The directing mechanisms of liquid directing agents of zeolite Y and zeolite L were studied by means of light transmission, ultracentrifugation, NMR, XRD and “cross-exchange” experiments. It was discovered that not ...The directing mechanisms of liquid directing agents of zeolite Y and zeolite L were studied by means of light transmission, ultracentrifugation, NMR, XRD and “cross-exchange” experiments. It was discovered that not only microcfystals of zeolites, but also cage structures of zeolites play the directing role for crystallization of zeolites.展开更多
The molar mass distribution of SSO in the first generation derived from the hydrolytic condensation oftwo trialkoxysilanes, [ 3- ( Methacryloxy ) propyl ] trimethoxysilane ( MPMS ) and vinyltrimethoxysilane ( VMS ) ,a...The molar mass distribution of SSO in the first generation derived from the hydrolytic condensation oftwo trialkoxysilanes, [ 3- ( Methacryloxy ) propyl ] trimethoxysilane ( MPMS ) and vinyltrimethoxysilane ( VMS ) ,are determined by UV-MALDI-TOF MS. The comparisons of theoretical masses with experimental masses arecalculated using the proposed compounds, which are assigned to formulas Tn (OH)m, Tn (OMe)y orTn(OH)x(OMe)y[T=RSiO1.5 (x+y)/2n, R=--(CH2)3OOCCH(CH3)CH2 and--CHCH2]. Both theproposed cage and ladder structures of SSO derived from similar sol-gel process of monomers are illustrated. Thecauses for the difference in structures between SSO M and SSO V is discussed as well.展开更多
Intramolecular[2+2]photocycloaddition is a reliable way to synthesize high-strained cyclobutylcontaining structures for high-value chemicals.Here we propose a photosensitized dimer of methyl cyclopentadiene(DMCPD)intr...Intramolecular[2+2]photocycloaddition is a reliable way to synthesize high-strained cyclobutylcontaining structures for high-value chemicals.Here we propose a photosensitized dimer of methyl cyclopentadiene(DMCPD)intramolecular[2+2]cycloaddition to synthesize an intriguing liquid caged fuel,namely 3,8-dimethylpentacyclic[5.3.0.0^(2,5).0^(3,9).0^(4.8)]decane(MPCD),with two four-membered rings,four five-membered rings and two methyl branched chains.The reaction conditions are optimized to obtain a high DMCPD conversion of 80.95%as well as a high MPCD selectivity of 74.19%.Based on the quenching experiment and low-temperature phosphorescence test,intramolecular[2+2]photocycloaddition complies with the Dexter triplet-energy-transfer mechanism,which is essentially double electron exchange between excited photosensitizer and DMCPD.Through kinetic studies,the reaction order(α=1)and the reaction kinetic equation related to light intensity and DMCPD concentration are obtained.MPCD has excellent physicochemical properties,with a high density of 0.964 g·cm^(-3),high net heat of combustion of 42.63 MJ·kg^(-1),relatively low kinetic viscosity of 25.03 mm^(2)·s^(-1)at(20℃),and high specific impulse of 328.19 s.展开更多
Perfluorocubane(C_(8)F_(8))has a hollow cage structure which can store an electron upon electrochemical reduction.Similarly,fullerenes can encapsulate various metallic species inside their cages to form endohedral met...Perfluorocubane(C_(8)F_(8))has a hollow cage structure which can store an electron upon electrochemical reduction.Similarly,fullerenes can encapsulate various metallic species inside their cages to form endohedral metallofullerenes(EMFs),and the possible existence of internal metal-metal bonds is important for understanding the nature of the chemical bond.Besides,although the spherical aromaticity for fullerenes has been proposed for decades,it is seldom reported for EMFs.展开更多
The vortex formed around the rolling ball and the high pressure region formed around the ball-raceway contact zone are the principle factors that barricades the lubricant entering the bearing cavity, and further cause...The vortex formed around the rolling ball and the high pressure region formed around the ball-raceway contact zone are the principle factors that barricades the lubricant entering the bearing cavity, and further causes improper lubrication. The investigation of the air phase flow inside the bearing cavity is essential for the optimization of the oil-air two-phase lubrication method. With the revolutionary reference frame describing the bearing motion, a highly precise air phase flow model inside the angular contact ball bearing cavity was build up. Comprehensive factors such as bearing revolution, ball rotation, and cage structure were considered to investigate the influences on the air phase flow and heat transfer efficiency. The aerodynamic noise was also analyzed. The result shows that the ball spinning leads to the pressure rise and uneven pressure distribution. The air phase velocity, pressure and cage heat transfer efficiency increase as the revolving speed increases. The operating noise is largely due to the impact of the high speed external flow on the bearing. When the center of the oil-air outlet fixes near the inner ring, the aerodynamic noise is reduced. The position near the inner ring on the bigger axial side is the ideal position to fix the lubricating device for the angular contact ball bearing.展开更多
Engineering the structure of the M₃N cluster within a fullerene cage by the combination of versatile metal ions is one of the most powerful strategies to build metallofullerenes with fine-tuned structures and properti...Engineering the structure of the M₃N cluster within a fullerene cage by the combination of versatile metal ions is one of the most powerful strategies to build metallofullerenes with fine-tuned structures and properties.However,alongside their compositional versatility,mixed-metal clusters pose a challenge for structural elucidation because of the overlapping positions of different metal atoms.Here,we expand the size of metal ions in M₂ScN@C₈₀to M=Nd³⁺(R³⁺=0.983Å),whose large ionic radius results in the pyramidalization of encapsulated Nd₂ScN,which is the first example of a pyramidal M₂ScN cluster inside C₈₀.The combination of the pyramidalization,strong alteration of Nd–N and Sc–N bond lengths,and an overlap of two cluster orientations results in four nitrogen sites,which were unambiguously located by single crystal X-ray diffraction(SC-XRD).We demonstrate that judicious modelling of non-metal and overlapping metal positions is paramount for precise SC-XRD determination of structural parameters in metallofullerenes,which will otherwise suffer from erroneous structural interpretations.These results deepen our understanding of the fascinating M₃N@C₈₀ and pave the way for better control over the fine-tuning of their structures and properties.展开更多
Understanding the exact position of metal atom(s)within a cage is critical for elucidating the structural characteristics,metal–cage interplay and stability mechanism of endohedral metallofullerenes(EMFs).But it beco...Understanding the exact position of metal atom(s)within a cage is critical for elucidating the structural characteristics,metal–cage interplay and stability mechanism of endohedral metallofullerenes(EMFs).But it becomes rather challenging for the emerging actinide EMFs due to the variable oxidation state and complex valence orbitals of the encapsulated metals.Herein,density functional theory calculations were carried out for all 25 reported Th/U-based mono-metallofullerenes(mono-EMFs)with well-defined single crystal structures.The electronic ground states of Th-and U-contained mono-EMFs are singlet and triplet/quintet,respectively.Th always formally assumes the IV oxidation state inside the cage,whereas U has the Ⅲ or IV valence state highly depending on the cage structure.Due to the considerable intramolecular charge transfer(Th:4e;U:3e or 4e),their metal–cage interactions are mainly ionic,but with non-negligible covalent components largely contributed by the spatially extended Th/U-5f orbitals.Importantly,all the internal Th^(4+)/U^(3+)/^(4+)cations can be located by only considering the frontier molecular orbital distributions of the corresponding empty cages rather than the electrostatic potentials of cage anions commonly used for the classic lanthanide mono-EMFs.Such an obvious deviation from the simple ionic model(M^(q+)@C_(2n)^(q−))is ascribed to the strong actinide–cage covalency,which leads to much lower actual metal charge than the formal one.Our work unprecedently finds the overlooked important role of cage orbitals in determining the internal metal positions of all actinide mono-EMFs.It not only demonstrates the uniqueness of actinide EMFs,but also could help understand the structural characteristics of more EMFs with multiple possible internal metal locations.展开更多
基金Department of Envirenmental Medicine, Bethune University of Medical Sciences
文摘The directing mechanisms of liquid directing agents of zeolite Y and zeolite L were studied by means of light transmission, ultracentrifugation, NMR, XRD and “cross-exchange” experiments. It was discovered that not only microcfystals of zeolites, but also cage structures of zeolites play the directing role for crystallization of zeolites.
基金Sponsored by the Foundation of Department of Science and Technology of Heilongjiang Province
文摘The molar mass distribution of SSO in the first generation derived from the hydrolytic condensation oftwo trialkoxysilanes, [ 3- ( Methacryloxy ) propyl ] trimethoxysilane ( MPMS ) and vinyltrimethoxysilane ( VMS ) ,are determined by UV-MALDI-TOF MS. The comparisons of theoretical masses with experimental masses arecalculated using the proposed compounds, which are assigned to formulas Tn (OH)m, Tn (OMe)y orTn(OH)x(OMe)y[T=RSiO1.5 (x+y)/2n, R=--(CH2)3OOCCH(CH3)CH2 and--CHCH2]. Both theproposed cage and ladder structures of SSO derived from similar sol-gel process of monomers are illustrated. Thecauses for the difference in structures between SSO M and SSO V is discussed as well.
基金support from the National Natural Science Foundation of China(22222808,22408272,U24A20547)the China National Postdoctoral Program for Innovative Talents(BX20240251)+3 种基金the Natural Science Foundation of Tianjin(24JCQNJC01820)the China Postdoctoral Science Foundation(2023M742592)the Aeronautical Science Foundation of China(2023Z073048003)the Haihe Laboratory of Sustainable Chemical Transformations。
文摘Intramolecular[2+2]photocycloaddition is a reliable way to synthesize high-strained cyclobutylcontaining structures for high-value chemicals.Here we propose a photosensitized dimer of methyl cyclopentadiene(DMCPD)intramolecular[2+2]cycloaddition to synthesize an intriguing liquid caged fuel,namely 3,8-dimethylpentacyclic[5.3.0.0^(2,5).0^(3,9).0^(4.8)]decane(MPCD),with two four-membered rings,four five-membered rings and two methyl branched chains.The reaction conditions are optimized to obtain a high DMCPD conversion of 80.95%as well as a high MPCD selectivity of 74.19%.Based on the quenching experiment and low-temperature phosphorescence test,intramolecular[2+2]photocycloaddition complies with the Dexter triplet-energy-transfer mechanism,which is essentially double electron exchange between excited photosensitizer and DMCPD.Through kinetic studies,the reaction order(α=1)and the reaction kinetic equation related to light intensity and DMCPD concentration are obtained.MPCD has excellent physicochemical properties,with a high density of 0.964 g·cm^(-3),high net heat of combustion of 42.63 MJ·kg^(-1),relatively low kinetic viscosity of 25.03 mm^(2)·s^(-1)at(20℃),and high specific impulse of 328.19 s.
基金support from the National Natural Science Foundation of China(No.22171068)Natural Science Foundation of Hebei Province(B2022202036).
文摘Perfluorocubane(C_(8)F_(8))has a hollow cage structure which can store an electron upon electrochemical reduction.Similarly,fullerenes can encapsulate various metallic species inside their cages to form endohedral metallofullerenes(EMFs),and the possible existence of internal metal-metal bonds is important for understanding the nature of the chemical bond.Besides,although the spherical aromaticity for fullerenes has been proposed for decades,it is seldom reported for EMFs.
基金Project(2011CB706606) supported by the National Basic Research of ChinaProject(51405375) supported by the National Natural Science Foundation of China
文摘The vortex formed around the rolling ball and the high pressure region formed around the ball-raceway contact zone are the principle factors that barricades the lubricant entering the bearing cavity, and further causes improper lubrication. The investigation of the air phase flow inside the bearing cavity is essential for the optimization of the oil-air two-phase lubrication method. With the revolutionary reference frame describing the bearing motion, a highly precise air phase flow model inside the angular contact ball bearing cavity was build up. Comprehensive factors such as bearing revolution, ball rotation, and cage structure were considered to investigate the influences on the air phase flow and heat transfer efficiency. The aerodynamic noise was also analyzed. The result shows that the ball spinning leads to the pressure rise and uneven pressure distribution. The air phase velocity, pressure and cage heat transfer efficiency increase as the revolving speed increases. The operating noise is largely due to the impact of the high speed external flow on the bearing. When the center of the oil-air outlet fixes near the inner ring, the aerodynamic noise is reduced. The position near the inner ring on the bigger axial side is the ideal position to fix the lubricating device for the angular contact ball bearing.
基金support from the Deutsche Forschungsgemeinschaft(grants LI 3055/3-1,PO 1602/7-1,and PO 1602/11-1)the Jiangsu Specially Appointed Professorship,and the China Scholarship Council for the fellowship to WY。
文摘Engineering the structure of the M₃N cluster within a fullerene cage by the combination of versatile metal ions is one of the most powerful strategies to build metallofullerenes with fine-tuned structures and properties.However,alongside their compositional versatility,mixed-metal clusters pose a challenge for structural elucidation because of the overlapping positions of different metal atoms.Here,we expand the size of metal ions in M₂ScN@C₈₀to M=Nd³⁺(R³⁺=0.983Å),whose large ionic radius results in the pyramidalization of encapsulated Nd₂ScN,which is the first example of a pyramidal M₂ScN cluster inside C₈₀.The combination of the pyramidalization,strong alteration of Nd–N and Sc–N bond lengths,and an overlap of two cluster orientations results in four nitrogen sites,which were unambiguously located by single crystal X-ray diffraction(SC-XRD).We demonstrate that judicious modelling of non-metal and overlapping metal positions is paramount for precise SC-XRD determination of structural parameters in metallofullerenes,which will otherwise suffer from erroneous structural interpretations.These results deepen our understanding of the fascinating M₃N@C₈₀ and pave the way for better control over the fine-tuning of their structures and properties.
基金support from the National Natural Science Foundation of China(No.22171068)the Natural Science Foundation of Hebei Province(B2022202036)。
文摘Understanding the exact position of metal atom(s)within a cage is critical for elucidating the structural characteristics,metal–cage interplay and stability mechanism of endohedral metallofullerenes(EMFs).But it becomes rather challenging for the emerging actinide EMFs due to the variable oxidation state and complex valence orbitals of the encapsulated metals.Herein,density functional theory calculations were carried out for all 25 reported Th/U-based mono-metallofullerenes(mono-EMFs)with well-defined single crystal structures.The electronic ground states of Th-and U-contained mono-EMFs are singlet and triplet/quintet,respectively.Th always formally assumes the IV oxidation state inside the cage,whereas U has the Ⅲ or IV valence state highly depending on the cage structure.Due to the considerable intramolecular charge transfer(Th:4e;U:3e or 4e),their metal–cage interactions are mainly ionic,but with non-negligible covalent components largely contributed by the spatially extended Th/U-5f orbitals.Importantly,all the internal Th^(4+)/U^(3+)/^(4+)cations can be located by only considering the frontier molecular orbital distributions of the corresponding empty cages rather than the electrostatic potentials of cage anions commonly used for the classic lanthanide mono-EMFs.Such an obvious deviation from the simple ionic model(M^(q+)@C_(2n)^(q−))is ascribed to the strong actinide–cage covalency,which leads to much lower actual metal charge than the formal one.Our work unprecedently finds the overlooked important role of cage orbitals in determining the internal metal positions of all actinide mono-EMFs.It not only demonstrates the uniqueness of actinide EMFs,but also could help understand the structural characteristics of more EMFs with multiple possible internal metal locations.
