Anion exchange in trimethyl‐ and triphenyltin complexes with chromogenic ligands: solution equilibria and colorimetric anion sensing

A series of organotin(IV) compounds R₃Sn(A) where R = Me or Ph and A is a chromogenic nitrophenolate ligand were prepared and studied as possible colorimetric sensors for anions (F⁻, Cl⁻, Br⁻, AcO⁻, H₂PO₄⁻). Equilibrium constants for a complete set of reactions between R₃Sn(A) with A = 2‐amino‐4‐nitrophenolate (ANP) or 4‐nitrophenolate and anions (X⁻) involving formation of complexes R₃Sn(A)(X)⁻ and substitution products R₃Sn(X) and R₃Sn(X)₂⁻ were determined by UV‐vis and ¹H NMR titrations in MeCN and DMSO. The binding selectivity was AcO⁻ > F⁻ > H₂PO₄⁻ > Cl⁻ ≫ Br⁻ in both solvents and both for R = Me and Ph with higher affinity for R = Ph. Compounds with A = ANP were found to have the optimum properties as anion sensors allowing optical detection of F⁻, AcO⁻ and H₂PO₄⁻ anions in the 5–100 µM range by appearance of an intense absorption band of free ANP resulting from its substitution with the analyte. Selectivity and affinity of anion interactions with R₃Sn(ANP) are similar to those for thiourea receptors, but the organotin receptor produces a much larger naked eye detected optical signal, operates equally well in nonpolar and polar solvents and tolerates the presence of up to 20% vol. of water in DMSO. Copyright © 2011 John Wiley & Sons, Ltd.     

Negative Ion Formation by Thermal Surface Ionization of Sulfur Dioxide

The generation of negative ions from SO₂ in the gas phase was studied using the thermal surface ionization method. Six anion types were measured: O⁻, S⁻, SO⁻, and SO₂⁻ and anions with m/z=96 and m/z=128. The most abundant anion formed was S⁻ and the formation routes are discussed for each of the six anions. O⁻, S⁻, and SO⁻ are formed via dissociative electron attachment to the molecule, whereas the generation of SO₂⁻ and anions with m/z=96 and m/z=128 are probably associated with the formation of H₂SO₄ in the gas inlet system and the ion source. Using statistical thermodynamics the dissociation temperatures of SO₂ and SO in the gas phase are calculated and values of above 1800 °C are obtained for both molecules. We also estimated the optimal filament temperatures for the formation of all anions measured, indicating that for SO₂ the optimal temperature is related to the electron affinity of the molecules: the optimal temperature increases with decreasing value of the electron affinity for the molecule corresponding to the respective anion.     

The ab initio calculation of the band origin and vibrational frequencies of the Ã-X̃ system of HNCl using the non-rigid bender hamiltonian

A three-dimensional fit of ab initio MRD CI potential data has been made for the lowest two electronic states of the HNC1 molecule (X̃ ²A″ and à ²A'), and the corresponding vibrational frequencies and rotational energies have been computed using the non-rigid bender Hamiltonian. For the ground state the vibrational frequencies obtained are ν₁ = 2942 cm⁻¹, ν₂ = 1232 cm⁻¹, and ν₃ = 549 cm⁻¹, while the corresponding values for the first excited state are 3524,947 and 836 cm⁻¹ respectively. We calculate T_c(à ²A') 16200 cm⁻¹, T_o(òA') = 16400 cm⁻¹, and the Franck-Condon maximum, Ã(0,3,1)-X̃(0,0.0), is calculate at 19200 cm⁻¹(5200 Å).     

Rate constants of the near-resonant E-E energy exchange processes SeS(b0+) + O2(X3Σg−) ⇌ SeS(X10+) + O2(a1Δg)

SeS radicals generated in a fast flow system were excited to their b0⁺, ν' = 0 vibronic state by absorption of Raman-shifted dye laser pulses at 1280 nm. From time-resolved measurements of the b0⁺ → X₁0⁺ fluorescence as a function of added gas pressure, the radiative lifetime of the b0⁺ = 0 state (τ₀ = 400 ± 100 μs) and quenching rate constants for H₂, D₂, N₂, CO, O₂, and CO₂ were deduced. Quenching of SeS(b0⁺, ν'= 0) by O₂ is attributed to the near-resonant electronic- to-electronic energy-transfer process (1), SeS(b0⁺, ν'₁ = 0) + O₂(X³Σ_g⁻, ν″₁ = 0) ⇌ SeS(X₁0⁺, ν″_f = 0) + O₂(a¹Δ_g, ν'_f = 0)−77 cm⁻¹, for which (k₁ = (1.4±0.3) × 10⁻¹² cm³ s⁻¹ was obtained. On the assumption of detailed balancing, k₋₁ was calculated to be (3.0 ± 0.7) × 10⁻¹²cm³ s⁻¹.     

Velocity modulation laser spectroscopy of vibrationally excited CF+ determination of the molecular potential function

The lowest six vibrational hot bands of CF⁺ have been measured in a helium/C₂F₆ discharge by velocity modulation laser spectroscopy. A total of 56 transitions has been fitted to Dunham expansion for v = 0–7, yielding the parameters: ω_e = 1792.6654(18) cm⁻¹B_e = 1.7204176(75) cm⁻¹, Y₂₀, = −13.22968(54) cm⁻¹, and D₀ = 62086(30) cm⁻¹. The rotational temperature of CF⁺ in the plasma is near 650 K and the vibrational temperature is approximately 5200 K.     

Living cationic polymerization of vinyl ethers

The cationic polymerization of vinyl ethers initiated by CH₃-CH(OR)(I) / R₄N⁺A⁻ (R = Alkyl, A⁻ = ClO₄⁻, BF₄⁻, PF₆⁻, I⁻, NO₃⁻) shows the characteristics of a living polymerization. The rate of polymerization is a function of the solvent polarity, the temperature, the type and concentration of the ammonium salt. The experimental data can be explained on the basis of the secondary salt effect overlapped by some dipol-dipol interactions of the chain end and the added salt. Functionalization of the chain end with thermolabile azo functions yields polymeric initiator which was applied for the synthesis of blockcopolymers. Vinyl ethers functionalized with furylacrylic ester groups were polymerized and crosslinked via [2+2] cycloaddition.     

Combined microwave-optical barrier determination for molecules with a heavy symmetric internal top: CF3NO and CF3CHO

The torsional data for CF₃NO have been rein vest igated. A model with a single degree of freedom and three adjustable parameters is sufficient to fit data to v = 8 in the electronic ground state. For CF₃NO we obtain F_o = 1.9822(42) cm⁻¹, V₃ = 238.4(1.6) cm⁻¹ and V₆ = −5.8(1.6) cm⁻¹ or F_o = 1.9894(66) cm⁻¹,F₃= −0.194(55) cm⁻¹ and V₃ = 239.3(1.9) cm⁻¹. A similar treatment for CF₃CHO gives F_o = 1.97(14) cm⁻¹, V₃ = 305(25) cm⁻¹ and V₆ = −8.7(1.2) cm⁻¹. A need for a re-examination of the torsional fundamental is indicated for CF₃CHO. These studies support the general conclusion that for a heavy internal top the internal rotation constant, F_o, required to fit a range of torsional splittings is different from that calculated from structural considerations alone. The difference indicates a large change in F with torsional averaging.     

Vibrational relaxation of NH2|X2B1(O,v2, O)| radicals

Energy transfer processes in NH₂ radicals have been studied using the sensitive laser-induced fluorescence (LIF) technique. The NH₂ radicals were generated by infrared multiple-photon dissociation (IR MPD) of monomethylamine (CH₃NH₂), and the state-selected NH₂(v″₂ = 1) decay was observed by the LIF detection of [NH²]. The vibrational relaxation processes studied are NH₂(v″₂ = 1) + M → NH₂(v″₂ = O)+M, with M  He, Ne, Ar, Kr, H₂, D₂, CO, O₂, and total decay rate of NH₂(v″₂ = 1) in the presence of excess of CH₃NH₂. Rate constants of (3.41±0.03)×10⁻¹³, (1.75±0.09)×10⁻¹³, (3.03±0.08)× 10⁻¹³, (3.58±0.06)×10⁻¹³, (13.4±0.5)×10⁻¹³, (4.70±0.19)×10⁻¹³, (4.3±0.3)×10⁻¹³, (5.9±-0.4)×10⁻¹³, (9.2±0.5)×10⁻¹³), and 8.4×10⁻¹¹ cm³ molecule⁻¹ s⁻¹ were determined for the vibrational deactivation of NH₂(v″₂ = 1) by He, Ne, Ar, Kr, H², D₂, N₂, CO, O₂, and CH₃NH₂, respectively. The effect of the different collision partners on the relaxation rate is discussed. The results can be qualitatively well understood in terms of strong vibration—rotation coupling, due to the small moment of inertia of the NH₂ radicals.     

Kinetic studies on the reactions of Ru(II) tetraammines with CS2N−3

The kinetics of the reactions of Ru(II) complexes with CS₂N⁻₃ ions were studied spectrophotometrically. The formation rate constants data for trans-[Ru(NH₃)₄L(CS₂N₃)] are 2.2 × 10², 1.8 × 10 and 1.3 × 10² M⁻¹ s⁻¹ for L = SO^2-₃, HSO⁻₃ and P(OEt)₃), respectively [μ = 1.0 M (NaCF₃COO), 25°C]. Under the same experimental conditions, the values of k⁻¹ (specific rate for the aquation reaction) are 1.5 × 10⁻², 5.0 × 10⁻² and 4.5 × 10 s⁻¹ for L = SO²⁻₃, HSO⁻₃ and P(OEt)₃, respectively. The free-energy change (ΔG^≠) for the systems where L = P(OEt)₃ and SO²⁻₃ are in agreement within the experimental error. It was observed that the affinity of the CS₂N⁻₃ ion decreases with the increasing π-acidity of the auxiliary ligand L. The order of affinity of the CS₂N⁻₃ ion for the Ru(II) center studies is SO²⁻₃ > HSO⁻₃ > P(OEt)₃ >SO₂.     

Metal complexes of 4,5-dimethylpyrazole-3-carboxaldehyde phenylthiosemicarbazone

Several new transition metal complexes derived from 4,5-dimethyl-3-carboxaldehyde phenyl- thiosemicarbazone, LH, have been synthesized. The complexes are of stoichiometry, [CoL₂]X, X = Cl⁻, Br⁻, ClO⁻₄ or NO⁻₃, [MnL₂] and [CuX_nL_m], X = Cl⁻, Br⁻, NCS⁻ or N⁻₃; n = 1 or 0; m = 1 or 2 and L = the anion of LH. All complexes have been characterized by elemental analysis, spectral (i.r., electronic, NMR, ESR) and magnetic measurements. The ligand acts as tridentate monobasic co-ordinated to the metal ion via azomethine, pyrazole (N²) nitrogen atoms and the thiolo-sulphur. The ligand field and ESR parameters are used to interpret the nature of bonding of LH with the metal ion, ground state and the ligand field strength of LH and the various co-ordinated simple ions. The coupling constants of various co-ordinated nuclei with copper (II) are estimated from ESR spectra of copper (II) complexes.     

Small‐Molecule Anion Recognition by a Shape‐Responsive Bowl‐Type Dodecavanadate

A dodecavanadate, [V₁₂O₃₂]⁴⁻, is an inorganic bowl‐type host with a cavity entrance with a diameter of 4.4 Å in the optimized structure. Linear, bent, and trigonal planar anions are tested as guest anions and the formation of host–guest complexes, [V₁₂O₃₂(X)]⁵⁻ (X=CN⁻, OCN⁻, NO₂⁻, NO₃⁻, HCO₂⁻, and CH₃CO₂⁻), were confirmed by X‐ray crystallographic analyses and a ⁵¹V NMR spectroscopy study. The degree of distortion of the bowl from a regular to an oval shape depends on the type of guest anion. In ⁵¹V NMR spectroscopy, all chemical shifts of the host–guest complexes are clearly shifted after guest incorporation. The incorporation reaction rates for OCN⁻, NO₂⁻, HCO₂⁻, and CH₃CO₂⁻ are much larger than those of NO₃⁻ and halides. The incorporated nonspherical molecular anions in the dodecavanadate host are easily dissociated or exchanged for other anions, whereas spherical halides in the host are preserved without dissociation, even in the presence of the tested anions.     

A 2D cadmium metal–organic framework: Synthesis,structure and luminescence sensing for chromate,permanganate, cupric,silver and ferric

A multi-responsive Cd metal–organic framework {[Cd (ttpe)(H₂O)(ip)]•4H₂O•DMAC}_n ( 1•4H ₂ O•DMAC ) was synthesized using hydrothermal method (ttpe = 1,1,2,2-tetra(4-(1H-1,2,4-triazol-1-yl)phenyl)ethylene, ip = isophthalate, DMAC = N,N-dimethylacetamide), and characterized. 1 exhibits a 2D (4,4) network. The luminescent sensing experimrnts showed that 1•4H ₂ O•DMAC as a new MOF luminescent sensor can detect Cr₂O₇²⁻, CrO₄²⁻, MnO₄⁻, Cu²⁺, Ag⁺ and Fe³⁺ in aqueous solution with simultaneously high efficiency and high sensitivity. The quenching constants K_sv for Cr₂O₇²⁻, CrO₄²⁻, MnO₄⁻, Cu²⁺, Ag⁺ and Fe³⁺ are 4.231 × 10⁴ M⁻¹, 2.471 × 10⁴ M⁻¹, 6.459 × 10³ M⁻¹, 7.617 × 10³ M⁻¹, 1.563 × 10⁴ M⁻¹ and 3.574 × 10⁴ M⁻¹, respectively. The detection limits are 0.094 μM for Cr₂O₇²⁻, 0.108 μM for CrO₄^{2 −} , 0.346 μM for MnO₄⁻, 0.302 μM for Cu²⁺, 0.221 μM for Ag ⁺ , and 0.100 μM for Fe³⁺. 1•4H ₂ O•DMAC exhibits high photocatalytic efficiency for degradation of methylene blue under visible light irradiation.     

The crystal and molecular structure of octafluorobiphenylene,C12F8

Octafluorobiphenylene was made by heating 1,2-diiodotetrafluorobenzene in a sealed, evacuated tube with either copper, lead or bismuth. The crystal used for the diffraction studies was grown from hexane. Crystal data: C₁₂F₈, M_r = 296.116, monoclinic, A2/a, a = 21.140(2), b = 6.430(6), c = 36.340(3) ÅA, β = 123.76(3)°, U = 4106.73 ÅA³, Z = 16, D_m = 1.884 g cm⁻³, D_x = 1.907 g cm⁻³, λ(Cuka) = 1.5418 ÅA, μ = 1.810 mm⁻¹, F(000) = 2304, measurement temperature = 293K, R = 0.059 for 2230 reflections with I > 3σ(I).     

Low Temperature Activation of Tellurium and Resource-Efficient Synthesis of AuTe2 and Ag2Te in Ionic Liquids

The low temperature syntheses of AuTe₂ and Ag₂Te starting from the elements were investigated in the ionic liquids (ILs) [BMIm]X and [P₆₆₆₁₄]Z ([BMIm]⁺=1-butyl-3-methylimidazolium; X = Cl, [HSO₄]⁻, [P₆₆₆₁₄]⁺ = trihexyltetradecylphosphonium; Z = Cl⁻, Br⁻, dicyanamide [DCA]⁻, bis(trifluoromethylsulfonyl)imide [NTf₂]⁻, decanoate [dec]⁻, acetate [OAc]⁻, bis(2,4,4-trimethylpentyl)phosphinate [BTMP]⁻). Powder X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy revealed that [P₆₆₆₁₄]Cl is the most promising candidate for the single phase synthesis of AuTe₂ at 200 °C. Ag₂Te was obtained using the same ILs by reducing the temperature in the flask to 60 °C. Even at room temperature, quantitative yield was achieved by using either 2 mol % of [P₆₆₆₁₄]Cl in dichloromethane or a planetary ball mill. Diffusion experiments, ³¹P and ¹²⁵Te-NMR, and mass spectroscopy revealed one of the reaction mechanisms at 60 °C. Catalytic amounts of alkylphosphanes in commercial [P₆₆₆₁₄]Cl activate tellurium and form soluble phosphane tellurides, which react on the metal surface to solid telluride and the initial phosphane. In addition, a convenient method for the purification of [P₆₆₆₁₄]Cl was developed.     

Iodine-Chemisorption,Interpenetration and Polycatenation: Cationic MOFs and CPs from Group 13 Metal Halides and Di-Pyridyl-Linkers

Eight cationic, two-dimensional metal-organic frameworks (MOFs) were synthesized in reactions of the group 13 metal halides AlBr₃, AlI₃, GaBr₃, InBr₃ and InI₃ with the dipyridyl ligands 1,2-di(4-pyridyl)ethylene (bpe), 1,2-di(4-pyridyl)ethane (bpa) and 4,4’-bipyridine (bipy). Seven of them follow the general formula ²_∞[MX₂(L)₂]A, M=Al, In, X=Br, I, A⁻=[MX₄]⁻, I⁻, I₃⁻, L=bipy, bpa, bpe. Thereby, the porosity of the cationic frameworks can be utilized to take up the heavy molecule iodine in gas-phase chemisorption vital for the capture of iodine radioisotopes. This is achieved by switching between I⁻ and the polyiodide I₃⁻ in the cavities at room temperature, including single-crystal-to-single-crystal transformation. The MOFs are 2D networks that exhibit (4,4)-topology in general or (6,3)-topology for ²_∞[(GaBr₂)₂(bpa)₅][GaBr₄]₂⋅bpa. The two-dimensional networks can either be arranged to an inclined interpenetration of the cationic two-dimensional networks, or to stacked networks without interpenetration. Interpenetration is accompanied by polycatenation. Due to the cationic character, the MOFs require the counter ions [MX₄]⁻, I⁻ or I₃⁻ counter ions in their pores. Whereas the [MX₄]⁻, ions are immobile, iodide allows for chemisorption. Furthermore, eight additional coordination polymers and complexes were identified and isolated that elaborate the reaction space of the herein reported syntheses.     

The potentiometric determination of stability constants of sulfite and cobalt(II) in ionic strength 2.0 M (NaClO4). Use of the matrix method

Determination of the stability constants for the system Co(II)/SO₃²⁻, was made potentiometrically using SO₃²⁻/HSO₃⁻ as buffers. Computation and matrix methods lead to the following overall stepwise constants: β₁ = 4.3 x 10² M⁻¹, β₂ = 2.2 x 10⁴ M⁻² and β₃ = 3.0 x 10⁶ M⁻³. The partial constants (M⁻¹) obtained were: K₁ = 4.3 x 10², K₂ = 51 and K₃ = 1.4 x 10². The HSO₃⁻ competition was eliminated by using the extrapolation procedure.     

The Intrinsic 3[dσ*pσ] Emission of Binuclear Gold(I) Complexes with Two Bridging Diphosphane Ligands Lies in the Near UV; Emissions in the Visible Region Are Due to Exciplexes

A near-UV triplet emission from [Au₂(dcpm)₂](ClO₄)₂ has been discovered. Studies on the spectroscopic properties of the complexes [Au₂(dcpm)₂]Y₂ (Y=ClO₄⁻, PF₆⁻, CF₃SO₃⁻, [Au(CN)₂]⁻, Cl⁻, and I⁻; dcpm=bis(dicyclohexylphosphanyl)methane) support the assignment of the high-energy emissions at 360–368 nm to the ³[dσ*pσ] excited state, adducts of which exhibit exciplex emissions in the visible region with solvent or counterions (see schematic diagram).     

Mononuclear carbonyl manganese(I) and molybdenym(II) complexes with chelating biimidazole,bibenzimidazole or tetramethylbiimidazole ligands

The preparations and properties are described of novel anionic and neutral mononuclear biimidazolate (biim), bibenzimidazolate (bibzim), or tetramethylbiimidazolate (tmbiim) manganese(I) and molybdenum(II) complexes of the type [Et₄N][Mn(CO)₂L₂(bibzim)] (L = P(OEt)₃); [Et₄N][Mo(η⁵-C₅H₅)(CO)₂-(N)₂] ((N)₂²⁻ = biim²⁻, bibzim²⁻ tmbiim²⁻); [Mn(CO)_4−nL_n{H(N)₂}] (n = 1; H(N)₂⁻ Hbibzim⁻; L = P(OMe)₃, PEt₃), (n = 2; H(N)₂⁻ = Hbiim⁻, Hbibzim⁻; L = P(OPh)₃, P(OMe)₃, P(OEt)₃, P(OⁱPr)₃; [Mo(η⁵-C₅H₅)(CO)₂{H(N)₂}] (H(NN)₂⁻ = Hbiim⁻, Hbibzim⁻, Htmbiim⁻, in which the heterocyclic anions act as bidentate chelate groups. Treatment of the anionic complexes with MeI gives neutral derivatives of general formula [Mn(CO)₂L₂(Mebibzim)] (L = P(OMe)₃, P(OEt)₃) and [Mo(η⁵-C₅H₅)(CO)₂{Me(N)₂}] (Me(N)₂⁻ = Me-biim⁻, Mebibzim⁻, Metmbiim⁻. Cationic manganese(I) complexes of the type [Mn(CO)_4−nL_n{H₂(N)₂}][ClO₄ (n = 1; H₂ (N)₂ = H₂bibzim; L = P(Ome)₃, PEt₃), (n = 2; H₂(N)₂ = H₂biim, H₂bibzim; L = P(OPh)₃, P(OMe)₃, P(OEt)₃, P(OⁱPr)₃) have also been obtained by treating the corresponding neutral complexes with HClO₄. The structures of the complexes have been elucidated by molecular weight determinations, conductance data, and IR spectroscopy.     

Two-photon sequential absorption spectroscopy of the E(0+) state of iodine monofluoride

The energy levels of a new state of iodine monofluoride lying 5 eV above the ground state have been measured using the two-photon sequential absorption technique. Eleven vibrational levels of the state were measured. A vibrational and rotational analysis gives the spectroscopic constants as T_e = 41291.96 cm⁻¹, ω_e = 248.76 cm⁻¹, ω_eχ_e = 0.4951 cm⁻¹ and B_e = 0.12920 cm⁻¹. The state has 0⁺ character, and dissociates to I⁺ + F⁻ in the diabatic approximation.     

Transition metal carbonylates in nucleophilic aromatic substitution: II. Medium effects for substitution in 2-(pentacarbonylmanganese)-4,6-difluoro-1,3,5-triazine

Effects of counterion, solvent and solvating agents were studied for the reactions of transition metal carbonylates CpFe(CO)₂⁻, (Cp = C₅H₅), Re(CO)₅⁻¹, Mn(CO)₅⁻, CpW(CO)₃⁻¹, CpMo(CO)₃⁻ with 2-(pentacarbonylmagnanese)-4,6-difluoro-1,3,5-triazine. The observed trends substantiate the hypothesis of enhanced reactivity of contact ion pairs as compared to solvent-separated ion pairs and free ions.