A new layered mixed valence vanadium oxide, [CH 3NH 3] 2[(V ⅣO) 2(V ⅤO 4) 2], which contains interlamellar organic cations was prepared under hydrothermal conditions and its single crystal structure was determined. ...A new layered mixed valence vanadium oxide, [CH 3NH 3] 2[(V ⅣO) 2(V ⅤO 4) 2], which contains interlamellar organic cations was prepared under hydrothermal conditions and its single crystal structure was determined. It crystallizes in a triclinic system with space group P 1, a =0 625 59(8) nm, b =0 639 84(9) nm, c =0 747 19(10) nm, α =78 718(2)°, β =80 099(2)°, γ =77 100(2). The compound contains mixed valence V 4+ /V 5+ vanadium oxide layers constructed from VO 4 tetrahedra, pairs of edge sharing VO 5 square pyramid and methylamine with protonated organic amines occupying the interlayer space.展开更多
A novel Cu（II）-2,2＇-bipy-supported （bipy = bipyridine） mixed valence decatungstate, [Cu（2,2＇-bipy）2]2Na2W6^VW4^VIO30·2H2O 1, has been synthesized and structurally characterized by X-ray analysis. The crys...A novel Cu（II）-2,2＇-bipy-supported （bipy = bipyridine） mixed valence decatungstate, [Cu（2,2＇-bipy）2]2Na2W6^VW4^VIO30·2H2O 1, has been synthesized and structurally characterized by X-ray analysis. The crystal of 1 is of triclinic, space group P1^- with a= 10.9393（10）, b = 12.0492（2）, c = 12.3783（2）A, a = 80.631（10）, β= 70.226（10）, γ= 72.329（9）^o, V = 1459.64（4）A^3, Z = 1, Dc = 3.582 g/cm^3, F（000） = 1404, R = 0.0553 and wR = 0.1242 for 4607 observed reflections （I 〉 2σ（I））. The EPR spectrum of 1 indicates that its unpaired electrons are placed in the dx2-y2 orbital of the ground state of Cun. Furthermore, compound 1 shows an antiferromagnetic interaction.展开更多
Lead-based organic-inorganic hybrid perovskites have exhibited great potential in photovoltaics,achieving power conversion efficiencies(PCEs) exceeding 25%.However,the toxicity of lead and the instability of these mat...Lead-based organic-inorganic hybrid perovskites have exhibited great potential in photovoltaics,achieving power conversion efficiencies(PCEs) exceeding 25%.However,the toxicity of lead and the instability of these materials under moist conditions pose significant barriers to large-scale production.To overcome these limitations,researchers have proposed mixed-valence double perovskites,where Cs_(2)Au~ⅠAu~ⅢI_6 is a particularly effective absorber due to its suitable band gap and high absorptance efficiency.To further extend the scope of these lead-free materials,we varied the trivalent gold ion and halogen anion in Cs_(2)Au~ⅠAu~ⅢI_6,resulting in 18 new structures with unique properties.Further,using first-principles calculations and elimination criteria,we identified four materials with ideal band gaps,small effective carrier mass,and strong anisotropic optical properties.According to theoretical modeling,Cs_(2)AuSbCl_6,Cs_(2)AuInCl_6,and Cs_(2)AuBiCl_6 are potential candidates for solar cell absorbers,with a spectroscopic limited maximum efficiency(SLME) of approximately 30% in a 0.25 μm-thick film.These three compounds have not been previously reported,and therefore,our work provides new insights into potential materials for solar energy conversion.We aim for this theoretical exploration of novel perovskites to guide future experiments and accelerate the development of high-performance photovoltaic devices.展开更多
A novel mixed valance vanadium phosphate Na 3.6 H 1.4 P 2V 5O 18 ·11H 2O was synthesized by a hydrothermal method and its structure was characterized by X ray diffraction, infrared spectroscopy...A novel mixed valance vanadium phosphate Na 3.6 H 1.4 P 2V 5O 18 ·11H 2O was synthesized by a hydrothermal method and its structure was characterized by X ray diffraction, infrared spectroscopy, differential thermal analysis, and thermogravimetric analysis. Na 3.6 H 1.4 P 2V 5O 18 ·11H 2O crystallizes in the cubic system with the cell parameter a =1.601(8) nm. The ratio of V( Ⅳ)/ V(Ⅴ) in the compound is 3.55.展开更多
Reaction of the ligand dmpt（dmpt=6,7-dimethylbenzo[f][1,10]phenanthroline）with CuCl2 afforded mixed valent Cu（Ⅰ）/Cu（Ⅱ） discrete tetranuclear complexes[Cu（Ⅱ）Cl2（dmpt）Cu（Ⅰ）Cl]（1）,while the reaction of ...Reaction of the ligand dmpt（dmpt=6,7-dimethylbenzo[f][1,10]phenanthroline）with CuCl2 afforded mixed valent Cu（Ⅰ）/Cu（Ⅱ） discrete tetranuclear complexes[Cu（Ⅱ）Cl2（dmpt）Cu（Ⅰ）Cl]（1）,while the reaction of ligand dppz（dppz = dipyrido[3,2-a：20,30-c]phenazine） with divalent halogen copper salt CuX2（X=Cl,Br） gave one-dimensional chain mixed valent Cu（Ⅰ）/Cu（Ⅱ） complexes [Cu（Ⅱ）Cl2（dppz）Cu（Ⅰ）Cl]n（2） and discrete mixed valent Cu（Ⅰ）/Cu（Ⅱ）complexes [Cu（Ⅱ）Br2（dppz）（DMF）Cu（Ⅰ）Br]（3）. Complex 2 consists of a one-dimensional chain-dppzC u（Ⅱ）-Clμ2-Cu（Ⅰ）-Cl-dppzC u（Ⅱ）-Clμ2-Cu（Ⅰ）-with Cu（Ⅱ） and Cu（Ⅰ） atoms linked together by chloride anion. Complex 3 is a discrete complex,which is the same as complexes 1 and 2 involving two different copper valent Cu（Ⅰ） and Cu（Ⅱ）. The Cu（Ⅰ） ion presents a pseudo-trihedral geometry,while the Cu（Ⅱ） ion presents a slightly distorted square-pyramidal geometry. This fact proved that halogen ions play a vital role in the assembly procedure. Our research results demonstrate the structural diversification that can be achieved by halogen ions mediated. Moreover,halogen ions-mediated self-assembly may provide useful information for further design of compounds with novel structures and properties.展开更多
Cu metal and its oxides have attracted much attention for photocatalytic CO_(2)reduction reaction(CO_(2)RR),but the stability and effects of Cu oxidation states on CO_(2)RR are not fully understood.Cu^(x+)/Cu^(0)-load...Cu metal and its oxides have attracted much attention for photocatalytic CO_(2)reduction reaction(CO_(2)RR),but the stability and effects of Cu oxidation states on CO_(2)RR are not fully understood.Cu^(x+)/Cu^(0)-loaded graphitic carbon nitride(g-C_(3)N_(4))heterojunctions(Cu-CuO_(x)/g-C_(3)N_(4))are fabricated via a stepwise calcination method for efficient photocatalytic CO_(2)RR.Cu_(2)O is the main component of Cu-CuO_(x)and the mixed valence Cu includes Cu^(0),Cu^(+),and Cu^(2+),which play the role of charge trapping sites and redox catalytic centers during the photocatalytic CO_(2)RR process.The main products were CO and CH_(4)for the CO_(2)RR with production rates of 14.45 and 0.66μmol g^(-1)h^(-1)for CO and CH_(4),which were higher than those for g-C_(3)N_(4)and Cu-CuO_(x),respectively.This photocatalytic CO_(2)RR performance is attributed to the ultrafast switching of“Cu^(x+)−Cu^(0)”and e_(CB^(−))/h_(VB^(+))trapping transformation in Cu-CuO_(x)benefited from the built-in IEF between Cu-CuO_(x)and g-C_(3)N_(4),increasing the efficient photogenerated e_(CB^(−)),and enabling the stability of Cu-CuO_(x)/g-C_(3)N_(4).Cu^(x+)adsorbed by H_(2)O works as the electron trapping site to change to Cu^(0)and switch to the hole trapping site;Cu^(0)works as the hole trapping site to change to Cu^(x+)and switch to the electron trapping site,causing the CO_(2)RR of the adsorbed CO_(2).Moreover,the coordinated Cu^(0)and Cu^(+)species facilitate the activation of the adsorbed CO_(2)and^(∗)CO generation,these adsorbed^(∗)CO on Cu^(0)and Cu^(+)detected by in-situ DRIFTS quickly transformed to^(∗)CHO with a lower energy barrier benefited from the mixed Cu^(0)/Cu^(+)active sites during CORR to produce CH_(4).This finding provides a new insight into the influence of mixed valence Cu during photocatalytic CO_(2)RR.展开更多
A series of trimetallic cyanidometal-bridged compounds with the formula[CpMe_(x)Fe-NC-Ru-CN-FeCpMe_(x)]^(n+),N^(n+)(n=2,3 and 4;N=1,x=0;N=2,x=1;N=3,x=3;N=4,x=4;N=5,x=5),were synthesized and fully characterized.The eff...A series of trimetallic cyanidometal-bridged compounds with the formula[CpMe_(x)Fe-NC-Ru-CN-FeCpMe_(x)]^(n+),N^(n+)(n=2,3 and 4;N=1,x=0;N=2,x=1;N=3,x=3;N=4,x=4;N=5,x=5),were synthesized and fully characterized.The effect of the potential difference between the central and term-inal metals on the electron communication in these trinuclear mixed valence systems was investigated.N^(3+)and N^(4+)are the one-and two-electron oxidation products of N^(2+).Electrochemical measurements show the presence of electronic interactions between the two terminal Fe atoms.The electronic pro-perties of N^(3+)and N^(4+)were studied and compared using experimental spectroscopy and time-dependent density-functional calculations.As the number of methyl substituents on the cyclopentadiene ligand increases,the potential difference between the central and terminal redox centers increases and thus,the electron communication between the terminal Fe redox centers or between the neighboring Fe and Ru redox centers becomes weaker.All the mixed valence compounds show localized character.展开更多
Two new high-nuclearity mixed-valence Mn clusters,Mn_(19)and Mn_(21),were synthesised utilising an alkylamine-based flexible ligand with five alkoxo-bridging groups,1,3-bis-diethanolamino-2-propanol(H_(5)bdp).They wer...Two new high-nuclearity mixed-valence Mn clusters,Mn_(19)and Mn_(21),were synthesised utilising an alkylamine-based flexible ligand with five alkoxo-bridging groups,1,3-bis-diethanolamino-2-propanol(H_(5)bdp).They were obtained from the reaction of Mn(O_(2)CPh)_(2)·2H_(2)O with H_(5)bdp·2HCl·H_(2)O and Et_(3)N in a 4:1:7 molar ratio in CH_(3)CN/CH_(3)OH mixed solution.The X-ray crystal structures revealed{Mn_(8)^(Ⅱ)Mn_(10)^(Ⅲ)Mn^(Ⅳ)}and{Mn_(6)^(Ⅱ)Mn_(15)^(Ⅲ)}mixed-valence cores composed around{Mn_(7)O_(8)}corner-shared double cubanes.Magnetic susceptibility measurements on both complexes indicated dominant intramolecular antiferromagnetic interactions between Mn ions.No clear SMM behaviour was observed above 1.8 K due to the non-parallel alignment of magnetic anisotropy axes of the Mn^(Ⅲ)ions.展开更多
The reaction of[Co(PMe_(3))_(4)](1)with a redox-active NNN pincer ligand(L_(1))led us to isolate a unique binuclear cobalt complex([(PMe_(3))_(2)Co^(II)(L_(1)^(3−))CoI(PMe_(3))_(3)](2))anchored by a three-electron red...The reaction of[Co(PMe_(3))_(4)](1)with a redox-active NNN pincer ligand(L_(1))led us to isolate a unique binuclear cobalt complex([(PMe_(3))_(2)Co^(II)(L_(1)^(3−))CoI(PMe_(3))_(3)](2))anchored by a three-electron reduced L_(1)in its unusual coordination mode.Such an unprecedented binuclear pincer/allyl cobalt complex consisting of the mixed-valence oxidation state of cobalt ions(+1 and+2)is confirmed by various analytical techniques(XPS,EPR,and UV–vis),and the experimentally determined electronic structure is well corroborated by detailed theoretical studies based on DFT calculations.展开更多
In this work,we report two multi-component MOFs[CH_(3)NH_(2)CH_(3)]_(2)[Fe_(2)^(Ⅲ)M_(10)^(Ⅱ)(tz)(11)(HCO_(2))_(12)(btc)_(5/3)](M_(10)^(Ⅱ)=Fe_(10)^(Ⅱ)for 1 and M_(10)^(Ⅱ)=Fe_(2)^(Ⅱ)Co^(8)_(Ⅱ)for 2)obtained by so...In this work,we report two multi-component MOFs[CH_(3)NH_(2)CH_(3)]_(2)[Fe_(2)^(Ⅲ)M_(10)^(Ⅱ)(tz)(11)(HCO_(2))_(12)(btc)_(5/3)](M_(10)^(Ⅱ)=Fe_(10)^(Ⅱ)for 1 and M_(10)^(Ⅱ)=Fe_(2)^(Ⅱ)Co^(8)_(Ⅱ)for 2)obtained by solvothermal reaction of benzene-1,3,5-tricarboxylate(btc)and 1,2,4 triazole(tz),Fe^(Ⅱ)and Fe^(Ⅲ)/Co^(Ⅱ)in DMF.In the complexes,several different types of metal rings(9,12-number metal ions)are generated,and the connection of those rings gives the complicated three-dimensional structure.The two complexes exhibit electronic conductivity and good alkali stability,which makes them potential OER electrocatalysts.It is revealed that the cobalt ion greatly enhances the OER performance,and the electrode prepared using 2 shows a low overpotential of 339 mV at 10 mA cm^(−1).展开更多
A two-dimensional,mixed-valence[Ni(dmit)_(2)]compound,[C8-Apy]2[Ni(dmit)_(2)]_(3)(1)(where dmit^(2-)=2-thioxo-1,3-dithiole-4,5-dithiolate and Apy^(+)=4-amino-1-alkylpyridinium),was prepared and its structure was fully...A two-dimensional,mixed-valence[Ni(dmit)_(2)]compound,[C8-Apy]2[Ni(dmit)_(2)]_(3)(1)(where dmit^(2-)=2-thioxo-1,3-dithiole-4,5-dithiolate and Apy^(+)=4-amino-1-alkylpyridinium),was prepared and its structure was fully characterized.The molecular solid displays a layered structure along the crystallographic c-axis with a[Ni(dmit)_(2)]layer constructed from alternating straight chains of[Ni(dmit)_(2)]^(0) and two-legged ladder chains of[Ni(dmit)_(2)]^(1-).Compound 1 shows an antiferromagnetic,spin-dimer with pairwise interaction magnetic behavior and a semiconducting nature in addition to a rapid,clear and stable response of photoconductivity under UV irradiation.The magnetic coupling nature of 1 was analyzed using the‘broken-symmetry’density functional theory(DFT)approach.The electronic band structure was calculated using the CASTEP program and was used to investigate the theoretical transport and photoconductive behavior of 1.This work suggests that mixed-valence[Ni(dmit)_(2)]compounds have great potential as the building blocks for new photoconductor based materials.展开更多
Valence-delocalized bimetallic copper cores are found at the biological CuA sites,which are well-known for their electron transfer reactivity accompanying the transition between fully delocalized Class III and partial...Valence-delocalized bimetallic copper cores are found at the biological CuA sites,which are well-known for their electron transfer reactivity accompanying the transition between fully delocalized Class III and partially delocalized Class II sites.Understanding the electron transfer reactivity of CuA sites when both delocalizations are available within the same ligand platform would be helpful,but few complexes with the same ligand scaffold have been reported.Here,we report the syntheses and characterization of two different classes of bimetallic copper complexes Na(THF)_(x){^(NMe2)[NNNN]Cu}_(2)(1)and ^(NMe2)[NNNN]Cu_(2)(OAc)(2)using the same tetradentate ligand NMe_(2)[NNNN].X-ray crystallographic studies revealed that the coordination environments around bimetallic cores in 1 are distorted,whereas those for 2 are symmetric.The electron paramagnetic resonance(EPR)spectrum of 1 was deconvoluted using the different contributions from each copper,which was supported by the characteristic intervalence charge transfer(IVCT)bands of Robin-Day Class II partial delocalization observed in the UV-vis spectrum.The symmetric coordination environment of 2 matches the fully delocalized Class III copper ions,as confirmed by the characteristic septet hyperfine splitting in the EPR spectrum and IVCT band in the UV-vis spectrum.The crystallographic data and electronic spectra were successfully reproduced using the DFT and TD-DFT calculations.Frontier molecular orbital(FMO)analysis revealed that the SOMO of 1 is 3d_(z^(2-))based,while that of 2 is 3d_(x^(2)-y^(2))-based.Finally,the observed structural and electronic variations of bimetallic mixed valence cores gave rise to the reactivity differences as demonstrated with tests of O_(2),Ph_(3)CCl,and DPPH radical scavenging assays.展开更多
The development of noble-metal-free and efficient metal–organic frameworks(MOFs)as heterogeneous catalysts for carbon dioxide(CO_(2))conversion is of particular interest,but remains challenging.In this study,a Cu^(Ⅰ...The development of noble-metal-free and efficient metal–organic frameworks(MOFs)as heterogeneous catalysts for carbon dioxide(CO_(2))conversion is of particular interest,but remains challenging.In this study,a Cu^(Ⅰ)/Cu^(Ⅱ) mixed-valence MOF(1)was synthesized,consisting of copper(Ⅰ)cyclic trinuclear units(Cu^(Ⅰ)-CTUs)and Cu^(Ⅱ)-paddlewheel units.The MOF featured a(3,4,4)-c network topology,which is rarely reported in the literature.Interestingly,1 demonstrated efficient catalytic activity in the cyclization reaction of epoxides or propargyl amines with CO_(2) with excellent yields(i.e.,81%to 99%for 12 examples).Additionally,it showed high reusability,maintaining the catalytic performance for at least five cycles without a loss in efficiency.Of significant note,MOF 1 delivered high catalytic activity with a turnover frequency of 142.8 h^(−1)(23.8 h^(−1) based on Cu)for the synthesis of oxazolidinones at ambient temperature,showcasing its potential as an effective catalyst for CO_(2) conversion reactions.展开更多
Cerium dioxide(CeO_(2))octahedra were synthesized by a facile microwave-assisted hydrothermal method.The structure and morphology were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM)and trans...Cerium dioxide(CeO_(2))octahedra were synthesized by a facile microwave-assisted hydrothermal method.The structure and morphology were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results showed that octahedra were enclosed by eight(111)facets with an edge length of 180 nm.展开更多
A new compound Na_(5)Mn_(4)(PO_(4))_(4)F_(4)·2H_(2)O was successfully obtained,featuring a typical channel structure composed of rarely mixed valence Mn^(2+)/Mn^(3+)spin chains and PO_(4) tetrahedra,where H_(2)O ...A new compound Na_(5)Mn_(4)(PO_(4))_(4)F_(4)·2H_(2)O was successfully obtained,featuring a typical channel structure composed of rarely mixed valence Mn^(2+)/Mn^(3+)spin chains and PO_(4) tetrahedra,where H_(2)O molecules are located inside the channels.Magnetic measurements show that this compound possesses successive multiple magnetic transitions at low temperature.展开更多
A series of luminescent dinuclear mixed-valence gold alkynyl complexes,[(tBuC^N^CtBu)Au^(Ⅲ)(CuC)-AuⅠ(PPh3)],[(RC^N^CR)Au^(Ⅲ)(CuCCuC)Au^(Ⅰ)(PPh3)](R=H,tBu),[(RC^N^CR)Au^(Ⅲ)(CuCC6H4CuC)Au^(Ⅰ)(PPh3)](R=H,tBu),and[(...A series of luminescent dinuclear mixed-valence gold alkynyl complexes,[(tBuC^N^CtBu)Au^(Ⅲ)(CuC)-AuⅠ(PPh3)],[(RC^N^CR)Au^(Ⅲ)(CuCCuC)Au^(Ⅰ)(PPh3)](R=H,tBu),[(RC^N^CR)Au^(Ⅲ)(CuCC6H4CuC)Au^(Ⅰ)(PPh3)](R=H,tBu),and[(RC^N^CR)Au^(Ⅲ)(CuCC6H4CuC)Au^(Ⅰ)(P(C6H4R’-p)3)](R=H;R’=OMe,Cl)as well as the precursor complexes,[Au^(Ⅲ)(tBuC^N^CtBu)(CuCSiMe3)]and[Au^(Ⅲ)(tBuC^N^CtBu)(CuCH)],have been synthesized and their electrochemical properties have been investigated.The molecular structures of a number of dinuclear mixed-valence gold alkynyl complexes have been determined by X-ray crystallography.For complexes with a butadiynyl bridge,the emission was derived from an admixture of metalperturbed triplet intraligand(3IL)[π-π^(*)(RC^N^CR)]and[π-π^(*)(CuC-CuC)]states while for complexes with a 1,4-diethynylbenzene bridge,the emission was assigned as derived from the excited state of the 3IL[π→π^(*)(CuCC6H4CuC)]origin.Computational studies have also been performed for selected complexes to support the assignment of the spectroscopic origin and the nature of the photophysical properties.展开更多
A key requirement for the implementation of molecular quantum dot cellular automata(mQCA)is the ordered attachment of molecules on surfaces.In this work we explore by means of state-of-the art quantum chemistry calcul...A key requirement for the implementation of molecular quantum dot cellular automata(mQCA)is the ordered attachment of molecules on surfaces.In this work we explore by means of state-of-the art quantum chemistry calculations different aspects of the deposition of a mixed-valence Ru2+complex on Au(111),underlined as a promising component in mQCA.展开更多
We documented(ⅰ) the decolorization of wastewater in visible light,which contains methyl orange,crystal violet and indigo carmine dyes,using La_(0.7)Sr_(0.3)Mn_(1-x)Fe_(x)O_(3)(x=0.0,0.05,0.1 and 0.5) manganites and(...We documented(ⅰ) the decolorization of wastewater in visible light,which contains methyl orange,crystal violet and indigo carmine dyes,using La_(0.7)Sr_(0.3)Mn_(1-x)Fe_(x)O_(3)(x=0.0,0.05,0.1 and 0.5) manganites and(ⅱ) efficient separation of photocatalysts from water using magnetic field.These ceramic photocatalysts were sintered at 1050℃ for 12 h.Ceramics were characterized by X-ray diffraction(XRD),soft X-ray absorption spectroscopy(SXAS),Fourier transform infrared spectroscopy(FTIR) and UV-visible diffuse reflectance spectroscopy(DRS).SXAS studies show the presence of Mn(Mn^(3+)/Mn^(4+)) and Fe(Fe^(3+)/Fe^(4+)) mixes valences in Fe-doped compositions.Optical band gap is found in visible light range for La_(0.7)Sr_(0.3)Mn_(1-x)Fe_(x)O_(3)(x=0.0,0.05,0.1) compositions.La_(0.7)Sr_(0.3)MnO_(3) degrades 94.6% methyl orange in7 min,81.9% crystal violet in 10 min and 99.1% indigo carmine in 5 min.La_(0.7)Sr_(0.3)Mn_(0.9)Fe_(0.1)O_(3) degrades the 92.6% methyl orange dye solution in 9 min,94.8% crystal violet in 25 min and 97.1% indigo carmine in3 min.Parent and Fe doped manganites can be separated in 60 s from wastewater.展开更多
Two distinct copper coordination polymers, namely [Cu^Ⅱ2（2,5-pydc）2（bpp）2]·H2O（1） and Cu2^ⅠCu^Ⅱ（2,5-pydc）2（bpp）2（2）（2,5-pydc = pyridine-2,5-dicarboxylic acid, bpp = 1,3-bi（4-pyridyl）propane）, h...Two distinct copper coordination polymers, namely [Cu^Ⅱ2（2,5-pydc）2（bpp）2]·H2O（1） and Cu2^ⅠCu^Ⅱ（2,5-pydc）2（bpp）2（2）（2,5-pydc = pyridine-2,5-dicarboxylic acid, bpp = 1,3-bi（4-pyridyl）propane）, have been successfully synthesized through hydrothermal conditions under different temperatures. Single-crystal X-ray structural analysis revealed that both complexes 1 and 2 are 3D frameworks. Complex 1 is an 8-connected 2-fold interpenetrating network based on [Cu（2,5-pydc）]4 molecular building block（MBB）, and also can be simplified as a 4-connected net if the Cu（Ⅱ） ion is regarded as an independent node, whereas 2 shows a（4,4）-connected non-interpenetrated framework which contains mixed valence Cu（Ⅰ/Ⅱ） centers. The results demonstrate that temperature plays a significant role in the final structures of the complexes.展开更多
Doped lanthanum manganites La_(1-x)Ca_(x)MnO_(3) with five different concentrations of Ca(x=0.1,0.2,0.3,0.4 and 0.5) were synthesized by high-temperature solidstate reaction method and characterized.The prepared sampl...Doped lanthanum manganites La_(1-x)Ca_(x)MnO_(3) with five different concentrations of Ca(x=0.1,0.2,0.3,0.4 and 0.5) were synthesized by high-temperature solidstate reaction method and characterized.The prepared samples were experimentally analyzed by X-ray diffraction(XRD),ultraviolet-visible spectroscopy(UV-Vis),scanning electron microscopy/energy dispersive spectroscopy(SEM/EDS) and vibrating sample magnetometer(VSM)measurements.Orthorhombic structure is confirmed for this compound from powder X-ray diffraction data.The XRD data confirm the shrinkage in the unit cell of synthesized samples for increasing calcium concentration.The UV-Visible analysis for the estimation of optical band gap(E_(g)) reveals that the band gap decreases with the incorporation of Ca.The synthesized samples were investigated for charge density distribution using maximum entropy method,utilizing the XRD data sets.From the charge density analysis,it is found that the bond lengths for La-O and Mn-O bonds decrease with the addition of Ca.The ionic nature between La and O atoms and covalent nature between Mn and O atoms are enhanced for 40% of calcium-doping.For 50% of Ca-doped sample,ionic nature between La and O atoms and covalent nature between Mn and O atoms decrease.All the prepared samples exhibit ferromagnetism at 20 K and paramagnetism at 300 K.展开更多
基金Supported by the National Natural Science Foundation of China(No.2 0 1710 10 )
文摘A new layered mixed valence vanadium oxide, [CH 3NH 3] 2[(V ⅣO) 2(V ⅤO 4) 2], which contains interlamellar organic cations was prepared under hydrothermal conditions and its single crystal structure was determined. It crystallizes in a triclinic system with space group P 1, a =0 625 59(8) nm, b =0 639 84(9) nm, c =0 747 19(10) nm, α =78 718(2)°, β =80 099(2)°, γ =77 100(2). The compound contains mixed valence V 4+ /V 5+ vanadium oxide layers constructed from VO 4 tetrahedra, pairs of edge sharing VO 5 square pyramid and methylamine with protonated organic amines occupying the interlayer space.
基金Supported by the NNSFC (90206040)NSF of Fujian Province (2006F3134, 2005J058)
文摘A novel Cu（II）-2,2＇-bipy-supported （bipy = bipyridine） mixed valence decatungstate, [Cu（2,2＇-bipy）2]2Na2W6^VW4^VIO30·2H2O 1, has been synthesized and structurally characterized by X-ray analysis. The crystal of 1 is of triclinic, space group P1^- with a= 10.9393（10）, b = 12.0492（2）, c = 12.3783（2）A, a = 80.631（10）, β= 70.226（10）, γ= 72.329（9）^o, V = 1459.64（4）A^3, Z = 1, Dc = 3.582 g/cm^3, F（000） = 1404, R = 0.0553 and wR = 0.1242 for 4607 observed reflections （I 〉 2σ（I））. The EPR spectrum of 1 indicates that its unpaired electrons are placed in the dx2-y2 orbital of the ground state of Cun. Furthermore, compound 1 shows an antiferromagnetic interaction.
基金the National Natural Science Foundation of China (22175180, 21975260)。
文摘Lead-based organic-inorganic hybrid perovskites have exhibited great potential in photovoltaics,achieving power conversion efficiencies(PCEs) exceeding 25%.However,the toxicity of lead and the instability of these materials under moist conditions pose significant barriers to large-scale production.To overcome these limitations,researchers have proposed mixed-valence double perovskites,where Cs_(2)Au~ⅠAu~ⅢI_6 is a particularly effective absorber due to its suitable band gap and high absorptance efficiency.To further extend the scope of these lead-free materials,we varied the trivalent gold ion and halogen anion in Cs_(2)Au~ⅠAu~ⅢI_6,resulting in 18 new structures with unique properties.Further,using first-principles calculations and elimination criteria,we identified four materials with ideal band gaps,small effective carrier mass,and strong anisotropic optical properties.According to theoretical modeling,Cs_(2)AuSbCl_6,Cs_(2)AuInCl_6,and Cs_(2)AuBiCl_6 are potential candidates for solar cell absorbers,with a spectroscopic limited maximum efficiency(SLME) of approximately 30% in a 0.25 μm-thick film.These three compounds have not been previously reported,and therefore,our work provides new insights into potential materials for solar energy conversion.We aim for this theoretical exploration of novel perovskites to guide future experiments and accelerate the development of high-performance photovoltaic devices.
文摘A novel mixed valance vanadium phosphate Na 3.6 H 1.4 P 2V 5O 18 ·11H 2O was synthesized by a hydrothermal method and its structure was characterized by X ray diffraction, infrared spectroscopy, differential thermal analysis, and thermogravimetric analysis. Na 3.6 H 1.4 P 2V 5O 18 ·11H 2O crystallizes in the cubic system with the cell parameter a =1.601(8) nm. The ratio of V( Ⅳ)/ V(Ⅴ) in the compound is 3.55.
基金Supported by the Science and Technology Planning Project of Shengli College China University of Petroleum(No.13070316)
文摘Reaction of the ligand dmpt（dmpt=6,7-dimethylbenzo[f][1,10]phenanthroline）with CuCl2 afforded mixed valent Cu（Ⅰ）/Cu（Ⅱ） discrete tetranuclear complexes[Cu（Ⅱ）Cl2（dmpt）Cu（Ⅰ）Cl]（1）,while the reaction of ligand dppz（dppz = dipyrido[3,2-a：20,30-c]phenazine） with divalent halogen copper salt CuX2（X=Cl,Br） gave one-dimensional chain mixed valent Cu（Ⅰ）/Cu（Ⅱ） complexes [Cu（Ⅱ）Cl2（dppz）Cu（Ⅰ）Cl]n（2） and discrete mixed valent Cu（Ⅰ）/Cu（Ⅱ）complexes [Cu（Ⅱ）Br2（dppz）（DMF）Cu（Ⅰ）Br]（3）. Complex 2 consists of a one-dimensional chain-dppzC u（Ⅱ）-Clμ2-Cu（Ⅰ）-Cl-dppzC u（Ⅱ）-Clμ2-Cu（Ⅰ）-with Cu（Ⅱ） and Cu（Ⅰ） atoms linked together by chloride anion. Complex 3 is a discrete complex,which is the same as complexes 1 and 2 involving two different copper valent Cu（Ⅰ） and Cu（Ⅱ）. The Cu（Ⅰ） ion presents a pseudo-trihedral geometry,while the Cu（Ⅱ） ion presents a slightly distorted square-pyramidal geometry. This fact proved that halogen ions play a vital role in the assembly procedure. Our research results demonstrate the structural diversification that can be achieved by halogen ions mediated. Moreover,halogen ions-mediated self-assembly may provide useful information for further design of compounds with novel structures and properties.
基金support of the National Natu-ral Science Foundation of China(No.62004143,22476058,and 22076052)the Key R&D Program of Hubei Province(No.2022BAA084).
文摘Cu metal and its oxides have attracted much attention for photocatalytic CO_(2)reduction reaction(CO_(2)RR),but the stability and effects of Cu oxidation states on CO_(2)RR are not fully understood.Cu^(x+)/Cu^(0)-loaded graphitic carbon nitride(g-C_(3)N_(4))heterojunctions(Cu-CuO_(x)/g-C_(3)N_(4))are fabricated via a stepwise calcination method for efficient photocatalytic CO_(2)RR.Cu_(2)O is the main component of Cu-CuO_(x)and the mixed valence Cu includes Cu^(0),Cu^(+),and Cu^(2+),which play the role of charge trapping sites and redox catalytic centers during the photocatalytic CO_(2)RR process.The main products were CO and CH_(4)for the CO_(2)RR with production rates of 14.45 and 0.66μmol g^(-1)h^(-1)for CO and CH_(4),which were higher than those for g-C_(3)N_(4)and Cu-CuO_(x),respectively.This photocatalytic CO_(2)RR performance is attributed to the ultrafast switching of“Cu^(x+)−Cu^(0)”and e_(CB^(−))/h_(VB^(+))trapping transformation in Cu-CuO_(x)benefited from the built-in IEF between Cu-CuO_(x)and g-C_(3)N_(4),increasing the efficient photogenerated e_(CB^(−)),and enabling the stability of Cu-CuO_(x)/g-C_(3)N_(4).Cu^(x+)adsorbed by H_(2)O works as the electron trapping site to change to Cu^(0)and switch to the hole trapping site;Cu^(0)works as the hole trapping site to change to Cu^(x+)and switch to the electron trapping site,causing the CO_(2)RR of the adsorbed CO_(2).Moreover,the coordinated Cu^(0)and Cu^(+)species facilitate the activation of the adsorbed CO_(2)and^(∗)CO generation,these adsorbed^(∗)CO on Cu^(0)and Cu^(+)detected by in-situ DRIFTS quickly transformed to^(∗)CHO with a lower energy barrier benefited from the mixed Cu^(0)/Cu^(+)active sites during CORR to produce CH_(4).This finding provides a new insight into the influence of mixed valence Cu during photocatalytic CO_(2)RR.
基金the National Science Foundation of China(21973095)for financial support。
文摘A series of trimetallic cyanidometal-bridged compounds with the formula[CpMe_(x)Fe-NC-Ru-CN-FeCpMe_(x)]^(n+),N^(n+)(n=2,3 and 4;N=1,x=0;N=2,x=1;N=3,x=3;N=4,x=4;N=5,x=5),were synthesized and fully characterized.The effect of the potential difference between the central and term-inal metals on the electron communication in these trinuclear mixed valence systems was investigated.N^(3+)and N^(4+)are the one-and two-electron oxidation products of N^(2+).Electrochemical measurements show the presence of electronic interactions between the two terminal Fe atoms.The electronic pro-perties of N^(3+)and N^(4+)were studied and compared using experimental spectroscopy and time-dependent density-functional calculations.As the number of methyl substituents on the cyclopentadiene ligand increases,the potential difference between the central and terminal redox centers increases and thus,the electron communication between the terminal Fe redox centers or between the neighboring Fe and Ru redox centers becomes weaker.All the mixed valence compounds show localized character.
基金supported by JSPS KAKENHI Grant Numbers 25248014 and 26410065.
文摘Two new high-nuclearity mixed-valence Mn clusters,Mn_(19)and Mn_(21),were synthesised utilising an alkylamine-based flexible ligand with five alkoxo-bridging groups,1,3-bis-diethanolamino-2-propanol(H_(5)bdp).They were obtained from the reaction of Mn(O_(2)CPh)_(2)·2H_(2)O with H_(5)bdp·2HCl·H_(2)O and Et_(3)N in a 4:1:7 molar ratio in CH_(3)CN/CH_(3)OH mixed solution.The X-ray crystal structures revealed{Mn_(8)^(Ⅱ)Mn_(10)^(Ⅲ)Mn^(Ⅳ)}and{Mn_(6)^(Ⅱ)Mn_(15)^(Ⅲ)}mixed-valence cores composed around{Mn_(7)O_(8)}corner-shared double cubanes.Magnetic susceptibility measurements on both complexes indicated dominant intramolecular antiferromagnetic interactions between Mn ions.No clear SMM behaviour was observed above 1.8 K due to the non-parallel alignment of magnetic anisotropy axes of the Mn^(Ⅲ)ions.
基金the funding agencies SERB(CRG/2019/004185 and SPR/2019/001145)CSIR(01(2933)/18/EMR-II),and IIT Bombay for their financial support+1 种基金GR would like to thank DST and SERB(CRG/2018/00430,DST/CSA-03/2018-10SB/SJF/2019-20/12)for funding.PK would like to thank CSIR,DAAD and SERB for funding.AS would like to thank CSIR.PK and AS also thank the Department of Chemistry,IIT Bombay,for the instrumentation and server facilities.
文摘The reaction of[Co(PMe_(3))_(4)](1)with a redox-active NNN pincer ligand(L_(1))led us to isolate a unique binuclear cobalt complex([(PMe_(3))_(2)Co^(II)(L_(1)^(3−))CoI(PMe_(3))_(3)](2))anchored by a three-electron reduced L_(1)in its unusual coordination mode.Such an unprecedented binuclear pincer/allyl cobalt complex consisting of the mixed-valence oxidation state of cobalt ions(+1 and+2)is confirmed by various analytical techniques(XPS,EPR,and UV–vis),and the experimentally determined electronic structure is well corroborated by detailed theoretical studies based on DFT calculations.
基金supported by the NSFC of China(21871209,21571139 and 22035003).
文摘In this work,we report two multi-component MOFs[CH_(3)NH_(2)CH_(3)]_(2)[Fe_(2)^(Ⅲ)M_(10)^(Ⅱ)(tz)(11)(HCO_(2))_(12)(btc)_(5/3)](M_(10)^(Ⅱ)=Fe_(10)^(Ⅱ)for 1 and M_(10)^(Ⅱ)=Fe_(2)^(Ⅱ)Co^(8)_(Ⅱ)for 2)obtained by solvothermal reaction of benzene-1,3,5-tricarboxylate(btc)and 1,2,4 triazole(tz),Fe^(Ⅱ)and Fe^(Ⅲ)/Co^(Ⅱ)in DMF.In the complexes,several different types of metal rings(9,12-number metal ions)are generated,and the connection of those rings gives the complicated three-dimensional structure.The two complexes exhibit electronic conductivity and good alkali stability,which makes them potential OER electrocatalysts.It is revealed that the cobalt ion greatly enhances the OER performance,and the electrode prepared using 2 shows a low overpotential of 339 mV at 10 mA cm^(−1).
基金the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe National Nature Science Foundation of China(grant no.91122011,21071080 and 21271103)for financial support.
文摘A two-dimensional,mixed-valence[Ni(dmit)_(2)]compound,[C8-Apy]2[Ni(dmit)_(2)]_(3)(1)(where dmit^(2-)=2-thioxo-1,3-dithiole-4,5-dithiolate and Apy^(+)=4-amino-1-alkylpyridinium),was prepared and its structure was fully characterized.The molecular solid displays a layered structure along the crystallographic c-axis with a[Ni(dmit)_(2)]layer constructed from alternating straight chains of[Ni(dmit)_(2)]^(0) and two-legged ladder chains of[Ni(dmit)_(2)]^(1-).Compound 1 shows an antiferromagnetic,spin-dimer with pairwise interaction magnetic behavior and a semiconducting nature in addition to a rapid,clear and stable response of photoconductivity under UV irradiation.The magnetic coupling nature of 1 was analyzed using the‘broken-symmetry’density functional theory(DFT)approach.The electronic band structure was calculated using the CASTEP program and was used to investigate the theoretical transport and photoconductive behavior of 1.This work suggests that mixed-valence[Ni(dmit)_(2)]compounds have great potential as the building blocks for new photoconductor based materials.
基金supported by the National Research Foundation of Korea(NRF),funded by the Korea government(MIST)(grant no.RS-2023-00245147 to K.L.and 2020R1C1C1007535 to I.H.H)Learning&Academic Research Institution for Master’s PhD students,and Postdocs(LAMP)Program of the National Research Foundation of Korea(NRF)grant funded by the Ministry of Education(RS-2023-00301974)the Nurion supercomputer,with the kind support of the Korea Institute of Science and Technology Information(KISTI)Supercomputing Center(KSC-2024-CRE-0036).
文摘Valence-delocalized bimetallic copper cores are found at the biological CuA sites,which are well-known for their electron transfer reactivity accompanying the transition between fully delocalized Class III and partially delocalized Class II sites.Understanding the electron transfer reactivity of CuA sites when both delocalizations are available within the same ligand platform would be helpful,but few complexes with the same ligand scaffold have been reported.Here,we report the syntheses and characterization of two different classes of bimetallic copper complexes Na(THF)_(x){^(NMe2)[NNNN]Cu}_(2)(1)and ^(NMe2)[NNNN]Cu_(2)(OAc)(2)using the same tetradentate ligand NMe_(2)[NNNN].X-ray crystallographic studies revealed that the coordination environments around bimetallic cores in 1 are distorted,whereas those for 2 are symmetric.The electron paramagnetic resonance(EPR)spectrum of 1 was deconvoluted using the different contributions from each copper,which was supported by the characteristic intervalence charge transfer(IVCT)bands of Robin-Day Class II partial delocalization observed in the UV-vis spectrum.The symmetric coordination environment of 2 matches the fully delocalized Class III copper ions,as confirmed by the characteristic septet hyperfine splitting in the EPR spectrum and IVCT band in the UV-vis spectrum.The crystallographic data and electronic spectra were successfully reproduced using the DFT and TD-DFT calculations.Frontier molecular orbital(FMO)analysis revealed that the SOMO of 1 is 3d_(z^(2-))based,while that of 2 is 3d_(x^(2)-y^(2))-based.Finally,the observed structural and electronic variations of bimetallic mixed valence cores gave rise to the reactivity differences as demonstrated with tests of O_(2),Ph_(3)CCl,and DPPH radical scavenging assays.
基金support from the National Funded Postdoctoral Researcher Program of China(no.GZC20230969)support from the Guangdong Basic and Applied Basic Research Foundation(no.2024A1515010897)+3 种基金supported financially by the National Natural Science Foundation of China(no.22371091,21975104 and 22150004)the Guangdong Major Project of Basic and Applied Research(no.2019B030302009)the Open Fund of Guangdong Provincial Key Laboratory of Functional Supramolecular Coordination Materials and Applications(no.2020B121201005)the Open Project Program of Jiangxi Provincial Key Laboratory of Functional Crystalline Materials Chemistry(20212BCD42018).
文摘The development of noble-metal-free and efficient metal–organic frameworks(MOFs)as heterogeneous catalysts for carbon dioxide(CO_(2))conversion is of particular interest,but remains challenging.In this study,a Cu^(Ⅰ)/Cu^(Ⅱ) mixed-valence MOF(1)was synthesized,consisting of copper(Ⅰ)cyclic trinuclear units(Cu^(Ⅰ)-CTUs)and Cu^(Ⅱ)-paddlewheel units.The MOF featured a(3,4,4)-c network topology,which is rarely reported in the literature.Interestingly,1 demonstrated efficient catalytic activity in the cyclization reaction of epoxides or propargyl amines with CO_(2) with excellent yields(i.e.,81%to 99%for 12 examples).Additionally,it showed high reusability,maintaining the catalytic performance for at least five cycles without a loss in efficiency.Of significant note,MOF 1 delivered high catalytic activity with a turnover frequency of 142.8 h^(−1)(23.8 h^(−1) based on Cu)for the synthesis of oxazolidinones at ambient temperature,showcasing its potential as an effective catalyst for CO_(2) conversion reactions.
基金supported by the National Natural Science Foundation of China(No:21373010 and No:51602322)the Youth Innovation Promotion Association CAS(No:2015141)+2 种基金the Shanxi Province Science Foundation for Youths(No:201701D211005)the CAS Interdisciplinary Innovation Team(No:BK2018001)the Excellent Youth Scholars of State Key Laboratory of Coal Conversion(No:2016BWZ001)。
文摘Cerium dioxide(CeO_(2))octahedra were synthesized by a facile microwave-assisted hydrothermal method.The structure and morphology were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results showed that octahedra were enclosed by eight(111)facets with an edge length of 180 nm.
基金financially supported by the National Natural Science Foundation of China(NSFC)(no.22175173).
文摘A new compound Na_(5)Mn_(4)(PO_(4))_(4)F_(4)·2H_(2)O was successfully obtained,featuring a typical channel structure composed of rarely mixed valence Mn^(2+)/Mn^(3+)spin chains and PO_(4) tetrahedra,where H_(2)O molecules are located inside the channels.Magnetic measurements show that this compound possesses successive multiple magnetic transitions at low temperature.
基金supported by the French National Research Agency(ANR)/Research Grants Council(RGC)Joint Research Scheme(A-HKU704/12)the Research Grants Council Theme-Based Research Scheme(TBRS)(T23-713/11)of the Hong Kong Special Administrative Region.
文摘A series of luminescent dinuclear mixed-valence gold alkynyl complexes,[(tBuC^N^CtBu)Au^(Ⅲ)(CuC)-AuⅠ(PPh3)],[(RC^N^CR)Au^(Ⅲ)(CuCCuC)Au^(Ⅰ)(PPh3)](R=H,tBu),[(RC^N^CR)Au^(Ⅲ)(CuCC6H4CuC)Au^(Ⅰ)(PPh3)](R=H,tBu),and[(RC^N^CR)Au^(Ⅲ)(CuCC6H4CuC)Au^(Ⅰ)(P(C6H4R’-p)3)](R=H;R’=OMe,Cl)as well as the precursor complexes,[Au^(Ⅲ)(tBuC^N^CtBu)(CuCSiMe3)]and[Au^(Ⅲ)(tBuC^N^CtBu)(CuCH)],have been synthesized and their electrochemical properties have been investigated.The molecular structures of a number of dinuclear mixed-valence gold alkynyl complexes have been determined by X-ray crystallography.For complexes with a butadiynyl bridge,the emission was derived from an admixture of metalperturbed triplet intraligand(3IL)[π-π^(*)(RC^N^CR)]and[π-π^(*)(CuC-CuC)]states while for complexes with a 1,4-diethynylbenzene bridge,the emission was assigned as derived from the excited state of the 3IL[π→π^(*)(CuCC6H4CuC)]origin.Computational studies have also been performed for selected complexes to support the assignment of the spectroscopic origin and the nature of the photophysical properties.
基金support through grant PGC2018-101689-B-I00 funded by MCIN/AEI/10.13039/501100011033。
文摘A key requirement for the implementation of molecular quantum dot cellular automata(mQCA)is the ordered attachment of molecules on surfaces.In this work we explore by means of state-of-the art quantum chemistry calculations different aspects of the deposition of a mixed-valence Ru2+complex on Au(111),underlined as a promising component in mQCA.
基金the UGC-DAE-Consortium for Scientific Research (CSR),Indore Centre for providing financial support under the CRS project scheme fordoing SXAS experiments and P.Singh for project fellowship。
文摘We documented(ⅰ) the decolorization of wastewater in visible light,which contains methyl orange,crystal violet and indigo carmine dyes,using La_(0.7)Sr_(0.3)Mn_(1-x)Fe_(x)O_(3)(x=0.0,0.05,0.1 and 0.5) manganites and(ⅱ) efficient separation of photocatalysts from water using magnetic field.These ceramic photocatalysts were sintered at 1050℃ for 12 h.Ceramics were characterized by X-ray diffraction(XRD),soft X-ray absorption spectroscopy(SXAS),Fourier transform infrared spectroscopy(FTIR) and UV-visible diffuse reflectance spectroscopy(DRS).SXAS studies show the presence of Mn(Mn^(3+)/Mn^(4+)) and Fe(Fe^(3+)/Fe^(4+)) mixes valences in Fe-doped compositions.Optical band gap is found in visible light range for La_(0.7)Sr_(0.3)Mn_(1-x)Fe_(x)O_(3)(x=0.0,0.05,0.1) compositions.La_(0.7)Sr_(0.3)MnO_(3) degrades 94.6% methyl orange in7 min,81.9% crystal violet in 10 min and 99.1% indigo carmine in 5 min.La_(0.7)Sr_(0.3)Mn_(0.9)Fe_(0.1)O_(3) degrades the 92.6% methyl orange dye solution in 9 min,94.8% crystal violet in 25 min and 97.1% indigo carmine in3 min.Parent and Fe doped manganites can be separated in 60 s from wastewater.
基金supported by the application basis research key project of Yunnan Province science and technology department(201401CB00299)the major project of Qujing Normal University(2012ZD002)
文摘Two distinct copper coordination polymers, namely [Cu^Ⅱ2（2,5-pydc）2（bpp）2]·H2O（1） and Cu2^ⅠCu^Ⅱ（2,5-pydc）2（bpp）2（2）（2,5-pydc = pyridine-2,5-dicarboxylic acid, bpp = 1,3-bi（4-pyridyl）propane）, have been successfully synthesized through hydrothermal conditions under different temperatures. Single-crystal X-ray structural analysis revealed that both complexes 1 and 2 are 3D frameworks. Complex 1 is an 8-connected 2-fold interpenetrating network based on [Cu（2,5-pydc）]4 molecular building block（MBB）, and also can be simplified as a 4-connected net if the Cu（Ⅱ） ion is regarded as an independent node, whereas 2 shows a（4,4）-connected non-interpenetrated framework which contains mixed valence Cu（Ⅰ/Ⅱ） centers. The results demonstrate that temperature plays a significant role in the final structures of the complexes.
文摘Doped lanthanum manganites La_(1-x)Ca_(x)MnO_(3) with five different concentrations of Ca(x=0.1,0.2,0.3,0.4 and 0.5) were synthesized by high-temperature solidstate reaction method and characterized.The prepared samples were experimentally analyzed by X-ray diffraction(XRD),ultraviolet-visible spectroscopy(UV-Vis),scanning electron microscopy/energy dispersive spectroscopy(SEM/EDS) and vibrating sample magnetometer(VSM)measurements.Orthorhombic structure is confirmed for this compound from powder X-ray diffraction data.The XRD data confirm the shrinkage in the unit cell of synthesized samples for increasing calcium concentration.The UV-Visible analysis for the estimation of optical band gap(E_(g)) reveals that the band gap decreases with the incorporation of Ca.The synthesized samples were investigated for charge density distribution using maximum entropy method,utilizing the XRD data sets.From the charge density analysis,it is found that the bond lengths for La-O and Mn-O bonds decrease with the addition of Ca.The ionic nature between La and O atoms and covalent nature between Mn and O atoms are enhanced for 40% of calcium-doping.For 50% of Ca-doped sample,ionic nature between La and O atoms and covalent nature between Mn and O atoms decrease.All the prepared samples exhibit ferromagnetism at 20 K and paramagnetism at 300 K.
