CNN Pincer Ruthenium Catalysts for Hydrogenation and Transfer Hydrogenation of Ketones: Experimental and Computational Studies

Reaction of [RuCl(CNN)(dppb)] ( 1‐Cl ) (HCNN=2‐aminomethyl‐6‐(4‐methylphenyl)pyridine; dppb=Ph₂P(CH₂)₄PPh₂) with NaOCH₂CF₃ leads to the amine‐alkoxide [Ru(CNN)(OCH₂CF₃)(dppb)] ( 1‐OCH₂CF₃ ), whose neutron diffraction study reveals a short RuO ??? HN bond length. Treatment of 1‐Cl with NaOEt and EtOH affords the alkoxide [Ru(CNN)(OEt)(dppb)] ? (EtOH)_n ( 1‐OEt?n EtOH ), which equilibrates with the hydride [RuH(CNN)(dppb)] ( 1‐H ) and acetaldehyde. Compound 1‐OEt?n EtOH reacts reversibly with H₂ leading to 1‐H and EtOH through dihydrogen splitting. NMR spectroscopic studies on 1‐OEt?n EtOH and 1‐H reveal hydrogen bond interactions and exchange processes. The chloride 1‐Cl catalyzes the hydrogenation (5 atm of H₂) of ketones to alcohols (turnover frequency (TOF) up to 6.5×10⁴ h^?1, 40 °C). DFT calculations were performed on the reaction of [RuH(CNN′)(dmpb)] ( 2‐H ) (HCNN′=2‐aminomethyl‐6‐(phenyl)pyridine; dmpb=Me₂P(CH₂)₄PMe₂) with acetone and with one molecule of 2‐propanol, in alcohol, with the alkoxide complex being the most stable species. In the first step, the Ru‐hydride transfers one hydrogen atom to the carbon of the ketone, whereas the second hydrogen transfer from NH₂ is mediated by the alcohol and leads to the key “amide” intermediate. Regeneration of the hydride complex may occur by reaction with 2‐propanol or with H₂; both pathways have low barriers and are alcohol assisted.     

Rational Design of Specific Recognition Molecules for Simultaneously Monitoring of Endogenous Polysulfide and Hydrogen Sulfide in the Mouse Brain

A biosensor was created for the simultaneous monitoring of endogenous H₂S_n and H₂S in mouse brains and exploring their roles in activation of the TRPA1 channel under two types of brain disease models: ischemia and Alzheimer's disease (AD). Based on DFT calculations and electrochemical measurements, two probes, 3,4‐bis((2‐fluoro‐5‐nitrobenzoyl)oxy)‐benzoic acid (M_PS‐1) and N‐(4‐(2,5‐dinitrophenoxy) phenyl)‐5‐(1, 2‐dithiolan‐3‐yl)pentanamide (M_HS‐1), were synthesized for specific recognition of H₂S_n and H₂S. Through co‐assembly of the two probes at the mesoporous gold film with good anti‐biofouling ability and electrocatalytic activity, this microsensor showed high selectivity for H₂S_n and H₂S against potential biological interferences. The biosensor can simultaneously determine the concentration of H₂S_n from 0.2 to 50 μm , as well as that of H₂S from 0.2 to 40 μm . The expression of TRPA1 protein positively correlated with levels of H₂S_n under both ischemia and AD.     

Peptide Conjugates for Directing the Morphology and Assembly of 1D Nanoparticle Superstructures

Designed peptide conjugates molecules are used to direct the synthesis and assembly of gold nanoparticles into complex 1D nanoparticle superstructures with various morphologies. Four peptide conjugates, each based on the gold‐binding peptide (AYSSGAPPMPPF; PEP_Au), are prepared: C₁₂H₂₃O‐AYSSGAPPMPP ( 1 ), C₁₂H₂₃O‐AYSSGAPPMPPF ( 2 ), C₁₂H₂₃O‐AYSSGAPPMPPFF ( 3 ), and C₁₂H₂₃O‐AYSSGAPPMPPFFF ( 4 ). The affect that C‐terminal hydrophobic F residues have on both the soft‐assembly of the peptide conjugates and the resulting assembly of gold nanoparticle superstructures is examined. It is shown that the addition of two C‐terminal F residues ( 3 ) leads to thick, branched 1D gold nanoparticle superstructures, whereas the addition of three C‐terminal F residues ( 4 ) leads to bundling of thin 1D nanoparticle superstructures.     

Magnetically polymeric nanocarriers for targeting delivery of curcumin and hyperthermia treatments toward cancer cells

Magnetically polymeric nanocarriers, Cur‐FA‐SAMN, were designed and synthesized for targeting, therapeutic treatments to cancer cells. Amine‐group immobilized iron oxides, Fe₃O₄‐NH₂, were attached on the surface of self‐assembled tri‐block copolymer, poly[(acrylic acid)‐block‐(N‐isopropylacrylamide)‐block‐(acrylic acid)] synthesized via reversible addition‐fragmentation chain‐transfer polymerization. For the purpose of targeting effect, folic acid was grafted on the surface of Fe₃O₄‐NH₂ attached nanoparticles. The nanocarriers were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, vibrating sample magnetometer, and UV‐Vis spectral analysis. Therefore, a hydrophobic anti‐cancer drug, curcumin, gained water dispersity, and stable storage via encapsulating into and on the magnetically polymeric nanocarriers, and the release behaviors were studied in vitro, with and without high frequency magnetic field. Biocompatibility and cytotoxicity of inherent and curcumin‐loaded nanocarriers were investigated by MTT assay. Results displayed that our nanocarriers have no cytotoxicity while curcumin‐loaded nanocarriers offered significant death to MCF‐7, human breast camcer cells. Intracellular‐uptake experiments demonstrated tremendous uptake and the destroying effect to MCF‐7 cells, most of the cancer cells were killed and the surviving ones were surrounded by the curcumin‐loaded nanocarriers. According to the aforementioned characteristics, these magnetically polymeric nanocarriers will be able to apply as a potential device for practical therapy. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2706–2713     

Aminotroponiminate and a Related Diimine as Ligands for Tungsten Complexes

Reaction of N‐isopropyl‐2‐(isopropylamino)troponimine, {(i‐Pr)₂ATI}H, with fac‐[W(CO)₃(NCMe)₃] yield the complex tungsten‐tetracarbonyl‐N, N'‐diisopropyl‐1, 2‐diimino‐3, 5‐cycloheptadiene ( 1 ), in which the ligand is tautomerized from the enamino to the imino isomer. As a result of the rearrangement the conjugate 10 π electron system of the ligand is destroyed. Further, treatment of compound 1 with an excess of KH in THF leads to the ionic complex [K(THF)₂][{(i‐Pr)₂ATI}W(CO)₄] ( 2 ). In the presence of diglyme the corresponding complex [K(diglyme)₂][{(i‐Pr)₂ATI}W(CO)₄] ( 3 ) is obtained. All compounds have been characterized by spectroscopic methods. Complex 1 has also been investigated by single crystal X‐ray diffraction.     

A Cation and Anion Dual Doping Strategy for the Elevation of Titanium Redox Potential for High‐Power Sodium‐Ion Batteries

Titanium‐based polyanions have been intensively investigated for sodium‐ion batteries owing to their superior structural stability and thermal safety. However, their low working potential hindered further applications. Now, a cation and anion dual doping strategy is used to boost the redox potential of Ti‐based cathodes of Na₃Ti_0.5V_0.5(PO₃)₃N as a new cathode material for sodium ion batteries. Both the Ti³⁺/Ti⁴⁺ and V³⁺/V⁴⁺ redox couples are reversibly accessed, leading to two distinctive voltage platforms at ca. 3.3 V and ca. 3.8 V, respectively. The remarkably improved cycling stability (86.3 %, 3000 cycles) can be ascribed to the near‐zero volume strain in this unusual cubic symmetry, which has been demonstrated by in situ synchrotron‐based X‐ray diffraction. First‐principles calculations reveal its well‐interconnected 3D Na diffusion pathways with low energy barriers, and the two‐sodium‐extracted intermediate NaTi_0.5V_0.5(PO₃)₃N is also a stable phase according to formation energy calculations.     

Alternative Synthesis of C60‐Diphenylaminofluorene Derivatives for Nonlinear Photonic Applications: Method of Preparation and Characterization

An alternative synthetic route for the preparation of key intermediate synthons 7‐α‐bromoacetyl‐2‐diphenylaminofluorene (α‐BrDPAF‐H) and 7‐α‐bromoacetyl‐9,9‐dialkyl‐2‐diphenylaminofluorene (α‐BrDPAF‐C_n) was demonstrated. The latter reactions involved the first step of dialkylation of 2‐bromofluorene at C₉ position of the fluorene moiety, the second step of a diphenylamino group attachment at C₂ position of the resulting dialkylfluorene, and the third step of Friedel‐Craft acylation of α‐bromoacetyl group at C₇ position of dialkylated diphenylaminofluorene. From the intermediates α‐BrDPAF‐H and α‐BrDPAF‐C_n, a series of C₆₀‐keto‐DPAF nanostructures, such as the fullerene monoadducts C₆₀(>DPAF‐H) and C₆₀(>DPAF‐C_n), where n is 2, 4, or 10, were synthesized in a reasonable yield. Molecular mass ions of the dyads C₆₀(>DPAF‐H), C₆₀(>DPAF‐C₂), C₆₀(>DPAF‐C₄), and C₆₀(>DPAF‐C₁₀) were clearly detected in positive ion matrix‐assisted laser desorption ionization mass spectrum (MALDI–MS) that confirmed the composition mass of each compound synthesized.     

Sorafenib and its tosylate salt: a multikinase inhibitor for treating cancer

Sorafenib, a drug that targets malignant cancer cells and cuts off the blood supply feeding the tumour, has been crystallized as the free base, 4‐(4‐{3‐[4‐chloro‐3‐(trifluoromethyl)phenyl]ureido}phenoxy)‐N‐methylpyridine‐2‐carboxamide, C₂₁H₁₆ClF₃N₄O₃, (I), and as a tosylate salt, 4‐(4‐{3‐[4‐chloro‐3‐(trifluoromethyl)phenyl]ureido}phenoxy)‐2‐(N‐methylcarbamoyl)pyridinium 4‐methylbenzenesulfonate, C₂₁H₁₇ClF₃N₄O₃⁺·C₇H₇O₃S⁻, (II). In both structures, the sorafenib molecule is in an extended conformation. The pyridine‐2‐carboxamide group exhibits a syn conformation of the N atoms in (I), whereas an almost anti orientation is present in (II). In both crystal structures, the two terminal groups, viz. pyridine‐2‐carboxamide and the trifluorophenyl ring, are oriented differently to the conformations found in enzyme‐bound sorafenib. The sorafenib molecules in (I) are linked into zigzag chains by N—H...O hydrogen bonds, whereas in (II) the presence of the additional tosylate anion results in the formation of chains of fused hydrogen‐bonded rings. This study reveals the variations in the solid‐state conformation of the sorafenib molecule in different crystalline environments.     

Ruthenium bidentate phosphine complexes for the coordination and catalytic dehydrogenation of amine- and phosphine-boranes

Addition of the amine–boranes H₃B ? NH₂tBu, H₃B ? NHMe₂ and H₃B ? NH₃ to the cationic ruthenium fragment [Ru(xantphos)(PPh₃)(OH₂)H][BAr^F₄] ( 2 ; xantphos=4,5‐bis(diphenylphosphino)‐9,9‐dimethylxanthene; BAr^F₄=[B{3,5‐(CF₃)₂C₆H₃}₄]^?) affords the η¹‐B? H bound amine–borane complexes [Ru(xantphos)(PPh₃)(H₃B ? NH₂tBu)H][BAr^F₄] ( 5 ), [Ru(xantphos)(PPh₃)(H₃B ? NHMe₂)H][BAr^F₄] ( 6 ) and [Ru(xantphos)(PPh₃)(H₃B ? NH₃)H][BAr^F₄] ( 7 ). The X‐ray crystal structures of 5 and 7 have been determined with [BAr^F₄] and [BPh₄] anions, respectively. Treatment of 2 with H₃B ? PHPh₂ resulted in quite different behaviour, with cleavage of the B? P interaction taking place to generate the structurally characterised bis‐secondary phosphine complex [Ru(xantphos)(PHPh₂)₂H][BPh₄] ( 9 ). The xantphos complexes 2 , 5 and 9 proved to be poor precursors for the catalytic dehydrogenation of H₃B ? NHMe₂. While the dppf species (dppf=1,1′‐bis(diphenylphosphino)ferrocene) [Ru(dppf)(PPh₃)HCl] ( 3 ) and [Ru(dppf)(η⁶‐C₆H₅PPh₂)H][BAr^F₄] ( 4 ) showed better, but still moderate activity, the agostic‐stabilised N‐heterocyclic carbene derivative [Ru(dppf)(ICy)HCl] ( 12 ; ICy=1,3‐dicyclohexylimidazol‐2‐ylidene) proved to be the most efficient catalyst with a turnover number of 76 h^?1 at room temperature.     

Azulene‐Based Macrocyclic Receptors for Recognition and Sensing of Phosphate Anions

Herein we report the synthesis and detailed studies of the anion‐binding properties of two 20‐membered macrocyclic tetramide receptors: one symmetrical, containing two identical azulene‐based bisamide units, the other a hybrid, containing a dipicolinic bisamide unit and an azulene‐based bisamide unit. Analysis of the crystal structures of the macrocyclic receptors revealed their preference for adopting similar well‐preorganized bent‐sheet conformations, both as free receptors and in their complexes with anions. Studies of the optical properties of both receptors revealed abilities to selectively sense phosphate anions (H₂PO₄^?, HP₂O₇^3?), allowing for naked‐eye detection of the presence of these guests in DMSO. Binding studies in solution confirmed that the receptors bind strongly to a series of anions even in highly demanding media, such as mixtures of DMSO with water or with methanol. Comparison of the anion affinity of linear analogues with that of the macrocyclic receptors evidenced the importance of macrocyclic topology. Quantitative analysis revealed that the macrocyclic receptors are selective for H₂PO₄^? over other anions. The affinity to H₂PO₄^? seen for the symmetrical receptor, containing two azulene‐based subunits, is much higher than for the hybrid macrocycle containing both the azulene‐based and pyridine‐derived subunits. This highlights that the azulene‐based building block serves efficiently as both a binding site and a structure‐preorganizing motif.     

Efficient organotin catalysts for urethanes: kinetic and mechanistic investigations

Dibenzyltin bis(2‐ethylhexanoate) 1 (4‐Y C₆H₄CH₂)₂Sn(OC(O)R¹)₂ [Y = H, 1a; MeO, 1b; Cl, 1c; Me, 1d; and R¹ = MeCH₂CH₂CH₂CH(Et) ] were synthesized either from the reaction of corresponding dibenzyltin dichlorides with silver 2‐ethylhexanoate or from the reaction of dibenzyltin oxides with 2‐ethylhexanoic acid. Compound 1a was further utilized as a catalyst for the reaction of mono‐ and di‐isocyanates [PhNCO, CH₃C₆H₃‐2,4‐(NCO)₂ and OCN(CH₂)₆NCO] with alcohols (primary, secondary, tertiary, cyclohexcyl, alkyl, allyl, benzyl and aryl) leading to the formation of the corresponding urethanes. The catalytic efficiencies of 1 vis‐à‐vis industrially known organotin catalysts have been determined through kinetic studies for the reaction of PhNCO and n‐BuOH at various temperatures. Compounds 1a, 1c and 1d show higher efficiency than dibutyltin bis(2‐ethylhexanoate). FTIR studies further provide mechanistic insights into the catalytic cycle, which comprises pre‐coordination of isocyanate to tin(IV), formation of stannyl carbamate and generation of dibenzyl(alkoxy)carboxylate as the active catalyst. Copyright © 2000 John Wiley & Sons, Ltd.     

Monodispers and Multifunctional Magnetic Composite Core Shell Microspheres for Demulsification Applications

Iron oxide@Poly(Glycidylmethacrylate‐methyl methacrylate‐divinyl benzene) magnetic composite core shell microspheres Fe₃O₄@P(GMA‐MMA‐DVB) with epoxy group on the surface was designed and synthesized by solvothermal process followed by distillation polymerization. The surface epoxy group was modified with amino group of ethylene diamine (EDA) to prepare Fe₃O₄@P(GMA‐MMA‐DVB)/NH₂ microspheres, and then effects of modification on the structure, interfacial behavior and hence demulsification of the amino modified epoxy coating were examined. The prepared magnetic microspheres were characterized using a laser particle size analyzer, transmission electron microscopy, Fourier transform infrared spectroscopy, vibrating sample magnetometry, and thermogravimetric analysis. Fourier transform infrared spectrometer analysis indicates the presence of epoxy group, amino group and Fe₃O₄ in the final Fe₃O₄@P(GMA‐MMA‐DVB) and Fe₃O₄@P(GMA‐MMA‐DVB)/NH₂ magnetic core shell microspheres. Our experimental results show that Fe₃O₄@P(GMA‐MMA‐DVB)/NH₂ magnetic core shell microspheres exhibit good interfacial and demulsification properties and able to remove emulsified water from stable emulsion. The resulting microspheres showed excellent magnetic properties and further these can be recycled and reused by magnetic separation.     

Oxidative and Photochemical Stability of Ionomers for Fuel‐Cell Membranes

To predict hydroxyl‐radical‐initiated degradation of new proton‐conducting polymer membranes based on sulfonated polyetherketones (PEK) and polysulfones (PSU), three nonfluorinated aromatics are chosen as model compounds for EPR experiments, aiming at the identification of products of HO^.‐radical reactions with these monomers. Photolysis of H₂O₂ was chosen as the source of HO^. radicals. To distinguish HO^.‐radical attack from direct photolysis of the monomers, experiments were carried out in the presence and absence of H₂O₂. A detailed investigation of the pH dependence was performed for 4,4′‐sulfonylbis[phenol] ( SBP ), bisphenol A (= 4,4′‐isopropylidenebis[phenol]; BPA ), and [1,1′‐biphenyl]‐4,4′‐diol ( BPD ). At pH ≥ pK_A of HO^. and H₂O₂, reactions between the model compounds and O₂^.? or ¹O₂ are the most probable ways to the phenoxy and ‘semiquinone’ radicals observed in this pH range in our EPR spectra. A large number of new radicals give evidence of multiple hydroxylation of the aromatic rings. Investigations at low pH are particularly relevant for understanding degradation in polymer‐electrolyte fuel cells (PEFCs). However, the chemistry depends strongly on pH, a fact that is highly significant in view of possible pH inhomogeneities in fuel cells at high currents. It is shown that also direct photolysis of the monomers leads to ‘semiquinone’‐type radicals. For SBP and BPA , this involves cleavage of a C? C bond.     

Common Pathway for K562 Cells Endocytosis and Release of Gac-Tf and Ga2-Tf via a Transferrin Receptor

There has been an increasing interest in the use of gallium in anticancer activity. However, whether the uptakes of two species of transferrin, including digallium transferrin (Ga₂‐Tf) and the C‐terminal monogallium transferrin (Ga_C‐Tf) by cells, are different is not well understood. In this work the mechanism of both species passing in and out K562 cells has been established by using ¹²⁵I‐labeled transferrin. There were about (1.5±0.08)×10⁵ binding sites per cell surface. Both Ga₂‐Tf and Ga_C‐Tf were recycled to the cell exterior with a protracted endocytic cycle compared to apotransferrin (apoTf). The cycling time from the internalization to release was calculated about t_1/2= (3.15±0.055) min for apoTf, t_1/2= (4.69±0.09) min for Ga₂‐Tf and t_1/2= (4.78±0.15) min for Ga_C‐Tf. The result implies that metal dissociating from transferrin in acidic endosomes was likely to be the key step. Both Ga₂‐Tf and Ga_C‐Tf into K562 cells are transferrin receptor‐mediated process with a similar rate of endocytosis and release. Our present observations provide useful information for better targeted drugs in specific therapy.     

Design,synthesis and crystallographic study of novel indole‐based cyano derivatives as key building blocks for heteropolycyclic compounds of major complexity

A four‐stage reaction sequence has been designed and developed for the synthesis of highly functionalized enolate esters as key building blocks for the synthesis of novel heteropolycyclic compounds of potential pharmaceutical value. The sequence starts with simple commercially available indoles and proceeds via 3‐(indol‐3‐yl)‐3‐oxopropanenitriles, which react with 2‐bromobenzaldehyde to form the corresponding chalcones; these are readily reduced to dihydrochalcones, which are in turn acylated to form the enolate esters. The compounds in this sequence have been characterized by IR and ¹H and ¹³C NMR spectroscopy, by mass spectrometry and by elemental analysis. The molecular and supramolecular structures are reported for representative examples, namely (E )‐3‐(2‐bromophenyl)‐2‐(1‐methyl‐1H‐indole‐3‐carbonyl)acrylonitrile, C₁₉H₁₃BrN₂O, (Ib ), (2RS )‐2‐(2‐bromobenzyl)‐3‐(1‐methyl‐1H‐indol‐3‐yl)‐3‐oxopropanenitrile, C₁₉H₁₅BrN₂O, (IIb ), and (2RS )‐3‐(1‐benzyl‐1H‐indol‐3‐yl)‐2‐(2‐bromobenzyl)‐3‐oxopropanenitrile, C₂₅H₁₉BrN₂O, (IIc ), the latter two of which crystallize with Z ′ = 2, and (E )‐1‐(1‐acetyl‐1H‐indol‐3‐yl)‐3‐(2‐bromophenyl)‐2‐cyanoprop‐1‐en‐1‐yl acetate, C₂₂H₁₇BrN₂O, (III), and (E )‐1‐(1‐benzyl‐1H‐indol‐3‐yl)‐3‐(2‐bromophenyl)‐2‐cyanoprop‐1‐en‐1‐yl benzoate, C₃₂H₂₃BrN₂O, (IV). The structure of the related chalcone (E )‐2‐benzoyl‐3‐(2‐bromophenyl)prop‐2‐enenitrile, (V), has been redetermined at 100 K, where it is monoclinic, as opposed to the triclinic form reported at ambient temperature.     

Nanoscale MnII‐Coordination Polymers for Cell Imaging and Heterogeneous Catalysis

A mixed ligand approach was exploited to synthesize a new series of Mn^II‐based coordination polymers (CPs), namely, CP1 {[Mn(μ‐dpa)(μ‐4,4′‐bp)]?MeOH}_∞, CP2 {[Mn₃(μ‐dpa)₃(2,2′‐bp)₂]}_∞, CP3 {[Mn₃(μ‐dpa)₃(1,10‐phen)₂]?2 H₂O}_∞, CP4 {[Mn(μ‐dpa)(μ‐4,4′‐bpe)_1.5]?H₂O}_∞, CP5 {[Mn₂(μ‐dpa)₂(μ‐4,4′‐bpe)₂]? DEF}_∞, and CP6 {[Mn(μ‐dpa)(μ‐4,4′‐bpe)_1.5]? DMA}_∞ (dpa=3,5‐dicarboxyphenyl azide, 2,2′‐bp=2,2′‐bipyridine, 1,10‐phen=1,10‐phenanthroline, 4,4′‐bpe=1,2‐bis(4‐pyridyl)ethylene, 4,4′‐bp=4,4′‐bipyridine, DEF=N,N‐diethylformamide, DMA=N,N‐dimethylacetamide), to develop multifunctional CPs. Various techniques, such as single‐crystal X‐ray diffraction (SXRD), FTIR spectroscopy, elemental analysis, and thermogravimetric analysis, were employed to fully characterize these CPs. The majority of the CPs displayed a four‐connected sql topology, whereas CP4 and CP6 exhibited a two‐dimensional SnS network architecture, which was further entangled in a polycatenation mode. Compound CP1 displayed an open framework structure. The CPs were scaled down to the nanoregime in a ball mill for cell imaging studies. Whereas CP2 and CP4 were employed for cell imaging with RAW264.7 cells, CP1 was exploited for both cell imaging and heterogeneous catalysis in a cyanosilylation reaction.     

Mechanism for the direct synthesis of tryptophan from indole and serine: a useful NMR technique for the detection of a reactive intermediate in the reaction mixture

The reaction mechanism for the biomimetic synthesis of tryptophan from indole and serine in the presence of Ac₂O in AcOH was investigated. Although the time‐course ¹H‐NMR spectra of the reaction of 5‐methoxyindole with N‐acetylserine were measured in the presence of (CD₃CO)₂O in CD₃CO₂D, the reactive intermediate could not be detected. This reaction was conducted without 5‐methoxyindole in order to elucidate the reactive intermediate, but the intermediate could not be isolated from the reaction mixture. Since the intermediate would be expected to have a very short life time, and therefore be very difficult to detect by conventional analytical methods, the structure of the intermediate was elucidated using a 2D‐NMR technique, diffusion‐ordered spectroscopy (DOSY). Two intermediates were detected and confirmed to be 2‐methyl‐4‐methyleneoxazol‐5(4H)‐one and 2‐methyl‐4‐hydroxymethyloxazol‐5(4H)‐one. The present results demonstrated that DOSY is a powerful tool for the detection of unstable intermediates. Copyright © 2010 John Wiley & Sons, Ltd.     

Controllable Syntheses of Porous Metal–Organic Frameworks: Encapsulation of LnIII Cations for Tunable Luminescence and Small Drug Molecules for Efficient Delivery

Two porous metal–organic frameworks (MOFs), [Zn₃(L)(H₂O)₂] ? 3 DMF ? 7 H₂O ( MOF‐1 ) and [(CH₃)₂NH₂]₆[Ni₃(L)₂(H₂O)₆] ? 3 DMF ? 15 H₂O ( MOF‐2 ), were synthesized solvothermally (H₆L=1,2,3,4,5,6‐hexakis(3‐carboxyphenyloxymethylene)benzene). In MOF ‐ 1 , neighboring Zn^II trimers are linked by the backbones of L ligands to form a fascinating 3D six‐connected framework with the point symbol (4¹².6³) (4¹².6³). In MOF‐2 , eight L ligands bridge six Ni^II atoms to generate a rhombic‐dodecahedral [Ni₆L₈] cage. Each cage is surrounded by eight adjacent ones through sharing of carboxylate groups to yield an unusual 3D porous framework. Encapsulation of Ln^III cations for tunable luminescence and small drug molecules for efficient delivery were investigated in detail for MOF‐1 .     

Combining Topological and Steric Constraints for the Preparation of Heteroleptic Copper(I) Complexes

Heteroleptic copper(I) complexes have been prepared from a macrocyclic ligand incorporating a 2,9‐diphenyl‐1,10‐phenanthroline subunit ( M30 ) and two bis‐phosphines, namely bis[(2‐diphenylphosphino)phenyl] ether (POP) and 1,3‐bis(diphenylphosphino)propane (dppp). In both cases, the diphenylphosphino moieties of the PP ligand are too bulky to pass through the 30‐membered ring of M30 during the coordination process, hence the formation of C_2v‐symmetrical pseudo‐rotaxanes is prevented. When POP is used, X‐ray crystal structure analysis shows the formation of a highly distorted [Cu( M30 )(POP)]⁺ complex in which the POP ligand is only partially threaded through the M30 unit. This compound is poorly stable as the Cu^I cation is not in a favorable coordination environment due to steric constraints. By contrast, in the case of dppp, the bis‐phosphine ligand undergoes both steric and topological constraints and adopts a nonchelating coordination mode to generate [Cu₂( M30 )₂(μ‐dppp)](BF₄)₂. This compound exhibits metal‐to‐ligand charge transfer (MLCT) emission characterized by a very large Stokes’ shift (≈200 nm) that is not attributed to a dramatic structural distortion between the ground and the emitting states but to very weak MLCT absorption transitions at longer wavelengths. Accordingly, [Cu₂( M30 )₂(μ‐dppp)](BF₄)₂ shows unusually high luminescence quantum yields for Cu^I complexes, both in solution and in the solid state (0.5 and 7 %, respectively).     

Surface-modified TiO(2) nanoparticles as affinity probes and as matrices for the rapid analysis of phosphopeptides and proteins in MALDI-TOF-MS

We utilized three different types of TiO₂ nanoparticles (NPs) namely TiO₂‐dopamine, TiO₂‐CdS and bare TiO₂ NPs as multifunctional nanoprobes for the rapid enrichment of phosphopeptides from tryptic digests of α‐ and β‐casein, milk and egg white using a simplified procedure in MALDI‐TOF‐MS. Surface‐modified TiO₂ NPs serve as effective matrices for the analysis of peptides (gramicidin D, HW6, leucine‐enkephalin and methionine‐enkephalin) and proteins (cytochrome c and myoglobin) in MALDI‐TOF‐MS. In the surface‐modified TiO₂ NPs‐based MALDI mass spectra of these analytes (phosphopetides, peptides and proteins), we found that TiO₂‐dopamine and bare TiO₂ NPs provided an efficient platform for the selective and rapid enrichment of phosphopeptides and TiO₂‐CdS NPs efficiently acted as the matrix for background‐free detection of peptides and proteins with improved resolution in MALDI‐MS. We found that the upper detectable mass range is 17 000 Da using TiO₂‐CdS NPs as the matrix. The approach is simple and straightforward for the rapid analysis of phosphopeptides, peptides and proteins by MALDI‐MS in proteome research.