically and electrochemically reversible processes are observed when the weakly coordinating [B(C₆F₅)₄]⁻ is used as the anionic component of the supporting electrolyte. In this case, data obtained via cyclic voltammetry, chronoamperometry and chronocoulometry are consistent with ideal reversible one electron oxidation processes and a soluble cationic product. Diffusion coefficients of the monomers, polymers, ferrocene and decamethyferrocene are reported in the CH₂Cl₂/[NBu₄][B(C₆F₅)₄] system. Importantly, reversible potentials that are easily obtained under these conditions show that the acyl or methyl linkers, through which the ferrocenyl group is attached to the neo-pentylenediol component, tune the redox properties of the polymers. Electrochemical studies with a glassy carbon electrode modified with microcrystals of the PmFT polymer conducted in aqueous (with KCl supporting electrolyte) or neat ionic liquid ([bmpyr][TFSA]) media also are reported. Different mechanisms apply in each of these cases.     

On the influence of the heterocyclic ring substituents on the structure of dimethylthallium pyrimidine-2-thionato complexes. Crystal structure of dimethyl-(4-trifluoromethylpyrimidine-2-thionate)thallium(III): a compound with intermolecular C-H ? π interactions

The complex [Me₂Tl(4-CF₃pymS)] has been prepared by reacting 4-trifluoromethylpyrimidine-2-thione (4-CF₃pymSH) with dimethylthallium(III) hydroxide in methanol. The resulting compound has a polymeric chain structure, with the thallium atom coordinated by two nitrogen and two sulfur atoms from two different ligands, which act as bridges between two metal atoms, as well as by two carbon atoms of the methyl groups. An intermolecular C-H ? π interaction is observed between an H atom of each methyl group and one of the pyrimidine rings of the neighbouring chain. The structure of the complex is discussed in terms of the IR absorptions, the ¹H, ¹³C and ²⁰⁵Tl NMR spectra and FAB data.