Researches On Molecular Magnetic Materials Based On The 4d Metal Ion Of Mo

Heptacyanomolybdate-based magnetic material have attracted extensive attentions in the field of molecular magnetism and have made important progresses.However,the rational design and synthesis of heptacyanomolybdate-based magnetic material remain a challenge due to the complexity of this system.The work in this dissertation studies the design,synthesis,and characterization of magnetic molecules based on the[Mo?(CN)7]4-building block.Interesting magnetic compounds including low-dimensional and high-dimensional 3d-4d compounds,a series of 4f-4d compounds and other magnetic compounds with the oxidized Mo? ions have been prepared and characterized.The main structure of this paper consists of the following contents:Chapter 1 presented an extensive survey of the literature of cyano-bridged molecular magnetic materials of single-molecule magnets,single-chain magnets,spin crossover complexes,long-range magnetic ordering complexes,multifunctional magnets and so on,focusing on the research status wherein the[Mo?(CN)7]4-precursor directs the assembly of molecular magnetic materials,as well as the difficulties in related fields.The research ideas and contents of this dissertation were presented.Chapter 2 mainly focused on the synthesis and magnetic characterization of low-dimensional compounds constructed from 3d metals and the[Mo?(CN)7]4-unit.First,using a hexadentate chelating ligand,we have obtained a trinuclear Mn2Mo(1)and a pentanuclear Mn4Mo(2)compounds based on[Mo?(CN)7]4-.The Mo? ions in these compounds are in slightly distorted pentagonal bipyramidal configurations.In 1,the[Mo?(CN)7]4-unit connects two Mn? ions using two axial cyanides,while in 2,it connects four Mn? ions using two axial as well as two non-adjacent equatorial cyanides.Magnetic studies show that antiferromagnetic interactions between Mo? and Mn? ions in both 1 and 2,giving rise to their ground spin states of 9/2 and 19/2,respectively.Compound 1 is a single molecule magnet with an effective energy barrier of 56.5 K(39.2 cm-1,?0=3.8 ×10-8)and blocking temperature of 2.7 K.2 is just a simple paramagnet,probably due to the nonlinear of Mn-N?C bond angles and non-Ising anisotropy magnetic exchange.Furthermore,a hexanuclear compound Mn4Mo2(3)with a pentatentate chelate ligand and four isomorphic decanuclear Fe? and Ni?compounds 4RR/4SS and 5RR/5SS using chiral diamine ligands of RR/SS-Ph2en were constructed.Magnetic studies show that antiferromagnetic interactions were observed through cyanide in compound 3,which is also only a simple paramagnet.We failed to characterize the magnetic properties of 4RR/4SS and 5RR/5SS because of their very low yield and extreme air sensitivity.In addition,we have also obtained a one-dimensional(1D)ladder chain(6)based on the[Mo?(CN)7]4-unit.Due to the non-negligible interchain magnetic interactions,this compound shows long-range magnetic ordering with the critical temperature of 13 K.Chapter 3 mainly studied some high-dimensional compounds constructed from 3d metals and the[Mo?(CN)7]4-unit.Three 2D compounds(7,8RR and 8SS)and two 3D compounds(9 and 10)were synthesized successfully.The 2D compounds were synthesized using tetradentate macrocyclic ligands and chiral cyclohexanediamine,while the 3D compounds were synthesized using different amide ligands.Interestingly,although the 2D compounds are air sensitive,the crystals of the 3D compounds are stable in the air.Magnetic studies showed that the 2D compounds and the 3D compounds exhibit long-range ferrimagnetic ordering with the ordering temperatures of 23,40,80 and 80 K,respectively.Moreover,spin reorientation and spin frustration are possible in the 3D compounds.Chapter 4 mainly studied the complexes constructed from 4f metals and the[Mo?(CN)7]4-unit.Using a hexadentate chelate ligand,we have obtained a series of 4f-4d complexes with lanthanide ranging from La3+ to Ho3+.These compounds are the first successful assembly of 4f metal ions and[Mo?(CN)7]4-.Compounds 11LaMo and 12prMo have 1D structures,with 1D banded and zigzag chain,respectively.All the Mo ions in these structures are[Mo?(CN)7]4-units.13LnMo represents a series of isomorphic 2D compounds with rare earth ions ranging from Ce3+ to Ho3+,where some of the[Mo?(CN)7]4-unit was oxidized to the diamagnetic[Mo?(CN)8]4-unit.These 4f-4d compounds are not stable in air.Magnetic studies show that 11LaMo displays single-ion paramagnetism,while other compounds are simple paramagnets with possible weak antiferromagnetic interactions between the 4f and Mo? ions.Chapter 5 illustrates three cases where the[Mo?CN)7]4-unit was oxidized during the reaction processes.Three types of diamagnetic units,namely[Mo?(L)O(CN)n]n-4,[Mo?O2(CN)4]2-and[MoIV(CN)8]4-were thus obtained.Firstly,we have obtained a series of isomorphic polynuclear compounds Ln7Mo(14Ln,Ln = Tb3+,Dy3+,Ho3+,Yb3+),in which the[MoIV(tmphen)O(CN)3]+ unit act as a counter cation.Magnetic properties of these compounds are mainly due to the Ln7 clusters,among which compound 14Dy exhibits the property of a single molecule magnet with an effective energy barrier of 51.6 K(35.8 cm-1,?0= 1.7 x 10-5).Secondly,we have obtained several 1D chain complexes,illustrated by one 1D chain constructed by 3d metal ion Ni? and Mo?(15).In this compound,the[Mo?O2(CN)4]2-units connect the Ni? ions to form a 1D structure.Because of the diamagnetism of Mo?,this 1D chain exhibits only the paramagnetism of Ni? ions.Thirdly,we have also obtained many[Mo?(CN)8]4-containing compounds,which turned out to be a common problem in our experiments.Three compounds,including a pentanuclear Fe?-Mo? cluster(16),a 1D Mn?-Mo?chain(17)and a 3D Ni?-Mo? magnet(18),were characterized structurally.Chapter 6 summarized the main results of this dissertation.Prospects of future studies in this field were proposed.