A 19F NMR Study on the Interaction of the Hexafluoroanions of Group IV Elements with Cations in Solutions

In view of previous studies of tetrafluoroborate solutions¹, it appeared interesting to continue further investigations on the interactions of fluorocomplexes with different cations, in general, and of the MF₆ ^2- fluoro complexes, in particular. In this communication, the high resolution ¹⁹F NMR data are given for the aqueous and water-acetone solutions of silicon, germanium, tin and titanium hexafluorocomplexes, containing paramagnetic (Co²⁺, Ni²⁺, Cu²⁺, Cr³⁺) and diamagnetic (Be²⁺, Mg²⁺, Zn²⁺, NH₄ ⁺) cations.     

Investigation of cation–anion interaction in 1‐(2‐hydroxyethyl)‐3‐methylimidazolium‐based ion pairs by density functional theory calculations and experiments

Gas‐phase structure, hydrogen bonding, and cation–anion interactions of a series of 1‐(2‐hydroxyethyl)‐3‐methylimidazolium ([HOEMIm]⁺)‐based ionic liquids (hereafter called hydroxyl ILs) with different anions (X = [NTf₂]^–, [PF₆]^–, [ClO₄]^–, [BF₄]^–, [DCA]^–, [NO₃]^–, [AC]^– and [Cl]^–), as well as 1‐ethyl‐3‐methylimizolium ([EMIm]⁺)‐based ionic liquids (hereafter called nonhydroxyl ILs), were investigated by density functional theory calculations and experiments. Electrostatic potential surfaces and optimized structures of isolated ions, and ion pairs of all ILs have been obtained through calculations at the Becke, three‐parameter, Lee–Yang–Parr/6‐31 + G(d,p) level and their hydrogen bonding behavior was further studied by the polarity and Kamlet–Taft Parameters, and ¹H‐NMR analysis. In [EMIm]⁺‐based nonhydroxyl ILs, hydrogen bonding preferred to be formed between anions and C2–H on the imidazolium ring, while in [HOEMIm]⁺‐based hydroxyl ILs, it was replaced by a much stronger one that preferably formed between anions and OH. The O–H···X hydrogen bonding is much more anion‐dependent than the C2–H···X, and it is weakened when the anion is changed from [AC]^– to [NTf₂]^–. The different interaction between [HOEMIm]⁺ and variable anion involving O–H···X hydrogen bonding resulted in significant effect on their bulk phase properties such as ¹H‐NMR shift, polarity and hydrogen‐bond donor ability (acidity, α). Copyright © 2011 John Wiley & Sons, Ltd.     

In situ 1H NMR Study of Nanoreactor Interaction NH3–H2O in Zeolite Nanopores

The interaction between ammonium NH₃ and H₂O molecules in zeolitic nanopores is studied by in situ ¹H nuclear magnetic resonance (NMR) method. The powder and single crystal samples of natural zeolites, heulandites Ca₄[Al₈Si₂₈O₇₂]·24H₂O and clinoptilolite (Na, K,Ca_1/2)₆[Al₆Si₃₀O₇₂], were used as the model system. It is shown that penetration of NH₃ into the zeolitic nanopores is accompanied by disordering of the hydrogen sublattice of zeolitic water and by the fast proton exchange NH₃ + H₂O ? [NH₄]⁺ + [OH]^? characterized by correlation frequency v _c = ~40 kHz. Another nanoreactor interactions are represented by interaction of [NH₄]⁺ ions with exchangeable Na⁺ and Ca²⁺ ions of the zeolitic structure. The slow ionic exchange [NH₄]⁺ → [Na,Ca_1/2]⁺ and binding of [NH₄]⁺ in cationic sites of the framework were visualized by NMR spectroscopy along with stepwise release of (Na,Ca_1/2)OH from zeolitic pores to the external surface of zeolite grains.     

NMR and DFT studies on persistent carbocations derived from benzo[kl]xanthene,dibenzo[d,d′]benzo[1,2‐b:4,3‐b′]difuran,and dibenzo[d,d′]benzo[1,2‐b:4,5‐b′]difuran in superacidic media

Persistent carbocations generated by the protonation of hetero‐polycyclic aromatic compounds with oxygen atom(s) were studied by experimental NMR and density function theory calculations. Benzo[kl]xanthene ( 1 ), dibenzo[d,d′]benzo[1,2‐b:4,3‐b′]difuran ( 2 ), and dibenzo[d,d′]benzo[1,2‐b:4,5‐b′]difuran ( 3 ) were synthesized by the annulation of arenediazonium salts. Compound 1 in FSO₃H‐SbF₅ (4:1)/SO₂ClF and 3 in FSO₃H‐SbF₅ (1:1)/SO₂ClF ionized to 1aH⁺ with protonation at C(4) and to 3aH⁺ with protonation at C(6), and these cations were successfully observed by NMR at low temperatures. The density function theory calculations indicated that 1aH⁺ and 3aH⁺ were the most stable protonated carbocations and that 2 should ionize to 2aH⁺ with protonation at C(6). According to the changes in ¹³C chemical shifts (Δδ¹³C), the positive charge was delocalized into the naphthalene unit for 1aH⁺ , into one benzo[b,d]furan unit for 2aH⁺ , and into one benzo[b,d]furan unit for 3aH⁺ . Copyright © 2015 John Wiley & Sons, Ltd.     

Relativistic effects in PtF6 and isoelectronic octahedral groups: Magnetic susceptibility, 19F NMR, and ab initio calculations

The temperature-independent paramagnetism and high O _h symmetry of PtF₆ molecules in solids (at 77 K) and of the octahedral molecular complexes [IrF₆]^? in KIrF₆ and [OsF₆]^2? in K₂OsF₆ are shown to be consistent with the model of strong spin-orbit coupling of 5d ⁴ electrons.     

Higher reactivity of 3‐pyridinium boronic acid compared with 3‐pyridinium boronate ion toward 4‐isopropyltropolone in acidic aqueous solution: fundamental reaction analyses for an effective organoboron‐based chemosensor

The pK_as of 3‐pyridylboronic acid and its derivatives were determined spectrophotometrically. Most of them had two pK_as assignable to the boron center and pyridine moiety. The pK_a assignment performed by ¹¹B nuclear magnetic resonance spectroscopy revealed that both boron centers in 3‐pyridylboronic acid [3‐PyB(OH)₂] and the N‐methylated derivative [3‐(N‐Me)Py⁺B(OH)₂] have strong acidities (pK_a = 4.4 for both). It was found that introduction of a substituent to pyridine‐C atom in 3‐pyridylboronic acid drastically increased the acidity of the pyridinium moiety, but decreased the acidity of the boron center, whereas the introduction to pyridine‐N atom had no influence on the acidity of the boron center. Kinetic studies on the complexation reactions of 3‐pyridinium boronic acid [3‐HPy⁺B(OH)₂] with 4‐isopropyltropolone (Hipt) carried out in strongly acidic aqueous solution indicated that the positive charge on the boronic acid influenced little on its reactivity; 3‐HPy⁺B(OH)₂ reacts with Hipt and protonated H₂ipt⁺, and its reactivity was in line with those of a series of boronic acids. Kinetics in weakly acidic aqueous solution revealed that 3‐HPy⁺B(OH)₂ reacts with Hipt faster than its conjugate boronate [3‐HPy⁺B(OH)₃^–], which is consistent with our recent results. The reactivity of 3‐(N‐Me)Py⁺B(OH)₂ towards Hipt was also examined kinetically; the reactivities of 3‐(N‐Me)Py⁺B(OH)₂ and 3‐(N‐Me)Py⁺B(OH)₃^– are almost the same as those of their original 3‐HPy⁺B(OH)₂ and 3‐HPy⁺B(OH)₃^–, respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

Mössbauer characterization of iron and cobalt dinitrosyl derivatives of 1,1′-bis(diphenylphosphino)ferrocene

The interest in the synthesis and reactivity of organometallic compounds which have two or more different metals in the same molecule has grown in recent years, due to the new chemical properties that they can present. In this work, we report the Mössbauer characterization of dppfFe(CO)₃ and two novel compounds, dppfFe(NO)₂ and [dppfCo(NO)₂]⁺[SbF₆]^–, where dppf =1,1-bis(diphenylphosphino)ferrocene. The complexes were also characterized by IR and³¹P NMR. The Mössbauer parameters of the dppfFe(NO)₂ and dppfFe(CO)₃, show two iron sites in the same proportions while for [dppfCo(NO)₂ ⁺[SbF₆]^– only one site was observed.     

Lithium solvation and diffusion in the 1‐butyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquid

The Raman spectra of (1 − x)(BMITFSI), xLiTFSI ionic liquids, where 1‐butyl‐3‐methylimidazolium cation (BMI⁺) and bis(trifluoromethane‐sulfonyl)imide anion (TFSI⁻) are analyzed for LiTFSI mole fractions x < 0.4. As expected from previous studies on similar TFSI‐based systems, most lithium ions are shown to be coordinated within [Li(TFSI)₂]⁻ anionic clusters. The variation of the self‐diffusion coefficients of the ¹H, ¹⁹F, and ⁷Li nuclei, measured by pulsed‐gradient spin‐echo NMR (PGSE‐NMR) as a function of x, can be rationalized in terms of the weighted contribution of BMI⁺ cations, TFSI⁻ ‘free’ anions, and [Li(TFSI)₂]⁻ anionic clusters. This implies a negative transference number for lithium. Copyright © 2008 John Wiley & Sons, Ltd.     

The role of Sb in the structure of Sb2O3–B2O3 binary glasses—an NMR and Mössbauer spectroscopy study

Glasses of general formula xSb₂O₃ (1−x)B₂O₃ (0x0.8) have been prepared by conventional melt- quenching. Mössbauer spectroscopy shows that a fraction of the Sb³⁺ is converted to Sb⁵⁺ and this fraction increases with x. High-field ¹¹B MAS NMR gives well-resolved resonances from boron atoms which are 3- and 4-coordinated to oxygen. The fraction of 4-coordinated boron, N₄, goes through a maximum value of 0.12±0.01 at x=0.5. The position of the maximum in N₄ is consistent with the cation potential for Sb³⁺, as observed for other systems. However, the low value of N₄ at this maximum is not so readily explained. The values are similar to those predicted if [BO₄]⁻ were stabilised by [SbO₄]⁺ but the trends with composition are different.     

CNDO studies of Y-Ba-Cu-O superconductors II. Simple models of YBa2Cu3Ox

The electronic structure of YBa₂Cu₃O_x (x=6 and 7) is investigated using the CNDO molecular orbital method. Electronic structures of model clusters [Cu₃O₁₀]^–15, [Ba₈Cu₃O₁₀]⁺¹, [Y₈Cu₃O₁₀]⁺⁹ of the non-superconducting (x=6) and [Cu₃O₁₂]^–17, [Ba₈Cu₃O₁₂]^–1, [Y₈Cu₃O₁₂]⁺⁷ of the superconducting (x=7) phases are compared. Y and Ba layers cause a considerable electron density transfer from the central Cu(1) region.     

Single‐crystal Raman spectroscopy of brandholzite Mg[Sb(OH)6]2•6H2O and bottinoite Ni[Sb(OH)6]2• 6H2O and the polycrystalline Raman spectrum of mopungite Na[Sb(OH)6]

The single‐crystal Raman spectra of minerals brandholzite and bottinoite, formula M[Sb(OH)₆]₂•6H₂O, where M is Mg⁺² and Ni⁺², respectively, and the non‐aligned Raman spectrum of mopungite, formula Na[Sb(OH)₆], are presented for the first time. The mixed metal minerals comprise alternating layers of [Sb(OH)₆]⁻¹ octahedra and mixed [M(H₂O)₆]⁺²/[Sb(OH)₆]⁻¹ octahedra. Mopungite comprises hydrogen‐bonded layers of [Sb(OH)₆]⁻¹ octahedra linked within the layer by Na⁺ ions. The spectra of the three minerals were dominated by the Sb O symmetric stretch of the [Sb(OH)₆]⁻¹ octahedron, which occurs at approximately 620 cm⁻¹. The Raman spectrum of mopungite showed many similarities to spectra of the di‐octahedral minerals, supporting the view that the Sb octahedra give rise to most of the Raman bands observed, particularly below 1200 cm⁻¹. Assignments have been proposed on the basis of the spectral comparison between the minerals, prior literature and density functional theory (DFT) calculations of the vibrational spectra of the free [Sb(OH)₆]⁻¹ and [M(H₂O)₆]⁺² octahedra by a model chemistry of B3LYP/6‐31G(d) and lanl2dz for the Sb atom. The single‐crystal spectra showed good mode separation, allowing most of the bands to be assigned to the symmetry species A or E. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and Characterization of New Cationic Fe(III),Co(II) and Ni(II) Complexes Containing Isatin/Triphenylphosphine Mixed Ligands

New cationic Fe(III),Co(II) and Ni(II) mixed ligand complexes containing both triphenylphosphine and isatin ligands were prepared and characterized using conventional physical and chemical methods of analysis

(I.R., UV-Vis., and ¹H NMR). Microanalytical data of the investigated complexes are consistent with the formulations. [Fe(Isa)₂ {P(Ph)₃}₂]³⁺, [Co(Isa)₂ {P(Ph)₃}₂]²⁺ and [Ni(Isa)₂ {P(Ph)₃}₂]²⁺, (Where Isa = Isatin and P(Ph)₃ = Triphenylphosphine).

The prepared complexes are soluble in polar solvents and could be of potential use in bio-inorganic applications.     

Self‐assembly of a [2]pseudorotaxane complex by the threading of a nitrobenzimidazol‐based guest on dibenzo‐24‐crown ether host

A new derivative of the previously reported 1,2‐bis(benzimidazol‐2‐yl)ethane motif, cation [1H₂]²⁺, was synthesized under microwave irradiation and fully characterized by solution NMR, high‐resolution mass spectrometry, cyclic voltammetry and X‐ray crystallography. This cation presents a linear geometry and incorporates nitro substituents as electrochemical handles. In solution, cation [1H₂]²⁺, is capable of threading the cavity of dibenzo‐24‐crown‐8 ether host (DB24C8) giving rise to a [2]pseudorotaxane complex [1H₂?DB24C8]²⁺, regardless of the counterion, [CF₃SO₃]^? or [CF₃COO] ^?. The interpenetrated structure of [1H₂?DB24C8]²⁺ was proven by solution NMR and X‐ray crystallography. This host–guest complex is held together by several non‐covalent interactions, such as hydrogen bonding and ion‐dipole. An electrochemical study of [1H₂]²⁺ in the presence of variable amounts of DB24C8 was performed; due to the irreversible redox behavior of cation [1H₂]²⁺, it was not possible to electrochemically control the association/dissociation process with DB24C8. Copyright © 2014 John Wiley & Sons, Ltd.     

Formation and photofragmentation properties of isolated aromatic amino acid-silver cluster hybrids

The formation of isolated [ (Trp-2H)+Ag₉] ⁺ and [ (Tyr-2H)+Ag₉] ⁺ amino-acid-Ag₉ hybrids is reported. The photofragmentation yields of the aromatic amino acid-silver cluster hybrids, as well as those of the protonated tryptophan and tyrosine molecules ([Trp+H]⁺ and [Tyr+H]⁺) have been recorded. The fragmentation yields of the complexes are higher than the yields for [Trp+H]⁺and [Tyr+H]⁺ and present an extension of the fragmentation on the red side of the spectrum. The photofragmentation spectrum of [ Trp+Ag₉] ⁺ was recently reported [Mitric et al., J. Chem. Phys. 127, 134301 (2007)]. While the optical spectra of substituted [ (Trp-2H)+Ag₉] ⁺ and non-substituted [ Trp+Ag₉] ⁺ complexes are very similar, a strong modification of the fragmentation channels between the two complexes is observed. The fragmentation channels are sensitive to the type of bonding in aromatic amino acid-silver cluster hybrids and can be used as fingerprints of structures.     

Determination of Trace Mercury by Solid Substrate-Room Temperature Phosphorimetry Quenching Method Based on Catalytic Effect of Hg2+on Formation of the Ion Association Complex [Sn(XO)6]4+·[(Fin)4]

A new method for the determination of trace mercury by solid substrate-room temperature phosphorimetry (SS-RTP) quenching method has been established. In glycine-HCl buffer solution, xylenol orange (XO) can react with Sn⁴⁺ to form the complex [Sn(XO)₆]⁴⁺. [Sn(XO)₆]⁴⁺ can interact with Fin⁻ (fluorescein anion) to form the ion associate [Sn(XO)₆]⁴⁺·[(Fin)₄]⁻, which can emit strong and stable room temperature phosphorescence (RTP) on polyamide membrane (PAM). Hg²⁺ can catalyze H₂O₂ oxidizing the ion association complex [Sn(XO)₆]⁴⁺·[(Fin)₄]⁻, which causes the RTP to quench. The ΔIp value is directly proportional to the concentration of Hg²⁺ in the range of 0.016–1.6 fg spot⁻¹ (corresponding concentration: 0.040–4.0 pg ml⁻¹, 0.40 μl spot⁻¹), and the regression equation of working cure is ΔIp=10.03+83.15 m Hg²⁺ (fg spot⁻¹), (r=0.9987, n=6) and the detection limit (LD) is 3.6 ag spot⁻¹(corresponding concentration: 9.0×10^–15 g ml⁻¹, the sample volume: 0.4 μl). This simple, rapid, accurate method is of high selectivity and good repeatability, and it has been successfully applied to the determination of trace mercury in real samples. The reaction mechanism for catalyzing H₂O₂ oxidizing the ion association complex ([Sn(XO)₆]⁴⁺·[(Fin)₄]⁻) SS-RTP quenching method to determine trace mercury is also discussed.     

Synthesis and Spectral Study of Several Solid M3[Eu(2,6-Pyridinedicarboxylate)3] Salts (M=Li+, Na+, K+, Rb+, Cs+, NH4 +, and Pyridinium+)

Abstract

Salts of the [Eu(2,6-pyridinedicarboxylate)₃]^3- complex anion and various monovalent inorganic and organic counterions (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, NH₄ ⁺, and pyridinium⁺) have been synthesized and studied by emission spectroscopy. The Eu³⁺ ion emission spectra exhibited by these salts have been observed with high resolution (less than 1.0 cm^?1) and at low temperature (77 K). The emission spectra of these compounds indicate that changing the attached counterion does not affect the site symmetry observed by the europium ion beyond slight distortions indicated by small shifts in the energies of the Eu³⁺ electronic levels.     

Structure of Na2O·MO·SiO2·CaF2 (M=Mg,Ca) oxyfluoride glasses

(9−x)CaO·xMgO·15Na₂O·60SiO₂·16CaF₂(x=0, 2, 4, 6, and 9) oxyfluoride glasses were prepared. Utilizing the Raman scattering technique together with ²⁹Si and ¹⁹F MAS NMR, the effect of alkaline metal oxides on the Q species of glass was characterized. Raman results show that as magnesia is added at the expense of calcium oxide, the disproportional reaction Q³→Q⁴+Q² (Qⁿ is a SiO₄ tetrahedron with n bridging oxygens) prompted due to the high ionic field strength of magnesia, magnesium oxide entered into the silicate network as tetrahedral MgO₄, and removed other modifying ions for charge compensation. This reaction was confirmed by ²⁹Si MAS NMR. ¹⁹F MAS NMR results show that fluorine exists in the form of mixed calcium sodium fluoride species in all glasses and no Si–F bonds were formed. As CaO is gradually replaced by MgO (x=6, 9), a proportion of the magnesium ions combines with fluorine to form the MgF⁺ species. Meanwhile, some part of Na⁺ ions complex F⁻ in the form of F–Na(6).     

Synthesis,spectroscopic, thermal and electrical conductivity studies of three charge transfer complexes formed between 1,3-di[(<Emphasis Type="Italic">E</Emphasis>)-1-(2-hydroxyphenyl)methylideneamino]-2-propanol Schiff base and different acceptors

Charge-transfer complexes (CTC) resulting from interactions of 1,3-di[(E)-1-(2-hydroxyphenyl) methylideneamino]-2-propanol Schiff base with some acceptors such as iodine (I₂), bromine (Br2), and picric acid (PiA) have been isolated in the solid state in a chloroform solvent at room temperature. Based on elemental analysis, UV-Vis, infrared, and ¹H NMR spectra, and thermogravimetric analysis (TG/DTG) of the solid CTC, [(Schiff)(I₂)] (1), [(Schiff)(Br₂)] complexes with a ratio of 1:1 and [(Schiff)(PiA)₃] complexes with 1:3 have been prepared. In the picric acid complex, infrared and ¹H NMR spectroscopic data indicate that the charge-transfer interaction is associated with a hydrogen bonding, whereas the iodine and bromine complexes were interpreted in terms of the formation of dative ion pairs [Schiff⁺, I₂^∙−] and [Schiff⁺, Br₂^∙−], respectively. Kinetic parameters were obtained for each stage of thermal degradation of the CT complexes using Coats–Redfern and Horowitz–Metzger methods. DC electrical properties as a function of temperature of these charge transfer complexes have been studied.     

New dithiacrown–ether butadienyl dyes: synthesis,structure, and complex formation with heavy metal cations

Benzothiazole type butadienyl dyes containing a dithia‐15‐crown‐5 ( 2a ) or dithia‐18‐crown‐6 ether ( 2b ) moieties were synthesized. The structures of dyes 2a , b and their complexes with Ag⁺ and Pb²⁺ were studied by an X‐ray crystallography. It was found that the conformations of dithiacrown–ether moieties of dyes 2a , b are unfavorable for complex formation and change significantly upon binding of Ag⁺ or Pb²⁺. The complexation of 2a , b with Ag⁺, Cd²⁺, Pb²⁺, and Hg²⁺ in water–acetonitrile mixtures with different contents of water (P_W = 0–75%, v/v) was studied by ¹H NMR, UV–Vis spectroscopy, and polarography. In anhydrous acetonitrile, the stability constants of 1:1 complexes change in the sequence Cd²⁺ < Pb²⁺ ≤ Ag⁺ << Hg²⁺ in the case of 2a and in the sequence Cd²⁺ < Ag⁺ < Pb²⁺ << Hg²⁺ in the case of 2b . As P_W increases, the thermodynamic stability of Ag⁺ complexes increases. The opposite effect is observed for the complexes with Cd²⁺, Pb²⁺, and Hg²⁺. When P_W ～ 50%, the stability constants of complexes with Cd²⁺ and Pb²⁺ become too small to be measured. The selectivity of ligands 2a , b toward Hg²⁺ versus Ag⁺ is very high at any P_W values (selectivity coefficients > 10⁴). The complexation of 2a , b with Hg²⁺ at P_W ≤ 50% is accompanied by a substantial hypsochromic effect. This allows dithiacrown‐containing butadienyl dyes to be used as selective optical molecular sensors for heavy metal ions, in particular, in aqueous solutions. Copyright © 2009 John Wiley & Sons, Ltd.     

P2O5-CuI-CuCl系统非晶态铜离子导体的EXAFS,IR,Raman光谱研究

本文用透射法EXAFS和IR,Raman光谱等手段研究了以P₂O₅,为基体的非晶态铜离子导体的微观结构,得出了非晶结构网络中存在[PO₄]^3-,[CuO₄]^6-,[CuO₃I]^5-,[PO₃I]^2-等四元骨架结构单元,Cu⁺在结构网络空隙中有两种不同的分布状况。并在此基础上对材料在50℃左右存在的二级相变及Cu⁺的其它传导性能进行了定性的描述。 关键词：