Reaction of α,β-unsaturated ketones with guanidine. Substituent effects on the protonation constants of 2-amino-4,6-diarylpyrimidines

1,3-Diaryl-2-propen-1-ones, I, reacted with guanidine hydrochloride (II) in the presence of 3 moles of sodium hydroxide to give the corresponding 2-amino-4,6-diarylpyrimidines, III. The structure and configuration of the products are based on chemical and spectroscopic evidence. The protonation constants of these compounds (series A and series B) have been determined in 50 volume percent ethanol-water medium. Excellent linear correlations are obtained when pK_a values of the two series of 2-amino-4,6-diarylpyrimidines, IIIa-j and IIIk-r, are plotted against the substituent constant, ^σx, and the polar substituent constant, ^σ* xC₆H₄, for substituted phenyl groups. The pK_a values have also been correlated with the extended Hammett equation. The correlation follows the equations: Series A; pK_a = 3.273 - 0.820σI,X - 0.662σR,X Series B; pK_a = 3.169 - 0.424σI,X - 0.137σR,X     

Pictet‐spengler synthesis of pyrazole‐fused β‐carbolines

The synthesis of new pyrazolo[4,3‐c]β‐carbolines ( 8a,b ) is achieved by condensation of the appropriate aldehyde with 3‐(4‐amino‐1,3‐dimethylpyrazol‐5‐yl)indole ( 4 ) under Pictet‐Spengler reaction conditions. Regioselective cyclization occurred at the usual indole C‐2 position as evidenced from the ¹H‐and ¹³C nmr spectra of 8a,b which lack the pyrrolic H‐2 signal, present in 4 (δ 7.26, 1H, d, J_ch‐NH = 2‐5 Hz).     

Switchable Surface Wettability by Using Boronic Ester Chemistry

Here, we report for the first time the use of a boronic ester as an efficient tool for reversible surface post‐functionalization. The boronic ester bond allows surfaces to be reversibly switched from hydrophilic to hydrophobic. Based on the well‐known boronic acid/glycol affinity, this strategy offers the opportunity to play with surface hydrophobic properties by adding various boronic acids onto substrates bearing glycol groups. The post‐functionalization can then be reversed to regenerate the starting glycol surface. This pathway allows for the preparation of various switchable surfaces for a large range of applications in biosensors, liquid transportation, and separation membranes.     

氮掺杂碳包埋钴纳米粒子电催化合成过氧化氢

电催化还原氧是一种新兴的可持续生产过氧化氢(H2O2)的合成技术,寻找低成本、高活性和高选择性的电催化剂是该技术实际应用的关键.钴氮掺杂的碳材料因含有钴氮(Co-Nx)催化活性位,成为一类新兴的可促进H2O2电化学合成的材料.本文采用低能耗干式球磨外加控制热解的方法来制备包含许多Co-Nx结构的钴氮掺杂碳材料.该方法使用材料廉价,即将醋酸钴、2-甲基咪唑和Ketjenblack EC-600JD高纯度且导电的碳黑分别作为金属、氮和碳的前体.在酸性介质中的电化学测试结果表明,该材料的氧还原反应电流密度明显增加,同时起始电位向正方向移动.该催化剂在较大电位范围内对H2O2的选择性约为90％.H2O2整体电解实验表明,H2O2产率达到100mmol gcat?1 h?1,H2O2法拉第效率达到85％(0.3Vvs.RHE条件下2h).耐久性测试(在0.3Vvs.RHE条件下6h)表明,催化剂表现出相对稳定的性能,且在整个测试循环中,法拉第效率达到约85％,表明催化剂在实际应用中具有良好的耐久性.催化剂表现出较高的电催化合成H2O2活性和选择性可能是由于形成了Co-Nx活性位,以及酸性环境和应用电位等其它因素的影响.     

The kinetics and molecular modeling of the complexation of tenoxicam with cyclodextrins in solution

The effect of cyclodextrins on photodegradation of tenoxicam (TEN) was studied at pH 4, 7 and 10. After 60 min of irradiation with UV light, the photodegradation was extensive. All cyclodextrins (alpha, beta, or gamma) stabilize TEN and reduce the rate of photodegradation. The largest effect of cyclodextrins is at pH 7. Molecular modeling results help to explain and manipulate the results. The results are discussed and compared with other results from previous studies.     

Pictet-Spengler Synthesis of Some Thiophene[c]-Fused β-Carbolines

Summary. 5-(Substituted) thieno[2′,3′:5,6]pyrido[3,4-b]indoles were synthesized via cyclocondensation of 3-(3-aminothien-2-yl)indole with the appropriate aldehyde in the presence of boron trifluoride etherate under Pictet-Spengler reaction conditions. The constitution of the new compounds is evidenced from analytical and spectral (NMR and MS) data.     

Role of Ceria in the Design of Composite Materials for Elemental Mercury Removal

The necessity to drastically act against mercury pollution has been emphatically addressed by the United Nations. Coal‐fired power plants contribute a great deal to the anthropogenic emissions; therefore, numerous sorbents/catalysts have been developed to remove elemental mercury (Hg⁰) from flue gases. Among them, ceria (CeO₂) has attracted significant interest, due to its reversible Ce³⁺/Ce⁴⁺ redox pair, surface‐bound defects and acid‐base properties. The removal efficiency of Hg⁰ vapor depends among others, on the flue gas composition and temperature. CeO₂ can be incorporated into known materials in such a way that the abatement process can be effective at different operating conditions. Hence, the scope of this account is to discuss the role of CeO₂ as a promoter, active phase and support in the design of composite Hg⁰ sorbents/catalysts. The elucidation of each of these roles would allow the integration of CeO₂ advantageous characteristics to such degree, that tailor‐made environmental solution to complex issues can be provided within a broader application scope. Besides, it would offer invaluable input to theoretical calculations that could enable the materials screening and engineering at a low cost and with high accuracy.     

推广的相互作用玻色子模型中基于对偶代数结构的量子相变研究(英文)

本工作将相互作用玻色子模型推广为包含f-和p-玻色子的情形。利用仿射型代数方法,通过对偶代数结构数值计算了多分量玻色型对力问题。利用对偶关系解析构建了与哈密顿量及其基底相联系的,由幺正的粒子数守恒和非粒子数守恒算符构成的准旋代数。在经该模型对106-116Cd偶偶核素实验能谱拟合的基础上,计算了基态和低激发态中各种玻色子占有率,准γ带中相邻能级摇摆等几个能特征该区域核素形状相变的序参量。从而展示了这些中重质量核从振动到γ-不稳定运动的形状相变行为。An extension of the original interacting boson model to the multi-level case including negative parity f-and p-bosons is made. An affinealgebraic approach is applied to solve the multi-level pairing problem numerically via the dual algebraic structure. The duality relation is explicitly used to construct the number-conserving unitary and number-nonconserving quasi-spin algebra, related with the Hamiltonian and the corresponding bases. After fitting to the experimental level energies of even-even 106-116Cd, several order parameters to signify the shape (phase) transition, such as occupation numbers of the bosons in the ground and a few lowest excited states, the level energy staggering in the (quasi)-γ band, are calculated to demonstrate the shape (phase) transitional behavior of these medium mass transitional nuclei.     

Hydrothermal synthesis of a mixed-valence hexamolybdate cluster: crystal structure of [HN(CH2CH2)3N]2[HMoVMoVI5O19]·[N(CH2CH2)3N]

The hydrothermal reaction of MoO₃, V, Na₂WO₄· 2H₂O, [N(CH₂CH₂)₃N](1,4-diazabicyclo[2.2.2] octane), and H₂O at 160°C for 90h gave dark-brown crystals of [HN(CH₂CH₂)₃N]₂[HMo^VMo^VI ₅O¹⁹]·[N(CH₂CH₂)₃N], (1), in 40% yield. Complex (1) is the first one-electron reduced mixed-valence hexamolybdate to be crystallized and structurally characterized. The crystal structure of (1) consists of discrete [HMo^VMo^VI ₅O₁₉]^2– anions, [HN-(CH₂CH₂)₃N]⁺ cations, and neutral [N(CH₂CH₂)₃N] molecules of crystallization.