In this work,we report three isostructural Fe_(4)Ln_(4)wheel type complexes with molecular formula[{Fe_(4)(dea)_(4)Dy_(4)(deaH)8(μ2-OMe)_(4)}(NO_(3))_(4)]·4(H_(2)O)(1),[{Fe_(4)(dea)_(4)Gd_(4)(deaH)8(μ2-OMe)_(4)...In this work,we report three isostructural Fe_(4)Ln_(4)wheel type complexes with molecular formula[{Fe_(4)(dea)_(4)Dy_(4)(deaH)8(μ2-OMe)_(4)}(NO_(3))_(4)]·4(H_(2)O)(1),[{Fe_(4)(dea)_(4)Gd_(4)(deaH)8(μ2-OMe)_(4)}·(NO_(3))_(4)]·_(4)(H_(2)O)·_(4)(MeOH)(2)and[{Fe_(4)(dea)_(4)Y_(4)(deaH)_(8)(μ2-OMe)_(4)}(NO_(3))_(4)]·_(4)(H_(2)O)·6(MeOH)(3),(where dea=diethanolamine).Detailed structural analysis discloses that the_(4)Ln^(Ⅲ)and_(4)Fe^(Ⅲ)ions are connected alternatively in a cyclic arrangement through the oxo-bridging of methanol and diethanolamine molecules.The detailed magnetic measurements reveal the presence of ferromagnetic exchange interactions between the Ln^(Ⅲ)and Fe^(Ⅲ)centers in complexes 1 and 2,whereas a weak antiferromagnetic interaction is observed between Fe^(Ⅲ)centers in complex 3.In addition,complex 1 shows slow magnetic relaxation behavior(U_(eff)=9.8 K)under zero field and a remarkable entropy change was observed for complex 2 at 7 T magnetic field(magnetocaloric effect=31.15 J kg^(−1)K^(−1)).The ab initio calculations disclose the presence of strong axial anisotropy and a minimum transverse component(gx=0.002_(4),gy=0.0062,and gz=19.82)in the ground state of each Dy^(Ⅲ)ion for complex 1.It was also found that the local anisotropy axis on each Dy^(Ⅲ)ion is arranged in a vortex-like structure as observed in single molecule toroics(SMTs).From BS-DFT calculations,it was found that the exchange interactions between Fe-Ln metal centers mainly follow the charge transfer process between 3d and_(4)f orbitals.展开更多
基金the SRF fellowship and S.K.thanks CSIR(project no.01(2974)/19/EMR-II)SERB(project no.CRG/2018/000072)Government of India and IISER Bhopal for generous financial support.
文摘In this work,we report three isostructural Fe_(4)Ln_(4)wheel type complexes with molecular formula[{Fe_(4)(dea)_(4)Dy_(4)(deaH)8(μ2-OMe)_(4)}(NO_(3))_(4)]·4(H_(2)O)(1),[{Fe_(4)(dea)_(4)Gd_(4)(deaH)8(μ2-OMe)_(4)}·(NO_(3))_(4)]·_(4)(H_(2)O)·_(4)(MeOH)(2)and[{Fe_(4)(dea)_(4)Y_(4)(deaH)_(8)(μ2-OMe)_(4)}(NO_(3))_(4)]·_(4)(H_(2)O)·6(MeOH)(3),(where dea=diethanolamine).Detailed structural analysis discloses that the_(4)Ln^(Ⅲ)and_(4)Fe^(Ⅲ)ions are connected alternatively in a cyclic arrangement through the oxo-bridging of methanol and diethanolamine molecules.The detailed magnetic measurements reveal the presence of ferromagnetic exchange interactions between the Ln^(Ⅲ)and Fe^(Ⅲ)centers in complexes 1 and 2,whereas a weak antiferromagnetic interaction is observed between Fe^(Ⅲ)centers in complex 3.In addition,complex 1 shows slow magnetic relaxation behavior(U_(eff)=9.8 K)under zero field and a remarkable entropy change was observed for complex 2 at 7 T magnetic field(magnetocaloric effect=31.15 J kg^(−1)K^(−1)).The ab initio calculations disclose the presence of strong axial anisotropy and a minimum transverse component(gx=0.002_(4),gy=0.0062,and gz=19.82)in the ground state of each Dy^(Ⅲ)ion for complex 1.It was also found that the local anisotropy axis on each Dy^(Ⅲ)ion is arranged in a vortex-like structure as observed in single molecule toroics(SMTs).From BS-DFT calculations,it was found that the exchange interactions between Fe-Ln metal centers mainly follow the charge transfer process between 3d and_(4)f orbitals.
