简介:Anewseriesofliquidcrystalscomprisingeightheterocyclicisoflavoneesters,7-alkanoyloxy-3-[4’-(3-methylbutyloxyphenyl)]-4H-1-benzopyran-4-onesexhibitingenantiotropicnematic(N)andsmecticC(SmC)phasesweresynthesizedandinvestigated.Themesomorphicpropertiesofallderivativeswereinvestigatedbymeansofdifferentialcalorimetryandpolarizedopticalmicroscopy.WideangleX-raydiffractiontechniquewasemployedtoinvestigatethemolecularpackingassociatedwiththeintermolecularinteractionaswellasthecorrelationbetweenthethermalbehaviourofthesecompoundswiththeiranisotropypropertieswithinamesophase.
简介:Auranylcompound,K4UO2(CO3)3hasbeencharacterizedbypowderX-raydiffractionmethod.M.W.=606.46,monoclinic,C2/c(No.15),a=1.0240(7),b=0.9198(4),c=1.2222(12)nm,β=95.12(4)°,V=1.1466(5)nm3,Z=4,Dm=3.468g/cm3,Dc=3.513g/cm,λ(CuKα1)=O.1540598nm,T=298K.ThestructurewassolvedbyheavyatommethodandFouriersynthesis,andrefinedbyfull-matrixleast-squaresmethodtoR=0.1185for275reflections.Theuranium(Ⅵ)atomisinaneight-coordinatedistortedhexagonal-bipyramidalenvironmentwithcreasyfanshape.Thelinearuranylgroupapproachestoperpendiculartotheequatorialplaneinwhichthreecarbonategroupsarechelated.U(Ⅵ)hastwolinearoxygenatomsclosertoit(U-O=0.1767(5)nm)thansixotherneighbours(U-Orangingfrom0.2516to0.2568nm).Thedistancesbetweencarbonatomsanduncoordinatedoxygenatomsare0.122(1)and0.123(1)nm,whicharedistinctlydifferentfromthosebetweencarbonandcoordinatedoxygenatoms(mean0.134(6)nm).Thisfactrevealsthenon-eq-uivalenceofoneoxygenatomtotheothertwoineachcarbonate.InK4UO2(CO3)3,theO-Odis-tancefortheadjacentcarbonategroupsis0.2794(4)nmapproachingtothesumofVanderWaalsradiioftwooxygenatoms.TheK-Odistancesvarybetween0.2667and0.3131nm,andeachanionisimmediatelysurroundedbysixpotassiumions,onlyfourofwhichcanbeconsideredtobelongtothesamestructuralformulaunit,andtheyaresymmetricallylocatedaboveandbelowtheequatorialplane.
简介:AnovelcrystalcharacterizationinstrumenthasbeenbuiltupinwhichacombinationofX-raymultiplediffractionandX-raytopographyisappliedtoenablingthecross-correlationbetweenmicro-crystallographicsymmetryanditsspatialdependenceinrelationtolatticedefects.Thisfacilityisusedtoexamine,inaselfconsistentmanner,growthsector-dependantchangestoboththecrystallographicstructureandthelatticedefectsassociatedwiththeactionofhabit-modifyingadditivesinanumberofrepresentativecrystalgrowthsystems.Inaddition,thenewinstrumentcanbeusedtoprobemicro-crystallographicaspects(suchasdistortiontocrystalsymmetry)andrelatetheseinaspatiallyresolvedmannertothecrystaldefectstructureincrystalsdopedwithknownhabitmodifiers.
简介:Aseriesoftitlecompoundsaswellastheirprecursorsweresynthesizedbyprecursorroute.TheirPXRDpatternswerecharacterizedwithZrW2O8orZrMo2O8modelbyRietveldmethod.Thethermalcontractionsofthecompoundsweredeterminedaccordingtothevariable-temperaturePXRDdataandNTEcoefficientswerepresented.Thetwo-phasemixtureofZrW0.4Mo1.6O8wasalsoanalyzedindividually.
简介:ThehydrolysisofcephanoneinTritonX-100micelleandTritonX-100/n-C5H11OH/H2O(O/W)microemulsionwerestudiedbymeansofUV-Visabsorptionspectroscopy.Theresultsshowthatcomparedwithwater,TritonX-100micelleandTritonX-100/n-C5H11OH/H2O(O/W)microemulsioncaninhibitthehydrolysisofcephanone.TheinhibitioneffectsofTritonX-100micelleandTritonX-100/n-C5H11OH/H2O(O/W)microemulsiononthehydrolysisofcephanonearerelatedtothelocationofcephanoneintheinterphasesofTritonX-100micellesandTritonX-100/n-C5H11OH/H2O(O/W)microemulsiondroplets.
简介:在MP2/6-311++G**水平上优化乙烯酮自由基与LiX(X=F,Cl,Br)形成锂键复合物.当卤素的电负性很强(如F元素),使得Li原子处于缺电子状态,此时,电子给体会把电子偏移向锂,形成共价性较强的锂键.而当卤素的电负性减弱时,锂键中主要成分逐渐变为离子键,并且此时锂键性质还要受电子给体影响.另外,由于HCCO为缺电子结构,电负性较弱且体积较大的卤素中的孤对电子会与HCCO之间通过静电相互作用,使得HCCO…Li—X键夹角变小,接近120°.锂键性质对HCCO…LiX(X=F,Cl,Br)复合物中Li—X的伸缩振动频率有直接影响.当锂键表现为共价性时,该频率红移,而当锂键表现为离子性时,该频率蓝移.但是,由于Cl的电负性与O的接近,C的电负性与Br接近所以,在O…Li…Cl和C…Li…Br中容易形成共振结构,导致远大于在其他复合物中的红移.
简介:ThecatalyticactivitiesofMnOx-WO3/TiO2forselectivecatalyticreduction(SCR)ofNOwithNH3wereinvestigatedinawiderangeoftemperatureandreactioncondition.ItyieldedaNOxconversionof80.3%-99.6%andaN2productselectivityof100%-98.7%during100°Cto350°Catgashourlyspacevelocity(GHSV)=18900h-1.Inthepresenceof0.01%SO2and6%H2Oat120°C,theNOxconversioncanmaintain98.5%.At300°Candwith0.07%SO2inreactantstream,theNOxconversionstabilizedat99%ashighasthecommercialV-W/TiO2catalyst'slevel.Thesteady-statekineticsstudyshowsthatO2playedapromotingrole.Inthepresenceoflessthan1.5%O2,NOxconversioncanincreasesharplywiththeincreaseofO2concentration.ThereactionorderwaszerowithrespecttoNH3andfirstwithrespecttoNOwithexcessO2andH2O.Thekineticsactiveenergy(Ea)ofMn-W/TiO2wascalculatedtobe6.24kJ/molaccordingtothekineticexperimentatvarioustemperatures,muchlowerthanthoseofothercatalystsreportedintheliterature.Mn-W/TiO2isanexcellentcatalystforSCRofNOwithNH3bynow.
简介:Twoseriesofmixedoxides,CoAlMandMgAlM(M=Cr,Mn,Fe,Co,Ni,Cu),werepreparedbycalciningtheircorrespondinghydrotalcite-likecompounds(HTLc).TheratioofMg:Al:M(orCo:Al:M)was3:1:1.ThecatalyticactivityofallsamplesforthereactionofNO+COwasinvestigated.TheresultsshowedthattheactivityofCoAlMwasmuchhigherthanthatofMgAlM.ThestructureandthepropertyofredoxwerecharacterizedbyXRDandH2-TPR.TheresultsindicatedthatonlyMgOphasewasobservedaftercalciningMgAlMhydrotalcites,andthetransitionmetalsbecamemorestable.Thespinel-likephaseappearedinallofCoAlMsamplesafterthecalcination,andthetransitionmetalswerechangedtobemoreactive,andeasilyreduced.TheactivitiesofthreeseriesofmixedoxidesCoAlCuobtainedfromdifferentpreparationmethods,differentratioofCo:Al:Cuandatdifferentcalcinationtemperatures,werestudiedindetailforproposingthemechanismofreaction.TheabilityofadsorptionofNOandCO
简介:PolycrystallinesBi0.5Ca0.5–xLaxFe0.3Mn0.7O3(x=0,0.05,0.10,0.15,0.20,0.25)werepreparedbymoltensaltmethodandshowedperovskiteorthorhombicstructurewithspacegroupPnma.Themagneticmeasurementsindicatethatthecompoundsexhibitantiferromagneticbehaviorinatemperaturerangeof4―300K.ThemeasurementsoftransportpropertiessuggestthatthesubstitutionofLaforCaenhancedtheconductivity,andakinkappearedonthecurveoftemperaturedependenceofresistivityat275K,whichisrelatedtothespin-reorientationinthesamples.
简介:Tris)(η5-cyclopentadienyl-μ-carbonyl-iron)-μ3-nitrosylclusterwasobtainedfromthereactionofcyclopentadienyldicarbonylirondimerwithnitrogenmonoxideinxylene.Theclusterwascharacterizedbyelementalanalyses,IR,MSand1HNMR.Thecrystalstructureof[(η5-C5H5)(μ-CO)Fe]3(μ3-NO).C4H8OwasdeterminedbyX-raydiffractionanalysis.ItcrystallizesintheorthorhombicspacegroupPnma,a=9.053(2),6=10.545(2),c=22.525(4)A,V=2150.3(7)A3,Z=4,Dc=1.68g.cm-3;structuresolutionandrefinementbasedon1141reflectionswithI>3.0(I)(MoKa,A=0.71073A)convergedatR=0.0540.Theinfraredabsorptionbandat1325cm-1oftheμ3-NOinthecluster,whichisredshifted,showsthatμ3-NOisactivated.