In this study we present a(re-)investigation into cyclodimethylsiloxanes in relation to silyl-ether bonding towards alkali metal ions.We demonstrate that all(non-radioactive)alkali metal ions can be incorporated into ...In this study we present a(re-)investigation into cyclodimethylsiloxanes in relation to silyl-ether bonding towards alkali metal ions.We demonstrate that all(non-radioactive)alkali metal ions can be incorporated into D_(n) cyclosiloxane frameworks(D=(SiMe_(2)O),n=5–8),employing appropriate cation–anion combinations.Starting with the Li^(+)cation we were able to observe the coordination of D_(5) with Li^(+)based on a suitable X-ray structure after reacting D_(5) with LiI and GaI_(3).Due to template effects,the dinuclear coordination compound[Li2(D_(5))(D_(6))(GaI_(4))_(2)](1)was obtained.The direct reaction of D_(6) with LiI and GaI_(3) yields[Li(D_(6))GaI_(4)](2)in quantitative yield.Na^(+)ions could be trapped in D_(6) and D_(7) ligand moieties after the conversion of NaI,GaI_(3),and the respective siloxane.The molecular structure of[Na(D_(6))GaI_(4)](3)reveals a six-fold coordinated Na^(+)ion,which is located on top of the siloxane D_(6).In the case of[Na(D_(7))(DCM)GaI_(4)](4),the larger ligand D_(7) provides 15-crown-5-like geometry in which the sodium ion is coordinated by the ligand in a coplanar fashion and further saturated by the solvent DCM(DCM=dichloromethane).The K^(+)ion was bound within the D_(7) ligand in a similar manner and[K(D_(7))(DCM)GaI_(4)](5)could be characterized.Due to the resemblance of NH_(4)^(+)to K^(+),this cation was also employed for complex formation.Counterintuitively,we were able to synthesize and characterize the first ever non-metal-cyclosiloxane coordination compound.After the conversion of D_(6) with NH_(4)I and GaI_(3),the compound[NH_(4)(D_(7))][Ga_(2)I_(7)](6)was obtained.The ammonium cation favors D_(7) coordination over D_(6),and the willing formation of hydrogen bonding in such a siloxane moiety was realized.As these compounds could be obtained,we also tested the limits of silyl-ether bonding.Therefore,we reacted D_(8) with in situ generated Rb[GaI_(4)]and Cs[GaI_(4)].In the case of Rb^(+),we could cumbersomely characterize[Rb(D_(8))(DCM)GaI_(4)](7)via an X-ray structure,as well as by means of mass spectrometry,but the compound starts decomposing readily in solution.The reaction with the Cs^(+)salt failed.To obtain meaningful spectroscopic data from a Rb^(+)compound and to somehow obtain a Cs^(+)complex,we employed the weakly coordinating anion[Al_(F)]^(−)(Al_(F)^(−)=[Al{OC(CF_(3))_(3)}_(4)]^(−)).The conversion of M[Al_(F)]then yielded 11[M(D_(8))AL_(F)](M=Rb:8;M=Cs^(+):9)in the solid state.Both compounds 8 and 9 were fully characterized.Finally,we aimed at synthesizing 2:1 complexes of such siloxanes.The reactions of excess D_(5) with K[Al_(F)]and D_(6) with Cs[Al_(F)]turned out to be expedient and,in the forms of[K(D_(5))_(2)][Al_(F)](10)and[Cs(D_(6))_(2)][Al_(F)](12),the first ever sandwich-type complexes observed bearing a cyclosiloxane ligand were characterized.展开更多
Tomographic synthetic aperture radar(TomoSAR)has the ability to separate mixed scatterers,making it highly suitable for urban 3-dimensional(3D)reconstruction.However,Urban TomoSAR imaging still faces challenges such a...Tomographic synthetic aperture radar(TomoSAR)has the ability to separate mixed scatterers,making it highly suitable for urban 3-dimensional(3D)reconstruction.However,Urban TomoSAR imaging still faces challenges such as resolution limitations,multipath effects,the uncertainty on the flight track,and registration errors,resulting in sparse point clouds with holes and low accuracy.In this paper,we propose a Geometric Semantic Enhanced TomoSAR Reconstruction Algorithm(Geo-SETRA)for urban area.Geo-SETRA integrates geometric structures,extracted from TomoSAR point clouds,as prior distributions for elevation estimation using Bayesian methods.We first construct a sparse optimization model based on both compressed sensing and maximum a posteriori estimation,and also give its solution.Further,the Cramér-Rao lower bound of this algorithm is derived to theoretically illustrate how it improves imaging accuracy.Both simulated data and real-data experiments prove that our method is feasible and effective in urban 3D reconstruction.As a result,our method successfully produced a dense and realistic 3D scattering model for urban areas with minimal postprocessing,preserving detailed geometric structures and retaining over 80%of the points in the final model.展开更多
Chirality is a widespread phenomenon in nature,where two non-superimposable enantiomers exist with one being the mirror image of the other.The interplay between chirality and magnetism has recently drawn intensive int...Chirality is a widespread phenomenon in nature,where two non-superimposable enantiomers exist with one being the mirror image of the other.The interplay between chirality and magnetism has recently drawn intensive interest in non-centrosymmetric magnetic materials absent of both spatial and time inversion symmetries[1].Among various chiral magnetic effects,the electrical manifestation of the magneto-chiral effect is crucial for both fundamental science and technological applications[2,3].The non-reciprocal resistance depending on the inner product of the magnetic field(H)and the current density U),termed the electrical magneto-chiral effect(eMChE),has recently been demonstrated in correlated oxides[4,5].展开更多
基金financially supported by the Deutsche Forschungsgemeinschaft(DFG).
文摘In this study we present a(re-)investigation into cyclodimethylsiloxanes in relation to silyl-ether bonding towards alkali metal ions.We demonstrate that all(non-radioactive)alkali metal ions can be incorporated into D_(n) cyclosiloxane frameworks(D=(SiMe_(2)O),n=5–8),employing appropriate cation–anion combinations.Starting with the Li^(+)cation we were able to observe the coordination of D_(5) with Li^(+)based on a suitable X-ray structure after reacting D_(5) with LiI and GaI_(3).Due to template effects,the dinuclear coordination compound[Li2(D_(5))(D_(6))(GaI_(4))_(2)](1)was obtained.The direct reaction of D_(6) with LiI and GaI_(3) yields[Li(D_(6))GaI_(4)](2)in quantitative yield.Na^(+)ions could be trapped in D_(6) and D_(7) ligand moieties after the conversion of NaI,GaI_(3),and the respective siloxane.The molecular structure of[Na(D_(6))GaI_(4)](3)reveals a six-fold coordinated Na^(+)ion,which is located on top of the siloxane D_(6).In the case of[Na(D_(7))(DCM)GaI_(4)](4),the larger ligand D_(7) provides 15-crown-5-like geometry in which the sodium ion is coordinated by the ligand in a coplanar fashion and further saturated by the solvent DCM(DCM=dichloromethane).The K^(+)ion was bound within the D_(7) ligand in a similar manner and[K(D_(7))(DCM)GaI_(4)](5)could be characterized.Due to the resemblance of NH_(4)^(+)to K^(+),this cation was also employed for complex formation.Counterintuitively,we were able to synthesize and characterize the first ever non-metal-cyclosiloxane coordination compound.After the conversion of D_(6) with NH_(4)I and GaI_(3),the compound[NH_(4)(D_(7))][Ga_(2)I_(7)](6)was obtained.The ammonium cation favors D_(7) coordination over D_(6),and the willing formation of hydrogen bonding in such a siloxane moiety was realized.As these compounds could be obtained,we also tested the limits of silyl-ether bonding.Therefore,we reacted D_(8) with in situ generated Rb[GaI_(4)]and Cs[GaI_(4)].In the case of Rb^(+),we could cumbersomely characterize[Rb(D_(8))(DCM)GaI_(4)](7)via an X-ray structure,as well as by means of mass spectrometry,but the compound starts decomposing readily in solution.The reaction with the Cs^(+)salt failed.To obtain meaningful spectroscopic data from a Rb^(+)compound and to somehow obtain a Cs^(+)complex,we employed the weakly coordinating anion[Al_(F)]^(−)(Al_(F)^(−)=[Al{OC(CF_(3))_(3)}_(4)]^(−)).The conversion of M[Al_(F)]then yielded 11[M(D_(8))AL_(F)](M=Rb:8;M=Cs^(+):9)in the solid state.Both compounds 8 and 9 were fully characterized.Finally,we aimed at synthesizing 2:1 complexes of such siloxanes.The reactions of excess D_(5) with K[Al_(F)]and D_(6) with Cs[Al_(F)]turned out to be expedient and,in the forms of[K(D_(5))_(2)][Al_(F)](10)and[Cs(D_(6))_(2)][Al_(F)](12),the first ever sandwich-type complexes observed bearing a cyclosiloxane ligand were characterized.
基金supported by the National Natural Science Foundation of China(grant numbers 61991421,61991424,and 61991420).
文摘Tomographic synthetic aperture radar(TomoSAR)has the ability to separate mixed scatterers,making it highly suitable for urban 3-dimensional(3D)reconstruction.However,Urban TomoSAR imaging still faces challenges such as resolution limitations,multipath effects,the uncertainty on the flight track,and registration errors,resulting in sparse point clouds with holes and low accuracy.In this paper,we propose a Geometric Semantic Enhanced TomoSAR Reconstruction Algorithm(Geo-SETRA)for urban area.Geo-SETRA integrates geometric structures,extracted from TomoSAR point clouds,as prior distributions for elevation estimation using Bayesian methods.We first construct a sparse optimization model based on both compressed sensing and maximum a posteriori estimation,and also give its solution.Further,the Cramér-Rao lower bound of this algorithm is derived to theoretically illustrate how it improves imaging accuracy.Both simulated data and real-data experiments prove that our method is feasible and effective in urban 3D reconstruction.As a result,our method successfully produced a dense and realistic 3D scattering model for urban areas with minimal postprocessing,preserving detailed geometric structures and retaining over 80%of the points in the final model.
基金financially supported by the National Key R&D Program of China(2022YFA1403000 and 2022YFA1403300)the National Natural Science Foundation of China(52072244,12104305,12074080,12274088,11874054,and 12104301)+3 种基金the Science and Technology Commission of Shanghai Municipality(21JC1405000 and 21PJ410800)The research used resources from Analytical Instrumentation Center(#SPST-AIC10112914)C?EM(EM02161943)in Shanghai Tech Universitysupported by the U.S.DOE Office of Science-Basic Energy Sciences,under Contract No.DE-AC02-06CH11357。
文摘Chirality is a widespread phenomenon in nature,where two non-superimposable enantiomers exist with one being the mirror image of the other.The interplay between chirality and magnetism has recently drawn intensive interest in non-centrosymmetric magnetic materials absent of both spatial and time inversion symmetries[1].Among various chiral magnetic effects,the electrical manifestation of the magneto-chiral effect is crucial for both fundamental science and technological applications[2,3].The non-reciprocal resistance depending on the inner product of the magnetic field(H)and the current density U),termed the electrical magneto-chiral effect(eMChE),has recently been demonstrated in correlated oxides[4,5].
