Two tetranuclear lanthanide complexes with the formulas[Dy_(4)(HL)_(4)(OAc)_(2)(H_(2)O)_(2)]·2Et_(3)NH·2CH_(3)CN(1)and[Gd_(4)(HL)_(4)(OAc)_(2)(H_(2)O)_(2)]·2Et_(3)NH·2CH_(3)OH·4CH_(3)CN(2)(H_(...Two tetranuclear lanthanide complexes with the formulas[Dy_(4)(HL)_(4)(OAc)_(2)(H_(2)O)_(2)]·2Et_(3)NH·2CH_(3)CN(1)and[Gd_(4)(HL)_(4)(OAc)_(2)(H_(2)O)_(2)]·2Et_(3)NH·2CH_(3)OH·4CH_(3)CN(2)(H_(4)L=N,N’-bis(3-hydroxylsalicylidene)benzene-1,2-diamine)were structurally and magnetically characterized.Dynamic magnetic studies revealed that complex 1 exhibits two distinct slow magnetic relaxation processes under a zero direct current(dc)field and the extracted energy barriers(U_(eff))of the low-temperature and high-temperature relaxation processes reach 207(2)K and 353(3)K,respectively,which are among the highest U_(eff) values of reported tetranuclear dysprosium molecular nanomagnets.More strikingly,as for complex 1,the open hysteresis loop behavior is detected until 5 K(6.5 K for the diluted sample),and a coercive field of 453 Oe is observed at 1.8 K,which is unusually seen in tetranuclear lanthanide single-molecule magnets.Further magnetic studies of diluted samples combined with ab initio calculation indicate that the Dy^(Ⅲ)–Dy^(Ⅲ) interactions play a crucial role in suppressing quantum tunneling of magnetization and consequently resulted in the bulk magnet-like hysteresis behavior.Additionally,the Gd-congener 2 displays the magnetocaloric effect(MCE)with a magnetic entropy change(−ΔS_(m))of 20.8 J kg^(-1) K^(−1) at 2 K for ΔH=7 T.展开更多
基金supported by the NSFC(no.22071047)the Heilongjiang Provincial Natural Science Foundation of China(LH2019B016).
文摘Two tetranuclear lanthanide complexes with the formulas[Dy_(4)(HL)_(4)(OAc)_(2)(H_(2)O)_(2)]·2Et_(3)NH·2CH_(3)CN(1)and[Gd_(4)(HL)_(4)(OAc)_(2)(H_(2)O)_(2)]·2Et_(3)NH·2CH_(3)OH·4CH_(3)CN(2)(H_(4)L=N,N’-bis(3-hydroxylsalicylidene)benzene-1,2-diamine)were structurally and magnetically characterized.Dynamic magnetic studies revealed that complex 1 exhibits two distinct slow magnetic relaxation processes under a zero direct current(dc)field and the extracted energy barriers(U_(eff))of the low-temperature and high-temperature relaxation processes reach 207(2)K and 353(3)K,respectively,which are among the highest U_(eff) values of reported tetranuclear dysprosium molecular nanomagnets.More strikingly,as for complex 1,the open hysteresis loop behavior is detected until 5 K(6.5 K for the diluted sample),and a coercive field of 453 Oe is observed at 1.8 K,which is unusually seen in tetranuclear lanthanide single-molecule magnets.Further magnetic studies of diluted samples combined with ab initio calculation indicate that the Dy^(Ⅲ)–Dy^(Ⅲ) interactions play a crucial role in suppressing quantum tunneling of magnetization and consequently resulted in the bulk magnet-like hysteresis behavior.Additionally,the Gd-congener 2 displays the magnetocaloric effect(MCE)with a magnetic entropy change(−ΔS_(m))of 20.8 J kg^(-1) K^(−1) at 2 K for ΔH=7 T.
