Sol hydrolysis and condensation reaction time influence the sensitivity of class II xerogel-based sensing materials

Simplicity of preparation, a wide variety of precursors, and numerous processing variables (e.g., pH, time, temperature) are often described as attractive aspects of sol–gel derived materials. In the current work we create a series of O₂-responsive xerogel-based sensor films by simultaneously co-hydrolyzing and co-condensing tetramethylorthosilane and n-octyltriethoxysilane. Tris(4,7′-diphenyl-1,10′-phenanthroline) ruthenium(II) ([Ru(dpp)₃]²⁺) is used as the O₂-responsive luminophore. We determine the effects of [Ru(dpp)₃]²⁺ addition time to the sol and the sol hydrolysis and condensation reaction time (H&C) on the xerogel film O₂ sensitivity. [Ru(dpp)₃]²⁺ addition time has no significant effect on the O₂ sensitivity; H&C effects the O₂ sensitivity. The highest O₂ sensitivity is seen at early H&C (0.5 h). This behavior arises because TMOS and C8-TMOS react at different rates to form sols. At early H&C the co-hydrolysis and co-condensation reactions are not complete and the so formed sols are rich in C8-TMOS in comparison to their composition at longer H&C. At longer H&C, the TMOS and C8-TMOS co-hydrolyze and co-condense more completely. SEM images show that xerogel films formed at early H&C is more porous in comparison to those formed a longer H&C. The results of these experiments: (a) highlight the importance of documenting how sols are processed and xerogels formed and (b) demonstrate the use of a single sol formulation and H&C to create suites of sensor materials with different responses.     

Nanosized magnesium oxide as catalyst for the rapid and green synthesis of substituted 2-amino-2-chromenes

A nanosized magnesium oxide catalyzed three-component condensation reaction of aldehyde, malononitrile, and α-naphthol proceeded rapidly in water-PEG to afford corresponding 2-amino-2-chromenes in high yields at room temperature. The greener protocol was found to be fairly general and the catalyst was reused in subsequent reactions with consistent activity.     

Substituent effect on the formation of organically-modified silicate-phosphate alternating copolymer through nonaqueous acid–base reaction

Organically-modified silicate-phosphate and silicate-phosphite copolymers were prepared through nonaqueous acid–base reaction. The inductive effect of the organic substituent of the starting materials such as organically-modified chlorosilane and phosphorous acid on the acid–base reaction was investigated by ³¹P NMR measurement and ab initio molecular orbital calculation. The condensation reaction takes place by nucleophilic addition of phosphate ion (or phosphite ion) to chlorosilane through S_N2 mechanism to form silicate-phosphate (or phosphite) network. The reactivity of the acid–base pair can be controlled by changing the inductive effect of the organic substituents on the starting materials.     

娃儿藤碱类似物DCB-3501的全合成及其细胞毒性

以3,4-二甲氧基苯甲醛与3,4-二甲氧基苯乙酸为起始原料,经Perkin缩合、自由基氧化偶联反应、Swern氧化、还原胺化及付克酰基化等7步反应全合成了娃儿藤碱类似物DCB-3501,其结构经¹H NMR和ESI-MS确证。体外细胞毒性测试结果表明：DCB-3501对人结肠癌细胞HCT116、人胃癌细胞BGC-823、人肝癌细胞HepG-2、人宫颈癌细胞HeLa和人大细胞肺癌细胞H460的IC₅₀分别为20.0 μmol·L^-1, 50.9 μmol·L^-1, 2.1 μmol·L^-1, 65.8 μmol·L^-1和30.8 μmol·L^-1。     

新型二(取代苯基亚甲基)丙酮的合成

以稀碱为催化剂,取代苯甲醛或取代水杨醛分别与丙酮于室温经Claisen－Schmidt缩合反应合成了10个新型的二（取代苯基亚甲基）丙酮化合物（2a~2j）,其结构经¹H NMR, IR, ESI-MS和元素分析表征。     

Synthesis,Characterization, and Biological Activity of Substituted Thiazole-5-carboxaldehydes and Their Ylidenenitriles Derivatives

The Vilsmeier–Haack reaction of 2-amino -4-(4-substituted phenyl)-thiazoles 1, in the presence of micellar media, gives formylated derivatives 2, which upon hydrolysis afforded thiazole-5-carboxaldehydes 3. Microwave-assisted Knoevenagel condensation of 3 with active methylene compounds, in the presence of piperidine as catalyst, gives excellent yields of ylidenenitrile compounds 4. The structures of the newly synthesized compounds were established on the basis of elemental analysis, IR, ¹H NMR, and ¹³C NMR spectral analysis. All newly synthesized compounds were screened for antibacterial activity using two Gram-positive and one Gram-negative bacterial species and their antifungal activity was screened using two fungal species.     

Stereoselective Synthesis and Alkylation of N-Methylmorpholinium 4,5-trans-4-(2-chlorophenyl)-3-cyano-6-hydroxy-5-(2-thenoyl)-6-trifluoromethyl-1,4,5,6-tetrahydropyridine-2-thiolate. Molecular and Crystal Structure of 4,5-trans-4-(2-chlorophenyl)-3-cyano-6-hydroxy-2-methallylthio-5-(2-thenoyl)-6-trifluoromethyl-1,4,5,6-tetrahydropyridine

The condensation of 2-chlorobenzaldehyde with cyanothioacetamide and 2-thenoyltrifluoroacetone in the presence of N-methylmorpholine takes place stereoselectively and leads to the formation of N-methylmorpholinium 4,5-trans-4-(2-chlorophenyl)-3-cyano-6-hydroxy-5-(2-thenoyl)-6-trifluoromethyl-1,4,5,6-tetrahydropyridine-2-thiolate. The latter was used to synthesize the corresponding 2-alkylthiotetrahydropyridines. The structure of 4,5-trans-4-(2-chlorophenyl)-3-cyano-6-hydroxy-2-methallylthio-5-(2-thenoyl)-6-trifluoromethyl-1,4,5,6-tetrahydropyridine was determined by X-ray crystallographic analysis.     

活性炭负载壳聚糖催化室温无溶剂Knoevenagel缩合反应

通过活性炭(AC)负载壳聚糖(CS)的方法,制备了负载型的"壳聚糖/活性炭"催化剂(CS/AC)。利用FT-IR、XRD、TG-DTG、SEM、BET、元素分析等方法对催化剂进行表征,并系统研究了该催化剂在Knoevenagel缩合反应中的催化性能。结果表明,催化剂具有较好的活性,在室温无溶剂条件下,可以催化一系列芳香醛化合物与活泼亚甲基化合物进行缩合反应,产率均在80%以上;且反应体系放大100倍时,仍然保持较高的催化效率;此外,该催化剂具有较好稳定性,重复使用8次后,仍然保持较高的催化活性。     

3-杂环胺基甲烯基-6-烷基(芳基)-5,6-二氢-2H-吡喃-2,4-二酮的合成及生物活性的研究

异构体;氢键;3-杂环胺基甲烯基-6-烷基(芳基)-5;6-二氢-2H-吡喃-2;4-二酮的合成及生物活性的研究     

Mechanisms of surface diffusion

Mechanisms of surface diffusion of single atoms, molecules and atomic clusters on flat terraces (with and without a driving force) of metal and semiconductor surfaces are discussed, focusing on our recent scanning tunneling microscopy (STM) results. Experimental evidence leading to these conclusions is presented. Besides the commonly known hopping mechanism, there are many other mechanisms. In Arrhenius analysis, a linear behavior can be expected for only some of the simpler mechanisms.