Synthesis, Structures And Magnetism Of N,N′-bis(3-methoxy-salicylidene)cyclohex Ane-1,2-diamine Lanthanide Complexes

With potential application in high-density information storage and quantum computing, Salen-type lanthanide complexes have attracted considerable attention because of their unique structural diversities and better magnetic perfo rmance. In this paper, five series of twenty- five Salen-type lanthanide complexes have been designed and normal synthesized by semi-rigid hexadentate Salen-type ligand N,N′-bis(3- methoxy-salicylidene)cyclohexane-1,2-diamine and various lanthanide salts under different reactive conditions. The molecular structures of the complexes 1-25 and the ligand have been determined and characterized by single-crystal X-ray diffraction, elemental analysis, UV spectrum, IR spectrum, TG-DSC and powder X-ray diffraction. In addition, their magnetic properties have been studied systemically. The results are listed as following:The reactions of the ligand and Ln(NO3)3·6H2O afford five nitrate mononuclear lanthanide clusters [Ln(H2L)(NO3)3]·CH3CN [Ln = Dy(1), Tb(2), Ho(3), Er(4), Yb(5)]. The structural analysis indicates that the center ion is deca-coordinated with hexadecahedron geometry. The magnetic studies indicate that complex 1 exhibit frequence-dependence and slow magnetic relaxation under an applied dc field with the effective energy barrier 23.15 K. Complex 1 is the first Salen-type mononuclear field- induced SMM. The reactions of the ligand and Ln(C l O4)3·9H2O afford six perchlorate dinuclear lanthanide clusters [Ln2 L2(CH3OH)3]Cl O4·2CH2Cl2·2CH3OH [Ln = Dy(6), Tb(7), Ho(8), Er(9), Yb(10), Gd(11)]. The structural analysis indicates that two center ions of the series of complexes 6-11 are bridged by two phenoloxy O atoms and one methoxy O atom which are forming a shuttle-shaped core. The magnetic studies indicate that complex 6 is a SMM exhibiting slow magnetic relaxation with effective energy barrier 21.71 K under zero dc field.With trithylamine, the reactions of the ligand and Ln C l3·6H2O afford four chloride tetranuclear lanthanide clusters [Ln4(L)2(HL)2Cl2(μ3-OH)2]2Cl2(OH)2·3CH3CH2OH·H2O [Ln = Dy(12) and Eu(13)], [Ln4(L)2(HL)2Cl2(μ3-OH)2]Cl2·5CH3OH·4CH2C l2 [Ln = Tb(14) and Ho(15)]. The structural analysis indicates that the center ions of complexes 12-16 are symmetrical with eight-coordination adopting a distorted bicapped triangular prism with C2 v point group and nine-coordination modes forming a distorted monocapped square antiprism with C4 v point group and the chloride ion is terminal coordinated with center ions. The magnetic studies indicate that complex 12 exhibit two magnetic relaxation under zero dc field with the effective energy barrier of 55.71 K which is the highest among the Salen-type tetranuclear Dy-SMMs.With trithylamine, the reactions of the ligand and Ln(NO3)3·6H2O afford seven nitrate tetranuclear lanthanide clusters [Ln4(L)2(HL)2(NO3)2(μ3-OH)2](NO3)2·4H2O [Ln = Dy(16), Tb(17), Ho(18), Er(19), Gd(20), Eu(21), Yb(22)]. The structural analysis indicates that the complexes 16-22 with nitrate terminal coordinated are similar to the complexes 12-15. The magnetic studies indicate that complex 16 exhibit slow magnetic relaxation under zero dc field with the effective energy barrier of 48.14 K. Complex 18 exhibit slow magnetic relaxation obviously under an added dc field.With trithylamine, the reactions of the ligand and Ln(C l O4)3·9H2O afford three perchlorate tetranuclear lanthanide clusters [Dy4L2(HL)2(CH3CH2OH)2(μ3-OH)2]·Cl O4·CH2Cl2(23), [Ln4L2(HL)2(Cl O4)2(μ3-OH)2]·Cl O4·2CH2Cl2 [Ln = Tb(24) and Ho(25)]. The structural analysis indicates that the complexes 24 and 25 are similar to the complexes 12-22 in which the center ions of complexes 24 and 25 are symmetrical and terminal coordinated by perchlorate. The magnetic studies indicate that complex 23 exhibit frequence-dependence signals but without magnetic relaxation phenomenon under zero dc field.