Two isomers of metallofullerene Dy_(2)S@C_(82)with sulfur-bridged Dy ions exhibit broad magnetic hysteresis with sharp steps at sub-Kelvin temperature.Analysis of the level crossing events for different orientations o...Two isomers of metallofullerene Dy_(2)S@C_(82)with sulfur-bridged Dy ions exhibit broad magnetic hysteresis with sharp steps at sub-Kelvin temperature.Analysis of the level crossing events for different orientations of a magnetic field showed that even in powder samples,the hysteresis steps caused by quantum tunneling of magnetization can provide precise information on the strength of intramolecular Dy…Dy interactions.A comparison of different methods to determine the energy difference between ferromagnetic and antiferromagnetic states showed that sub-Kelvin hysteresis gives the most robust and reliable values.The ground state in Dy_(2)S@C_(82)has ferromagnetic coupling of Dy magnetic moments,whereas the state with antiferromagnetic coupling in C_(s)and C_(3)v cage isomers is 10.7 and 5.1 cm^(-1)higher,respectively.The value for the C_(s)isomer is among the highest found in metallofullerenes and is considerably larger than that reported in non-fullerene dinuclear molecular magnets.Magnetization relaxation times measured in zero magnetic field at sub-Kelvin temperatures tend to level off near 900 and 3200 s in C_(s)and C_(3)v isomers.These times correspond to the quantum tunneling relaxation mechanism,in which the whole magnetic moment of the Dy_(2)S@C_(82)molecule flips at once as a single entity.展开更多
Low-symmetry metal-organic cages(MOCs)have received increasing attention due to their complex structures and more advanced functions.Here,we report a new MOC cage with a unique trigonal bipyramidal configuration,[M_(5...Low-symmetry metal-organic cages(MOCs)have received increasing attention due to their complex structures and more advanced functions.Here,we report a new MOC cage with a unique trigonal bipyramidal configuration,[M_(5)L_(6)],constructed via the combination effects of coordination bonds and π…π interactions.A series of structures(BIF-136 to BIF-141)based on this[M_(5)L_(6)]cage were synthesized by the self-assembly of BH(bim)_(3)-ligands and Ni(II)ions under various solvothermal conditions.Each[M_(5)L_(6)]consists of two[M_(4)L_(3)]defective cubic cages sharing three metal nodes,which include two geometric types of flexible Ni(Ⅱ)centers(tetrahedral and octahedral).Benefiting from these modifiable metal centers,these cage-based crystals realized abundant coordination environments and a dimension transition from a 0D cage to a 1D cage-based chain,accompanied by modulations of conjugation degrees,electronic push-pull effects and band gaps.Due to their diverse structural features,we have systematically investigated their third-order nonlinear optical(NLO)properties.To our surprise,these structures show a typical reverse saturated absorption(RSA)response.In particular,BIF-141 achieves excellent optical limiting(OL)performance with a low minimum normalized transmittance(T_(min))of 0.20.This study not only provides a new strategy for constructing low-symmetry cages but also contributes to the understanding of the mechanism of their optical applications.展开更多
基金the European Union’s Horizon 2020 research and innovation programme,European Research Council(grant agreement no.648295 to A.A.P.)Marie Skłodowska-Curie action(grant agreement no.748635 to S.M.A.)+1 种基金the Deutsche Forschungsgemeinschaft(grants PO 1602/4-1 and 1602/5-1 to A.A.P.)the Swiss National Science Foundation(Projects No.200021L_147201 and No.206021_-150784 to T.G.)。
文摘Two isomers of metallofullerene Dy_(2)S@C_(82)with sulfur-bridged Dy ions exhibit broad magnetic hysteresis with sharp steps at sub-Kelvin temperature.Analysis of the level crossing events for different orientations of a magnetic field showed that even in powder samples,the hysteresis steps caused by quantum tunneling of magnetization can provide precise information on the strength of intramolecular Dy…Dy interactions.A comparison of different methods to determine the energy difference between ferromagnetic and antiferromagnetic states showed that sub-Kelvin hysteresis gives the most robust and reliable values.The ground state in Dy_(2)S@C_(82)has ferromagnetic coupling of Dy magnetic moments,whereas the state with antiferromagnetic coupling in C_(s)and C_(3)v cage isomers is 10.7 and 5.1 cm^(-1)higher,respectively.The value for the C_(s)isomer is among the highest found in metallofullerenes and is considerably larger than that reported in non-fullerene dinuclear molecular magnets.Magnetization relaxation times measured in zero magnetic field at sub-Kelvin temperatures tend to level off near 900 and 3200 s in C_(s)and C_(3)v isomers.These times correspond to the quantum tunneling relaxation mechanism,in which the whole magnetic moment of the Dy_(2)S@C_(82)molecule flips at once as a single entity.
基金supported by the National Natural Science Foundation of China(22275192).
文摘Low-symmetry metal-organic cages(MOCs)have received increasing attention due to their complex structures and more advanced functions.Here,we report a new MOC cage with a unique trigonal bipyramidal configuration,[M_(5)L_(6)],constructed via the combination effects of coordination bonds and π…π interactions.A series of structures(BIF-136 to BIF-141)based on this[M_(5)L_(6)]cage were synthesized by the self-assembly of BH(bim)_(3)-ligands and Ni(II)ions under various solvothermal conditions.Each[M_(5)L_(6)]consists of two[M_(4)L_(3)]defective cubic cages sharing three metal nodes,which include two geometric types of flexible Ni(Ⅱ)centers(tetrahedral and octahedral).Benefiting from these modifiable metal centers,these cage-based crystals realized abundant coordination environments and a dimension transition from a 0D cage to a 1D cage-based chain,accompanied by modulations of conjugation degrees,electronic push-pull effects and band gaps.Due to their diverse structural features,we have systematically investigated their third-order nonlinear optical(NLO)properties.To our surprise,these structures show a typical reverse saturated absorption(RSA)response.In particular,BIF-141 achieves excellent optical limiting(OL)performance with a low minimum normalized transmittance(T_(min))of 0.20.This study not only provides a new strategy for constructing low-symmetry cages but also contributes to the understanding of the mechanism of their optical applications.
