The cyanide groups of letrozole(1-[bis(4-cyanophenyl)methyl]-1,2,4-triazole) were hydrolyzed into the carboxylic groups under alkaline conditions. Then the hydrolysis product(1-[bis(4-carboxylphenyl)methyl]-1,2,4-tria...The cyanide groups of letrozole(1-[bis(4-cyanophenyl)methyl]-1,2,4-triazole) were hydrolyzed into the carboxylic groups under alkaline conditions. Then the hydrolysis product(1-[bis(4-carboxylphenyl)methyl]-1,2,4-triazole, H2ltzda) reacted with Co(NO3)2·6H2O in the presence of different bipyridl-typed ligands under hydrothermal conditions. As a result, two new Co(Ⅱ) MOFs were obtained, formulated as [Co2(ltzda)2(bpp)2]n(1) and {[Co2(ltzda)2(bpy)]·4H2O}n(2)(bpp = 1,3-di(4-pyridyl)propane, bpy = 4,4’-bipyridine). Two MOFs have been characterized by single-crystal X-ray diffraction, thermogravimetric analysis and magnetic measure. 1 displays a 2D metal-organic framework containing wave layers and 2 shows a pillared-layer structure existing in a 2-fold interpenetrated mode.展开更多
We report the preparation,spectroscopic characterisation,crystal structure determination and cryomagnetic investigation of three cobalt(II)complexes of formula trans-[Co(bim)_(4)(NCS)_(2)](1),[Co(bim)_(2)(NCO)_(2)](_(...We report the preparation,spectroscopic characterisation,crystal structure determination and cryomagnetic investigation of three cobalt(II)complexes of formula trans-[Co(bim)_(4)(NCS)_(2)](1),[Co(bim)_(2)(NCO)_(2)](_(2))and[Co(bim)_(2)(N_(3))_(2)]_(n)(_(3))(bim=1-benzylimidazole).The structure of 1 is made up of neutral[Co(bim)_(4)(NCS)_(2)]mononuclear units,where the cobalt(II)ion is six-coordinate with four monodentate bim ligands in equatorial positions and two N-thiocyanato groups in the axial sites building a slightly compressed octahedron.展开更多
By introducing different β-diketonate coligands 1,3-diphenyl-1,3-propanedione(dbm)and acetylacetonate(acac),two series of new tetranuclear rare earth(RE)complexes[RE_(4)(dbm)_(4)L_(6)(μ_(3)-OH)_(2)]·xCH_(3)CN&#...By introducing different β-diketonate coligands 1,3-diphenyl-1,3-propanedione(dbm)and acetylacetonate(acac),two series of new tetranuclear rare earth(RE)complexes[RE_(4)(dbm)_(4)L_(6)(μ_(3)-OH)_(2)]·xCH_(3)CN·yCH_(2)Cl_(2)(RE=Y(1),Gd(2),Tb(3),Dy(4),Ho(5),Er(6)and Lu(7))and[RE_(4)(acac)_(4)L_(6)(μ_(3)-OH)_(2)]·xCH_(3)CN(RE=Gd(8),Tb(9)and Dy(10))based on 8-hydroxyquinoline Schiff base have been synthesized and characterized.RE_(4) clusters display subtle variation in the coordination geometry of RE^(Ⅲ) ion,but display remarkably dissimilar magnetic behaviors.Magnetic studies show that 2 and 8 act as cryogenic magnetic refrigerants,while 4 and 10 exhibit different slow magnetic relaxation.With the optimized dc fields,two Dy_(4) clusters both show multiple magnetic relaxation processes by comparing with the zero dc field due to the quantum tunneling of magnetization is mostly suppressed.Interestingly,complex 10 displays two-step relaxation processes occur with U_(eff)=37.49 K(FR)and 89.89 K(SR)in the absence of an external field,and one with U_(eff)=116.20 K in the presence of a 1500 Oe optimum field.These diversities originate from the substituent group(-C_(6)H_(5) and-CH_(3))of β-diketonate coligands in the differences between steric hindrance and electron-donating effect.Additionally,the luminescence properties of 1,3,7,and 9 were investigated.展开更多
Three dinuclear Dy(Ⅲ)complexes,[Dy_(2)(tfa)_(4)L_(2)](1),[Dy_(2)(TTA)_(4)L_(2)](2)and[Dy_(2)(dbm)_(4)L_(2)·2CH_(3)CN·0.5H_(2)O](3)(tfa=trifluoroacetylacetonate,TTA=2-thenoyltrifluoroacetone,dbm=dibenzoylmet...Three dinuclear Dy(Ⅲ)complexes,[Dy_(2)(tfa)_(4)L_(2)](1),[Dy_(2)(TTA)_(4)L_(2)](2)and[Dy_(2)(dbm)_(4)L_(2)·2CH_(3)CN·0.5H_(2)O](3)(tfa=trifluoroacetylacetonate,TTA=2-thenoyltrifluoroacetone,dbm=dibenzoylmethane and HL=2-[((4-bromophenyl)-imino)methyl]-8-hydroxyquinoline,have been synthesized,and structurally and magnetically characterized.The Dy(Ⅲ)ions are eight-coordinated with two bidentate β-diketonate and two μ_(2)-O bridging 8-hydroxyquinoline Schiff base ligands.Magnetic studies reveal that 1-3 exhibit different magnetic relaxation behaviors with the anisotropic barriers of 9.61 K(1),54.81 K(2)and 30.98 K(3),respectively.The different magnetic relaxation behaviors of the three Dy_(2)complexes originate from the different chemical environments of the central Dy3+ions with different β-diketonate coligands.展开更多
Ferroelastic materials have rich properties,which have important applications in memory devices,multifunctional devices and novel controllable devices,but few ferroelastic crystals based on metal coordination complexe...Ferroelastic materials have rich properties,which have important applications in memory devices,multifunctional devices and novel controllable devices,but few ferroelastic crystals based on metal coordination complexes have been reported.Herein,we have introduced coligands in the structure to obtain a ferroelastic complex{Mn[(i-Pr)_(3)PO](dca)_(2)}(1),[dca=N(CN)_(2)^(−),(i-Pr_(3)PO)=triisopropylphosphine oxide],with a new topology(3,5)-connected binodal network.The dca ligands of 1 show two different bonding modes,μ-1,5-andμ-1,3,5-bridging,to form a 3D structure.Stimulation by high temperature leads to more intense molecular motion and greater symmetry changes,thus producing a high-temperature(390 K)ferroelastic phase transition with the Aizu symbol mmmF2/m.The full elastic constants of 1 were calculated using density functional theory to describe the Young’s modulus,shear modulus and Poisson’s ratio,and the results indicate that 1 is a ductile material.In addition,1 emits blue light under excitation at 380 nm.This provides new ideas for the exploration and design of molecular ferroelastic materials with elaborate structures and excellent properties.展开更多
Abstract:Six novel peroxo complexes of rare earth metals containing 1, 10 - phen as a coligand Re2H2O2phen2Cl6 nC2H5OH (n=0. 5 for La,Nd; n = 1 for Sin .Gd,Dy, Y)have been prepared They were characterized by elementa...Abstract:Six novel peroxo complexes of rare earth metals containing 1, 10 - phen as a coligand Re2H2O2phen2Cl6 nC2H5OH (n=0. 5 for La,Nd; n = 1 for Sin .Gd,Dy, Y)have been prepared They were characterized by elemental analysis,IR, TG-DTA and X-ray powder diffraction.展开更多
Three pairs of homochiral Ag(Ⅰ)enantiomers formulated as[Ag_(2)(L_(R))(pa)]_(n)/[Ag_(2)(Ls)(pa)]_(n)(R1/S1,H_(2)pa=phthalic acid),[Ag_(2)(L_(R))(tda)]_(n)·H_(2)O/[Ag_(2)(Ls)(tda)]_(n)·H_(2)O(R2/S2,H_(2)tda=...Three pairs of homochiral Ag(Ⅰ)enantiomers formulated as[Ag_(2)(L_(R))(pa)]_(n)/[Ag_(2)(Ls)(pa)]_(n)(R1/S1,H_(2)pa=phthalic acid),[Ag_(2)(L_(R))(tda)]_(n)·H_(2)O/[Ag_(2)(Ls)(tda)]_(n)·H_(2)O(R2/S2,H_(2)tda=3,4-thiophene dicarboxylic acid),and[Ag_(4)(L_(R))_(2)(3-npa)_(2)]_(n)/[Ag_(4)(Ls)_(2)(3-npa)2]_(n)(R3/S3,3-H_(2)npa=3-nitrophthalic acid)were prepared by using different dicarboxylic acid coligands via the reactions of AgNO_(3)with enantiopure monobidentate N-donor heterocyclic ligands named(+)/(−)-4,5-pinenepyridyl-2-pyrazine(LS/L_(R)),respectively.Ⅰnvestigations on the nonlinear optical(NLO)response suggest R1/S1 and R2/S2 enantiomers present very strong third-harmonic generation(THG)responses,and the lowest THG intensities of R1/S1 and R2/S2 are 244 and 142 times that ofα-SiO_(2),respectively.However,R3/S3 enantiomers only exhibit mild second-harmonic generation(SHG)response(0.36×KDP).A comparative study on the molecular structures of these Ag(Ⅰ)enantiomeric pairs reveals that both the symmetry and degree ofπ-conjugation of the dicarboxylate ligands are mainly responsible for their different NLO responses.Our research result not only provides a feasible method of constructing coordination polymers(CPs)with strong THG response but also points out an effective strategy for switching NLO behaviors from THG to SHG response.展开更多
A tetranuclear cubane-type complex[Co_(4)(ntfa)_(4)(CH_(3)O)_(4)(CH_(3)OH)_(4)](1)with a{Co_(4)O_(4)}core,and a mononuclear complex[Co(ntfa)_(2)(CH_(3)OH)_(2)](2)have been rationally obtained by adjusting the ratio of...A tetranuclear cubane-type complex[Co_(4)(ntfa)_(4)(CH_(3)O)_(4)(CH_(3)OH)_(4)](1)with a{Co_(4)O_(4)}core,and a mononuclear complex[Co(ntfa)_(2)(CH_(3)OH)_(2)](2)have been rationally obtained by adjusting the ratio of theβ-diketonate and Co(II)ions,with the synthetic processes being monitored by in situ microcalorimetry.Then,following synthetic conditions to obtain 2,but using three distinct N-donor coligands-2,2’-bipyridyl(bpy),6,6’-dimethyl-2,2’-bipyridyl(6,6-(CH_(3))_(2)-bpy)and 5,5’-dimethyl-2,2’-bipyridyl(5,5-(CH_(3))_(2)-bpy)-three novel mononuclear complexes have been obtained,[Co(ntfa)_(2)(bpy)_(2)](3),[Co(ntfa)_(2)(6,6-(CH_(3))_(2)-bpy)_(2)](4)and[Co(ntfa)_(2)(5,5-(CH_(3))_(2)-bpy)_(2)](5).The introduction of different capping coligands-as singlecrystal X-ray crystallography ascertains-fine-tunes the structures,with changes in both the distortion degree of the coordination geometry and the intermolecular interactions,which have a direct impact on the magnetic properties of these complexes.Magnetic investigations reveal field-induced single-ion magnet behavior in all complexes with distinct energy barriers(Ueff)-39.06(1),36.65(2),36.32(3),28.26(4)and 15.85 K(5).Magnetic experiments together with HF-EPR measurements and theoretical calculations demonstrate that 2 features easy-axis magnetic anisotropy(D=-60.48 cm^(-1)),whereas 3-5 show easy-plane magnetic anisotropies-D=+70.77 cm^(-1) for 3,+35.71 cm^(-1) for 4,and+51.28 cm^(-1) for 5.To our knowledge,such reversal of anisotropic nature driven by coligands is unprecedented.展开更多
A new 1D coordination polymer,[Fe_(3)(μ_(2)-bntrz)_(6)(bntrz)_(2)(μ_(2)-tcnsme)_(2)](tcnsme)_(4)·4H_(2)O(1·4H_(2)O),based on[Fe_(3)(μ_(2)-bntrz)_(6)]trinuclear units covalently linked by symmetric double ...A new 1D coordination polymer,[Fe_(3)(μ_(2)-bntrz)_(6)(bntrz)_(2)(μ_(2)-tcnsme)_(2)](tcnsme)_(4)·4H_(2)O(1·4H_(2)O),based on[Fe_(3)(μ_(2)-bntrz)_(6)]trinuclear units covalently linked by symmetric double cyanocarbanion coligands involving 12-membered metallacycles has been prepared and characterised.The crystal structure of 1·4H_(2)O revealed a trinuclear fragment,[Fe_(3)(μ_(2)-bntrz)_(6)(bntrz)_(2)(μ_(2)-tcnsme)_(2)]^(4+),composed of a central Fe^(Ⅱ)ion(Fe1)and two external metal ions(Fe2),similar to that described for the discrete trinuclear complex[Fe_(3)(μ_(2)-bntrz)_(6)(tcnset)_(6)](2)previously reported.Magnetic studies of 1·4H_(2)O showed a continuous gradual decrease of the magnetic signal,characteristic of the presence of a complete one-step gradual HS to LS transition(T_(1/2)=281 K)different from the abrupt one described for 2.This difference has been attributed to the presence of competing ferro-and anti-ferroelastic interactions,induced,respectively,by the intra-(μ_(2)-bntrz)and inter-trimer(μ_(2)-tcnsme)covalent links in 1·4H_(2)O.TGA and powder X-ray diffraction analyses revealed that 1·4H_(2)O shows a complete and reversible“dehydration(1)/hydration(1·4H_(2)O)”process that occurs,respectively,by heating 1·4H_(2)O at 370 K and by soaking in water the dehydrated sample(1).The magnetic behaviour of 1 exhibits a two-step SCO transition at ca.245 K.Thanks to the combined magnetic and vibrational infrared data allowing correct extraction of the contribution of the two Fe^(Ⅱ)active centres(one central Fe1 and two external Fe2 ions),the first step(370-245 K)was attributed to a concomitant HS/LS switching of the central Fe1 and a half of the Fe2 ions and the second one,occurring below 245 K,was attributed to the HS/LS transition of the remaining HS state among the randomly distributed Fe2 external ions.Photomagnetic experiments have been performed for both hydrated(1·4H_(2)O)and dehydrated(1)phases.As expected from their thermal transition temperatures,no photomagnetic response was observed for 1·4H_(2)O at 638 nm nor at 450 nm,while the dehydrated phase(1)shows an increase of the magnetic moment,reaching a maximum of 1.4 cm^(3)K mol^(−1)at 22 K,followed by the thermallyinduced HS to LS relaxation with TLIESST=41 K.展开更多
基金supported by the Project of Science&Technology in Henan Province(No.172102310441)the National Natural Science Foundation of China(No.21571093)
文摘The cyanide groups of letrozole(1-[bis(4-cyanophenyl)methyl]-1,2,4-triazole) were hydrolyzed into the carboxylic groups under alkaline conditions. Then the hydrolysis product(1-[bis(4-carboxylphenyl)methyl]-1,2,4-triazole, H2ltzda) reacted with Co(NO3)2·6H2O in the presence of different bipyridl-typed ligands under hydrothermal conditions. As a result, two new Co(Ⅱ) MOFs were obtained, formulated as [Co2(ltzda)2(bpp)2]n(1) and {[Co2(ltzda)2(bpy)]·4H2O}n(2)(bpp = 1,3-di(4-pyridyl)propane, bpy = 4,4’-bipyridine). Two MOFs have been characterized by single-crystal X-ray diffraction, thermogravimetric analysis and magnetic measure. 1 displays a 2D metal-organic framework containing wave layers and 2 shows a pillared-layer structure existing in a 2-fold interpenetrated mode.
基金supported by the Polish National Agency for Academic Exchange(PPN/BEK/2018/1/00239/U/00001/01)the Ministerio Español de Ciencia e Innovación(Projects CTQ2016-75068P and PID2019-109735GB-I00Unidad de Excelencia María de Maetzu MDM-2015-0538).
文摘We report the preparation,spectroscopic characterisation,crystal structure determination and cryomagnetic investigation of three cobalt(II)complexes of formula trans-[Co(bim)_(4)(NCS)_(2)](1),[Co(bim)_(2)(NCO)_(2)](_(2))and[Co(bim)_(2)(N_(3))_(2)]_(n)(_(3))(bim=1-benzylimidazole).The structure of 1 is made up of neutral[Co(bim)_(4)(NCS)_(2)]mononuclear units,where the cobalt(II)ion is six-coordinate with four monodentate bim ligands in equatorial positions and two N-thiocyanato groups in the axial sites building a slightly compressed octahedron.
基金supported financially by the National Natural Science Foundation of China(No.21473121,21571138)the Key Laboratory of Advanced Energy Materials Chemistry(Ministry of Education,NanKai University,Opening Foundation).
文摘By introducing different β-diketonate coligands 1,3-diphenyl-1,3-propanedione(dbm)and acetylacetonate(acac),two series of new tetranuclear rare earth(RE)complexes[RE_(4)(dbm)_(4)L_(6)(μ_(3)-OH)_(2)]·xCH_(3)CN·yCH_(2)Cl_(2)(RE=Y(1),Gd(2),Tb(3),Dy(4),Ho(5),Er(6)and Lu(7))and[RE_(4)(acac)_(4)L_(6)(μ_(3)-OH)_(2)]·xCH_(3)CN(RE=Gd(8),Tb(9)and Dy(10))based on 8-hydroxyquinoline Schiff base have been synthesized and characterized.RE_(4) clusters display subtle variation in the coordination geometry of RE^(Ⅲ) ion,but display remarkably dissimilar magnetic behaviors.Magnetic studies show that 2 and 8 act as cryogenic magnetic refrigerants,while 4 and 10 exhibit different slow magnetic relaxation.With the optimized dc fields,two Dy_(4) clusters both show multiple magnetic relaxation processes by comparing with the zero dc field due to the quantum tunneling of magnetization is mostly suppressed.Interestingly,complex 10 displays two-step relaxation processes occur with U_(eff)=37.49 K(FR)and 89.89 K(SR)in the absence of an external field,and one with U_(eff)=116.20 K in the presence of a 1500 Oe optimum field.These diversities originate from the substituent group(-C_(6)H_(5) and-CH_(3))of β-diketonate coligands in the differences between steric hindrance and electron-donating effect.Additionally,the luminescence properties of 1,3,7,and 9 were investigated.
基金supported financially by the National Natural Science Foundation of China(no.21271137,21571138 and 21561014).
文摘Three dinuclear Dy(Ⅲ)complexes,[Dy_(2)(tfa)_(4)L_(2)](1),[Dy_(2)(TTA)_(4)L_(2)](2)and[Dy_(2)(dbm)_(4)L_(2)·2CH_(3)CN·0.5H_(2)O](3)(tfa=trifluoroacetylacetonate,TTA=2-thenoyltrifluoroacetone,dbm=dibenzoylmethane and HL=2-[((4-bromophenyl)-imino)methyl]-8-hydroxyquinoline,have been synthesized,and structurally and magnetically characterized.The Dy(Ⅲ)ions are eight-coordinated with two bidentate β-diketonate and two μ_(2)-O bridging 8-hydroxyquinoline Schiff base ligands.Magnetic studies reveal that 1-3 exhibit different magnetic relaxation behaviors with the anisotropic barriers of 9.61 K(1),54.81 K(2)and 30.98 K(3),respectively.The different magnetic relaxation behaviors of the three Dy_(2)complexes originate from the different chemical environments of the central Dy3+ions with different β-diketonate coligands.
基金supported by the National Natural Science Foundation of China(22275033)supported by the Big Data Computing Center of Southeast University.
文摘Ferroelastic materials have rich properties,which have important applications in memory devices,multifunctional devices and novel controllable devices,but few ferroelastic crystals based on metal coordination complexes have been reported.Herein,we have introduced coligands in the structure to obtain a ferroelastic complex{Mn[(i-Pr)_(3)PO](dca)_(2)}(1),[dca=N(CN)_(2)^(−),(i-Pr_(3)PO)=triisopropylphosphine oxide],with a new topology(3,5)-connected binodal network.The dca ligands of 1 show two different bonding modes,μ-1,5-andμ-1,3,5-bridging,to form a 3D structure.Stimulation by high temperature leads to more intense molecular motion and greater symmetry changes,thus producing a high-temperature(390 K)ferroelastic phase transition with the Aizu symbol mmmF2/m.The full elastic constants of 1 were calculated using density functional theory to describe the Young’s modulus,shear modulus and Poisson’s ratio,and the results indicate that 1 is a ductile material.In addition,1 emits blue light under excitation at 380 nm.This provides new ideas for the exploration and design of molecular ferroelastic materials with elaborate structures and excellent properties.
文摘Abstract:Six novel peroxo complexes of rare earth metals containing 1, 10 - phen as a coligand Re2H2O2phen2Cl6 nC2H5OH (n=0. 5 for La,Nd; n = 1 for Sin .Gd,Dy, Y)have been prepared They were characterized by elemental analysis,IR, TG-DTA and X-ray powder diffraction.
基金the National Natural Science Foundation of China(No.21701150 and 21371156)the school doctorial foundation of Zhengzhou University of Light Industry(No.2016BSJJ028)Zhongyuan Science and Technology Innovation Leading Talents(214200510017).
文摘Three pairs of homochiral Ag(Ⅰ)enantiomers formulated as[Ag_(2)(L_(R))(pa)]_(n)/[Ag_(2)(Ls)(pa)]_(n)(R1/S1,H_(2)pa=phthalic acid),[Ag_(2)(L_(R))(tda)]_(n)·H_(2)O/[Ag_(2)(Ls)(tda)]_(n)·H_(2)O(R2/S2,H_(2)tda=3,4-thiophene dicarboxylic acid),and[Ag_(4)(L_(R))_(2)(3-npa)_(2)]_(n)/[Ag_(4)(Ls)_(2)(3-npa)2]_(n)(R3/S3,3-H_(2)npa=3-nitrophthalic acid)were prepared by using different dicarboxylic acid coligands via the reactions of AgNO_(3)with enantiopure monobidentate N-donor heterocyclic ligands named(+)/(−)-4,5-pinenepyridyl-2-pyrazine(LS/L_(R)),respectively.Ⅰnvestigations on the nonlinear optical(NLO)response suggest R1/S1 and R2/S2 enantiomers present very strong third-harmonic generation(THG)responses,and the lowest THG intensities of R1/S1 and R2/S2 are 244 and 142 times that ofα-SiO_(2),respectively.However,R3/S3 enantiomers only exhibit mild second-harmonic generation(SHG)response(0.36×KDP).A comparative study on the molecular structures of these Ag(Ⅰ)enantiomeric pairs reveals that both the symmetry and degree ofπ-conjugation of the dicarboxylate ligands are mainly responsible for their different NLO responses.Our research result not only provides a feasible method of constructing coordination polymers(CPs)with strong THG response but also points out an effective strategy for switching NLO behaviors from THG to SHG response.
基金support from the National Natural Science Foundation of China(21863009,U20A2073)the Natural Science Foundation of Ningxia Province(2020AAC02005)+5 种基金the Discipline Project of Ningxia(NXYLXK2017A04)the Guizhou Education Department Youth Science and Technology Talents Growth Project(No.KY[2020]158)the 2019 Post-doctoral Junior Leader-Retaining Fellowship,la Caixa Foundation(ID100010434 and fellowship code LCF/BQ/PR19/11700011)the“Generalitat Valenciana”(SEJI/2020/034)the“Ramón y Cajal”program(J.F.-S.)support from the European Research Council under the European Union’s Horizon 2020 research and innovation programme/ERC Grant Agreement No.814804,MOF-reactors.
文摘A tetranuclear cubane-type complex[Co_(4)(ntfa)_(4)(CH_(3)O)_(4)(CH_(3)OH)_(4)](1)with a{Co_(4)O_(4)}core,and a mononuclear complex[Co(ntfa)_(2)(CH_(3)OH)_(2)](2)have been rationally obtained by adjusting the ratio of theβ-diketonate and Co(II)ions,with the synthetic processes being monitored by in situ microcalorimetry.Then,following synthetic conditions to obtain 2,but using three distinct N-donor coligands-2,2’-bipyridyl(bpy),6,6’-dimethyl-2,2’-bipyridyl(6,6-(CH_(3))_(2)-bpy)and 5,5’-dimethyl-2,2’-bipyridyl(5,5-(CH_(3))_(2)-bpy)-three novel mononuclear complexes have been obtained,[Co(ntfa)_(2)(bpy)_(2)](3),[Co(ntfa)_(2)(6,6-(CH_(3))_(2)-bpy)_(2)](4)and[Co(ntfa)_(2)(5,5-(CH_(3))_(2)-bpy)_(2)](5).The introduction of different capping coligands-as singlecrystal X-ray crystallography ascertains-fine-tunes the structures,with changes in both the distortion degree of the coordination geometry and the intermolecular interactions,which have a direct impact on the magnetic properties of these complexes.Magnetic investigations reveal field-induced single-ion magnet behavior in all complexes with distinct energy barriers(Ueff)-39.06(1),36.65(2),36.32(3),28.26(4)and 15.85 K(5).Magnetic experiments together with HF-EPR measurements and theoretical calculations demonstrate that 2 features easy-axis magnetic anisotropy(D=-60.48 cm^(-1)),whereas 3-5 show easy-plane magnetic anisotropies-D=+70.77 cm^(-1) for 3,+35.71 cm^(-1) for 4,and+51.28 cm^(-1) for 5.To our knowledge,such reversal of anisotropic nature driven by coligands is unprecedented.
基金funded by the French CNRS(MITI Project),Mol-CoSM ANR Project No.ANR-20-CE07-0028-01financial support from“Région de Bretagne and Universitéde Brest”financial support of the Polish National Science Centre within the Opus project no.2020/39/B/ST5/02815.
文摘A new 1D coordination polymer,[Fe_(3)(μ_(2)-bntrz)_(6)(bntrz)_(2)(μ_(2)-tcnsme)_(2)](tcnsme)_(4)·4H_(2)O(1·4H_(2)O),based on[Fe_(3)(μ_(2)-bntrz)_(6)]trinuclear units covalently linked by symmetric double cyanocarbanion coligands involving 12-membered metallacycles has been prepared and characterised.The crystal structure of 1·4H_(2)O revealed a trinuclear fragment,[Fe_(3)(μ_(2)-bntrz)_(6)(bntrz)_(2)(μ_(2)-tcnsme)_(2)]^(4+),composed of a central Fe^(Ⅱ)ion(Fe1)and two external metal ions(Fe2),similar to that described for the discrete trinuclear complex[Fe_(3)(μ_(2)-bntrz)_(6)(tcnset)_(6)](2)previously reported.Magnetic studies of 1·4H_(2)O showed a continuous gradual decrease of the magnetic signal,characteristic of the presence of a complete one-step gradual HS to LS transition(T_(1/2)=281 K)different from the abrupt one described for 2.This difference has been attributed to the presence of competing ferro-and anti-ferroelastic interactions,induced,respectively,by the intra-(μ_(2)-bntrz)and inter-trimer(μ_(2)-tcnsme)covalent links in 1·4H_(2)O.TGA and powder X-ray diffraction analyses revealed that 1·4H_(2)O shows a complete and reversible“dehydration(1)/hydration(1·4H_(2)O)”process that occurs,respectively,by heating 1·4H_(2)O at 370 K and by soaking in water the dehydrated sample(1).The magnetic behaviour of 1 exhibits a two-step SCO transition at ca.245 K.Thanks to the combined magnetic and vibrational infrared data allowing correct extraction of the contribution of the two Fe^(Ⅱ)active centres(one central Fe1 and two external Fe2 ions),the first step(370-245 K)was attributed to a concomitant HS/LS switching of the central Fe1 and a half of the Fe2 ions and the second one,occurring below 245 K,was attributed to the HS/LS transition of the remaining HS state among the randomly distributed Fe2 external ions.Photomagnetic experiments have been performed for both hydrated(1·4H_(2)O)and dehydrated(1)phases.As expected from their thermal transition temperatures,no photomagnetic response was observed for 1·4H_(2)O at 638 nm nor at 450 nm,while the dehydrated phase(1)shows an increase of the magnetic moment,reaching a maximum of 1.4 cm^(3)K mol^(−1)at 22 K,followed by the thermallyinduced HS to LS relaxation with TLIESST=41 K.
