Inorganic-organic hybrids of the p,p'-diphenylmethylenediphosphinate ligand with bivalent metals: a new 2D-layered phenylphosphinate zinc(II) complex

By reaction of Zn(CH₃COO)₂ with p,p′-diphenylmethylenediphosphinic acid in water a new inorganic–organic polymeric hybrid of formula [Zn(CH₂(P(Ph)O₂)₂)] has been synthesized and completely characterized. The X-ray analysis established that the structure consists of 2D-layered polymeric array, the 2D-sheets being built up through strong covalent linkages between the zinc metal and the oxygen donors of the phenylphosphinate ligand. The 2D-layers, which are featuring a mesh-net fashion, present voids of various dimensionality, up to 24-membered rings. The organic parts of the hybrid ligand, namely the phenyl rings, are shielding the inorganic skeleton of the layers, preventing the propagation of the polymer in the third dimension. No water molecules are present in the lattice, both of coordination and crystallization. Crystal data are: monoclinic, P2₁Ic, a=11.840(2), b=9.646(9), c=12.516(5) Å, β=95.03(2), V=1423.9(15) ų, Z=4. The solid material has been characterized by ³¹P MAS NMR spectroscopy and thermogravimetric analysis.

Synthesis and reactivity of para-substituted benzoylmethyltellurium(II and IV) compounds: observation of intermolecular C-H-O hydrogen bonding in the crystal structure of (p-MeOC6H4COCH2)2TeBr2

Bis(p-substituted benzoylmethyl)tellurium dibromides, (p-YC₆H₄COCH₂)₂TeBr₂, (y=H (1a), Me (1b), MeO (1c)) can be prepared
either by direct insertion of elemental Te across CRf-Br bonds (where C_Rf refers to α-carbon of a functionalized organic moiety) or by the oxidative addition of bromine to (p-YC₆H₄COCH₂)₂Te (y = H (2a), Me (2b), MeO (2c)). Bis(p-substituted benzoylmethyl)tellurium dichlorides, (p-YC₆H₄COCH₂)₂TeCh (y = H (3a), Me (3b), MeO (3c)), are prepared by the reaction of the bis(p-substituted benzoylmethyl)tellurides 2a--c with S0₂Cl₂, whereas the corresponding diiodides (p-YC₆H₄COCH₂)₂Teh (y = H
(4a), Me (4b), MeO (4c)) can be obtained by the metathetical reaction of la--c with KI, or alternatively, by the oxidative addition of
iodine to 2a--c. The reaction of 2a--c with allyl bromide affords the diorganotellurium dibrornides la--c, rather than the expected
triorganotelluronium bromides. Compounds 1-4 were characterized by elemental analyses, IR spectroscopy, ¹H, ^l3C and ¹²⁵Te
NMR spectroscopy (solution and solid-state) and in case of Ie also by X-ray crystallography. (p-MeOC₆H₄COCH₂)₂TeBr₂ (1c) provides, a rare example, among organotellurium compounds, of a supramolecular architecture, where C-H-O hydrogen bonds appear to be the non-covalent intermolecular associative force that dominates the crystal packing.

The reactivity of bis(para-methoxyphenyl)telluroxide towards triflic acid and diphenylphosphinic acid. Theoretical considerations of the protonation and hydration process of diorganotelluroxanes

The reaction of (p-MeOC₆H₄)₂TeO with two equivalents of HO₃SCF₃ and HO₂PPh₂ provided the tetraorganoditelluroxanes (F₃CSO₃)(p-MeOC₆H₄)₂TeOTe(p-MeOC₆H₄)₂(O₃SCF₃) (1) and (Ph₂PO₂)(p-MeOC₆H₄)₂TeOTe(p-MeOC₆H₄)₂(O₂PPh₂)·2 Ph₂PO₂H (2) in good yields. Compounds 1 and 2 were characterized by solution and solid-state ³¹P and ¹²⁵Te NMR spectroscopy, IR spectroscopy, electrospray mass spectrometry, conductivity measurements and single crystal X-ray diffraction. In solution, compound 1 undergoes an electrolytic dissociation and reversibly reacts with traces of water to give the mononuclear cation [(p-MeOC₆H₄)₂TeOH]⁺ and triflate anions. Theoretical aspects of the protonation and hydration of model telluroxanes R₂TeO (R = H, Me, Ph) were investigated by preliminary DFT calculations and compared to the corresponding selenoxanes R₂SeO. The tellurium dihydroxides R₂Te(OH)₂ seem to be more stable than the hydrogen-bonded complexes R₂TeO·H₂O.

The first dimeric trioganotin fluoride : stabilization by unsymmetrically oriented menthyl substituents

In the solid state, (-)-tris([1R,2S,5R]-menthyl)tin fluoride, Men₃SnF (6), exhibits a dimeric structure in which one tin atom is four-coordinate and the other five-coordinate. This novel dimeric association mode is attributed to the orientation of the unsymmetrical menthyl groups, which are arranged to allow a minimum Sn···Sn separation of 4.84 Å within the dimer. The exocyclic isopropyl groups of the menthyl groups point in opposite directions on each tin atom of the dimer, thus preventing further association (Sn···Sn separation outside the dimer 10.49 Å). ¹¹⁹Sn and ¹⁹F MAS NMR spectroscopy were utilized to probe the diverse coordination numbers found by X-ray crystallography for the geometries of the two tin and fluorine sites. In solution, 6 is a monomer at both room temperature and -100 °C. However, upon addition of Bu₄NF, 6 is in equilibrium with [(Men₃SnF)₂F]- (6a), [Men₃SnF₂]^- (6b), and noncoordinating fluoride anions.

The interplay of secondary Te···N, Te···O, Te···I and I···I interactions, Te···π contacts and π-stacking in the supramolecular structures of [{2-(4-nitrobenzylideneamino)-5-methyl}phenyl](4-methoxyphenyl)tellurium dihalides

The unsymmetrical1y substituted diorganotellurium dihalides [2-(4,4'-N0₂C₆H₄CHNC₆H₃Me]RTeX₂ (R = 4-MeOC₆H₄, X = Cl,
1a; Br, 1b; I, 1c; R =4-MeC₆H₄ ; X = Cl, 2; R =C₆H₅, X = Cl, 3) were prepared in good yields and characterized by solution and solid-state ¹²⁵Te NMR spectroscopy, IR spectroscopy and X-ray crystallography. In the solid-state, molecular structures of 1a and 1c possess scarcely observed 1,4-type intramolecular Te···N secondary interaction. Crystal packing of these compounds show an unusually rich diversity of intermolecular secondary, Te·· ·0, Te· .. \ and 1···1 interactions, Te·· ·π contacts as well as extensive
π-stacking of the organic substituents.

The reactivity of diorganotellurium oxides towards phenol and o-nitrophenol. Hypervalent and secondary bonding of four different product classes

The reaction of the diorganotellurium oxides R2TeO (R = Ph, p-MeOC6H4, p-Me2NC6H4) with phenol and o-nitrophenol produces diorganotellurium hydroxy phenolates, R2Te(OH)OPh (1, R = Ph; 2, R = p-MeOC6H4; 3, R = p-Me2NC6H4), diorganotellurium bis(phenolates) R2Te(OPh)2 (4, R = Ph; 5, R = p-MeOC6H4; 6, R = p-Me2NC6H4), tetraorganoditelluroxane bis(o-nitrophenolates), (R′O)R2TeOTeR2(OR′) (7, R = p-MeOC6H4; 8, R = p-Me2NC6H4; R′ = o-NO2C6H4), and a hexaphenyltritelluroxane bis(o-nitrophenolate) (R′O)Ph2TeOTePh2OTePh2(OR′) (9, R′ = o-NO2C6H4), respectively. The redistribution reactions of R2Te(OPh)2 (4, R = Ph; 5, R = p-MeOC6H4; 6, R = p-Me2NC6H4) with the corresponding diorganotellurium oxides R2TeO and diorganotellurium dichlorides R2TeCl2 (R = Ph, p-MeOC6H4, p-Me2NC6H4) give rise to the formation of moisture sensitive tetraorganoditelluroxane bis(phenolates) (PhO)R2TeOTeR2(OPh) (10, R = Ph; 11, R = p-MeOC6H4; 12, R = p-Me2NC6H4) and diorganotellurium chloro phenolates, R2Te(Cl)OPh (13, R = Ph; 14, R = p-MeOC6H4; 15, R = p-Me2NC6H4), respectively. The reaction of the diorganotellurium oxides R2TeO with the corresponding diorganotellurium dichlorides R2TeCl2 (R = Ph, p-MeOC6H4, p-Me2NC6H4) affords tetraorganoditelluroxane dichlorides ClR2TeOTeR2Cl (16, R = Ph; 17, R = p-MeOC6H4; 18, R = p-Me2NC6H4) as air-stable solid materials. The reactivity of 1–18 can be rationalized by the kinetic lability of the Te–O and Te–Cl bonds. Compounds 1–18 have been characterized by solution and solid-state 125Te NMR spectroscopy and 2, 4, 6, 7, 9, 17, and 18 have also been analyzed by X-ray crystallography.

Copper and zinc mediated oligomerisation of Aß peptides

The accumulation of senile plaques composed primarily of aggregated amyloid β-peptide (Aβ), is the major characteristic of Alzheimer’s disease. Many studies correlate plaque accumulation and the presence of metal ions, particularly copper and zinc. The metal binding sites of the amyloid Aβ peptide of Alzheimer’s disease are located in the N-terminal region of the full-length peptide. In this work, the interactions with metals of a model peptide comprising the first 16 amino acid residues of the amyloid Aβ peptide, Aβ(1–16), were studied. The effect of Cu²⁺ and Zn²⁺ binding to Aβ(1–16) on peptide structure and oligomerisation are reported. The results of ESI-MS, gel filtration chromatography and NMR spectroscopy demonstrated formation of oligomeric complexes of the peptide in the presence of the metal ions and revealed the stoichiometry of Cu²⁺ and Zn²⁺ binding to Aβ(1–16), with Cu²⁺ showing a higher affinity for binding the peptide than Zn²⁺.

Studies of hypervalent organotin complexes and organotin clusters

(119)Sn, (31)P and (13)C variable temperature NMR spectroscopies have been used to examine the effective coordination spheres in solution of a series of hypervalent organotin(IV) dithiolate compounds RnSnXm(S-S)4-n-m where R = Ph, Me, nBu, tBu; X = Cl, Br; (S-S) = S2CNR'2, S2COR', S2P(OR')2 (R' = Me, Et, iPr) and n = 1, 2, 3; m = 0,1,2. Stereochemical nonrigidity is a common phenomenon found for these hypervalent compounds. On the basis of heteronuclear NMR data and X-ray crystallographic data, dynamic behaviors of these hypervalent compounds have been established. The system of hypervalent organotin(IV) fluoride complexes has also been investigated by variable temperature heteronuclear NMR techniques. A series of monomeric pentacoordinate complexes [RnSnC1mF5-n-m]-(R = Ph, Me, nBu, tBu; n = 2, 3; m - 0, 1, 2, 3) and dimeric complexes [(Me3SnX)F(Me3SnX')]- (X = F, Cl; X' = F, Cl) and hexacoordinate complexes [RnSnClmF6-n.m]2- (R = Ph, Me, nBu; n = 1, 2; m = (X 1, 2, 3,4) are identified in solution. The fluoride is of higer affinite to tin than the chloride. The stereochemistry and dynamic behavior of these complexes in solution has been studied. Fluoride ion may induce phenyl group disproportionation of phenyhin(IV) compounds. It is also found that in pentacoordinate diorganotin complexes, such as [Ph2SnCl2F]- and [Ph2SnClF2]- fluorine can be less apicophilic than chlorine. Studies of stereochemistry and dynamic behavior of bi-functional Lewis acid bis(haloorganosiannes) have also been carried out. The bis(haloorganostannes) exhibit strong chelate ability towards halide, with high selectivity on fluoride, forming heterocyclic chelating rings, the stability of which depend on the ring size. In further exploration of the Lewis acidity of organotin(IV) halides, complexation of organotin(IV) halides with bis(tertiary phosphinc) ligands has been studied by 119Sn and 31P NMR spectroscopy and X-ray crystallography. The phenyl group disproportionation is often observed in the complexation reaction. Furthermore, organotin(IV) clusters such as [(RSn)12O14(OH)6]Cl2-2H2O (R = iPr, nBu) have been successfully prepared by base hydrolysis of RSnCl3. These clusters contain 12 tin atoms in one molecule and the cores of the clusters are dications. Other organotin clusters such as [nBuSn(O)O2CCH3]6 and [(nBuSn(OH)O2PPh2)3][O2PPh2) are readily formed by reaction of the 12-tin-atom cluster with an appropriate acid. The reactivity of and interconversion between organotin(FV) clusters have also been studied.

Structure and transport properties in an N,N-substituted pyrrolidinium tetrafluoroborate plastic crystal system

The structure and transport of N-propyl-N-methylpyrrolidinium tetrafluoroborate (P₁₃BF₄) has been investigated over a wide temperature range in consequence to exhibiting properties suitable for potential solid-state superionic electrolyte applications. Prior to melting, the organic salt, P₁₃BF₄, transforms into a plastic crystal phase. Intrinsic conductivity in this solid, phase I (45–65 °C), is comparable to that in the melt (_~10⁻³ S cm⁻¹). Ionic motion and transport properties were investigated by ¹H and ¹¹B nuclear magnetic resonance (NMR) spectroscopy. Pressure-induced plastic flow in this system may accommodate volume changes in device application and to this extent, X-ray diffraction (XRD) has been used. Scanning electron microscopy (SEM) revealed complex surface morphology and lattice imperfections associated with the strong orientational disorder of the plastic state.

Surprising effect of nanoparticle inclusion on ion conductivity in a lithium doped organic ionic plastic crystal

Doping lithium bis(trifluoromethanesulfonyl)amide (Li[NTf₂]) into the N-ethyl,N′-methylpyrrolidinium bis(trifluoromethanesulfonyl)amide ([C₂mpyr][NTf₂]) plastic crystal material has previously indicated order of magnitude enhancements in ion transport and conductivity over pure [C₂mpyr][NTf₂]. Recently, conductivity enhancements in this ionic plastic crystal induced by SiO₂ nanoparticles have also been reported. In this work the inclusion of SiO₂ nanoparticles in Li ion doped [C₂mpyr][NTf₂] has been investigated over a wide temperature range by differential scanning calorimetry (DSC), impedance spectroscopy, positron annihilation lifetime spectroscopy (PALS), Raman spectroscopy, NMR spectroscopy and scanning electron microscopy (SEM). Solid state ¹H NMR indicates that the addition of the nanoparticles increases the mobility of the [C₂mpyr] cation and positron lifetime spectroscopy (PALS) measurements indicate an increase in mean defect size and defect concentration as a result of nanoparticle inclusion, especially with 10 wt% SiO₂. Thus, the substantial drop in ion conductivity observed for this doped nanocomposite material was surprising. This decrease is most likely due to the decrease in mobility of the [NTf₂] anion, possibly by its adsorption at the SiO₂/grain boundary interface and concomitant decrease in mobility of the Li ion.

Proton transport in choline dihydrogen phosphate/H3PO4 mixtures

Mixtures of the plastic crystal material choline dihydrogen phosphate [Choline][DHP] and phosphoric acid, from 4.5 mol% to 18 mol% H₃PO₄, were investigated and shown to have significantly higher proton conductivity compared to the pure [Choline][DHP]. This was particularly evident from the electrochemical hydrogen reduction reaction and the proton NMR diffusion measurements, in addition to ionic conductivity measured from the impedance spectroscopy. The ionic conductivity was observed to increase by more than an order of magnitude in phase I (i.e. the highest temperature solid phase in [Choline][DHP]) reaching up to 10⁻² S cm⁻¹. The multinuclear NMR spectroscopy data suggest that, at least on the timescale of the NMR measurement, the H⁺ cations and [DHP] anions are equivalent in both phases. The pulsed field gradient NMR diffusion measurements of the 18 mol% acid sample indicate that all three ions are mobile, however the H⁺ diffusion coefficient is an order of magnitude higher than for the [Choline] cation or the [DHP] anion, and therefore conduction in these materials is dominated by proton conductivity. The thermal stability, as measured by TGA, is unaffected with increasing acid additions and remains high; i.e. no significant mass loss below 200 °C.

Fluorescent and electrochemical sensing of (poly)phosphate nucleotides by ferrocene functionalised with two (ZnII-TACN-pyrene) complexes

The [Fc[BOND]bis{ZnII(TACN)(Py)}] complex, comprising two ZnII(TACN) ligands (Fc=ferrocene; Py=pyrene; TACN=1,4,7-triazacyclononane) bearing fluorescent pyrene chromophores linked by an electrochemically active ferrocene molecule has been synthesised in high yield through a multistep procedure. In the absence of the polyphosphate guest molecules, very weak excimer emission was observed, indicating that the two pyrene-bearing ZnII(TACN) units are arranged in a trans-like configuration with respect to the ferrocene bridging unit. Binding of a variety of polyphosphate anionic guests (PPi and nucleotides di- and triphosphate) promotes the interaction between pyrene units and results in an enhancement in excimer emission. Investigations of phosphate binding by 31P NMR spectroscopy, fluorescence and electrochemical techniques confirmed a 1:1 stoichiometry for the binding of PPi and nucleotide polyphosphate anions to the bis(ZnII(TACN)) moiety of [Fc[BOND]bis{ZnII(TACN)(Py)}] and indicated that binding induces a trans to cis configuration rearrangement of the bis(ZnII(TACN)) complexes that is responsible for the enhancement of the pyrene excimer emission. Pyrophosphate was concluded to have the strongest affinity to [Fc[BOND]bis{ZnII(TACN)(Py)}] among the anions tested based on a six-fold fluorescence enhancement and 0.1 V negative shift in the potential of the ferrocene/ferrocenium couple. The binding constant for a variety of polyphosphate anions was determined from the change in the intensity of pyrene excimer emission with polyphosphate concentration, measured at 475 nm in CH3CN/Tris-HCl (1:9) buffer solution (10.0 mM, pH 7.4). These measurements confirmed that pyrophosphate binds more strongly (Kb=(4.45±0.41)×106 M−1) than the other nucleotide di- and triphosphates (Kb=1–50×105 M−1) tested.

Ionic liquid electrolyte for lithium metal batteries : physical, electrochemical, and interfacial studies of N-Methyl-N-butylmorpholinium Bis(fluorosulfonyl)imide

The ionic liquid (IL) N-methyl-N-butylmorpholinium bis(fluorosulfonyl)imide (C₄mmor FSI) is examined from physical and electrochemical perspectives. Pulsed field gradient NMR spectroscopy shows that ion diffusivities are low compared with similar, non-ethereal ILs. Ionicity values indicate that above room temperature, less than 50% of ions contribute to conductivity.

Lithium cycling in symmetrical cells using a C₄mmor FSI-based electrolyte is best demonstrated at elevated temperatures. Specific capacities of 130 mAh g⁻¹ are achieved in a Li−LiFePO₄ battery at 85 °C. FT-IR spectroscopic investigations of lithium electrodes suggest the presence of alkoxide species in the solid electrolyte interphase (SEI), implying a ring-opening reaction of C₄mmor with lithium metal. In contrast, the SEI derived from N-methyl-N-propylpiperidinium FSI lacks the alkoxide signature but shows signs of alkyl unsaturation, and the activation energy for Li+ transport through this SEI is slightly lower than that for the C₄mmor-derived SEI. Our detailed findings give insight into the capabilities and limitations of rechargeable lithium metal batteries utilizing a C₄mmor FSI electrolyte.

Antibacterial activity of stevioside towards food-borne pathogenic bacteria

This study determines the inhibitory effect of Stevia rebaudiana leaf extracts and its purified bioactive compound ‘stevioside’ against food-related pathogens. The S. rebaudiana solvent extracts (1000 μg/mL) displayed antibacterial activity to Serratia marcescens, Klebsiella pneumoniae, Bacillus cereus, Pseudomonas aeruginosa, B. subtilis, Alcaligenes denitrificans and Salmonella typhimurium. Of the six solvents, ethanol and acetone extracts displayed the highest zone of inhibition. The bioactive compound from S. rebaudiana was purified by solvent extraction, thin-layer chromatography followed by structural characterization by spectroscopy evidence. Purified stevioside prevented the growth of tested bacterial species, i.e. B. subtilis, K. pneumoniae and S. typhimurium. Significant zone of inhibition (12 mm) was observed against B. cereus which proposes potential application of stevioside in foods to increase their shelf life.