Geometries,vibrational frequencies,and electron affinities of X2Cl (X=C,Si,Ge) clusters

Ab initio quantum chemical calculations have been performed on X₂Cl^? and X₂Cl (X = C, Si, Ge) clusters. The geometrical structures, vibrational frequencies, electronic properties and dissociation energies are investigated at the Hartree–Fock (HF), Møller–Plesset second‐ and fourth‐order (MP2, MP4), CCSD(T) level with the 6‐311+G(d) basis set. The X₂Cl (X = C, Si, Ge) and X₂Cl^? (X = Si, Ge) take a bent shape obtained at the ground state, while C₂Cl^? has a linear structure. The impact on internal electron transfer between the X₂Cl and the corresponding anional clusters is studied. The three different types of electron affinities (EAs) at the CCSD(T) are reported. The most reliable adiabatic electronic affinities, obtained at the CCSD(T)/cc‐pvqz level of theory, are predicted to be 3.30, 2.62, and 1.98 eV for C₂Cl, Si₂Cl, and Ge₂Cl, respectively. The calculated EAs of C₂Cl and Ge₂Cl are in good agreement with theoretical results reported. The correlation effects and basis sets effects on the geometrical structures and dissociation energies are discussed. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Design, synthesis, and binding affinities of pyrrolinone-based somatostatin mimetics

[structure: see text] Tetrapyrrolinone somatostatin (SRIF) mimetics (cf. 1), based on a heterochiral (D,L-mixed) pyrrolinone scaffold, were designed, synthesized, and evaluated for biological activity. The iterative synthetic sequence, incorporating the requisite functionalized coded and noncoded amino acid side chains, comprised a longest linear synthetic sequence of 23 steps. Binding affinities at two somatostatin receptor subtypes (hsst 4 and 5) reveal micromolar activity, demonstrating that the d,l-mixed pyrrolinone scaffold can be employed to generate functional mimetics of peptide beta-turns.     

Microfluidic synthesis of high-valence programmable atom-like nanoparticles for reliable sensing

Synthesis of programmable atom-like nanoparticles (PANs) with high valences and high yields remains a grand challenge. Here, a novel synthetic strategy of microfluidic galvanic displacement (μ-GD) coupled with microfluidic DNA nanoassembly is advanced for synthesis of single-stranded DNA encoder (SSE)-encoded PANs for reliable surface-enhanced Raman scattering (SERS) sensing. Notably, PANs with high valences (e.g., n-valence, n = 12) are synthesized with high yields (e.g., >80%) owing to the effective control of interfacial reactions sequentially occurring in the microfluidic system. On the basis of this, we present the first demonstration of a PAN-based automatic analytical platform, in which sensor construction, sample loading and on-line monitoring are carried out in the microfluidic system, thus guaranteeing reliable quantitative measurement. In the proof-of-concept demonstration, accurate determination of tetracycline (TET) in serum and milk samples with a high recovery close to 100% and a low relative standard deviation (RSD) less than 5.0% is achieved by using this integrated analytical platform.

A novel synthetic strategy is presented for microfluidic preparation of programmable atom-like nanoparticles with high valences and high yields.     

Room‐Temperature Solution‐Processed PbS Quantum Dot Solar Cells

Colloidal quantum dots (CQDs) are attractive absorber materials for high‐efficiency photovoltaics because of their facile solution processing, bandgap tunability due to quantum confinement effect, and multi‐exciton generation. To date, all published performance records for PbS CQDs solar cells have been based on the conventional hot‐injection synthesis method. This method usually requires relatively strict conditions such as high temperature and the utility of expensive source material (pyrophoric bis(trimethylsilyl) sulfide (TMS‐S)), limiting the potential for large‐scale and low‐cost synthesis of PbS CQDs. Here we report a facile room‐temperature synthetic method to produce high‐quality PbS CQDs through inexpensive ionic source materials including Pb(NO₃)₂ and Na₂S in the presence of triethanolamine (TEA) as the stabilizing ligand. The PbS CQDs were successfully prepared with an average particle size of about 5 nm. Solar cells based on the as‐synthesized PbS CQDs show a preliminary power conversion efficiency of 1.82%. This room‐temperature and low‐cost synthesis of PbS CQDs will further benefit the development of solution‐processed CQD solar cells.     

SINGLE AND BINARY ADSORPTION PERFORMANCE OF SALICYLIC ACID AND 5-SULFOSALICYLIC ACID ONTO HYPERCROSSLINKED POLYMERIC ADSORBENTS

Single and binary adsorption behaviors of salicylic acid and 5-sulfosalicylic acid onto hypercrosslinked polymeric adsorbents, i.e. NDA-101 and NDA-99 were investigated. The Freundlich model can successfully describe all the adsorption isotherms tested, which indicates a favorable and exothermic adsorption process. The adsorption of salicylic acid relies on π-π interaction, while the electrostatic interaction further influences the adsorption of 5-sulfosalicylic acid onto NDA-99. The adsorptive capacity of salicylic acid on NDA-99 decreases but increases on NDA-101 with 5-sulfosalicylic acid as the background component in a binary solute system. The amount of 5-sulfosalicylic acid adsorbed was decreased with the increase in initial concentration of salicylic acid on both adsorbents. The competition for the adsorption sites is considered to be predominant in the solid-to-liquid interaction process. The adsorption selectivity of salicylic acid onto NDA-101 is higher than onto NDA-99 by more than an order of magnitude. Thus, combination technique involving NDA-101 followed by NDA-99 can be effectively applied to separate and recover salicylic acid and 5-sulfosalicylic acid from wastewater.     

2,3,7‐Triazabicyclo[3.3.0]octenes Prepared by Tandem Cascade Reaction of Allyl Azides and Olefinic Dipolarophiles

Tandem cascade reactions of allylazides and olefinic dipolarophiles to give cis‐fused 2,3,7‐triazabicyclo [3.3.0]octenes ( 5, 6 or 7 ) are reported. Therein, an intermolecular dipolar cycloaddition of azide and alkene gave a triazoline which was followed by isomerization of the triazoline to a diazoester ( 4 ) and then an intramolecular dipolar cycloaddition from the diazo functional group and the double bond in 4 to give 5 . Compound 5 may further more undergo a Michael addition to give 7‐substituted‐ 2,3,7‐ triazabicyclo [3.3.0]oct‐2‐ene ( 6 ) or a tautomerization to give 2,3,7‐triazabicyclo[3.3.0]oct‐3‐ene ( 7 ). The reaction may be manipulated to stop at a particular stage by adopting a suit able solvent or an appropriate temperature.     

胶束增溶光度法同时测定铂、铑、钯和金的研究

本文研究了贵金属Pt、Rh、Pd和Au在SnCl_2-BRB-AG-乳化剂OP离子缔合物体系中显色反应的条件,采用偏最小二乘回归法对上述体系重迭光谱进行解析及数据处理。结果表明,该体系灵敏度高,表观摩尔吸光系数可达1.74×10～6～2.47×10～6L·mol～-1·cm～-1;体系稳定性较好。应用本文方法对混合试样中Pt、Rh、Pd、Au进行同时测定,取得较满意的结果。     

Several modified piezoelectric quartz crystals for determination of omethoate

A chromatographic method for the determination of transition metals in human hair samples is described. The method involves the separation of Cu, Pb, Zn, Ni, Co, Cd and Mn in a C18 column coated with sodium hexadecane-sulfonate (SHS) and spectrophotometric detection (520 nm) after post-column reaction of the eluted metals with 4-(2-pyridylazo)-resorcinol (PAR). The eluent was a 100 mM tartrate solution adjusted to pH 3.1 with a 2 M sodium hydroxide solution (flow-rate=1.0 ml min(-1)). A good separation of the eluted metals (specially for Cu/Pb and Zn/Ni) has been achieved. The detection limits, expressed as mug l(-1), were 2.2 (Cu), 8.0 (Pb), 2.8 (Zn), 1.5 (Ni), 1.5 (Co), 12.0 (Cd), and 1.4 (Mn). A microwave-assisted closed vessel acid digestion procedure with HNO(3)+HClO(4) (4+1 ml) was used for the hair samples solubilisation. Nineteen hair samples were analysed with the proposed method. The results were in good agreement with those obtained by atomic absorption spectrometry (AAS).     

The Aldol Reaction of Allenolates with Aldehydes in the Presence of Magnesium Diiodide (MgI2) as Catalyst

Stereoselective synthesis of (Z)‐α‐(hydroxyalkyl)‐β‐iodoacrylates (=(2Z)‐2‐(hydroxyalkyl)‐3‐iodoprop‐2‐enoates) was achieved in a one‐pot coupling reaction from methyl prop‐2‐ynoate, Me₃SiI, and an alkanal under mild conditions with MgI₂ as catalyst (→ 1 – 9 ; see Table and Scheme 1). Baylis‐Hillman β‐iodo adducts were generated in excellent yields with high (Z)‐selectivity. The conversion of methyl prop‐2‐ynoate to an active methyl 3‐iodo‐1‐[(trimethylsilyl)oxy]allenolate intermediate in situ followed by carbonyl addition is proposed as the reaction sequence (Schemes 1 and 2).     

Tasumatrols P – T,Five New Taxoids from Taxus sumatrana

The phytochemical investigation of the more polar fractions from the leaves and twigs of Taxus sumatrana (Taxaceae) afforded five new taxane diterpene esters, tasumatrols P–T ( 1 – 5 ) possessing an 11(15→1),11(10→9)‐diabeotaxane skeleton. Compounds 1, 4 , and 5 contain an α‐hydroxy group at C(14), while 3 has no OH group at either C(13) or C(14). Compound 2 is a natural 4,5‐acetonide derivative, while 4 has an unusual spiro‐connected 2‐hydroxy‐2‐phenyl‐1,3‐dioxolane ring. Ten known taxoids, were also isolated in the course of the chromatographic fractionation. Five additional new O‐acetyl derivatives 3a, 4a, 4b, 5a , and 5b were prepared from the taxanes 3 – 5 . The structures of all new compounds were established on the basis of their spectroscopic analyses. Compound 1 showed mild cytotoxic activity against human Hela and Daoy tumor cells.