Aurophilic interactions in cationic gold complexes with two isocyanide ligands. Polymorphic yellow and colorless forms of [(cyclohexyl isocyanide)2AuI](PF6) with distinct luminescence

Crystallographic studies of yellow and colorless forms of [(C(6)H(11)NC)(2)Au(I)](PF(6)) show that they are polymorphs with differing, but close, contacts between the gold atoms which form extended chains. In the colorless polymorph the gold cations form linear chains with a short Au...Au contact (3.1822(3) A) indicative of an aurophilic attraction. The structure of the yellow polymorph is more complicated with four independent cations forming kinked, slightly helical chains with very short Au...Au contacts of 2.9803(6), 2.9790(6), 2.9651(6), and 2.9643(6) A. However, in the related compound, [(CH(3)NC)(2)Au(I)](PF(6)), each cation is surrounded by six hexafluorophosphate ions and there is no close Au...Au contact despite the fact that the isocyanide ligand has less steric bulk. The crystalline colorless and yellow polymorphs are both luminescent at 298 K, lambda(max): 424 nm (colorless) or 480 nm (yellow). Colorless solutions of the two polymorphs have identical absorption spectra and are nonluminescent at room temperature. Freezing solutions of [(C(6)H(11)NC)(2)Au(I)](PF(6)) produces intense luminescence which varies depending upon the solvent involved. Each polymorph melts to give a colorless but luminescent liquid which reverts to the yellow polymorph upon cooling.     

Discontinuous and continuous separation of the monomeric and dimeric forms of human bone morphogenetic protein-2 from renaturation batches

Bone morphogenetic protein-2 (BMP-2) is one of the most interesting of the approximately 14 BMPs which belong to the transforming-growth-factor-beta (TGF-beta) superfamily. BMP-2 induces bone formation and thus plays an important role as a pharmaceutical protein. Recently, rhBMP-2 has been produced in form of inactive inclusion bodies in Escherichia coli. After solubilization and renaturation the biologically active dimeric form of rhBMP-2 can be generated. However, inactive monomers of BMP-2 are also formed during the renaturation process which must be separated from the active dimeric BMP-2. The purpose of this paper is to present: (a) results of an experimental study of a chromatographic separation of the monomeric and dimeric forms; and (b) a concept for a continuous counter-current simulated moving bed (SMB) process. The capacity of heparin as stationary phase was estimated for different salt concentrations in the mobile phase. A simulation study of a three-zone SMB process was performed applying a two step salt gradient. The results reveal the potential of the process for the purification of the dimeric BMP-2.     

Micellization of monomeric and dimeric (gemini) surfactants in polar nonaqueous-water-mixed solvents

Dimeric or gemini surfactants are novel surfactants that are finding a great deal of discussion in the academic and industrial arena. They consist of two hydrophobic chains and two polar head groups covalently linked by a spacer. Data on critical micelle concentration (cmc) and degree of counterion dissociation (α) are reported on bis-cationic C₁₆H₃₃N⁺(CH₃)₂–(CH₂)_s–N⁺(CH₃)₂C₁₆H₃₃, 2Br⁻, referred to as 16-s-16, for spacer lengths s=4, 5, 6 in aqueous and in polar nonaqueous (1-propanol, 2-methoxyethanol or methyl cellosolve, dimethyl sulfoxide, acetonitrile)-water-mixed solvents. The behavior is compared with conventional monomeric surfactant cetyltrimethylammonium bromide (CTAB). Thermodynamic parameters are obtained from the temperature dependence of the cmc values. It is observed that micellization tendency of the surfactants decreases in the presence of polar nonaqueous solvents. However, detailed studies with dimethylsulfoxide (DMSO) show that the geminis nearly outclass the micellization-arresting property of this solvent. Also, within geminis, higher spacer length is found suitable for showing micellization even with high DMSO content (50% v/v). The implications of these results of gemini micellization may be useful in micellar catalysis in polar nonaqueous solvents.     

Adventures in crystallization. Crystalline salts containing one, two, or even three chemically distinct cations obtained from solutions of [(cyclohexyl isocyanide)(4)Rh(I)]+

By judicious selection of crystallization conditions, it has been possible to obtain the salts of a common building block, [(RNC)4Rh(I)]+, in single-crystal form suitable for X-ray diffraction. Salts that contain a single type of cation include deep green [(C6H11NC)12Rh(I)3](SbF6)3, deep green [(C6H11NC)12Rh(I)3](AsF6)3, and straw yellow [(C6H11NC)8Rh(II)2Cl2](BF4)2 (in addition to the previously isolated trimeric deep green [(i-PrNC)12RhI3]Cl3 x 4.5 H2O, monomeric, [(C6H11NC)4 Rh(I)](BPh4), and [(i-PrNC)4Rh(I)](BPh4) (both yellow), and red, dimeric [(C6H11NC)8Rh(I)2]Cl2 x 0.5C6H6 x 2H2O). Ordered crystals of [(C6H11NC)12Rh(I)3](SbF6)3 contain linear Rh3 units, while those of [(C6H11NC)12Rh(I)3](AsF6)3 show disorder which is consistent with the presence of linear or bent Rh3 units. The formation of green [(C6H11NC)12Rh(V/III)3Cl2][(C6H11NC)12Rh(I)3]Cl6, and brown [(C6H11NC)12Rh(V/III)3Cl2][(C6H11NC)8Rh(I)2][(C6H11NC)4RhI]Cl6 x 16H2O x 3C6H6 along with unidentified red-brown cubes from an air-exposed solution of [(C6H11NC)4Rh(I)]Cl is reported. As their formulas indicate, green [(C6H11NC)12Rh(V/III)3Cl2][(C6H11NC)12Rh(I)3]Cl6, and brown [(C6H11NC)12Rh(V/III)3Cl2][(C6H11NC)8Rh(I)2][(C6H11NC)8Rh(I)]Cl6 x 16H2O x 3C6H6 contain two or three chemically distinct cations, respectively, but again are built from a common precursor, [(C6H11NC)4Rh(I)]+.     

Controlled synthesis of polymethylene-b-poly(ethylene glycol) as well as its crystallization and self-assembly behavior

Polymethylene-b-poly(ethylene glycol) (PM-b-PEG) with different block length ratio was synthesized by a combination of polyhomologation and coupling reaction. The effect of hydrophilic and hydrophobic block length on the crystallization process and self-assembly behavior of PM-b-PEG was self-assembled were investigated. The results showed that with the increase of methylene units, the crystallization temperature of PM block raised from 54.59?°C to 70.93?°C gradually, while that of the PEG block reduced from 17.54?°C to 15.23?°C. In addition, the amphiphilic PM-b-PEG was self-assembled into star-like micelles in water, and its diameter extended from 98.2?nm to 151.9?nm as the block length of hydrophobic PM increased from 30 to 70. And the micelles also exhibit super stability when the concentration of copolymer precursor is 0.50?～?0.90?mg/ml and the storage temperature lies in the range of 25?～?60?°C.     

Unexpected reactivity of 2-fluoro-4-(trifluoromethyl)-phenylacetonitrile: isolation and characterization of a trimeric impurity

An uncommon reactivity of 2-fluoro-4-(trifluoromethyl)-phenylacetonitrile, with the loss of three fluorine atoms, is herein reported, the resulting trimeric compound was isolated and characterized by NMR and MS/MS studies. An unprecedented mechanism has been proposed.     

RPTLC Determination of the Lipophilicity of Some New N-[(4-Arylpiperazin-1-yl)alkyl] spirosuccinimides

JPC – Journal of Planar Chromatography – Modern TLC - The lipophilicity of thirty-seven N-[(4-arylpiperazin-1-yl)alkyl]-2- azaspiro[4.4]nonane- and [4.5]decane-1,3-dione derivatives has...     

Different coordination modes of tetradentate Schiff bases in monomeric and dimeric oxorhenium(V) complexes

The reactions of the tetradentate amine-phenol type Schiff bases H₂sal₂en (1,2-ethylenebis(salicylideneimine) and H₂sal₂mp (1,2-benzylenebis(salicylideneimine)) with trans-[ReOCl₃(PPh₃)₂] or (n-Bu₄N)[ReOCl₄] in air gave the products (µ-O)[ReO(sal₂en)]₂ (1) and [ReOCl(sal₂mp)] (2), respectively. X-ray and spectroscopic studies have shown that 1 contains the linear O=Re–O–Re=O grouping, with the four donor atoms of sal₂en^2? coordinating in the square plane cis to the oxo ions. In 2, a cis oxo-chloro arrangement is observed with a phenolic oxygen being coordinated trans to the oxo group. The terminal Re=O bond lengths in 1 and 2 are 1.709(4) and 1.683(3)?Å, respectively.     

肉豆蔻中赭曲霉毒素的测定及赭曲霉毒素产毒菌的分离鉴定

建立了同时测定肉豆蔻中3种赭曲霉毒素的超高效液相色谱-串联质谱法(UPLC-MS/MS).样品经70％甲醇超声提取,HLB柱净化,采用Agilent Proshell 120 EC C18色谱柱,以乙腈(含0.1％甲酸)-水(含0.1％甲酸)为流动相进行梯度洗脱,于电喷雾离子源正负离子模式下多反应监测模式检测.结果表明...     

Enthalpy changes in oxidative addition reactions of iodine with monomeric and dimeric rhodium(I) complexes

The heat of reaction for addition of iodine to the planar complexes RhCl(CO)dppe, Rh(dppen)₂⁺, Rh(dppe)₂⁺ and to the dimer Rh₂Cl₂(CO)₂(dppm)₂ has been obtained by a calorimetric method. Iodine forms stronger Rh---I bonds with RhCl(CO)dppe than with the bichelate complexes. The presence of metal-metal interaction in the iodine addition compound of Rh₂Cl₂(CO)₂(dppm)₂ makes a significant contribution to the enthalpy change for the oxidative addition. The stereochemistry of the complexes are discussed on the basis of IR and ³¹P NMR spectra.     

New structural motifs in the aggregation of neutral gold(I) complexes: structures and luminescence from (alkyl isocyanide)AuCN

The preparation and X-ray crystal structures of (CyNC)Au(I)CN, (n-BuNC)Au(I)CN, and (i-PrNC)Au(I)CN.0.5CH(2)Cl(2) are reported and compared with those of (MeNC)Au(I)CN and (t-BuNC)Au(I)CN, which were previously described. These linear molecules are all organized through aurophilic interactions into three structural classes: simple chains ((CyNC)Au(I)CN and (t-BuNC)Au(I)CN), side-by-side chains in which two strands make Au...Au contact with each other ((n-BuNC)Au(I)CN), and nets in which multiple aurophilic interactions produce layers of gold(I) centers ((i-PrNC)Au(I)CN and (MeNC)Au(I)CN). All of these five solids dissolve to produce colorless, nonluminescent solutions with similar UV/vis spectra. However, each of the solids displays a unique luminescence with emission maxima occurring in the range 371-430 nm.     

The site of ionization in the acetylation of aliphatic esters by [(CH3CO)3]+

A series of esters RCOOR′ (where R, R′ = CH₃, CH₃CH₂, (CH₃)₂CH, (CH₃)₃C) were reacted with the [(CH₃CO)₃]⁺ ion from biacetyl in an ion cyclotron resonance spectrometer. A steric effect influences the rate of formation of stable products [RCOOR′·CH₃CO]⁺ and is used to determine that either oxygen of the ester may be initially acylated by [(CH₃CO)₃]⁺.     

Alkylation of the inverted porphyrin nickel(II) complex by dihalogenalkanes: formation of monomeric and dimeric derivatives

An efficient and simple method of modification of "inverted" porphyrin is provided by reactions of 5,10,15,20-tetraaryl-2-aza-21-carbaporphyrinatonickel(II) 2 with dihalogenalkanes under basic conditions. The substituents are bound to the internal carbon or external nitrogen of the inverted pyrrole depending on dihalogenalkane and basic catalyst. The monomeric 2- or 21-ethoxymethyl-substituted species are formed in the reaction of 2 with dihalomethanes and sodium ethoxide or ethanol in the presence of K(2)CO(3). A novel, dimeric 21,21'-ethylene-linked derivative 11 is obtained from 2 and ethylene bromide in dichloromethane in the presence of potassium carbonate end ethanol, while application of potassium tert-butoxide promotes formation of N-bromoethyl-substituted monomer 12. Reaction of 2 with propylene bromide in the presence of proton scavenger efficiently leads to the 21-allyl-substituted monomer 14 that is a product of the HBr elimination from a transient 21-bromopropyl-substituted species. The new compounds have been identified and characterized by means of mass spectrometry and optical and NMR spectroscopies. A single-crystal X-ray analysis performed for 12 allows discussion of structural parameters concerning the macrocycle and coordination core. Formation of deprotonated species [2](-), which is proposed as a key intermediate in the alkylation reaction, has been observed spectroscopically. Chirality of the N-substituted derivatives induced by protonation of the internal carbon is observed by NMR at low temperatures.     

Tannins of cornaceous plants. I. Cornusiins A, B and C, dimeric monomeric and trimeric hydrolyzable tannins from Cornus officinalis, and orientation of valoneoyl group in related tannins

Cornusiin A (1), cornusiin B (2) and cornusiin C (3), new dimeric, monomeric and trimeric hydrolyzable tannins, were isolated from the fruits of Cornus officinalis (Cornaceae). Their structures, including the orientation of the valoneoyl group in 1 and 3, were established on the basis of chemical and spectroscopic data. 2,3-Di-O-galloyl-D-glucose (7), 1,2,3-tri-O-galloyl-beta-D-glucose, 1,2,6-tri-O-galloyl-beta-D-glucose, 1,2,3,6-tetra-O-galloyl-beta-D-glucose, gemin D (5), isoterchebin, tellimagrandin I (6) and tellimagrandin II were also isolated from the fruits. The orientation of the valoneoyl group in camptothin A (14) and that in camptothin B (15), which had been isolated from Camptotheca acuminata (Nyssaceae), were also determined based on that in 1.     

Synthesis, structure, and properties of a dimeric chromium(II) pyrazolato complex with a long chromium-chromium distance. Maintenance of a dimeric structure in solution and interconversion between dimeric and monomeric structures

The synthesis, solid-state structure, and solution structure of Cr2(tBu2pz)4 are described. This complex is obtained by sublimation of the monomeric species Cr(tBu2pz)2(4-tBupy)2 and contains long chromium-chromium distances that are enforced by the divergent nature of the pyrazolato ligands.     

The exocyclic functionalisation of bis(thiosemicarbazonate) complexes of zinc and copper: the synthesis of monomeric and dimeric species

This paper reports the synthesis of bimetallic zinc thiosemicarbazone complexes with rigid aromatic linkers, using either 1,3- or 1,4- benzenediamines or 1,3- or 1,4- benzenedialdehydes as the basis of the linking groups. Non-rigid aliphatic diamines and dialdehydes were also used to link the zinc chelating units. Reaction of a bis(thiosemicarbazone) with a pendant NHNH(2) group with monoaldehydes or ketones gives a range of monomeric complexes with exocylic imine groups bearing a range of substituents. The zinc complexes can be quantitatively and rapidly transmetallated to the corresponding copper complexes and this route or direct reaction with the free ligand can be used to radiolabel the monomeric species with (64)Cu. In vivo and in vitro studies of one of the (64)Cu imine complexes shows substantial hypoxic selectivity and high tumour uptake in a murine model.     

Mechanisms of catalyst poisoning in palladium-catalyzed cyanation of haloarenes. remarkably facile C-N bond activation in the [(Ph3P)4Pd]/[Bu4N]+ CN- system

Reaction paths leading to palladium catalyst deactivation during cyanation of haloarenes (eq 1) have been identified and studied. Each key step of the catalytic loop (Scheme 1) can be disrupted by excess cyanide, including ArX oxidative addition, X/CN exchange, and ArCN reductive elimination. The catalytic reaction is terminated via the facile formation of inactive [(CN)4Pd]2-, [(CN)3PdH]2-, and [(CN)3PdAr]2-. Moisture is particularly harmful to the catalysis because of facile CN- hydrolysis to HCN that is highly reactive toward Pd(0). Depending on conditions, the reaction of [(Ph3P)4Pd] with HCN in the presence of extra CN- can give rise to [(CN)4Pd]2- and/or the remarkably stable new hydride [(CN)3PdH]2- (NMR, X-ray). The X/CN exchange and reductive elimination steps are vulnerable to excess CN- because of facile phosphine displacement leading to stable [(CN)3PdAr]2- that can undergo ArCN reductive elimination only in the absence of extra CN-. When a quaternary ammonium cation such as [Bu4N]+ is used as a phase-transfer agent for the cyanation reaction, C-N bond cleavage in the cation can occur via two different processes. In the presence of trace water, CN- hydrolysis yields HCN that reacts with Pd(0) to give [(CN)3PdH]2-. This also releases highly active OH- that causes Hofmann elimination of [Bu4N]+ to give Bu3N, 1-butene, and water. This decomposition mode is therefore catalytic in H2O. Under anhydrous conditions, the formation of a new species, [(CN)3PdBu]2-, is observed, and experimental studies suggest that electron-rich mixed cyano phosphine Pd(0) species are responsible for this unusual reaction. A combination of experimental (kinetics, labeling) and computational studies demonstrate that in this case C-N activation occurs via an S(N)2-type displacement of amine and rule out alternative 3-center C-N oxidative addition or Hofmann elimination processes.     

[(C6F5)2IF2][BF4], the First Salt with the Electrophilic Cation [(C6F5)2IF2]+: Synthesis,Reactivity, and Structure

The substitution of hypervalently bonded fluorine atoms in C₆F₅IF₄ was performed with C₆F₅BF₂ and resulted in the new salt [(C₆F₅)₂IF₂][BF₄]. The iodonium(V) salt was characterized by multi‐NMR and Raman spectroscopy and X‐ray crystal structure analysis. The fluorinating ability of the new electrophilic cation [(C₆F₅)₂IF₂]⁺ was exemplified in reactions with monovalent iodine compounds (C₆F₅I, p‐FC₆H₄I, and I₂) and with electron‐poor tri(organyl)pnictanes ER₃ (E = P, As, Sb, Bi; R = C₆F₅). In a heterogeneous reaction with CsF in MeCN the [(C₆F₅)₂IF₂]⁺ cation forms the dinuclear [{(C₆F₅)₂IF₂}₂F]⁺ cation.     

Acrylamide derivatives as antiallergic agents. I. Synthesis and structure-activity relationships of N-[(4-substituted 1-piperazinyl)alkyl]-3-(aryl and heteroaryl)acrylamides

A new series of acrylamide derivatives (7-10) were synthesized. Antiallergic activity of these compounds was evaluated and their structure-activity relationships were examined. Compound 10d, N-[4-(4-diphenylmethyl-1-piperazinyl)butyl]-3-(3-pyridyl)acrylamid e, showed antiallergic activity equivalent or superior to that of ketotifen in the rat passive cutaneous anaphylaxis (PCA) test by oral administration. Compound 10d, unlike ketotifen, had more potent in vitro 5-lipoxygenase inhibitory activity than caffeic acid, whereas its in vitro antihistamine activity was weaker than that of ketotifen. In addition, its inhibitory activity against histamine release from rat mast cells was approximately two-thirds as potent as that of disodium cromoglycate (DSCG). Compound 10d is a promising agent for treating a variety of allergic diseases.     

Supernucleophilic systems based on functionalized surfactants in the decomposition of 4-nitrophenyl esters derived from phosphorus and sulfur acids: II. Influence of the length of hydrophobic alkyl substituents on micellar effects of functionalized monomeric and dimeric imidazolium surfactants

New dimeric functionalized surfactants, 3,3′-[2-(hydroxyimino)propan-1,3-diyl]bis(1-alkyl-1H-imidazol-3-ium) dichlorides (Alk = C₁₂H₂₅, C₁₄H₂₉, C₁₆H₃₃), underlie the supernucleophilic microorganized systems capable of abnormally fast cleavage of acyl-containing substrates. Micellar effects both of monomeric and dimeric imidazolium surfactants in the cleavage processes of 4-nitrophenyl esters of diethylphosphonic, diethylphosphoric, and 4-toluenesulfonic acids are governed mostly by the hydrophobicity of the reaction components (acceleration ～10²–10³ times). The unquestionable advantage of dimeric surfactants is their especially low critical micelle concentrations (≤10^?5 mol L^?1), providing a possibility to attain the same micellar effects at the surfactant concentration lower by an order of magnitude (and yet even lower) than in the case of monomeric analogs.