Structural and magnetic diversity in tetraalkylammonium salts of anionic M[N(CN)2]3(-) (M = Mn and Ni) three-dimensional coordination polymers

Tetraalkylammonium cations, (NR4)+ (R = C3H7, C4H9, and C5H11), have been used as templates to form a new family of [M(dca)3]- [M = Mn and Ni; dca = dicyanamide or N(CN)2(-)] salts. The tetrapropylammonium (TPrA) salts possess a perovskite-type anion structure. (TPrA)[Mn(dca)3] (1) crystallizes in the tetragonal space group P42(1)c, with a = 16.2945(8) A, c = 17.4321(8) A, and V = 4628.4(6) A(3) at T = 298 K. At room temperature, (TPrA)[Ni(dca)3] (2) crystallizes in the orthorhombic space group Pnna, with a = 17.171(2) A, b = 22.992(2) A, c = 22.750(2) A, and V = 8981(2) A3, but undergoes a first-order phase transition within the temperature range 150-220 K to the tetragonal space group P42(1)c, with a = 16.0985(7) A, c = 17.0287(8) A, and V = 4413.2(5) A3 at T = 160 K. At 110 K, 2 returns to the Pnna space group with a = 17.116(2) A, b = 22.800(3) A, c = 22.641(3) A, and V = 8835(3) A3. The tetrabutylammonium (TBA) salts possess a triple rutile structure. (TBA)[Mn(dca)3] (3) crystallizes in the orthorhombic space group P2(1)2(1)2, with a = 16.0107(6) A, b = 16.0114(6), c = 21.5577(8) A, and V = 5526.4(5) A3. (TBA)[Ni(dca)3] (4) also crystallizes in the orthorhombic space group P2(1)2(1)2, with a = 15.6842(5) A, b = 15.6841(6) A, c = 21.1551(8) A, and V = 5204.0(5) A3. The tetrapentylammonium (TPnA) salts crystallize with a LiSbO3 structure type, space group Pnna. Lattice parameters for (TPnA)[Mn(dca)3] (5) are a = 13.2236(6) A, b = 11.6300(6) A, c = 20.3176(9) A, and V = 3124.6(4) A3, and for (TPnA)[Ni(dca)3] (6), a = 12.9380(4) A, b = 11.6233(4) A, c = 19.8038(7) A, and V = 2978.1(2) A3. Long-range antiferromagnetic ordering has been observed in the manganese salts below 2.1 K, as indicated by alternating current susceptibility measurements. Magnetic susceptibility data for the nickel salts do not show evidence for long-range magnetic ordering but can be described using an S = 1 zero-field splitting model with the exchange Hamiltonian H = -J sigma(S(i)S(i+1)) + D sigma((S(i)z)2) + g mu(beta)B sigma(S(i)), giving absolute value(D)/kB values that range between 1.98(1) K and 3.20(2) K.     

Poly[tetraphenylphosphonium copper(I)‐di‐μ2‐dicyanamido]

In the title compound, {(C₂₄H₂₀P)[Cu(C₂N₃)₂]}_n, the copper(I) dicyanamide anion forms a distorted three‐dimensional single diamondoid network. Templating tetraphenylphosphonium cations reside within the cavities of the polymeric anion.     

Spin canting in the 3D anionic dicyanamide structure (SPh(3))Mn(dca)(3) (Ph = phenyl, dca = dicyanamide)

Through use of the SPh(3)(+) (Ph = phenyl, C(6)H(5)) cation as a molecular template, a new three-dimensional Mn(dca)(3)(-) [dca = dicyanamide, N(CN)(2)(-)] anionic structure has been crystallized. At room temperature, (SPh(3))Mn(dca)(3) (1) crystallizes in the monoclinic space group P2(1)/c, with a = 11.7079(5) A, b = 12.8554(5) A, c = 16.8605(6) A, beta = 100.666(2) degrees, and V = 2493.8(3) A(3). Magnetic susceptibility measurements indicate that this salt exhibits a spin canted long range antiferromagnetically ordered ground state below 2.5 K.     

Influence of electrolyte nature on the separation selectivity of amphetamines in nonaqueous capillary electrophoresis: protonation degree versus ion pairing effects

The simultaneous analysis of Ecstasy and its derivatives in an acetonitrile-methanol (80:20 v/v) mixture was previously shown to be strongly dependent on the nature of the electrolyte (acetate versus formate). To elucidate the phenomena involved, systematic experiments were conducted in this solvent medium. Conductivity measurements allowed to evaluate the ion-pairing rate in the background electrolyte (BGE) and thereby distinguish between electrolyte concentration and ionic strength. The influence of electrolyte concentration on analyte effective mobilities micro(eff)) was studied by capillary electrophoresis (CE). As micro(eff) extrapolated to infinite dilution proved to be independent of the nature of the electrolyte, selectivity changes could not be attributed to a modification in the protonation degree of amphetamines. Experimental mobility data were then confronted to existing theoretical mobility models to discriminate between ion pairing or simple ionic strength effect. Ion-pair formation in a BGE containing acetate was highlighted with an ion-pairing model and ion-pair formation constants between each amphetamine and acetate ion were calculated.     

Potential of formamide and N-methylformamide in nonaqueous capillary electrophoresis coupled to electrospray ionization mass spectrometry. Application to the analysis of beta-blockers

A nonaqueous capillary electrophoresis (NACE) method, coupled with either UV or electrospray mass spectrometry (ESI-MS), is described for the simultaneous analysis of seven beta-blockers. The same electrolyte, namely 25 mM ammonium formate and 1 M formic acid, was used with different investigated organic solvents. In addition to frequently used organic solvents such as methanol (MeOH) and acetonitrile (MeCN), formamide and its derivatives were investigated. Formamide (FA) and N-methylformamide (NMF) present several interesting physico-chemical properties, one of them being a high dielectric constant (e). Since FA and NMF possess a high UV cutoff, beta-blockers with an absorbance above 250 nm were selected as model compounds in order to compare NACE-UV and NACE-MS performances. FA and NMF showed different selectivity compared to water, MeOH or MeCN, and also demonstrated a higher efficiency in terms of the number of theoretical plates (especially NMF). To overcome their unfavorable optical properties, hyphenation with MS detection appears as a promising technique, thanks to its benefits in terms of selectivity, sensitivity and universality. The practical compatibility of FA and NMF with ESI-MS detection in combination with a sheath liquid configuration was demonstrated. In comparison to UV detection, sensitivity was increased, while a high efficiency was maintained. In addition, the low and stable generated currents observed were evidences for the successful hyphenation with ESI-MS. Hence, FA and NMF seemed to be promising alternatives in NACE-ESI-MS, either used as pure organic solvent or as a mixture with MeOH or MeCN.     

Vortex penetration depth of κ-(ET)2Cu[N(CN)2]Br

The magnetic field dependence of the in-plane penetration depth λ_|(H) for single crystal κ-(ET)₂Cu[N(CN)₂]Br has been measured at 3, 9.6, and 36 MHz. Over a limited range, λ_| scales with a characteristic field that coincides with a shoulder in the λ_| vs. H curves. Above that field, λ_| increases sharply toward a second inflection point at that coincides with is close to the irreversibility line measured by magnetization. For fields larger than the penetration depth diverges, suggesting that the vortex lattice has melted. The field dependence at one frequency agrees qualitatively with a model of pinned vortices at low fields giving way to flux flow at higher fields. However, the observed frequency dependence deviates significantly from the predictions of this model, suggesting that collective effects play a major role. Our technique also yields a new measurement for the interplane penetration depth λ_⊥ ∼ 300 μm, implying an anisotropy .     

Poly[μ4‐sulfido‐tris(thiocyanato‐κN)tris(μ3‐1,2,4‐triazolato‐κ3N1:N2:N4)tetrazinc(II)]: a three‐dimensional zinc sulfide coordination polymer

The title compound, [Zn₄(C₂H₂N₃)₃(NCS)₃S]_n, is a three‐dimensional coordination polymer consisting of tetrahedral SZn₄ clusters bridged by triazole ligands. In the tetrahedral unit, three Zn atoms are connected to six bridging triazolate ligands, whereas the fourth Zn atom (site symmetry 3m) is bonded to three terminal thiocyanate anions that protrude into the void space created by the Zn–triazolate network. The network prototype is simple cubic, but a strong distortion along a body diagonal and the imposition of a polar direction by the arrangement of the molecular constituents lead to the trigonal space group R3m. This study demonstrates the use of the 3‐mercapto‐1,2,4‐triazole ligand as an effective source for sulfide ions in the synthesis of sulfide‐based coordination polymers.     

Particles at the airway interfaces of the lung

Inhaled particles may land on the surface of the lung’s airspaces. Upon making contact with the airway wall, the processes of retention and clearance begin. Particle retention depends on many factors; among these are: (1) particle size, shape, solubility, surface chemistry and elastic properties of both the particles and the lung surface. (2) The anatomical location of the deposition site. (3) The structures with which the particle interacts at the site of deposition, including the surfactant film at the air–liquid interface, the aqueous phase, free cells like macrophages, lymphocytes and granulocytes, the epithelial cells and dendritic cells that reside at the basal side of the epithelium. Particles, after their deposition are wetted and displaced towards the epithelium by the surfactant film during the retention process. In vitro experiments have demonstrated that the extent of particle immersion depends on the surface tension of the surfactant film. The lower the surface tension, the greater is the immersion of the particles into the aqueous phase. Experimental results demonstrate consistently greater immersion of smaller particles into a liquid substrate covered with a surfactant film than that for larger particles. The exact mechanism, especially the initial wetting process, is not yet understood and requires further experiments. Line tension is a possible explanation for the dependence of particle displacement on particle size.     

Optimization of the porous structure and polarity of polymethacrylate-based monolithic capillary columns for the LC-MS separation of enzymatic digests

The porous structure as well as the polarity of methacrylate ester-based monolithic stationary phases has been optimized to achieve the separation of various peptides originating from enzymatic digestion. The porous structure, determined by the size of both pores and microglobules, was varied through changes in the composition of porogenic solvents in the polymerization mixture, while the polarity was controlled through the incorporation of butyl, lauryl, or octadecyl methacrylate in the polymer backbone. Both the morphology and the chemistry of the monoliths had a significant effect on the retention and efficiency of the capillary columns. The best resolution of peptidic fragments obtained by digestion of Cytochrome c with trypsin in solution was obtained in a gradient LC-MS mode using a monolithic capillary column of poly(lauryl methacrylate-co-ethylene dimethacrylate) featuring small pores and small microglobules. Raising the temperature from 25 to 60 degrees C enabled separations to be carried out at 40% higher flow rates. Separations carried out at 60 degrees C with a steeper gradient proceeded without loss of performance in half the time required for a comparable separation at room temperature. Our preparation technique affords monolithic columns with excellent column-to-column and run-to-run repeatability of retention times and pressure drops.