Studies On The Synthesis,Structures And Magnetic Properties Of The Complexes Based On Aryldicarboxylate And Their Acylhydrazone Derivatives

Because of the urge for the information storage materials with high density and rapid response speed,as well as high-performance and environment-friendly refrigeration technology,the molecular magnetic materials which have great potential in these area have attracted significant attentions of the researchers.For the studies and application of the molecular magnetic materials,it is significant to construct complexes with novel structures and excellent magnetic properties through judicious choose of the ligands and carry on the researching to their magnetic properties.Aryldicarboxylate and acylhydrazones have play important roles in the construction of molecular magnetic materials based on infinite multidimensional polymers and definite polynuclear clusters,respectively.They also show corresponding potential in the regulation of magnetic properties of the complexes.On the basis of the research status about the structures and magnetic properties of the complexes with aryldicarboxylate and acylhydrazones,an aryldicarboxylate ligand and two acylhydrazone ligands with oxygen-containing bridging groups(hydroxyl or Oxynitride)between the bipolar coordinating groups were synthesized,namely,2-hydroxyl isophthalic acid(H3ipO),o-vanilin-pyridine-2,6-dimethyhydrazones-N-oxide(H4ovpho)and salicylaldehyde-pyridine-2,6-dimethyhydrazones-N-oxide(H4sapho).Through the optimization of reaction methods and conditions,35 complexes belonging to seven series were synthesized with these ligands and their structures and magnetic properties were studied fairly systematically.The structures of the complexes show all types of dimensions of 0D,1D,2D and 3D,and contain metal centres of 3d,4f and 3d-4f.Many of the members were found to show SMM behaviors or MCE.The research contents were shown as follows:1.Two types of 3d metal coordination polymers(CPs)were synthesized with H3ipO.The first type are 3D MOFs base on[24-MC-6]Metallacrown Clusters SBUs([24-MC-6]MOFs):[Co6(HipO)6]·6H2O(1),[Mn6(HipO)6]·6H2O(2),[Cd6(HipO)6]·6H2O(3)and[Zn6(HipO)6]·7H2O(4).These MOFs is the first type of hemometallic[24-MC-6]MOFs constructed without any auxiliary ligand,and their[24-MC-6]SBUs display a particular arrangement mode in the frameworks.Under the same synthesis condition different molar ratio of metal salts vs.ligand result in two 1D CPs in which the metal ions are bridged by single syn-anti carboxylate groups:[Co2(HipO)2(Py)2(H2O)2](5)and[Ni(HipO)(Py)H2O](6)(Py=pyridine).Out of our expection,the Ohydroxyl of H3ipO ligand in 1-6 didn't bridge any metal ions,however,the ligands show two kinds of special coordination modes which didn't appeared in previous documents.The magnetic studies indicated that 1 and 2 show anti ferromagnetic behaviors in the high temperature range and 1 show ferromagnetic behavior at low temperature,5 and 6 show cant-antiferromagnetism and ferromagnetism,respectively.Furthermore,MCE was found in 1,5 and 6,and 1 is the Co-complex with the highest-?Sm value up to now.2.The hydrothermal reactions of H3ipO and lanthanide nitrate afford two types of 4f metal CPs,namely,[Ln2(ipO)2(H2O)4]·2H2O(Tyep ?,Ln=Eu(7),Gd(8),Tb(9),Dy(10),Ho(11),Er(12))and[Tm4(ipO)4(H2O)4](Type ?,13).When the DMF was intruduced in to the reaction systems,another type of 4f metal CPs[Ln2(ipO)2(DMF)(H2O)](Type ?,Ln=Gd(14),Tb(15),Dy(16),Ho(17),Er(18)? Tm(19))were obtained.The CPs of three types are all 2D frameworks based on?Ln2} SBUs which are bridged by Ohydroxyl groups of ligands.However,they display interesting variation in the coordination geometris of the Ln3+,coordination modes of the ligands and the components of the SBUs due to the lanthanide contraction effects and solvent effects.The magnetic investgations indicated that two Gd-CP(8 and 14)exhibit good MCE and a Dy-CP(10)has SMM behavior.3.Under the same hydrothermal conditation,the reactions of H3ipO,lanthanide nitrate and copper acetate afford two types of Cu-Ln heterometallic CPs:[Ln4Cu8(ipO)8(ox)2(H2O)12](Tyep I,Ln = Sm(20);Eu(21)]and[Ln2Cu6(ip0)6(H2O)12][Type ?,ox=C2O42-;Ln=Gd(22);Tb(23);Dy(24)].The first type of CPs displays a 3D framework with a rare case of MoGe2 topology based on {Cu8} and {Ln2} SBUs,while the CPs of type ? exhibits a chain structure built up from?Cu6} SBUs and Ln ions.Both of the {Cu8} and {Cu6} SBUs consist of planar[Cu2(ipO)2]2-units linked together by weak Cu-O bonds and ?-? interactions.However,the decompositions of partial H3ipO ligands induced by lanthanide ions in type ?,which generate C2O42-to link the Ln3+ into?Ln2} SBUs,lead to the structural variation from type I to type II.The magnetic investigations revealed that 22 displays a MCE and 5 displays field induced SMM behaviors.4.H4ovpho ligand was synthesized from 2,6-pyridinedicarboxylic acid-N-oxide.Benefited from the feature of multi chaelating sites for H4ovpho and the successful introducing of anions,as well as the optismization of the reaction conditions,three types of Ln polynuclear clusters were obtained,namely,{Ln10}(Ln=Tb(25);Dy(26)),?Ln11}(Ln=Gd(27);Tb(28);Dy(29))and{Gd18}(30).The skeleton of {Ln10} clusters consist of two edge shared {Ln4}tetrahedron units and two ?Ln2} units locating in the positons of two wings of the cluster.For the structure that the Ln3+ locating in the vertex of {Ln4} teteahedron is bridged by ?2-Omethanol in {Ln10},it has not been reported in the previous documents.The {Ln11} clusters have a metal skeleton which is compoesed of two six-membered Ln rings.The two rings were linked together through sharing a Ln3+ and fianlly display a double boat configuration.As for ?Gd18?,different bridging oxygen in the ligand and the OAc-bridged the Gd3+into a metallic macrocycle.To the best of our konwledge,it is the circular Ln cluster with the higher neclears and the biggest size until now.The magnetc investgations indicated that {Tb10}(25),{Dy10}(26)and {Dy11}(28)have SMM behavior.It is also found that {Gd11}(27)and ?Gd18}(30)exhibit MCE.5.In order to investigate the affection of the end group in acylhydrazone ligands on the structures and magnetic properties of the resultant clusters,H4sapho was synthesised from 2,6-pyridinedicarboxylic acid-N-oxide.With the high molar raito of metal salts versus ligands,as well the synthesis method which could afford suit thermodynamics condition,a series of high nuclear Ln clusters {Ln24}(Ln=Gd(31),Tb(32),Dy(33),Ho(34),Er(35))were obtained.The Ooxynitride of H4sapho lost in the reaction process and the H4sapho is transformed to saph4-in situ,which is different to those of H4ovpho ligand in above polynuclear Ln clusters.With the help of OH-,the saph4-ligands bridge the Ln3+ to form the cage {Ln24} cluster.The magnetc investgations revealed that ?Gd24}(31)and ?Dy24}(33)show MCE and SMM behaviors,respectively.