Picrate Salts Research Articles

Luminescence of non-hygroscopic polymer electrolytes modified by europium picrate complexes

The luminescence features of new europium-based PEO electrolytes where the lanthanide ion is encapsulated into a ligand structure cage ( eg Eu 3+-picrate complexes with trans-1,4-dithiane-1,4-dioxide, TDTD) were reported. The complexes are non-hygroscopic and strongly luminescent in the temperature range of 10 to 300 K. The emission spectra were recorded in this temperature range and the corresponding lines assigned to the 5D 0.1→ 7F 0-4 transitions. The measured line widths, which are of the same order of magnitude of the one observed in crystals (1–2 Å), are approximately two orders of magnitude sharper than the ones observed in glasses and other Eu 3+-based polymeric materials. The Stark components of the 7F 0-4, 5D 0 levels and the corresponding barycenters were calculated and modeled by the superposition of the free ion Hamiltonian with a local-field perturbation. The average cation–nearest ligand distance was determined for the PEO-Eu(pic) 3TDTD 1.5 complexes and the results obtained, R̄ =2.45 Å, agree very well with the X-ray average ion–nearest ligands distances measured for the picrate salt, R̄ =2.448 Å.

Isolation of [Be3(μ-OH)3(H2O)6]3+. Synthesis, 9Be NMR Spectroscopy, and Crystal Structure of [Be3(μ-OH)3(H2O)6](picrate)3·6H2O

The synthesis, 9Be NMR spectrum, and molecular structure of the [Be3(μ-OH)3(H2O)6]3+ picrate salt are presented.

Potassium and Sodium Complexes of 1,3-calix[4]-bis-crown-6: Crystal and Molecular Structures, 1H-NMR Investigation and Molecular Dynamics Simulation

The crystal structures of two alkali metal complexes involving the ditopic receptor 1,3-calix[4]-bis-crown-6, Bis-C6, are reported. KBis-C6(NO3)·2CH3CN (1) crystallizes in the monoclinic space group C2/c: a = 18.025(8), b = 17.672(9), c = 17.454(13) Å, β = 97.55(5)°, V = 5511(9) Å3, Z = 4. Refinement led to a final conventional R value of 0.091 for 1563 reflections. The structure of (1) is isomorphous to those previously observed for the free ligand and some of its mono- and binuclear cesium complexes: the conformation of the ligand is the same in all cases, which results in nearly identical packings and cell parameters. The potassium ion is bonded to the six oxygen atoms of the crown-ether and two from nitrate ions. Na2 Bis-C6(NO3)2(H2O)2·CH3CN (2) crystallizes in the monoclinic space group P21/c: a = 13.487(6), b = 16.758(9), c = 23.542(15) Å, β = 101.17(4)°, V = 5220(8) Å3, Z = 4. Refinement led to a final conventional R factor of 0.14 for 2546 reflections. One sodium ion and one water molecule are included in each crown-ether moiety. The sodium ion is bonded to three oxygen atoms of the crown only, two from nitrate ions and the one of the water molecule, which also forms possible hydrogen bonds with two ether oxygen atoms. 1H-NMR experiments show that 1:1 potassium or sodium complexes are formed in chloroform solution from picrate salts, they also confirm the bonding mode observed in the solid state, with no evidence of π-interactions between the cations and the aromatic rings. Molecular dynamics simulations were performed in vacuo and in an explicit water phase on Bis-C6/NaNO3 mono- and binuclear complexes to study the influence of the nitrate counter-ion on the structural features of these complexes.

Tetraalkylammonium salts as additives in anionic polymerization of methyl methacrylate

AbstractThe anionic polymerization of methyl methacrylate was carried out in the presence of t‐BuOK/Quaternary ammonium salt (QAS) and α‐lithio‐ethylisobutyrate/QAS in toluene and THF. Seven QAS and one quaternary phosphonium salt of different size and shape were used as modifiers. With the aid of the model system alkali picrate/QAS, it was found that the interaction between the picrate salt and QAS in toluene does not proceed as a pure cation exchange reaction. Two types of adducts were distinguished: Initiator/QAS with a very long hydrocarbon chain (>C12) promote isotactic placement, while the adducts t‐BuOK/QAS with two or more bulky substituents produce a highly syndiotactic polymer with high conversion and comparatively low polydispersity in pure toluene.

The picrate anion as a versatile chelating counter-ion for the complexation of alkali and alkaline earth metal cations with ionophores: The 'picrate effect'

Abstract

Rare-earth-metal solvent extraction with calixarene phosphates

Several phosphate esters in which calixarenes act as either uni- or bi-dentate ligands towards PV have been investigated as solvent-extraction agents for the rare-earth metals (La to Lu, excluding Pm, plus Y). Extraction of picrate salts into dichloromethane, ethyl acetate and tributyl phosphate–hexane (1 : 1) is considerably enhanced by some of these esters but in no case is any marked selectivity exhibited, although some features of the observed extraction patterns suggest ways in which the molecular design of such extractants may be improved. Crystal structure determinations on two phosphate esters in which the calixarene unit is bidentate indicate that the relatively poor metal-ion binding abilities of these ligands may be a consequence of a preferred orientation of the phosphoryl donor groups in which they diverge from the macrocyclic ring. A crystal structure determination on the 2 : 1 complex of tetrakis-O-(diethoxyphosphoryl)-p-tert-butylcalix[4]arene and lanthanum picrate (2,4,6-trinitrophenolate) shows that a convergent array of phosphoryl donor groups can form in such cases where the functional groups are flexible. This does not, however, appear to lead to a particular enhancement of stability, as the complex readily dissociates into a 1 : 1 species in solution.

SCF-MO computational analysis of the geometric conformation and charge distribution in picric acid and alkali picrate salts

SCF-MO computations were employed in a study of picric acid, the –1 picrate ion, and Li, Na, and K picrates. Atomic coordinates from crystallographic structural analyses were used as initial parameters in the computation of the minimum-energy conformations of each free molecule at the 6-31G level. The Mulliken charge numbers for each atom in the optimized model molecules were calculated at the 6-31G** level. The induction and resonance effects of the OX group (X = H, Li, Na, K) on the trinitrophenyl ring are discussed. It is demonstrated that molecular (electron) isodensity surfaces (MIDCOs) describe charge-density results nicely compatible with the point Mulliken charge numbers. Key words: picrates, SCF-MO, charge distribution.

Bidentate and terdentate (P-N-S) complexes of a new thioether azine phosphine Z,E-PPh2CH2C(But)=N-N=C(Me)CH2S(C6H4Me-4) with molybdenum, tungsten, or platinum

Treatment of Z-PPh2CH2C(But)=NNH2 with 4-methylphenylthiomethyl methyl ketone gave the thioether azine phosphine Z,E-PPh2CH2C(But)=N-N=C(Me)CH2S(C6H4Me-4) 1, which with H2O2 gave the corresponding phosphine oxide 2. Treatment of 1 with [Mo(CO)3(η6-cht)] or [W(CO)3(NCEt)3] gave the yellow tricarbonyl complexes fac-[M(CO)3{PPh2CH2C(But)=N-N=C(Me)CH2S(C6H4Me-4)}] 3a (Mo) or 3b (W), respectively. Treatment of 1 with [Mo(CO)4(nbd)] gave the pale yellow tetracarbonylmolbdenum(0) complex [Mo(CO)4{PPh2CH2C(But)=N-N=C(Me)CH2S(C6H4Me-4)}] 4, in which the ligand 1 is bidentate through P and N. Oxidation of either 3a or 4 with 1 equivalent of bromine gave the orange neutral seven-coordinate dicarbonylmolybdenum(II) complex [MoBr2(CO)2{PPh2CH2C(But)=N-N=C(Me)CH2S(C6H4Me-4)}] 5, whereas the tungsten complex 3b with 1 equivalent of bromine gave the seven-coordinate tricarbonyltungsten(II) cation [WBr(CO)3{PPh2CH2C(But)=N-N=C(Me)CH2S(C6H4Me-4)}]+ isolated as the PF6 salt 6. Treatment of 1 with [PtCl2(NCMe)2]gave the yellow dichloroplatinum(II) complex [PtCl2{PPh2CH2C(But)=N-N=C(Me)CH2S(C6H4Me-4)}] 7, in which 1 is bidentate through P and N. When 7 was treated with NH4PF6 in methanol it gave the terdentate salt [PtCl{PPh2CH2C(But)=N-N=C(Me)CH2S(C6H4Me-4)}]PF68a. Deprotonation of 7 with NEt3-NaOH gave the orange neutral chloroplatinum(II) complex [PtCl{PPh2-CH2C(But)N-NC(Me)=CHS(C6H4Me-4)}] 9, containing a terdentate ene-hydrazone phosphine ligand. This neutral complex 9 was reprotonated using HBF4 to give the BF4 salt 8b. Treatment of the phosphine 1 with [PtMe2(cod)] gave the white dimethylplatinum(II) complex [PtMe2{PPh2CH2C(But)=N-N=C(Me)CH2S(C6H4Me-4)}] 10, containing the bidentate azine ligand. Treatment of 10 with MeI gave the white platinum(IV) iodide salt fac-[PtMe3{PPh2CH2C(But)=N-N=C(Me)CH2S(C6H4Me-4)}]I 11a in which the azine is terdentate. When 11a was treated with NH4PF6 in MeOH the PF6 salt 11b was obtained. Treatment of 10 with picric acid gave the yellow methylplatinum(II) picrate salt [PtMe{PPh2CH2C(But)=N-N=C(Me)CH2S(C6H4Me-4)}][OC6H2(NO2)3-2,4,6] 12 and methane. Infrared, 31P–[1H], 1H, and some 13C–[1H] NMRdata are given. Keywords: azine phosphine, thioether, metal-carbonyls, platinum.

Specific ion-molecule interactions of p-quinones in nitrobenzene. Hydrogen-bond complexing ability of p-quinones

Conductivity measurements were used to study the specific interactions between p-quinone molecules (1,4-benzoquinone, 1,4-naphthoquinone and 9,10-anthraquinone) and ions of pyridinium picrate salt in nitrobenzene. The results indicate that in nitrobenzene the enthalpies (−ΔH) of formation of complexes between pyridinium ions and p-quinone molecules increased with the p-quinone electron affinities (9,10-anthraquinone < 1, 4-naphthaquinone < 1,4-benzoquinone).

Evidence for cation-π interactions in calixcrown·KPic complexes from X-ray crystal structure analysis and energy calculations

The crystal and molecular structures of the 1,3-diisopropoxy-p-tertbutyl calix[4]arene crown-5 fixed in the partial cone conformation and that of its potassium picrate salt have been determined by single crystal X-ray diffraction studies. Energy calculations have been performed to gain more insight on the stabilizing cation…ligand interactions. The calculation of the total potential energy indicates that the contribution which comes from the electrostatic polarization induced by the electric field of the cation on the rotated nucleus gives a net stabilizing contribution of almost 6 kcal/mol. A comparison between the molecular geometry of some partial cone 1,3-disubstituted-p-tertbutylcalix[4]arene derivatives is reported and discussed in view of the preorganization principle.

Novel monoaza- and diazacrown ethers incorporating sugar units and their extraction ability towards picrate salts

A number of new 15- and 1 8-membered ring aza-crown (4, 5, 8–13, 17, 18) and lariat ethers (6, 7) incorporating glucose or galactose units have been synthesized in good yields by a simple route. Their extracting abilities were measured with Li+, Na+, K+ and NH 4 + cations. The substituents at the nitrogen atom and the type of monosaccharide affected this property significantly.

Stereochemical factors affecting second-sphere co-ordination of ferrioxamine B with cis-syn-cis and cis-anti-cis isomers of dicyclohexano-18-crown-6 in chloroform and a comparison with alkali-metal and ammonium cations

Second-sphere co-ordination of ferrioxamine B [Fe(HL)]+ by dicyclohexano-18-crown-6 (eicosahydrodibenzo[b,k][1,4,7,10,13,16]hexaoxacyclooctadecine) occurs through host–guest complex formation with the protonated amine side chain (CH2)5NH3+. The influence of steric factors on the association constants (Ka) for both nitrate and perchlorate salts of ferrioxamine B with cis-syn-cis and cis-anti-cis isomers of dicyclohexano-18-crown-6 (CE) in CHCl3 has been investigated. For comparison purposes, association of the perchlorate salt of the indium(III) analogue of ferrioxamine B [In(HL)]+ and the picrate salts of NH4+ and alkali-metal cations are included in this study (picrate = 2,4,6-trinitrophenolate). Although the absolute values of Ka for [M(HL)]X association with CE are strongly dependent on the anion identity, the selectivity ratio expressed for the syn crown ether isomer is 3 : 1 and is independent of anion variations. Comparison with alkali-metal and ammonium cations shows that the discrimination between syn and anti isomers of cis-dicyclohexano-18-crown-6 is dependent upon cation size and is the least for K+ where the ionic radius best matches the cavity size. While syn isomer discrimination in CHCl3 is closely related to the ionic radius, in water it is related to the hydrated radius. The syn over anti isomer preference exhibited by alkali-metal and ammonium cations is much more pronounced in water than in chloroform, which is likely due to the steric hindrance imposed by the large effective radius of the cations due to their hydration shell. Discrimination between the syn and anti isomers by [M(HL)]+ in CHCl3 is greater than expected based on comparison with the parent NH4+ ion. This is likely due to the significant steric requirements of the bulky metal complex molecule. The selectivity of the syn over the anti isomer is dominated by the preference of the bulky [M(HL)]+ complex for the less hindered face of the syn isomer.

Behaviour of hydrophobic pH indicators in aqueous–organic two-phase systems

Very hydrophobic indicators can remain completely in an organic phase, even in ionized form, but nevertheless respond to the pH of an equilibrated aqueous solution. They are useful to monitor the inaccessible aqueous phase of low water media, such as may be employed in enzymic processes. We present a theoretical model for the indicator response, based on the presence of both free ions and ion pairs in the organic phase. This adequately describes the behaviour observed with C15 alkyl esters of fluorescein at concentrations around 10–5 mol dm–3, as a function of aqueous pH and cation activity or concentration. Analysis of data for toluene suggests complete ion-pairing in the organic phase, with either tetraalkylammonium ions or dibenzol-8-crown-6 and Na+. In more polar solvents Na+ counter-ions can be extracted alone: fitting of the titration curves suggests complete dissociation in pentan-3-one and butan-1-ol, but partial ion-pairing in ethyl acetate. Fitted parameters obtained from the model may be related theoretically to other literature measurements, notably for picrate salt extraction, and are generally consistent.

Computer-aided design of liquid crystal type macrocycles for sensors

Macrocyclic compounds with liquid crystal properties show an interesting potential for sensor design as phase transitions can be seen on complexation with metal ions. In this work some novel macrocyclic compounds with side chains that could show liquid crystalline properties were investigated. Selectivity was investigated by solvent extraction of metal picrate salts. Chloroform was used as the solvent and the extraction method was validated with dibenzo-18-crown-6. Extraction values were calculated from analysis of the aqueous phase for the metals ions by ICP-AES, because high values were obtained with the spectrophotometric method due to the extraction of picric acid. No extraction was seen for the long chain liquid crystalline macrocycles and this was investigated further by molecular modelling. Minimized molecular models of the macrocycles showed that the side chains wrapped around the cavity (1.510 A radius), suggesting that complexation might be sterically hindered. A short chain macrocycle was then modelled and in this case there appeared to be more favourable access to the cavity. Extraction experiments were then carried out with the short chain macrocycle for potassium, silver and sodium picrate resulting in statistically significant extraction values of 9, 5 and 3%, respectively. The selectivity in extraction could be related to the cavity size, with the best extraction being for the largest metal ion. Immobilization of the liquid crystal macrocycles in an elastomer is suggested as a way of overcoming the steric hindrance. Molecular modelling is shown to be a useful tool for designing novel compounds for sensor design.

Deprotonation, deuteriation and substitution of the backbone of some azine diphosphine complexes of palladium and platinum: crystal structures of [Ptl(PPh2CHCButN–NCButCH2PPh2)] and [PtCl(PPh2CH2CButN–NCButCH2PPh2)][OC6H2(NO2)3-2,4,6

Treatment of the azine diphosphine Z,Z-PPh2CH2CButN–NCButCH2PPh2I with [PtCl2(cod)](cod = cycloocta-1,5-diene) in CHCl3 in the presence of NEt3 gave the neutral deprotonated chloroplatinum(II) complex [[graphic omitted]Ph2)], containing an ene–hydrazone backbone. The corresponding bromo- and iodo-analogues were prepared from it by metathesis. The analogous chloropalladium(II) complex was prepared by treating I with [PdCl2(NCPh)2] in the presence of NEt3. Treatment of it with LiBr or MgMel gave the corresponding bromo- and methyl-palladium(II) complexes, respectively. Treatment of the neutral complexes [[graphic omitted]Ph2)](M = Pt or Pd) with acids (HX) reprotonated the ene–hydrazone backbone to give the salts [[graphic omitted]Ph2)]X 4[X = picrate, formate or (1S)-7,7-dimethyl-2-oxobicyclo[2.2.1]heptane-1-methanesulfonate, M = Pt or Pd]. Treatment of [[graphic omitted]Ph2)] with 0.5 equivalent of NH2NH2·2HCl gave a mixture of the nine-membered ring complex [[graphic omitted]Ph2)] and its isomerie chloride salt [[graphic omitted]Ph2)]Cl. When [[graphic omitted]Ph2)], containing a nine-membered chelate ring, was heated to 75 °C in C6H6 the methylplatnum(II) complex, [[graphic omitted]Ph2)], containing the terdentate dehydroazine ligand, was formed by oxidative addition of NH followed by reductive elimination of CH4. Treatment of the same PtMe2 complex with 1 equivalent of picric acid gave the picrate salt [[graphic omitted]Ph2)][OC6H2(NO2)3], which with 1,8-diazabicyclo[5.4.0]undec-7-ene (dbu) gave [[graphic omitted]Ph2)], and with Mel followed by NH4PF6 gave fec-[[graphic omitted]Ph2)]PF6 which with dbu gave fac-[[graphic omitted]Ph2)]. Treatment of [[graphic omitted]Ph2)] with 1 equivalent of picric acid gave [[graphic omitted]Ph2)][OC6H2(NO2)3] which with dbu gave [[graphic omitted]Ph2)]. Treatment of I with [Pt(nb)3](nb = norbornene) gave the bridged binuclear platinum(0) complex [Pt2(nb)2(µ-PPh2CH2CButN–NCButCH2PPh2)2], containing an 18-atom ring. Treatment of this with MeO2CCCCO2Me displaced the norbornene to form the corresponding bis(dimethyl acetylenedicarboxylate) complex. When the former was heated to 75 °C in benzene [[graphic omitted]Ph2)] was formed. The bis(norbornene)platinum(0) complex also underwent oxidative addition with Mel to give [[graphic omitted]Ph2)]I, which with dbu gave [[graphic omitted]Ph2)]. Methods of forming the di- and tetra-deuteriated complexes containing the azine backbone, and also mono- and tri-deuteriated complexes containing the dehydroazine backbone are discussed (M = Pt or Pd). A novel method of functionalising (e.g. alkylation and halogenation) the ligand backbone by electrophilic attack on the enamine carbon in complexes of type 4 is described. The crystal structures of [[graphic omitted]Ph2)] and [[graphic omitted]Ph2)][OC6H2(NO2)3] were determined. Proton. 31P and some 13C NMR data are given.

Synthesis, metal-binding properties and polypeptide solubilization of ‘crowned’ arborols

The first dendritic crown ether polymers (‘crowned’ arborols: G1, G2 and G3) have been synthesized and characterized. The convergent synthetic method was found to be more convenient than the divergent synthetic method. The building block in the branch was prepared from N-benzyloxycarbonyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane and 3,5-bis(ethoxycarbonylmethoxy)benzoyl chloride. Since the basic repeating unit is the amino dicarboxylic acid, one can utilize the methods developed for peptide synthesis. Final products were obtained in moderate yields by coupling of each generational fragment with a core (benzene-1,3,5-tricarbonyl trichloride) followed by reduction of all amide linkages to tertiary amine linkages by borane–dimethyl sulfide. The complexation ability of these ‘crowned’ arborols was estimated by two-phase solvent extraction of alkali picrate salts. We found that some of these arborols can solubilize proteins in organic solvents.

Ion pair affinities of linear polyethers immobilized on poly(styrene-co-m-TMI) networks

Networks (RTMI) were synthesized by radical suspension polymerization of m-isopropenyl-α,α-dimethylbenzyl isocyanate (m-TMI), styrene, and divinylbenzene. They were then reacted with methoxypoly(ethylene glycol)s of molecular weights varying from 208 to 1900. The relative affinity of the immobilized polyethers for alkali metal ions in toluene was determined spectrophotometrically with alkali metal picrates (Pi - M + ) by means of the competition equilibrium Pi - M + N + L ⇄ Pi - M + L + N, where N is the RTMI-bound polyether and L is a ligand used to solubilize the picrate salt in toluene

The complexing ability of crown ethers incorporating glucose

The complexing (in CHCl3) and extracting abilities of 18-crown-6 type compounds (1–15) were measured with Li, Na, K and NH4 cations. The substituents on the sugar part affected these properties significantly (Ka=103–107). Some substituents, like acetyloxy groups (3) decreased whereas others, like tosyloxy groups (10, 11) significantly increased the complexing ability and thus changed the selectivity. The compound with four tosyloxy groups (11) shows an excellent picrate salt extracting ability in a CH2Cl2-water system.

Synthesis and structure of the picrate salt of 2,2'-bis[2N-(1,1,3,3-tetramethylguanidino)]biphenyl

C 22 H 34 N 6 2+ .2C 6 H 2 N 3 O 7 - cristallise dans P4 1 2 1 2 1 avec a=12.372, c=25.370A, Z=4; affinement jusqu'a R=0.0572. L'angle diedre entre les deux plans des cycles benzene est de 80.4° et la longueur de la liaison intercycle C-C est de 1.466A, l'une des plus courte observee dans les biphenyls. Observation de la delocalisation de la charge positive sur les trois atomes N de la guanidine

Structure of ion pairs in solid polymer electrolytes

The known change in the optical spectrum of alkali picrates as a function of the interionic ion pair distance was used to compare the process of ion pairing in liquid and solids (polymers) of identical composition. The polymer components of the solid polymer electrolytes were chiefly comb polymers of poly(methacrylate) with pendant oligo-oxyethylene chains. Spectra of the picrate salts dissolved in the polymers and in the corresponding monomers were compared. The results show a consistent bathochromic shift for lithium and sodium picrate in the polymers relative to solutions in the monomer, suggesting increased formation of oligo-oxyethylene-complexed loose (separated) ion pairs in the solid polymers. At very high salt content only tight ion pairs are found due to insufficient chelating oxyethylene units. Addition of propylene carbonate causes a rapid rise in the fraction of free ions. The implications of our findings for the study of solid polymer electrolytes are briefly discussed.