Cis-trans isomerization of [9]-annulenanion（1） and its 2-fluoro-,2-chloro-and 2-bromo-derivatives（2,3 and 4,respectively） were investigated at the HF/6-31G＊ and B3LYP/6-311＋＋G＊＊ levels of theory.Cis,cis,cis,c...Cis-trans isomerization of [9]-annulenanion（1） and its 2-fluoro-,2-chloro-and 2-bromo-derivatives（2,3 and 4,respectively） were investigated at the HF/6-31G＊ and B3LYP/6-311＋＋G＊＊ levels of theory.Cis,cis,cis,cis structures appear more stable than their corresponding cis,cis,cis,trans-isomers.The relative height of energy barriers for cis-trans isomerization is：2cis 〉1cis 〉3cis〉 4cis.This trend for the reverse trans-cis isomerization follows the electronegativity of the substituent at C-2（2trans 3trans 4trans 1trans）.展开更多
Phenylethynyl palladium(Ⅱ) complexes have proven to be effective catalysts for coordination polymerization of isocyanides. In this work, two new phenylethynyl palladium(Ⅱ) initiators bearing bromide(1b) and iodide(1...Phenylethynyl palladium(Ⅱ) complexes have proven to be effective catalysts for coordination polymerization of isocyanides. In this work, two new phenylethynyl palladium(Ⅱ) initiators bearing bromide(1b) and iodide(1c) were synthesized and applied for living polymerization of aryl and alkyl isocyanides. The coordinated halogen anions can significantly influence the kinetics of polymerization, with the observed order of reaction rates being 1c(Ⅰ)>1 b(Br)>1a(Cl). Impressively, 1c not only accelerates the reaction rate in both the initiation stage and propagation stage, but also can polymerize less active monomers that cannot be reacted by 1a. DFT calculations were then employed to understand the detailed mechanism and the halogen effects in this insertion polymerization process.展开更多
The hot corrosion behavior of Ti45 A18.5 Nb alloy was studied in the salt of Na_(2)SO_(4)and/or NaCl at 700℃.To improve the hot corrosion resistance,Ti45 A18.5 Nb alloy was anodized in fluorine-containing solution an...The hot corrosion behavior of Ti45 A18.5 Nb alloy was studied in the salt of Na_(2)SO_(4)and/or NaCl at 700℃.To improve the hot corrosion resistance,Ti45 A18.5 Nb alloy was anodized in fluorine-containing solution and pre-oxidized in air.Results showed that the combination of anodization and pre-oxidation can efficiently enhance the hot corrosion resistance of Ti45 A18.5 Nb alloy contaminated with Na_(2)SO_(4)or Na_(2)SO_(4)+NaCl deposits.This is because anodization and pre-oxidation result in the formation of compact AlOlayer which can act as a diffusion barrier to prevent sulfur,chlorine,and oxygen from attacking the alloy,therefore providing good resistance against hot corrosion.When exposed to NaCl deposit,however,no obvious improvement was achieved on the hot corrosion behavior no matter the alloy was anodized or further pre-oxidized in air.展开更多
The iodine-catalyzed nucleophilic addition of pyrrole to acetone has been studied by density functional theory at the level of Lanl2DZ＊. It has been shown that the first iodine molecule appears to have a remarkable c...The iodine-catalyzed nucleophilic addition of pyrrole to acetone has been studied by density functional theory at the level of Lanl2DZ＊. It has been shown that the first iodine molecule appears to have a remarkable catalytic effect on this reaction by halogen bond between carbonyl oxygen and iodine molecule, but the second one does not improve the reaction largely. In general, the nucleophilic addition at the C（2） site of pyrrole is more favorable than that at the C（3） site; however, this trend is not prominent or even changed in acetronitrile solvent for the indole system, which is consistent with the experimental result by Bandgar.展开更多
The ab initio method has been used to study the 1-3 H transfer reaction on formamidine substituted by halogen. The calculation results show that the substituted halogen has two effects on the 1-3 H transfer reaction...The ab initio method has been used to study the 1-3 H transfer reaction on formamidine substituted by halogen. The calculation results show that the substituted halogen has two effects on the 1-3 H transfer reaction: decreasing the activation energy and stabilizing the C=N double bond owing to the conjugative effect of p-π-p of products and transition states.展开更多
Controlling microstructure and thin film morphology of organic semiconductors by supramolecular arrangement is critical to improving their device performance. To realize well-controlling supramolecular assembly, a cor...Controlling microstructure and thin film morphology of organic semiconductors by supramolecular arrangement is critical to improving their device performance. To realize well-controlling supramolecular assembly, a core-expanded naphthalene diimides derivative （1） was designed and synthesized as an n-type organic semiconductor and also as a halogen bonding （XB） donor that could form complementary XBs with 2,2-dipyridine or 2,2-bipyrimidine acceptor. The XB interactions in the solid state of 1/2,2- dipyridine and 1/2,2-bipyrimidine were confirmed by a series of characterization methods, such as thermal gravimetric analysis （TGA）, X-ray photoelectron spectroscopy （XPS）, nuclear magnetic resonance （NMR） involving 13F NMR and solid-state 13C NMR. Organic field-effect transistors （OFETs） based on XB complexes 1/2,2-dipyridine or 1/2,2-bipyrimidine showed better device performance than that of devices based on pure 1, with the average electron mobility increased more than doubled （from 0.027cm2V-1 s-1 to 0.070cm2V-1 s-1）.展开更多
To shield TiAl alloy from hot corrosion attack,a compact protective coating was fabricated by the combination of aluminizing,anodization and pre-oxidation.The hot corrosion behavior of the coated-TiAl specimen was inv...To shield TiAl alloy from hot corrosion attack,a compact protective coating was fabricated by the combination of aluminizing,anodization and pre-oxidation.The hot corrosion behavior of the coated-TiAl specimen was investigated in the mixture salt consisting of 75 wt.%Na2SO4 and 25 wt.%NaCl at 700°C.Results indicated that the anodization and pre-oxidation were beneficial to the generation of Al2O3 layer,which could act as a diffusion barrier to prevent the molten salts and oxygen from diffusing into the alloy during exposure to a hot corrosion environment while the aluminizing coating could provide sufficient aluminum source to support the continuous formation of Al2O3 layer.Moreover,the internal stress of the coating was reduced due to the formation of a gradient coating consisting of TiAl3 and TiAl2.展开更多
采用间苯二酚二苯基磷酸酯(RDP)复配大环分子葫芦[6]脲(CB[6])对聚碳酸酯(PC)进行无卤阻燃改性。通过极限氧指数仪、锥形量热仪、热失重分析仪及扫描电子显微镜测试分析了阻燃体系的阻燃性能、热性能及燃烧炭层的微观形貌。结果表明,RDP...采用间苯二酚二苯基磷酸酯(RDP)复配大环分子葫芦[6]脲(CB[6])对聚碳酸酯(PC)进行无卤阻燃改性。通过极限氧指数仪、锥形量热仪、热失重分析仪及扫描电子显微镜测试分析了阻燃体系的阻燃性能、热性能及燃烧炭层的微观形貌。结果表明,RDP与CB[6]复配质量比为6∶2时阻燃效果最好,材料的极限氧指数达到32.5%,通过UL94 V-0级,热释放速率峰值(PHRR)降低至266 k W/m2;复配阻燃体系的加入改善了PC热稳定性,提高了阻燃复合材料的残炭率;复配阻燃体系能促进形成连续致密的膨胀炭层。展开更多
文摘Cis-trans isomerization of [9]-annulenanion（1） and its 2-fluoro-,2-chloro-and 2-bromo-derivatives（2,3 and 4,respectively） were investigated at the HF/6-31G＊ and B3LYP/6-311＋＋G＊＊ levels of theory.Cis,cis,cis,cis structures appear more stable than their corresponding cis,cis,cis,trans-isomers.The relative height of energy barriers for cis-trans isomerization is：2cis 〉1cis 〉3cis〉 4cis.This trend for the reverse trans-cis isomerization follows the electronegativity of the substituent at C-2（2trans 3trans 4trans 1trans）.
基金supported by the National Natural Science Foundation of China (21771049, 21622402)the Fundamental Research Funds for the Central Universities+2 种基金the National Thousand Young Talents Programthe Jiangsu Specially-Appointed Professor Planthe Natural Science Foundation of Jiangsu Province (BK20170631)
文摘Phenylethynyl palladium(Ⅱ) complexes have proven to be effective catalysts for coordination polymerization of isocyanides. In this work, two new phenylethynyl palladium(Ⅱ) initiators bearing bromide(1b) and iodide(1c) were synthesized and applied for living polymerization of aryl and alkyl isocyanides. The coordinated halogen anions can significantly influence the kinetics of polymerization, with the observed order of reaction rates being 1c(Ⅰ)>1 b(Br)>1a(Cl). Impressively, 1c not only accelerates the reaction rate in both the initiation stage and propagation stage, but also can polymerize less active monomers that cannot be reacted by 1a. DFT calculations were then employed to understand the detailed mechanism and the halogen effects in this insertion polymerization process.
基金supported by the National Natural Science Foundation of China(No.51971205)the Guangdong Basic and Applied Basic Research Foundation(No.2021B1515020056)the Basic Research Project of Shenzhen Science and Technology Innovation Program(No.JCYJ20190807154005593)。
文摘The hot corrosion behavior of Ti45 A18.5 Nb alloy was studied in the salt of Na_(2)SO_(4)and/or NaCl at 700℃.To improve the hot corrosion resistance,Ti45 A18.5 Nb alloy was anodized in fluorine-containing solution and pre-oxidized in air.Results showed that the combination of anodization and pre-oxidation can efficiently enhance the hot corrosion resistance of Ti45 A18.5 Nb alloy contaminated with Na_(2)SO_(4)or Na_(2)SO_(4)+NaCl deposits.This is because anodization and pre-oxidation result in the formation of compact AlOlayer which can act as a diffusion barrier to prevent sulfur,chlorine,and oxygen from attacking the alloy,therefore providing good resistance against hot corrosion.When exposed to NaCl deposit,however,no obvious improvement was achieved on the hot corrosion behavior no matter the alloy was anodized or further pre-oxidized in air.
基金the Natural Science Foundation of Zhejiang Province (Y406374)
文摘The iodine-catalyzed nucleophilic addition of pyrrole to acetone has been studied by density functional theory at the level of Lanl2DZ＊. It has been shown that the first iodine molecule appears to have a remarkable catalytic effect on this reaction by halogen bond between carbonyl oxygen and iodine molecule, but the second one does not improve the reaction largely. In general, the nucleophilic addition at the C（2） site of pyrrole is more favorable than that at the C（3） site; however, this trend is not prominent or even changed in acetronitrile solvent for the indole system, which is consistent with the experimental result by Bandgar.
基金Supported by the Yunnan Provincial Science and Technology Department (2003A0003M)
文摘The ab initio method has been used to study the 1-3 H transfer reaction on formamidine substituted by halogen. The calculation results show that the substituted halogen has two effects on the 1-3 H transfer reaction: decreasing the activation energy and stabilizing the C=N double bond owing to the conjugative effect of p-π-p of products and transition states.
基金supported financially by the National Natural Science Foundation of China(Nos.21502218 and 21522209)the "Strategic Priority Research Program"(No. XDB12010100)
文摘Controlling microstructure and thin film morphology of organic semiconductors by supramolecular arrangement is critical to improving their device performance. To realize well-controlling supramolecular assembly, a core-expanded naphthalene diimides derivative （1） was designed and synthesized as an n-type organic semiconductor and also as a halogen bonding （XB） donor that could form complementary XBs with 2,2-dipyridine or 2,2-bipyrimidine acceptor. The XB interactions in the solid state of 1/2,2- dipyridine and 1/2,2-bipyrimidine were confirmed by a series of characterization methods, such as thermal gravimetric analysis （TGA）, X-ray photoelectron spectroscopy （XPS）, nuclear magnetic resonance （NMR） involving 13F NMR and solid-state 13C NMR. Organic field-effect transistors （OFETs） based on XB complexes 1/2,2-dipyridine or 1/2,2-bipyrimidine showed better device performance than that of devices based on pure 1, with the average electron mobility increased more than doubled （from 0.027cm2V-1 s-1 to 0.070cm2V-1 s-1）.
基金The authors are grateful for the financial supports from the National Natural Science Foundation of China(51971205)Shenzhen Science and Technology Innovation Program,China(JCYJ20190807154005593)the Fundamental Research Funds for the Central Universities,China(19lgpy20).
文摘To shield TiAl alloy from hot corrosion attack,a compact protective coating was fabricated by the combination of aluminizing,anodization and pre-oxidation.The hot corrosion behavior of the coated-TiAl specimen was investigated in the mixture salt consisting of 75 wt.%Na2SO4 and 25 wt.%NaCl at 700°C.Results indicated that the anodization and pre-oxidation were beneficial to the generation of Al2O3 layer,which could act as a diffusion barrier to prevent the molten salts and oxygen from diffusing into the alloy during exposure to a hot corrosion environment while the aluminizing coating could provide sufficient aluminum source to support the continuous formation of Al2O3 layer.Moreover,the internal stress of the coating was reduced due to the formation of a gradient coating consisting of TiAl3 and TiAl2.
文摘采用间苯二酚二苯基磷酸酯(RDP)复配大环分子葫芦[6]脲(CB[6])对聚碳酸酯(PC)进行无卤阻燃改性。通过极限氧指数仪、锥形量热仪、热失重分析仪及扫描电子显微镜测试分析了阻燃体系的阻燃性能、热性能及燃烧炭层的微观形貌。结果表明,RDP与CB[6]复配质量比为6∶2时阻燃效果最好,材料的极限氧指数达到32.5%,通过UL94 V-0级,热释放速率峰值(PHRR)降低至266 k W/m2;复配阻燃体系的加入改善了PC热稳定性,提高了阻燃复合材料的残炭率;复配阻燃体系能促进形成连续致密的膨胀炭层。
