Synthesis,structures and full characterization of p-tert-butylcalix[5]arene mono-, di-, tri- and pentaanionic ligand precursors

The synthesis, complete characterization, and solid state conformation of a new series of p-tert-butylcalix[5]arene (Bu^tC5) mono-, di-, tri- and pentaanions are reported. X-ray structures of the alkali metal salts illustrate the strong influence of the alkali metal ion on the structure of the calixanion. The strength of the alkali metal base and its reaction stoichiometry play an important role in the conformation and level of deprotonation of the resulting anion. Reaction of Bu^tC5 in a 2:1 molar ratio with alkali metal bases M₂CO₃ (M = Rb, Cs), or in a 1:1 ratio with M₂CO₃ (M = Na, K), MOH (M = Na, K, Rb, Cs) or MH (M = Li, Na) produces Bu^tC5 monoanions, but Bu^tC5 reacts in a 1:1 molar ratio with M₂CO₃ (M = Rb, Cs) or a 1:2 molar ratio with MOC(CH₃)₃ (M = Na, K) to afford Bu^tC5 dianions. Due to the steric bulkiness of the Bu^t group no polymeric structures are observed. Alkali metal salts of trianionic Bu^tC5 were obtained in high yields from reactions of Bu^tC5 with MOC(CH₃)₃ (M = Li, Na, K), BuⁿLi, LiH and LiOH in a 1:3 molar ratio. Pentaanionic Bu^tC5 salts were obtained by the reaction with MOC(CH₃)₃ (M = Li, Na, K) or BuⁿLi in a 5:1 ratio. X-ray crystal structures of Bu^tC5 · Na and Bu^tC5 · Cs indicate that the size of the alkali metal influences the level of cation-π arene interactions and therefore the conformation of the Bu^tC5 unit; for example, Bu^tC5 · Na has a cone conformation while Bu^tC5 · Cs shows a flattened cone conformation. Cation-π arene interactions are observed in most of the calixarene salts.     

A stable alkyl hydride of a first row transition metal

Hydrogenolysis of a Cr(III) dialkyl precursor produced a binuclear chromium complex with a bridging hydride and a bridging alkyl; this structurally characterized organometallic compound is thermally very stable and does not undergo the expected reductive elimination of alkane.     

Antifreeze Protein‐Induced Selective Crystallization of a New Thermodynamically and Kinetically Less Preferred Molecular Crystal

The formation of a new, dihydrate crystalline form of 5‐methyluridine (m⁵U) was selectively induced by a protein additive, antifreeze protein (AFP) in a highly efficient manner (in 10^?6 molar scale, whereas known kinetic additives need 0.1 molar scale). The hemihydrate form (form I, the only previously known crystalline form of m⁵U) and the dihydrate form of m⁵U (form II) obtained herein were characterized using X‐ray crystallography and differential scanning calorimetry (DSC). Compared to form I, remarkably, form II is thermodynamically and kinetically less preferred. The presence of AFP can selectively inhibit the appearance of form I and hence allows the growth of form II, the pure form of which cannot grow directly from m⁵U supersaturated solutions under the same conditions. An explanation supported by both experimental and theoretical results is provided for the AFP‐induced selection process. Implications on AFP‐induced ice shape changes are also discussed. Control of crystallization from supersaturated solutions is of great interest in both fundamental research and practical applications in fields like chemistry, pharmacology and materials science. These findings suggest that crystallization processes with AFPs could be valuable for selective growth of hydrates and polymorphs of important pharmaceutical compounds.     

Investigation of the quantitative properties of the quadrupole orthogonal acceleration time-of-flight mass spectrometer with electrospray ionisation using 3,4-methylenedioxymethamphetamine

This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd.     

Terphenyl cyclooctatetraenyl compounds of samarium

The syntheses and molecular structures of a number of terphenyl-based compounds of the lanthanide element samarium are reported. Reaction of 2 equiv of DppLi (Dpp = 2,6-diphenylphenyl) with 1 equiv of SmCl(3) in tetrahydrofuran at room temperature yields (Dpp)(2)SmCl(micro-Cl)Li(THF)(3) (1). The one-pot reaction of 1 equiv of K(2)COT (COT(2)(-) = cyclooctatetraenyl dianion) with 1 equiv SmCl(3) in tetrahydrofuran at room temperature followed by addition of 1 equiv of terphenyllithium salt DppLi, DmpLi (Dmp = 2,6-dimesitylphenyl), or DanipLi (Danip = 2,6-di(o-anisol)phenyl) produces DppSmCOT(micro-Cl)Li(THF)(3) (2), DmpSm(THF)COT (3), and DanipSm(THF)COT (4), respectively. In the case of the Danip-based compound 4 the order of addition of reagents can be reversed producing the same compound, however, in considerably lower yield. Compound 2 can also be prepared by reaction of 1 with 1 equiv of K(2)COT in tetrahydrofuran. The molecular structure of the bis(terphenyl) compound 1 exhibits a formally four-coordinate metal atom. The molecular structures of the terphenyl COT compounds 2-4 feature monomeric complexes which are obtained either as a lithium chloride adduct (2) or as tetrahydrofuran adducts (3, 4). In 4 the Danip ligand adopts the meso form.     

Pyrene-Appended Fluorescent Tweezers Generated via the Weak-Link Approach and Their Halide Recognition Properties

Through the Weak-Link Approach, fluorescent condensed and open Cu(I) tweezer complexes were prepared and characterized. These complexes exhibit fluorescence-sensitive binding properties for halide anions. The solid-state structure of a non-fluorescent Rh(I) tweezer analogue, determined by X-ray crystallography, shows that the counter anion, Cl⁻, is trapped inbetween the two amide groups of the tweezer arms through hydrogen bonds. Although the tweezer binds Cl⁻, the open complex also binds Cl⁻, showing that the main role of the metal is to increase the local concentration of the pyrenyl amide moieties so that 2:1 binding can take place.     

电感耦合等离子体原子发射光谱法测定钛酸钡纳米粉体中7种杂质元素

钛酸钡纳米粉体样品用盐酸溶解,在所得样品溶液中用电感耦合等离子体原子发射光谱法测定了以氧化物存在于样品中的7种杂质元素(包括镁、锶、钾、钠、铝、硅及铁),对测定的光谱条件进行了试验并优化达到上述各元素的测定上限为0.1%(质量分数).测得方法的检出限(3S/b)为(单位μg·L-1):2.0(铝),1.0(铁),20.0(钾),0.2(镁),4.0(钠),3.0(硅)及0.5(锶).应用此方法分析了两件实样,所得结果的相对标准偏差(n=6)小于等于2.0%,对其中4种杂质元素(镁、钾、钠和锶)同时用HG/T 3587-1999标准中的方法作分析校核,所得结果与此方法结果一致.     

Novel metal complexes containing a chiral trinitrogen isoindoline-based pincer ligand: in situ synthesis and structural characterization

The first synthesis and characterization of metal coordinated complexes containing in situ prepared chiral trinitrogen 1,3-bis(4,5-dihydrooxazol-2-ylimino)isoindoline-based pincer ligands are reported. Two zinc complexes, isolated as Zn(L)(2), where L = 1,3-bis(4,5-dihydro-4-(R)-phenyloxazol-2-ylimino)isoindoline ((R,R)-5) or 1,3-bis(4,5-dihydro-4-(S)-iso-propyloxazol-2-ylimino)isoindoline ((S,S)-6), respectively, are reported. Complexes Zn((R,R)-5)(2) and Zn((S,S)-6)(2) were prepared in situ through the condensation of phthalonitrile with enantiopure 2-amino-4-(R)-phenyloxazoline ((R)-3) or 2-amino-4-(S)-iso-propyloxazoline ((S)-4) in the presence of ZnCl(2) at 80 °C in dry toluene over 3-4 days. The characterizations of Zn((R,R)-5)(2) and Zn((S,S)-6)(2) in both the solid (X-ray crystallography) and solution (multinuclear NMR spectroscopy) states are reported.