Controlling molecular magnetic anisotropy via structural engineering is delicate and fascinating,especially for single-molecule magnets(SMMs).Herein a family of dysprosium single-ion magnets(SIMs)sitting in pentagonal...Controlling molecular magnetic anisotropy via structural engineering is delicate and fascinating,especially for single-molecule magnets(SMMs).Herein a family of dysprosium single-ion magnets(SIMs)sitting in pentagonal bipyramid geometry have been synthesized with the variable-size terminal ligands and counter anions,through which the subtle coordination geometry of Dy(Ⅲ)can be finely tuned based on the size effect.The effective energy barrier(Ueff)successfully increases from 439 to 632 K and the magnetic hysteresis temperature(under a 200 Oe/s sweep rate)raises from 11 to 24 K.Based on the crystal-field theory,a semi-quantitative magneto-structural correlation deduced experimentally for the first time is revealed that the Ueff is linearly proportional to the structural-related value S20 corresponding to the axial coordination bond lengths and the bond angles.Through the evaluation of the remanent magnetization from hysteresis,quantum tunneling of magnetization(QTM)is found to exhibit negative correlation with the structural-related value Stun corresponding to the axial coordination bond angles.展开更多
The influence of heat treatment with different cooling rates on phase transition behaviors and magnetocaloric effect is systematically studied.Difference in atomic order is induced by changing cooling rates,where orde...The influence of heat treatment with different cooling rates on phase transition behaviors and magnetocaloric effect is systematically studied.Difference in atomic order is induced by changing cooling rates,where ordered phase is obtained in the furnace cooled（FC）sample while disordered phase is reserved in the water quenched（WQ）sample.The coupled magneto-structural transition is detected in both samples but the characteristic temperature significantly shifts to lower temperatures with increasing atomic order.Giant magnetic entropy change（ΔS_（mag））derived from magnetic field induced martensitic transformation is confirmed for both samples,and can be remarkably enhanced by the atomic ordering.The largestΔS_（mag） of 20.9J/（kg·K）is obtained at 307.5Kunder 5Tin the FC sample.展开更多
Compound 1 was first synthesized and characterized. Its crystal structure and magnetic property were determined and investigated. Discussion about the molecule packing in crystal and the macroscopic magnetism was also...Compound 1 was first synthesized and characterized. Its crystal structure and magnetic property were determined and investigated. Discussion about the molecule packing in crystal and the macroscopic magnetism was also presented, in combination with computing study of the spatial distribution over the molecule.展开更多
Crystal structures of new nitronyl nitroxide derivatives 1, 2 and 3 were determined with X-ray diffraction analysis: 1, monoclinic, C-2/c, a = 1.204 (5) nm; b = 0.9730 (5) nm, c = 2.7049 (10) nm, beta = 98.189 (15)deg...Crystal structures of new nitronyl nitroxide derivatives 1, 2 and 3 were determined with X-ray diffraction analysis: 1, monoclinic, C-2/c, a = 1.204 (5) nm; b = 0.9730 (5) nm, c = 2.7049 (10) nm, beta = 98.189 (15)degrees, V = 3.2315 (24) nm(3), Z = 8; 2, orthorhombic, Pbca, a = 0.61262(2) nm, b = 1.11426(6) nm, c = 2.30543(13) nm, V = 1.57373(13) nm(3), Z = 4; 3, monoclinic, P2(1)/n, a = 0.64253(4) nm, b = 2.55003(17) nm, c = 1.15497(6) nm, beta = 95.000(3)degrees, V = 1.8852(2) nm(3), Z = 4. Their magnetic properties were measured with SQUID and analyzed based on their crystal structures with simple singlet-triplet, modified one dimensional antiferromagnetic chain and modified singlet-triplet models respectively: 1, J/k(b) = -2.5 K; 2, J/k(b) = 7.8 K, theta = 2.8 K; 3, J/k(b) = -0.96 K, theta = 0.21 K.展开更多
A new dinuclear copper(Ⅱ)compound[Cu2(CH3COO)2(L)2(H2O)2]·4H2O(1,HL=4-pyridyl-NH-1,2,3-triazole)has been synthesized and characterized.Single-crystal X-ray diffraction showed that complex 1 crystallizes in monoc...A new dinuclear copper(Ⅱ)compound[Cu2(CH3COO)2(L)2(H2O)2]·4H2O(1,HL=4-pyridyl-NH-1,2,3-triazole)has been synthesized and characterized.Single-crystal X-ray diffraction showed that complex 1 crystallizes in monoclinic space group P21/c with a=0.8427(1),b=1.0981(1),c=1.3610(1)nm,β=93.364(4)°,V=1.2573(1)nm^3,Mr=643.56,Z=2,Dc=1.700 g/cm^3,μ=1.760 mm-1,R=0.0376,wR=0.0981,and possesses a planar Cu2N4 six-membered ring,in which both Cu(Ⅱ)ions are bridged by two 1,2,3-triazole ligands.The neighboring dinuclear molecules are bound by strong intermolecular hydrogen bonds to create 1-D chains expanding along the b axis,which further form a 3-D supramolecular framework.Magnetic susceptibility measurement indicated the presence of weak antiferromagnetic interactions within the complex.The best fit using spin Hamiltonian yields the magnetic coupling constant J=–14.82 cm^-1 above 30 K.The magnetic data are compared to those obtained for related double diazine bridged dinuclear copper(Ⅱ)complexes and magnetostructural correlations are discussed.展开更多
基金supported by the National Key Research and Development Program of China(2018YFA0306001)the National Natural Sciences foundation of China(21620102002,21822508,21821003)the Pearl River Talent Plan of Guangdong(2017BT01C161)。
文摘Controlling molecular magnetic anisotropy via structural engineering is delicate and fascinating,especially for single-molecule magnets(SMMs).Herein a family of dysprosium single-ion magnets(SIMs)sitting in pentagonal bipyramid geometry have been synthesized with the variable-size terminal ligands and counter anions,through which the subtle coordination geometry of Dy(Ⅲ)can be finely tuned based on the size effect.The effective energy barrier(Ueff)successfully increases from 439 to 632 K and the magnetic hysteresis temperature(under a 200 Oe/s sweep rate)raises from 11 to 24 K.Based on the crystal-field theory,a semi-quantitative magneto-structural correlation deduced experimentally for the first time is revealed that the Ueff is linearly proportional to the structural-related value S20 corresponding to the axial coordination bond lengths and the bond angles.Through the evaluation of the remanent magnetization from hysteresis,quantum tunneling of magnetization(QTM)is found to exhibit negative correlation with the structural-related value Stun corresponding to the axial coordination bond angles.
基金supported by the National Natural Science Foundations of China(Grant Nos.51331001, 51520105002,51601008,and 51601007)the Fundamental Research Funds for Central Universities
文摘The influence of heat treatment with different cooling rates on phase transition behaviors and magnetocaloric effect is systematically studied.Difference in atomic order is induced by changing cooling rates,where ordered phase is obtained in the furnace cooled（FC）sample while disordered phase is reserved in the water quenched（WQ）sample.The coupled magneto-structural transition is detected in both samples but the characteristic temperature significantly shifts to lower temperatures with increasing atomic order.Giant magnetic entropy change（ΔS_（mag））derived from magnetic field induced martensitic transformation is confirmed for both samples,and can be remarkably enhanced by the atomic ordering.The largestΔS_（mag） of 20.9J/（kg·K）is obtained at 307.5Kunder 5Tin the FC sample.
文摘Compound 1 was first synthesized and characterized. Its crystal structure and magnetic property were determined and investigated. Discussion about the molecule packing in crystal and the macroscopic magnetism was also presented, in combination with computing study of the spatial distribution over the molecule.
文摘Crystal structures of new nitronyl nitroxide derivatives 1, 2 and 3 were determined with X-ray diffraction analysis: 1, monoclinic, C-2/c, a = 1.204 (5) nm; b = 0.9730 (5) nm, c = 2.7049 (10) nm, beta = 98.189 (15)degrees, V = 3.2315 (24) nm(3), Z = 8; 2, orthorhombic, Pbca, a = 0.61262(2) nm, b = 1.11426(6) nm, c = 2.30543(13) nm, V = 1.57373(13) nm(3), Z = 4; 3, monoclinic, P2(1)/n, a = 0.64253(4) nm, b = 2.55003(17) nm, c = 1.15497(6) nm, beta = 95.000(3)degrees, V = 1.8852(2) nm(3), Z = 4. Their magnetic properties were measured with SQUID and analyzed based on their crystal structures with simple singlet-triplet, modified one dimensional antiferromagnetic chain and modified singlet-triplet models respectively: 1, J/k(b) = -2.5 K; 2, J/k(b) = 7.8 K, theta = 2.8 K; 3, J/k(b) = -0.96 K, theta = 0.21 K.
基金the National Natural Science Foundation of China(21002076,21441007)the Open Fund Project(No.KLSAOFM1709)of Ministry-of-Education Key Laboratory for the Synthesis and Application of Organic Function Molecules,Hubei UniversityNo.CX2018150 and No.CX2018132 supported by the Graduate Innovative Fund of Wuhan Institute of Technology。
文摘A new dinuclear copper(Ⅱ)compound[Cu2(CH3COO)2(L)2(H2O)2]·4H2O(1,HL=4-pyridyl-NH-1,2,3-triazole)has been synthesized and characterized.Single-crystal X-ray diffraction showed that complex 1 crystallizes in monoclinic space group P21/c with a=0.8427(1),b=1.0981(1),c=1.3610(1)nm,β=93.364(4)°,V=1.2573(1)nm^3,Mr=643.56,Z=2,Dc=1.700 g/cm^3,μ=1.760 mm-1,R=0.0376,wR=0.0981,and possesses a planar Cu2N4 six-membered ring,in which both Cu(Ⅱ)ions are bridged by two 1,2,3-triazole ligands.The neighboring dinuclear molecules are bound by strong intermolecular hydrogen bonds to create 1-D chains expanding along the b axis,which further form a 3-D supramolecular framework.Magnetic susceptibility measurement indicated the presence of weak antiferromagnetic interactions within the complex.The best fit using spin Hamiltonian yields the magnetic coupling constant J=–14.82 cm^-1 above 30 K.The magnetic data are compared to those obtained for related double diazine bridged dinuclear copper(Ⅱ)complexes and magnetostructural correlations are discussed.
