The reactions of anionic zirconium oxide clusters ZrxOy- with C2H6 and C4H10 are investi-gated by a time of flight mass spectrometer coupled with a laser vaporization cluster source.Hydrogen containing products Zr2O5H...The reactions of anionic zirconium oxide clusters ZrxOy- with C2H6 and C4H10 are investi-gated by a time of flight mass spectrometer coupled with a laser vaporization cluster source.Hydrogen containing products Zr2O5H- and Zr3O7H- are observed after the reaction. Den-sity functional theory calculations indicate that the hydrogen abstraction is favorable in the reaction of Zr2O5- with C2H6, which supports that the observed Zr2O5H- and Zr3O7H- are due to hydrogen atom abstraction from the alkane molecules. This work shows a newpossible pathway in the reaction of zirconium oxide cluster anions with alkane molecules.展开更多
MTBPyP (meso-tetrakis(4-N-benzylpyridyl)porphyrin, M=H-2, Zn) bearing positive charge has been shown to associate with SiW12O404- in water solution. The spectral evolution and Job's plots analyses reveal that the ...MTBPyP (meso-tetrakis(4-N-benzylpyridyl)porphyrin, M=H-2, Zn) bearing positive charge has been shown to associate with SiW12O404- in water solution. The spectral evolution and Job's plots analyses reveal that the relatively stable aggregates contain equal numbers of MTBPyP4(+) and SiW12O404-.展开更多
In the framework of density functional theory （DFT）, the electronic excitations and nonlinear optical （NLO） properties of six binuclear transition metal cluster anions with the formula of [Ch2M-（μ-Ch）2-M＇CN]^...In the framework of density functional theory （DFT）, the electronic excitations and nonlinear optical （NLO） properties of six binuclear transition metal cluster anions with the formula of [Ch2M-（μ-Ch）2-M＇CN]^2- （M = Mo, W; Ch = S, Se; M＇ = Cu, Ag） have been systemically investigated at both cases of gas phase and DMF solution. The obtained electronic absorption spectra reveal that the element replacements of metals M and ligands Ch have significant influence on the absorptions, especially on the low-lying ones. In addition, the transitions of μ-Ch→M are dominant for the low-lying excitations, whereas the transitions of M＇→M as well as Ch→M are mainly responsible for the higher excitations. The calculated molecular first and second hyperpolarizabilities present the remarkable element substitution and solvent effects. The analyses show that the transitions involving μ-Ch→M charge transfer make the critical contributions to the first hyperpolarizability t, and that the charge transfers from the moieties of MCh4 to M＇CN as well as those of μ-Ch→M and M＇→M are responsible for the second hyperpolarizability y. Moreover, the introduction of solvent leads to the results that the transitions within the moieties of MCh4 and M＇CN make larger contributions to the hyperpolarizability, especially to γ.展开更多
Using a laser vaporization/pulsed molecular beam cluster source,Al cluster anions and Al-C mixed cluster anions are produced and recorded by a time of flight mass spectrometer.Mass abundance spectra of the Al cluster ...Using a laser vaporization/pulsed molecular beam cluster source,Al cluster anions and Al-C mixed cluster anions are produced and recorded by a time of flight mass spectrometer.Mass abundance spectra of the Al cluster anions in the size range from Al_(2)^(-)to Al_(42)^(-)show that Al_(13)^(-),Al_(23)^(-),Al_(35)^(-),and slightly,Al_(37)^(-)are local maxima,as predicted by the electronic jellium model.Mixed clusters Aln C-and Aln C_(2)^(-)are also shown,among which the most abundant species are Al3 C2,Al6 C_(2)^(-),A_(l7)C^(-)and A_(l7)C_(2)^(-)in the small size range.The formation mechanism of these products is discussed.展开更多
Two lanthanide-oxo-cluster polymers were synthesized by hydrothermal reaction using Ln_2O_3 as initial lanthanide materials：[Ln_4（SO_4）_4（OH）_4（H_2O）_7]·_4H_2O（Ln = Er 1,Ho 2）,and characterized by PXRD,I...Two lanthanide-oxo-cluster polymers were synthesized by hydrothermal reaction using Ln_2O_3 as initial lanthanide materials：[Ln_4（SO_4）_4（OH）_4（H_2O）_7]·_4H_2O（Ln = Er 1,Ho 2）,and characterized by PXRD,IR spectra,X-ray single-crystal diffraction,2D IR correlation spectra and UV-visible absorption spectra.Single-crystal X-ray analyses reveal that compounds 1 and 2 are isostructural,and they are both crystallized in the orthorhombic system Pccn space group.Compound 1 is a 3D lanthanide cluster polymer based on tetranuclear cubane-like [Er_4（μ_3-OH）_4]^8＋ cations and SO_4^2- anions.The overall structure of 1 can be assigned to 6-connected pcu-type topology with the point symbol of（4^12.6^3）.展开更多
Photocatalytic water splitting and carbon dioxide photoreduction are considered eff ective strategies for alleviating the energy crisis and environmental pollution.Polynuclear metal-oxo clusters possess excellent elec...Photocatalytic water splitting and carbon dioxide photoreduction are considered eff ective strategies for alleviating the energy crisis and environmental pollution.Polynuclear metal-oxo clusters possess excellent electron storage/release ability and unique catalytic properties via intermetallic synergy,which enables them with great potential in environmentally friendly photosynthesis.Importantly,metal-oxo clusters with precise structure can not only act as high-effi ciency catalysts but also provide well-defi ned structural models for exploring structure-activity relationships.In this review,we systematically sum-marize recent progress in the catalytic application of polynuclear metal-oxo clusters,including polyoxometalate clusters,low-cost transition metal clusters,and metal-oxo-cluster-based metal-organic frameworks for water splitting and CO_(2)reduction.Furthermore,we discuss the challenges and solutions to the problems of polynuclear metal-oxo clusters in photocatalysis.展开更多
The fascinating chemical structure and broad application prospect of Keggin-type polyoxometalates(POMs)have attracted many chemists to explore and discover continuously.Unlike the traditional Keggin,larger metal atomi...The fascinating chemical structure and broad application prospect of Keggin-type polyoxometalates(POMs)have attracted many chemists to explore and discover continuously.Unlike the traditional Keggin,larger metal atomic radius,higher metal coordinated numbers,lower metal valence states and other features allow the group IVB metal-based Keggin(IVB-Keggin)more space and unknown in terms of structure and performance.Herein,density functional theory(DFT)calculations were performed to explore the influences including cores,shells,caps,and terminal ligands,et al.on IVB-Keggin,and analyze the possibility of novel structure synthesis.From the perspective of multi-layer onion-like clusters,molecular energy level,host-guest interaction energy,surface charge and covalent bond polarity can be further adjusted to achieve the oriented design of functional IVB-Keggin.These insights are expected to provide theoretical support for experimental synthesis,opening a new perspective to understand the growth of Keggin.展开更多
In this review,the history and outlook of gas-phase CO_(2)activation using single electrons,metal atoms,clusters(mainly metal hydride clusters),and molecules are discussed on both of the experimental and theoretical f...In this review,the history and outlook of gas-phase CO_(2)activation using single electrons,metal atoms,clusters(mainly metal hydride clusters),and molecules are discussed on both of the experimental and theoretical fronts.Although the development of bulk solid-state materials for the activation and conversion of CO_(2)into value-added products have enjoyed great success in the past several decades,this review focuses only on gas-phase studies,because isolated,well-defined gas-phase systems are ideally suited for high-resolution experiments using state-of-the-art spectrometric and spectroscopic techniques,and for simulations employing modern quantum theoretical methods.The unmatched high complementarity and comparability of experiment and theory in the case of gas-phase investigations bear an enormous potential in providing insights in the reactions of CO_(2)activation at the atomic level.In all of these examples,the reduction and bending of the inert neutral CO_(2)molecule is the critical step determined by the frontier orbitals of reaction participants.Based on the results and outlook summarized in this review,we anticipate that studies of gas-phase CO_(2)activations will be an avenue rich with opportunities for the rational design of novel catalysts based on the knowledge obtained on the atomic level.展开更多
The anionic products from the reactions between metal（M=Ag, Au, Pd, Pt, Pb and Bi） vapour produced by laser ablation and hexafluorobenzene seeded in carrier gas（Ar） were studied by means of a homemade reflectron t...The anionic products from the reactions between metal（M=Ag, Au, Pd, Pt, Pb and Bi） vapour produced by laser ablation and hexafluorobenzene seeded in carrier gas（Ar） were studied by means of a homemade reflectron time-of-flight mass spectrometry（RTOF-MS）. Experimental results show that the dominant products were [MmC6F6]^- complexes for the reactions ofAg, Au, Pd and Pt with C6F6, while the dominant products were [MmC6F5]^- complexes for the reactions of Pb and Bi with C6F6. The formation mechanisms of the products, including the adsorption of metal cluster anions on hexafluorobenzene and the C--F cleavage induced by metal cluster anions, were discussed.展开更多
The precise syntheses of transition-rare-earth metal clusters with desired structures remain a great challenge.Herein,by utilizing SO_(4)^(2-)anion released by in-situ decomposition of sodium dodecyl sulfate(SDS)as a ...The precise syntheses of transition-rare-earth metal clusters with desired structures remain a great challenge.Herein,by utilizing SO_(4)^(2-)anion released by in-situ decomposition of sodium dodecyl sulfate(SDS)as a template,a series of novel high-nuclearity 3d-4f clusters,formulated as[Ni_(24)Pr_(22)(μ_(3)-OH)_(31)(pida)_(24)(SO_(4))_(4)(NO_(3))_(9)(CH_(3)COO)_(3)]·Br_(4)·(NO_(3))_(11)·_(16)H_(2)O·25CH_(3)OH(1,H_(2)pida=N-phenyliminodiacetic acid),[Ni_(24)Nd_(22)(μ3-OH)_(31)(pida)_(24)(SO_(4))_(4)(NO_(3))_(9)(CH_(3)COO)_(3)]·Br_(4)·(NO_(3))_(11)·14H_(2)O·24CH_(3)OH(2)and[Ni_(24)Gd_(22)(μ3-OH)_(36)(bida)_(24)(SO_(4))_(7)(NO_(3))_(3)(CH_(3)COO)_(3)]·(SO_(4))·Br_(4)·(NO_(3))_(4)·31H_(2)O·32CH_(3)OH(3,H_(2)bida=N-benzyliminodiacetic acid),have been successfully isolated.X-ray crystal structure analyses reveal that all the cationic{Ni_(24)RE_(22)}cores in 1-3 possess a ball-like structure with C_(3v)symmetry,and can be viewed as consisting of an inner{RE_(22)}core and an outer{Ni_(24)}shell.From 1 and 2 to 3,due to the lanthanide contraction effect,the coordination numbers for rare-earth metal centers in{RE_(22)}are different,resulting in different number of SO_(4)^(2-)and NO_(3)^(-)anions to support and stabilize the skeleton structures.Meanwhile,the magnetic properties of complexes 1-3 were also studied.The result revealed that complexes 1-3 show antiferromagnetic/ferrimagnetic interactions,and 3 exhibits magneto-caloric effect at ultralow temperatures with a maximum-ΔSm(magnetic entropy change)value of 33.03 J·kg^(−1)·K^(−1)at 3.0 K and 7 T.展开更多
We report here the synthesis and characterization of two new members of the M2 E 12 family of endohe-dral Zintl clusters,[Fe_(2)Sn_(4)Bi_(8)]^(3-)and[Cr_(2)Sb_(12)]^(3-),both of which contain open-shell metal dimers e...We report here the synthesis and characterization of two new members of the M2 E 12 family of endohe-dral Zintl clusters,[Fe_(2)Sn_(4)Bi_(8)]^(3-)and[Cr_(2)Sb_(12)]^(3-),both of which contain open-shell metal dimers encap-sulated inside a triple-decker cluster of main-group atoms.The 75-electron[Fe_(2)Sn_(4)Bi_(8)]^(3-)cluster has a D4h-symmetric structure,while[Cr_(2)Sb_(12)]^(3-),despite having the same 75-electron count,is strongly dis-torted to a geometry that resembles a CrSb_(8)crown capped by a CrSb_(4)unit.The structural differences between the two are driven by the increasing availability of 3d electron density in the earlier transi-tion metal,which leads,ultimately,to different electronic configurations in the two clusters.The trends precisely mirror those observed in the ME_(10)and ME_(12)families containing a single transition metal ion.展开更多
提出了离子色谱法测定茶叶中F-、Cl-、NO2-、Br-、NO3-、H2PO4-、SO42-等无机阴离子的方法。采用Shodex IC SI-52 4E阴离子分离柱进行分离,以3.6mmol.L-1碳酸钠溶液和甲醇以体积比98比2混合所得溶液为淋洗液进行洗脱,从而实现7种阴离子...提出了离子色谱法测定茶叶中F-、Cl-、NO2-、Br-、NO3-、H2PO4-、SO42-等无机阴离子的方法。采用Shodex IC SI-52 4E阴离子分离柱进行分离,以3.6mmol.L-1碳酸钠溶液和甲醇以体积比98比2混合所得溶液为淋洗液进行洗脱,从而实现7种阴离子的分离。根据茶叶中分离出的7种阴离子含量的不同,利用聚类分析将16个茶叶样品进行分类。展开更多
基金This work was supported by the Chinese Academy of Sciences （Hundred Talents Fund）, the National Natural Science Foundation of China （No.20703048 and No.20803083）, and the Center of Molecular Science Foundation of Institute of Chemistry, Chinese Academy of Sciences （No.CMS-LX200902）.
文摘The reactions of anionic zirconium oxide clusters ZrxOy- with C2H6 and C4H10 are investi-gated by a time of flight mass spectrometer coupled with a laser vaporization cluster source.Hydrogen containing products Zr2O5H- and Zr3O7H- are observed after the reaction. Den-sity functional theory calculations indicate that the hydrogen abstraction is favorable in the reaction of Zr2O5- with C2H6, which supports that the observed Zr2O5H- and Zr3O7H- are due to hydrogen atom abstraction from the alkane molecules. This work shows a newpossible pathway in the reaction of zirconium oxide cluster anions with alkane molecules.
基金This work was supported by the National NatUral Science Foundation of China under grant! No.29733090 and No. 29803003 the Re
文摘MTBPyP (meso-tetrakis(4-N-benzylpyridyl)porphyrin, M=H-2, Zn) bearing positive charge has been shown to associate with SiW12O404- in water solution. The spectral evolution and Job's plots analyses reveal that the relatively stable aggregates contain equal numbers of MTBPyP4(+) and SiW12O404-.
基金the National Natural Science Foundation of China (No. 20573114)Foundation of Fujian Province (No. 2006F3133)
文摘In the framework of density functional theory （DFT）, the electronic excitations and nonlinear optical （NLO） properties of six binuclear transition metal cluster anions with the formula of [Ch2M-（μ-Ch）2-M＇CN]^2- （M = Mo, W; Ch = S, Se; M＇ = Cu, Ag） have been systemically investigated at both cases of gas phase and DMF solution. The obtained electronic absorption spectra reveal that the element replacements of metals M and ligands Ch have significant influence on the absorptions, especially on the low-lying ones. In addition, the transitions of μ-Ch→M are dominant for the low-lying excitations, whereas the transitions of M＇→M as well as Ch→M are mainly responsible for the higher excitations. The calculated molecular first and second hyperpolarizabilities present the remarkable element substitution and solvent effects. The analyses show that the transitions involving μ-Ch→M charge transfer make the critical contributions to the first hyperpolarizability t, and that the charge transfers from the moieties of MCh4 to M＇CN as well as those of μ-Ch→M and M＇→M are responsible for the second hyperpolarizability y. Moreover, the introduction of solvent leads to the results that the transitions within the moieties of MCh4 and M＇CN make larger contributions to the hyperpolarizability, especially to γ.
基金Supported by the National Natural Science Foundation of China under Grant No.29890210,and the National Climbing Project.
文摘Using a laser vaporization/pulsed molecular beam cluster source,Al cluster anions and Al-C mixed cluster anions are produced and recorded by a time of flight mass spectrometer.Mass abundance spectra of the Al cluster anions in the size range from Al_(2)^(-)to Al_(42)^(-)show that Al_(13)^(-),Al_(23)^(-),Al_(35)^(-),and slightly,Al_(37)^(-)are local maxima,as predicted by the electronic jellium model.Mixed clusters Aln C-and Aln C_(2)^(-)are also shown,among which the most abundant species are Al3 C2,Al6 C_(2)^(-),A_(l7)C^(-)and A_(l7)C_(2)^(-)in the small size range.The formation mechanism of these products is discussed.
基金supported by the National Natural Science Foundation of China(No.21473030)the Natural Science Foundation of Fujian Province(No.2013J01041)the Foundation of State Key Laboratory of Structural Chemistry(No.20130012)
文摘Two lanthanide-oxo-cluster polymers were synthesized by hydrothermal reaction using Ln_2O_3 as initial lanthanide materials：[Ln_4（SO_4）_4（OH）_4（H_2O）_7]·_4H_2O（Ln = Er 1,Ho 2）,and characterized by PXRD,IR spectra,X-ray single-crystal diffraction,2D IR correlation spectra and UV-visible absorption spectra.Single-crystal X-ray analyses reveal that compounds 1 and 2 are isostructural,and they are both crystallized in the orthorhombic system Pccn space group.Compound 1 is a 3D lanthanide cluster polymer based on tetranuclear cubane-like [Er_4（μ_3-OH）_4]^8＋ cations and SO_4^2- anions.The overall structure of 1 can be assigned to 6-connected pcu-type topology with the point symbol of（4^12.6^3）.
基金supported by National Natural Science Foundationof China(Grant No.21671113)the Science and Technology of Henan province in 2018(No.182102310873)+2 种基金2019 Special Project of Nanyang Normal University(Nos.2019ZX009 and 2019QN011)Project of Young Backbone Teachers in Colleges and Universities of Henan Province(No.2020GGJS180)2019 Henan Higher Education Teaching Reform Research and Practice Project(No.2019SJGLX093Y).
文摘Photocatalytic water splitting and carbon dioxide photoreduction are considered eff ective strategies for alleviating the energy crisis and environmental pollution.Polynuclear metal-oxo clusters possess excellent electron storage/release ability and unique catalytic properties via intermetallic synergy,which enables them with great potential in environmentally friendly photosynthesis.Importantly,metal-oxo clusters with precise structure can not only act as high-effi ciency catalysts but also provide well-defi ned structural models for exploring structure-activity relationships.In this review,we systematically sum-marize recent progress in the catalytic application of polynuclear metal-oxo clusters,including polyoxometalate clusters,low-cost transition metal clusters,and metal-oxo-cluster-based metal-organic frameworks for water splitting and CO_(2)reduction.Furthermore,we discuss the challenges and solutions to the problems of polynuclear metal-oxo clusters in photocatalysis.
基金financially supported by the National Natural Science Foundation of China(NSFC,Nos.22225109,22071109,92061101,22173016 and 22301084)the China Postdoctoral Science Foundation(No.2023M741232)。
文摘The fascinating chemical structure and broad application prospect of Keggin-type polyoxometalates(POMs)have attracted many chemists to explore and discover continuously.Unlike the traditional Keggin,larger metal atomic radius,higher metal coordinated numbers,lower metal valence states and other features allow the group IVB metal-based Keggin(IVB-Keggin)more space and unknown in terms of structure and performance.Herein,density functional theory(DFT)calculations were performed to explore the influences including cores,shells,caps,and terminal ligands,et al.on IVB-Keggin,and analyze the possibility of novel structure synthesis.From the perspective of multi-layer onion-like clusters,molecular energy level,host-guest interaction energy,surface charge and covalent bond polarity can be further adjusted to achieve the oriented design of functional IVB-Keggin.These insights are expected to provide theoretical support for experimental synthesis,opening a new perspective to understand the growth of Keggin.
基金National Key R&D Program of China(2018YFE0115000)the National Natural Science Foundation of China(22003027 and 22174073)+2 种基金the NSF of Tianjin City(19JCYBJC19600)the Frontiers Science Center for New Organic Matter of Nankai University(63181206)supported by the Air Force Office of Scientific Research(AFOSR)under grant number,FA9550-19-1-0077(KHB)。
文摘In this review,the history and outlook of gas-phase CO_(2)activation using single electrons,metal atoms,clusters(mainly metal hydride clusters),and molecules are discussed on both of the experimental and theoretical fronts.Although the development of bulk solid-state materials for the activation and conversion of CO_(2)into value-added products have enjoyed great success in the past several decades,this review focuses only on gas-phase studies,because isolated,well-defined gas-phase systems are ideally suited for high-resolution experiments using state-of-the-art spectrometric and spectroscopic techniques,and for simulations employing modern quantum theoretical methods.The unmatched high complementarity and comparability of experiment and theory in the case of gas-phase investigations bear an enormous potential in providing insights in the reactions of CO_(2)activation at the atomic level.In all of these examples,the reduction and bending of the inert neutral CO_(2)molecule is the critical step determined by the frontier orbitals of reaction participants.Based on the results and outlook summarized in this review,we anticipate that studies of gas-phase CO_(2)activations will be an avenue rich with opportunities for the rational design of novel catalysts based on the knowledge obtained on the atomic level.
基金Supported by the National Natural Science Foundation of China(No.20433080).
文摘The anionic products from the reactions between metal（M=Ag, Au, Pd, Pt, Pb and Bi） vapour produced by laser ablation and hexafluorobenzene seeded in carrier gas（Ar） were studied by means of a homemade reflectron time-of-flight mass spectrometry（RTOF-MS）. Experimental results show that the dominant products were [MmC6F6]^- complexes for the reactions ofAg, Au, Pd and Pt with C6F6, while the dominant products were [MmC6F5]^- complexes for the reactions of Pb and Bi with C6F6. The formation mechanisms of the products, including the adsorption of metal cluster anions on hexafluorobenzene and the C--F cleavage induced by metal cluster anions, were discussed.
基金support of National Natural Science Foundation of China(22375157 and 22271228)Special Support Plan of Shaanxi Province for Young Top-notch Talent,State Key Laboratory of Electrical Insulation and Power Equipment(No.EIPE23402)+1 种基金"Scientists+Engineers"Team Building Project of Qin Chuang Yuan(2022KXJ-088)the Medical-Engineering Cross Project of the First Affiliated Hospital of XJTU(QYJCO2).
文摘The precise syntheses of transition-rare-earth metal clusters with desired structures remain a great challenge.Herein,by utilizing SO_(4)^(2-)anion released by in-situ decomposition of sodium dodecyl sulfate(SDS)as a template,a series of novel high-nuclearity 3d-4f clusters,formulated as[Ni_(24)Pr_(22)(μ_(3)-OH)_(31)(pida)_(24)(SO_(4))_(4)(NO_(3))_(9)(CH_(3)COO)_(3)]·Br_(4)·(NO_(3))_(11)·_(16)H_(2)O·25CH_(3)OH(1,H_(2)pida=N-phenyliminodiacetic acid),[Ni_(24)Nd_(22)(μ3-OH)_(31)(pida)_(24)(SO_(4))_(4)(NO_(3))_(9)(CH_(3)COO)_(3)]·Br_(4)·(NO_(3))_(11)·14H_(2)O·24CH_(3)OH(2)and[Ni_(24)Gd_(22)(μ3-OH)_(36)(bida)_(24)(SO_(4))_(7)(NO_(3))_(3)(CH_(3)COO)_(3)]·(SO_(4))·Br_(4)·(NO_(3))_(4)·31H_(2)O·32CH_(3)OH(3,H_(2)bida=N-benzyliminodiacetic acid),have been successfully isolated.X-ray crystal structure analyses reveal that all the cationic{Ni_(24)RE_(22)}cores in 1-3 possess a ball-like structure with C_(3v)symmetry,and can be viewed as consisting of an inner{RE_(22)}core and an outer{Ni_(24)}shell.From 1 and 2 to 3,due to the lanthanide contraction effect,the coordination numbers for rare-earth metal centers in{RE_(22)}are different,resulting in different number of SO_(4)^(2-)and NO_(3)^(-)anions to support and stabilize the skeleton structures.Meanwhile,the magnetic properties of complexes 1-3 were also studied.The result revealed that complexes 1-3 show antiferromagnetic/ferrimagnetic interactions,and 3 exhibits magneto-caloric effect at ultralow temperatures with a maximum-ΔSm(magnetic entropy change)value of 33.03 J·kg^(−1)·K^(−1)at 3.0 K and 7 T.
基金supported by the National Natural Science Foundation of China(Nos.92161102,21971118)the Natural Science Foundation of Tianjin City(Nos.21JCZXJC00140,20JCYBJC01560)the 111 Project(No.B18030)from Ministry of Education China
文摘We report here the synthesis and characterization of two new members of the M2 E 12 family of endohe-dral Zintl clusters,[Fe_(2)Sn_(4)Bi_(8)]^(3-)and[Cr_(2)Sb_(12)]^(3-),both of which contain open-shell metal dimers encap-sulated inside a triple-decker cluster of main-group atoms.The 75-electron[Fe_(2)Sn_(4)Bi_(8)]^(3-)cluster has a D4h-symmetric structure,while[Cr_(2)Sb_(12)]^(3-),despite having the same 75-electron count,is strongly dis-torted to a geometry that resembles a CrSb_(8)crown capped by a CrSb_(4)unit.The structural differences between the two are driven by the increasing availability of 3d electron density in the earlier transi-tion metal,which leads,ultimately,to different electronic configurations in the two clusters.The trends precisely mirror those observed in the ME_(10)and ME_(12)families containing a single transition metal ion.
文摘提出了离子色谱法测定茶叶中F-、Cl-、NO2-、Br-、NO3-、H2PO4-、SO42-等无机阴离子的方法。采用Shodex IC SI-52 4E阴离子分离柱进行分离,以3.6mmol.L-1碳酸钠溶液和甲醇以体积比98比2混合所得溶液为淋洗液进行洗脱,从而实现7种阴离子的分离。根据茶叶中分离出的7种阴离子含量的不同,利用聚类分析将16个茶叶样品进行分类。
