Synthesis,Structure And Magnetic Properties Of Lanthanide Complexes Based On 1,3-Diamino-2-hydroxypropane Schiff Base Ligand

The past score years has achieved a rapid development in the design and construction of single-molecule magnets（SMMs）for their potentially applications such as high-density information storage and processing,quantum computing,spintronics,magnetism,optics,and electricity.Therefore,designing and synthesizing single-molecule magnet materials with specific structures and functions has been one of the hot topics pursued by scientists in many research fields in recent years.In this paper,three series of lanthanide complexes were synthesized by the reactionof1,3-diamino-2-hydroxypropane,2-pyridinecarbaldehydeand2-aldehyde-8-hydroxyquinoline.These compunds have been determined by single-crystal X-ray diffraction analysis,elemental analysis,IR spectra and thermal analysis.Furthermore,their magnetic properties have been studied by magnetic properties measurement system.The main research works is summarized as follows:1.TheconventionalsolutionreactionsofLn（NO₃）₃·6H₂Owith1,3-diamino-2-hydroxypropane and 2-pyridinecarbaldehyde in the presence of triethylamine afforded a series of lanthanide complexes:[Ln₂(C₁₅H₁₅N₄O)₂（NO₃）₄]·X（Ln=Gd（1）,X=6H₂O;Ln=Tb（2）,X=6H₂O;Ln=Dy（3）,X=2CH₃CN;Ln=Ho（4）,X=2CH₃CH₂OH;Ln=Er（5）,X=2CH₃CN）.Two heterogeneous isomorphous lanthanide binuclear clusters were synthesized by solvothermal method.Their general structure is:[Ln₂(C₉H₁₁N₃O)₂（NO₃）₄]（Ln=Dy（6）,Ho（7））.In the spontaneous assembly of complex 6-7,1,3-diamino-2-hydroxypropane and2-pyridinecarbaldehyde undergo a nucleophilic addition-elimination reaction to form a C-N-C-C-C-N hexahydropyrimidine ring.They were determined by single-crystal X-ray diffraction analysis and further analyzed by elemental analysis,IR spectra,thermogravimetric and magnetic susceptibility.The dc magnetic susceptibility studies of 1-7 indicate that both complexes exhibit a weak antiferromagnetic exchang interactions between the metal ions.The measurement of ac magnetic susceptibility shows that complex 3 does not show the behavior of the field-induced single-molecule magnet,while Complex 6 shows a significant frequency-dependent signal in both the real and imaginary parts of the magnetic susceptibility under zero dc external field,and the maximum value appears,indicating that complex 6 is a typical single-molecule magnet.2.The conventional solution reactions of Dy（Cl O₄）₃·6H₂O with the same ligand in the presenceoftriethylamineaffordedatetranuclearDy ^IIIcomplexes:[Dy₄(C₁₅H₁₅N₄O)₄（μ₂-OH）₄]·4Cl O₄^-（8）.Complex 8 is tetragonal system,I-4 space group,four Dy ^IIIions have the same coordination environment,are all eight-coordinate triangular dodecahedron.Variable-temperature dc magnetic susceptibility measurements of 8 indicating dominant antiferromagnetic exchange interactions between the Dy ^IIIions.The experimental results of ac susceptibility showed that the complex 8 has frequency-dependent signals in both the real and imaginary parts of the dc susceptibility in the zero dc field,and the peak appears,indicating that the complex 8 is a typical single-molecule magnet.3.The solvothermal reactions of Ln（NO₃）₃·6H₂O with 1,3-diamino-2-hydroxypropane and2-aldehyde-8-hydroxyquinolineinsteadof2-pyridinecarboxaldehyde（2-aldehyde-8-hydroxyquinoline adds a phenol group with electron-withdrawing effect compared to 2-pyridinecarboxaldehyde）in the presence of triethylamine afforded a series of lanthanide complexes:[Ln₄(C₂₃H₁₇N₄O₃)₂（μ₃-OH）₂（NO₃）₄（CH₃CH₂OH）₂]·x CH₃CN（Ln=Tb（9）,x=2;Dy（10）,x=0;Ho（11）,x=2;Er（12）,x=2）.X-ray single crystal diffraction shows that the complexes 9-12 are monoclinic system,P2₁/n space group.The dc magnetic susceptibility studies of 9-12 indicate that both complexes exhibit a weak antiferromagnetic exchang interactions between the metal ions.The measurement of ac magnetic susceptibility shows that the imaginary part of the ac susceptibility is frequency-dependent under a zero dc external field,exhibiting single-molecule magnet behavior,and the ac magnetic susceptibility of complex 10was measured under an applied dc field of 1500 Oe.The real and imaginary signals do not show peaks,so the complex 10 only exhibits single-molecule magnet behavior.