Circularly polarized luminescence(CPL)was evidenced for the first time in single crystals of a chiral-atmetal Dy(III)single-molecule magnet.This CPL is opposite for the enantiomers and was found to appear and become s...Circularly polarized luminescence(CPL)was evidenced for the first time in single crystals of a chiral-atmetal Dy(III)single-molecule magnet.This CPL is opposite for the enantiomers and was found to appear and become stronger at lower temperatures when the relaxation of the magnetization for the Dy centers is slower.The luminescence dissymmetry factor(g_(lum)up to±0.18)was found to have little dependence on the emission angle which permitted observing a similar CPL for an ensemble of micro-crystals of random orientations.The investigated Dy(III)compounds consist of bimetallic ZnLn units assembled by a Schiff base ligand,control of the stereochemistry of the Ln center was achieved using chiral[3-(trifluoromethylhydroxymethylene)-camphorate]−as anionic ligands.CPL was not found for the Eu(III)homologues.展开更多
Three biradical-bridged heterometallic chains,[LnCu_(2)(hfac)7(bisNITPhPy)]n(Ln^(Ⅲ)=Gd,1;Tb,2;Ho,3),were synthesized by means of a nitronyl nitroxide biradical bisNITPhPy([5-(4-pyridyl)-1,3-bis(1’-oxyl-3’-oxide-4...Three biradical-bridged heterometallic chains,[LnCu_(2)(hfac)7(bisNITPhPy)]n(Ln^(Ⅲ)=Gd,1;Tb,2;Ho,3),were synthesized by means of a nitronyl nitroxide biradical bisNITPhPy([5-(4-pyridyl)-1,3-bis(1’-oxyl-3’-oxide-4’,4’,5’,5’-tetramethyl-4,5-hydro-1H-imidazol-2-yl)]benzene;hfac=hexafluoroacetylacetonate).In these structures,the bisNITPhPy biradical serves as a pentadentate ligand to hold one Ln^(Ⅲ)ion through two neighboring aminoxyl(NO)moieties in chelating mode,while other two NO groups are coordinated to Cu(hfac)_(2)units,leading to a 1D Cu-Ln-birad chain.An additional terminal Cu(hfac)_(2)unit linked to a pyridine-N atom is found at the periphery.The magnetic susceptibility data of compound Gd have been analyzed with a closed ring model comprising three[Cu-Rad-Gd-Rad]units,which indicates ferromagnetic Gd(Ⅲ)-nitroxide and Cu(Ⅱ)-axial nitroxide interactions.The Tb derivative was found to behave as a single chain magnet with an energy barrier for magnetization reversal of 26 K.展开更多
A Ni(Ⅱ)complex harnessed in a pentagonal bipyramidal environment by a rigid N_(5)-macrocyclic ligand(i.e.1,3,10,12-tetramethyl-1,2,11,12-tetraaza[3](2,6)-pyridino[3](2,9)-1,10-phenanthrolinophane-2,10-diene)is shown ...A Ni(Ⅱ)complex harnessed in a pentagonal bipyramidal environment by a rigid N_(5)-macrocyclic ligand(i.e.1,3,10,12-tetramethyl-1,2,11,12-tetraaza[3](2,6)-pyridino[3](2,9)-1,10-phenanthrolinophane-2,10-diene)is shown to exhibit axial anisotropy with a ZFS D parameter in the order of−10 to−15 cm^(-1),and this anisotropy is not significantly changed by apical ligand substitution.Using the latter complex as a building unit,a ferromagnetic 1-D CN-bridged Ni-Cr coordination polymer with SCM behavior characterized by a barrier of magnetization reversal U_(eff)/k_(B)=54 K(37 cm^(-1))withτ0=2.28×10^(−11)s was obtained.The Cr(Ⅲ)complex involved in the design was chosen to favor parallel organization of the anisotropy axes of the Ni units along the 1-D array,and thus maximize the magnetic anisotropy of the supramolecular system.A related chain compound prepared with diamagnetic[Ni(CN)_(4)]^(2−)units,and a trinuclear CN-bridged[NiCr_(2)]complex enabled assessing respectively the magnetic anisotropy of Ni(Ⅱ)in this coordination sphere and its exchange interaction with Cr(Ⅲ)found to be ferromagnetic and of the order of 10 cm^(-1).The crystal structures and magnetic behaviors of all compounds are reported.展开更多
The promising magnetic behavior of heterospin systems has spurred the research of 2p-3d-4f heterotri-spin compounds.Such a magnetic system has crucial advantages:the strongest possible magnetic interactions resulting ...The promising magnetic behavior of heterospin systems has spurred the research of 2p-3d-4f heterotri-spin compounds.Such a magnetic system has crucial advantages:the strongest possible magnetic interactions resulting from the direct binding of the radicals to the metal ions,access to strong magnetic anisotropies arising from 4f ions,and novel magnetic behavior derived from the synergic or competitive magnetic interactions between three different spin carriers.Herein we review recent advances made toward a rational development of 2p-3d-4f complexes.Special attention is given to the 2p-3d-4f compounds exhibiting slow magnetic relaxation.展开更多
Pentagonal bipyramidal(PBP)complexes with a first-order spin–orbit coupling contribution can be readily obtained,mainly through chemical design optimization ensuring minimum structural distortion and a more symmetric...Pentagonal bipyramidal(PBP)complexes with a first-order spin–orbit coupling contribution can be readily obtained,mainly through chemical design optimization ensuring minimum structural distortion and a more symmetrical ligand field.This conclusion follows from the investigation of a series of five Fe(II)complexes:[FeL^(N5)(H_(2)O)Cl]Cl·4.5H_(2)O,1;[FeL^(N5)Cl_(2)]·3H_(2)O,2;[FeL^(N5)Br_(2)],3;[FeL^(N5)I_(2)],4;and[Fe_(0.12)Zn_(0.88)L^(N5)I_(2)],5(L^(N5) stands for the pentadentate macrocyclic ligand formed by the condensation of 2,6-diacetylpyridine and 2,9-di(α-methylhydrazino)-1,10-phenanthroline).Theoretical calculations revealed quasi-degeneracy of the dxz and dyz orbitals for the complexes with halide ligands at the apical positions(ΔE=91,134,and 142 cm^(−1),respectively,for 2–4).This small energy gap leads to SO states with very strong mixing of the ground and first excited quintet states.Therefore,the ZFS Hamiltonian is not suitable for modelling the magnetic properties of complexes 2–5.This does not apply for 1 withΔE=412 cm^(−1).The recorded magnetic behaviors indicated strong magnetic anisotropy;for 1 D=−24 cm^(−1) was obtained.The Br and I derivatives were found to behave as SMMs(with a U/k_(B) of about 90 K),the latter even in the absence of a static field.展开更多
基金supported by the French Research Agency(Agence Nationale de la Recherche,reference ANR-09-BLAN-0054-01).Authors are grateful to M.J.-F.Meunier and M.L.Réchignat(LCC)for technical assistance in magnetic data collection.
文摘Circularly polarized luminescence(CPL)was evidenced for the first time in single crystals of a chiral-atmetal Dy(III)single-molecule magnet.This CPL is opposite for the enantiomers and was found to appear and become stronger at lower temperatures when the relaxation of the magnetization for the Dy centers is slower.The luminescence dissymmetry factor(g_(lum)up to±0.18)was found to have little dependence on the emission angle which permitted observing a similar CPL for an ensemble of micro-crystals of random orientations.The investigated Dy(III)compounds consist of bimetallic ZnLn units assembled by a Schiff base ligand,control of the stereochemistry of the Ln center was achieved using chiral[3-(trifluoromethylhydroxymethylene)-camphorate]−as anionic ligands.CPL was not found for the Eu(III)homologues.
基金supported by the National Key R&D Program of China(2018YFA0306002)the National Natural Science Foundation of China(No.21773122 and 21471083)and the 111 Project(B12015).
文摘Three biradical-bridged heterometallic chains,[LnCu_(2)(hfac)7(bisNITPhPy)]n(Ln^(Ⅲ)=Gd,1;Tb,2;Ho,3),were synthesized by means of a nitronyl nitroxide biradical bisNITPhPy([5-(4-pyridyl)-1,3-bis(1’-oxyl-3’-oxide-4’,4’,5’,5’-tetramethyl-4,5-hydro-1H-imidazol-2-yl)]benzene;hfac=hexafluoroacetylacetonate).In these structures,the bisNITPhPy biradical serves as a pentadentate ligand to hold one Ln^(Ⅲ)ion through two neighboring aminoxyl(NO)moieties in chelating mode,while other two NO groups are coordinated to Cu(hfac)_(2)units,leading to a 1D Cu-Ln-birad chain.An additional terminal Cu(hfac)_(2)unit linked to a pyridine-N atom is found at the periphery.The magnetic susceptibility data of compound Gd have been analyzed with a closed ring model comprising three[Cu-Rad-Gd-Rad]units,which indicates ferromagnetic Gd(Ⅲ)-nitroxide and Cu(Ⅱ)-axial nitroxide interactions.The Tb derivative was found to behave as a single chain magnet with an energy barrier for magnetization reversal of 26 K.
文摘A Ni(Ⅱ)complex harnessed in a pentagonal bipyramidal environment by a rigid N_(5)-macrocyclic ligand(i.e.1,3,10,12-tetramethyl-1,2,11,12-tetraaza[3](2,6)-pyridino[3](2,9)-1,10-phenanthrolinophane-2,10-diene)is shown to exhibit axial anisotropy with a ZFS D parameter in the order of−10 to−15 cm^(-1),and this anisotropy is not significantly changed by apical ligand substitution.Using the latter complex as a building unit,a ferromagnetic 1-D CN-bridged Ni-Cr coordination polymer with SCM behavior characterized by a barrier of magnetization reversal U_(eff)/k_(B)=54 K(37 cm^(-1))withτ0=2.28×10^(−11)s was obtained.The Cr(Ⅲ)complex involved in the design was chosen to favor parallel organization of the anisotropy axes of the Ni units along the 1-D array,and thus maximize the magnetic anisotropy of the supramolecular system.A related chain compound prepared with diamagnetic[Ni(CN)_(4)]^(2−)units,and a trinuclear CN-bridged[NiCr_(2)]complex enabled assessing respectively the magnetic anisotropy of Ni(Ⅱ)in this coordination sphere and its exchange interaction with Cr(Ⅲ)found to be ferromagnetic and of the order of 10 cm^(-1).The crystal structures and magnetic behaviors of all compounds are reported.
基金supported by the National Natural Science Foundation of China(no.21471083)MOE Innovation Team(IRT13022)of China.
文摘The promising magnetic behavior of heterospin systems has spurred the research of 2p-3d-4f heterotri-spin compounds.Such a magnetic system has crucial advantages:the strongest possible magnetic interactions resulting from the direct binding of the radicals to the metal ions,access to strong magnetic anisotropies arising from 4f ions,and novel magnetic behavior derived from the synergic or competitive magnetic interactions between three different spin carriers.Herein we review recent advances made toward a rational development of 2p-3d-4f complexes.Special attention is given to the 2p-3d-4f compounds exhibiting slow magnetic relaxation.
文摘Pentagonal bipyramidal(PBP)complexes with a first-order spin–orbit coupling contribution can be readily obtained,mainly through chemical design optimization ensuring minimum structural distortion and a more symmetrical ligand field.This conclusion follows from the investigation of a series of five Fe(II)complexes:[FeL^(N5)(H_(2)O)Cl]Cl·4.5H_(2)O,1;[FeL^(N5)Cl_(2)]·3H_(2)O,2;[FeL^(N5)Br_(2)],3;[FeL^(N5)I_(2)],4;and[Fe_(0.12)Zn_(0.88)L^(N5)I_(2)],5(L^(N5) stands for the pentadentate macrocyclic ligand formed by the condensation of 2,6-diacetylpyridine and 2,9-di(α-methylhydrazino)-1,10-phenanthroline).Theoretical calculations revealed quasi-degeneracy of the dxz and dyz orbitals for the complexes with halide ligands at the apical positions(ΔE=91,134,and 142 cm^(−1),respectively,for 2–4).This small energy gap leads to SO states with very strong mixing of the ground and first excited quintet states.Therefore,the ZFS Hamiltonian is not suitable for modelling the magnetic properties of complexes 2–5.This does not apply for 1 withΔE=412 cm^(−1).The recorded magnetic behaviors indicated strong magnetic anisotropy;for 1 D=−24 cm^(−1) was obtained.The Br and I derivatives were found to behave as SMMs(with a U/k_(B) of about 90 K),the latter even in the absence of a static field.
