Molecular dynamics simulations are performed to observe the evolutions of 512 and 51262 cage-like water clusters filled with or without a methane molecule immersed in bulk liquid water at 250 K and 230 K. The lifetime...Molecular dynamics simulations are performed to observe the evolutions of 512 and 51262 cage-like water clusters filled with or without a methane molecule immersed in bulk liquid water at 250 K and 230 K. The lifetimes of these clusters are calculated according to their Lindemann index δ (t) using the criteria of δ≥0.07. For both the filled and empty clusters, we find the dynamics of bulk water determines the lifetimes of cage-like water clusters, and that the lifetime of 512 62 cage-like cluster is the same as that of 512 cage-like cluster. Although the methane molecule indeed makes the filled cage-like cluster more stable than the empty one, the empty cage-like cluster still has chance to be long-lived compared with the filled clusters. These observations support the labile cluster hypothesis on the formation mechanisms of gas hydrates.展开更多
Mesoporous carbons have been widely utilized as the sulfur host for lithium-sulfur （Li-S） batteries. The ability to engineer the porosity, wall thickness, and graphitization degree of the carbon host is essential fo...Mesoporous carbons have been widely utilized as the sulfur host for lithium-sulfur （Li-S） batteries. The ability to engineer the porosity, wall thickness, and graphitization degree of the carbon host is essential for addressing issues that hamper commercialization of Li-S batteries, such as fast capacity decay and poor high-rate performance. In this work, highly ordered, ultrathin mesoporous graphitic-carbon frameworks （MGFs） having unique cage-like mesoporosity, derived from self-assembled Fe304 nanoparticle superlattices, are demonstrated to be an excellent host for encapsulating sulfur. The resulting S@MGFs exhibit high specific capacity （1,446 mAh.g-1 at 0.15 C）, good rate capability （430 mAh.g-1 at 6 C）, and exceptional cycling stability （-0.049% capacity decay per cycle at 1 C） when used as Li-S cathodes. The superior electrochemical performance of the S@MGFs is attributed to the many unique and advantageous structural features of MGFs. In addition to the interconnected, ultrathin graphitic-carbon framework that ensures rapid electron and lithium-ion transport, the microporous openings between adjacent mesopores efficiently suppress the diffusion of polysulfides, leading to improved capacity retention even at high current densities.展开更多
Cage-like octa(trimethylsiloxy)silsesquioxane [(Me3SiO)SiO1.5]8 has been synthesized via the trimethylsilylation of cubic tetramethylammonium silicate octamer [(Me4NO)-SiO1.5]8 with chlorotrimethylsilane. The silicate...Cage-like octa(trimethylsiloxy)silsesquioxane [(Me3SiO)SiO1.5]8 has been synthesized via the trimethylsilylation of cubic tetramethylammonium silicate octamer [(Me4NO)-SiO1.5]8 with chlorotrimethylsilane. The silicate octamer can be selectively formed by the reaction of tetraethoxysilane Si(OEt)4 with aqueous tetramethylammonium hydroxide in equal展开更多
Coordination polymeric solid, {[Ag 2 (bpp) 2 (H 2 O) 2 ](chd)·9H 2 O} n (1) (bpp = 1,3-bis(4-pyridyl) propane, H 2 chd = 1,4-cyclo-hexanedicarboxylic acid), has been obtained by the solution phase ultrasonic synt...Coordination polymeric solid, {[Ag 2 (bpp) 2 (H 2 O) 2 ](chd)·9H 2 O} n (1) (bpp = 1,3-bis(4-pyridyl) propane, H 2 chd = 1,4-cyclo-hexanedicarboxylic acid), has been obtained by the solution phase ultrasonic synthesis techniques. The structure established through X-ray structural analysis shows that the compound traps an interesting 1D water tape built by the alternating "three-pointed star" cage-like pentameric and D 2h tetrameric clusters (C2/c, Z = 4; a = 30.37(2) , b = 9.271(5) , and c = 18.89(1) ; β = 128.47°; V = 4164(4) 3 ). The novelty of the present complex is the rarely crystallographic example of the cage-shaped water pentamer, which is usually ascribed to a less-stable species. A first-principle density functional theory (DFT) calculation demonstrates that the interconnectivity between cage-like pentamers and D 2h tetramers is beneficial for contribution to the structural stabilization of these less-stable water cluster species.展开更多
A chemical investigation on Sporormiella sp.led to the isolation and structural elucidation of tripodalsporormielones Ae C(1-3),a new class of polyketide possessing unprecedented cage-like skeletons with polyvdent bri...A chemical investigation on Sporormiella sp.led to the isolation and structural elucidation of tripodalsporormielones Ae C(1-3),a new class of polyketide possessing unprecedented cage-like skeletons with polyvdent bridged and fused ring systems.These polyketides with cage-like skeletons were characterized as a high non-protonated carbon-containing system,which resulted in few HMBC correlations observed and made the accurate structures hard to be obtained by NMR.Especially,some signals of non-protonated sp;carbons are weak and even unobservable in compound 1.In order to establish the structure of 1,the calculated NMR with DP4 evaluation was applied to determine the structure from the plausible structure candidates obtained from the detailed NMR analysis.Based on NMR experiments and calculated NMR,the structures of isolated compounds were established and confirmed by X-ray technology.Through chiral isolation,the optically pure enantiomers of 1 and 3 were obtained,and their absolute configurations were determined based on ECD quantum chemical calculation.Based on the isolated compounds and our previous work,1-3 would be derived from 3-methylorcinaldehyde,and their plausible biosynthetic mechanism was proposed.Furthermore,1 exhibited obvious short-term memory improvement activity on an Alzheimer’s disease fly model.展开更多
A novel Pd（ll） organometal catalyst with three-dimensional （3D） cage-like la3d cubic mesoporous structure and high surface area was prepared. In comparison with the corresponding catalyst with two-dimensional （2D...A novel Pd（ll） organometal catalyst with three-dimensional （3D） cage-like la3d cubic mesoporous structure and high surface area was prepared. In comparison with the corresponding catalyst with two-dimensional （2D） P6mm hexagonal mesoporous structure, the as-prepared catalyst exhibited higher activities in the water-medium Suzuki coupling reactions owing to the diminished diffusion limit. It showed comparable efficiencies with the Pd（PPh3）2C12 homogeneous catalyst and could be easily recycled and reused for five times without significant loss of activity.展开更多
A new tripod polyaromatic acid ligand H3TCM（H3TCM={2,4,6-tris1,3,5-trimethylbenzene}） and its binuclear rare earth complex \·2DMF were prepared and the structure of complex was characterized by single crystal X...A new tripod polyaromatic acid ligand H3TCM（H3TCM={2,4,6-tris1,3,5-trimethylbenzene}） and its binuclear rare earth complex \·2DMF were prepared and the structure of complex was characterized by single crystal X-ray diffraction. The complex crystallizes in triclinic crystal system, space group P1 with a=1.123 3（2） nm, b=1.374 1（2） nm, （c=）1.731 8（2） nm, α=78.19（1）°, β=80.02（1）°, γ=80.08（1）°, V=2.550 8（7） nm3, Z=1, （R=）0.035 8, wR=0.080 3. Two TCM ligands that are both in cis, cis, cis-conformations adopt face-to-face orientation and are joined together by two La3+ to a novel binuclear cage-like structure. Two DMF molecules are encapsulated in this cage by coordination. In addition, the other two free DMF molecules are embedded in the channels from the packing of these units along a and b axises.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.40102005 and No.49725205).
文摘Molecular dynamics simulations are performed to observe the evolutions of 512 and 51262 cage-like water clusters filled with or without a methane molecule immersed in bulk liquid water at 250 K and 230 K. The lifetimes of these clusters are calculated according to their Lindemann index δ (t) using the criteria of δ≥0.07. For both the filled and empty clusters, we find the dynamics of bulk water determines the lifetimes of cage-like water clusters, and that the lifetime of 512 62 cage-like cluster is the same as that of 512 cage-like cluster. Although the methane molecule indeed makes the filled cage-like cluster more stable than the empty one, the empty cage-like cluster still has chance to be long-lived compared with the filled clusters. These observations support the labile cluster hypothesis on the formation mechanisms of gas hydrates.
基金A. G. D. acknowledges the financial support from the National Basic Research Program of China （No. 2014CB845602）, Natural National Science Foundation of China （No. 21373052）, and Shanghai International Science and Technology Cooperation Project （No. 15520720100）. D. Y. is grateful for financial support from Natural National Science Foundation of China （Nos. 51373035, 51373040, 51573030, and 51573028）, and International Science and Technology Cooperation Program of China （No. 2014DFE40130）.
文摘Mesoporous carbons have been widely utilized as the sulfur host for lithium-sulfur （Li-S） batteries. The ability to engineer the porosity, wall thickness, and graphitization degree of the carbon host is essential for addressing issues that hamper commercialization of Li-S batteries, such as fast capacity decay and poor high-rate performance. In this work, highly ordered, ultrathin mesoporous graphitic-carbon frameworks （MGFs） having unique cage-like mesoporosity, derived from self-assembled Fe304 nanoparticle superlattices, are demonstrated to be an excellent host for encapsulating sulfur. The resulting S@MGFs exhibit high specific capacity （1,446 mAh.g-1 at 0.15 C）, good rate capability （430 mAh.g-1 at 6 C）, and exceptional cycling stability （-0.049% capacity decay per cycle at 1 C） when used as Li-S cathodes. The superior electrochemical performance of the S@MGFs is attributed to the many unique and advantageous structural features of MGFs. In addition to the interconnected, ultrathin graphitic-carbon framework that ensures rapid electron and lithium-ion transport, the microporous openings between adjacent mesopores efficiently suppress the diffusion of polysulfides, leading to improved capacity retention even at high current densities.
文摘Cage-like octa(trimethylsiloxy)silsesquioxane [(Me3SiO)SiO1.5]8 has been synthesized via the trimethylsilylation of cubic tetramethylammonium silicate octamer [(Me4NO)-SiO1.5]8 with chlorotrimethylsilane. The silicate octamer can be selectively formed by the reaction of tetraethoxysilane Si(OEt)4 with aqueous tetramethylammonium hydroxide in equal
基金supported by the National Natural Science Foundation of China (50971063)the Natural Science Foundation of Fujian Province (2003F006, 2010J01042, 2011J01047)+1 种基金the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry of Chinathe Startup Package Funding of Huaqiao University (10BS210) for supporting
文摘Coordination polymeric solid, {[Ag 2 (bpp) 2 (H 2 O) 2 ](chd)·9H 2 O} n (1) (bpp = 1,3-bis(4-pyridyl) propane, H 2 chd = 1,4-cyclo-hexanedicarboxylic acid), has been obtained by the solution phase ultrasonic synthesis techniques. The structure established through X-ray structural analysis shows that the compound traps an interesting 1D water tape built by the alternating "three-pointed star" cage-like pentameric and D 2h tetrameric clusters (C2/c, Z = 4; a = 30.37(2) , b = 9.271(5) , and c = 18.89(1) ; β = 128.47°; V = 4164(4) 3 ). The novelty of the present complex is the rarely crystallographic example of the cage-shaped water pentamer, which is usually ascribed to a less-stable species. A first-principle density functional theory (DFT) calculation demonstrates that the interconnectivity between cage-like pentamers and D 2h tetramers is beneficial for contribution to the structural stabilization of these less-stable water cluster species.
基金financially supported by grants from National Key Research and Development Program of China(2018YF A0903200/2018YFA0903201)the National Natural Science Foundation of China(81925037 and 81973213)+5 种基金Chang Jiang Scholars Program(Young Scholar)from the Ministry of Education of China(Hao Gao,2017)National High-level Personnel of Special Support Program(2017RA2259,China)the 111 Project of Ministry of Education of the People’s Republic of China(B13038)the Guangdong Natural Science Funds for Distinguished Young Scholar(2017A03036027,China)Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program(2017BT01Y036,China)K.C.Wong Education Foundation(Hao Gao,2016,China)。
文摘A chemical investigation on Sporormiella sp.led to the isolation and structural elucidation of tripodalsporormielones Ae C(1-3),a new class of polyketide possessing unprecedented cage-like skeletons with polyvdent bridged and fused ring systems.These polyketides with cage-like skeletons were characterized as a high non-protonated carbon-containing system,which resulted in few HMBC correlations observed and made the accurate structures hard to be obtained by NMR.Especially,some signals of non-protonated sp;carbons are weak and even unobservable in compound 1.In order to establish the structure of 1,the calculated NMR with DP4 evaluation was applied to determine the structure from the plausible structure candidates obtained from the detailed NMR analysis.Based on NMR experiments and calculated NMR,the structures of isolated compounds were established and confirmed by X-ray technology.Through chiral isolation,the optically pure enantiomers of 1 and 3 were obtained,and their absolute configurations were determined based on ECD quantum chemical calculation.Based on the isolated compounds and our previous work,1-3 would be derived from 3-methylorcinaldehyde,and their plausible biosynthetic mechanism was proposed.Furthermore,1 exhibited obvious short-term memory improvement activity on an Alzheimer’s disease fly model.
文摘A novel Pd（ll） organometal catalyst with three-dimensional （3D） cage-like la3d cubic mesoporous structure and high surface area was prepared. In comparison with the corresponding catalyst with two-dimensional （2D） P6mm hexagonal mesoporous structure, the as-prepared catalyst exhibited higher activities in the water-medium Suzuki coupling reactions owing to the diminished diffusion limit. It showed comparable efficiencies with the Pd（PPh3）2C12 homogeneous catalyst and could be easily recycled and reused for five times without significant loss of activity.
文摘A new tripod polyaromatic acid ligand H3TCM（H3TCM={2,4,6-tris1,3,5-trimethylbenzene}） and its binuclear rare earth complex \·2DMF were prepared and the structure of complex was characterized by single crystal X-ray diffraction. The complex crystallizes in triclinic crystal system, space group P1 with a=1.123 3（2） nm, b=1.374 1（2） nm, （c=）1.731 8（2） nm, α=78.19（1）°, β=80.02（1）°, γ=80.08（1）°, V=2.550 8（7） nm3, Z=1, （R=）0.035 8, wR=0.080 3. Two TCM ligands that are both in cis, cis, cis-conformations adopt face-to-face orientation and are joined together by two La3+ to a novel binuclear cage-like structure. Two DMF molecules are encapsulated in this cage by coordination. In addition, the other two free DMF molecules are embedded in the channels from the packing of these units along a and b axises.
