Substituent Effect Regulated Preparations,Structures And Magnetisms Of Azido-copper Molecule-based Magnetic Materials With Aromatic Carboxylic Acids Coligands

Molecule-based magnetic materials have potential applications on molecular switch,data storage and the molecular level of electronic equipment,and the construction of high-performence molecule-based magnetic materials has become a fascinating subject in the fields of material and coordination chemistry.As bridging ligands,azide and carboxylic acid are not only common"chemical bridge",but excellent "magnetic bridge".In this paper,based on azido-copper system,introducing the coligands of aromatic carboxylic acids with fluoro substituent to construct molecule-based magnetic materials,regulate the structure and magnetic of the objective compounds employing substituent effect,providing theoretical and experimental guidance for the preparation of high-performance molecule-based magnetic materials,the main conclusions are as follows:1.Solvothermal reactions of copper salts with NaN3 and carboxylate,led to the formations of a new magnetic compound,[Cu(3-fba)(N3)(C2H5OH)](3-fba = 3-fluorobenzoic acid)(1).The X-ray crystal structure analysis shows that only one crystallographically independent Cu(?)ion in the asymmetric unit of 1,forming a 1D Cu(?)chain with an alternating triple-bridge of EO-azido,syn,syn-carboxylate,and ?2-ethanol.Magnetic measurements reveal that the resulting compound is composed of ferromagnetically interacting ferromagnetic chains with the Cu-N-Cu angle of 105.95°.The dominant ferromagnetic couplings between neighbouring Cu(?)ions occurred in the compound(J= 59.74 cm-1)is due to the counter-complementarity of the multiple superexchange pathways,contributing to inspiring plots of ferromagnetic order(Tc = 11.0 K)and slow magnetic relaxation that are rarely observed in most of the reported azido-Cu(?)architectures.The heat-capacity experiments further emphasize the characteristic long-range ferromagnetic ordering in 1.Moreover,Density functional theory(DFT)calculations have been performed on the compound to obtain the qualitatively theoretical interpretation of the magnetic behaviors.2.Employing two benzoate derivatives with different numbers of non-coordinated fluoro-substituents,2-fluorobenzoic acid(2-Hfba)and 2,6-difluorobenzoic acid(2,6-Hdfba),two new azido-copper coordination polymers,[Cu(2-fba)(N3)(CH3OH)]n(2)and[Cu(2,6-dfba)(N3)(CH3OH)]n(3),have been successfully isolated,and then structurally and magnetically investigated.Single crystal structure analysis demonstrates that the metal cations in the two resulting compounds are connected by the alternating triple-bridge of ?-1,1-azido,syn,syn-carboxylate and ?2-methanol,contributing to analogously linear 1D Cu(?)chain-like motifs with slightly different intrachain and interchain geometric parameters.The fine-tuned structures lead to variant magnetic properties in the two title compounds.Although a dominant ferromagnetic coupling between adjacent Cu(?)ions within each chain due to the counter-complementarity of the multiple superexchange pathways is observed in both compounds,the interesting plots of magnetic ordering and slow magnetic relaxation,which are rare in most of the reported azido-Cu(?)architectures,only occur in compound 2,while 3 behaves as an antiferromagnet consisting of ferromagnetic Cu(?)chains.The heat-capacity experiments further emphasize the characteristic long-range ferromagnetic ordering in 2 and the typical behavior of antiferromagnets in 3.Moreover,density functional theory(DFT)calculations have been performed on both compounds to obtain the qualitatively theoretical interpretation of the magnetic behaviors.3.Based on two fluoro-substituted phenylacetate isomers,o-fluorophenylacetic acid(o-Hfpa)and p-fluorophenylacetic acid(p-Hfpa),two new Cu(?)-azido compounds,[Cu(o-fpa)(N3)(C2H5OH)]n(4)and[Cu(p-fpa)(N3)(C2H5OH)]n(5),have been prepared,and structurally and magnetically characterized.Single-crystal structure analyses indicate that compounds 4 and 5 consist of 1D chain-like coordination networks in which adjacent copper cations are linked by the alternating triple-bridges of ?-1,1-azido,syn,syn-carboxylate and?2-ethanol.For two title compounds,the diverse charge distributions on the carboxyl groups caused by distinct substituent effects of two phenylacetate coligands lead to the different structural parameters of intrachain Cu-Cu distances and Cu-N-Cu angles,further resulting in the disparity of magnetic behaviors.The dominant ferromagnetic couplings between neighbouring Cu(?)ions in two compounds(J = 87.08 cm-1 for 4,J= 66.05 cm-1 for 5)is due to the counter-complementarity of the multiple superexchange pathways,contributing to inspiring plots of ferromagnetic order(Tc=11.0 K for 4,9.5 K for 5)and slow magnetic relaxation that are rarely observed in most of the reported azido-Cu(?)architectures.Heat-capacity experiments further emphasize the characteristic long-range ferromagnetic ordering in compounds 4 and 5.Magneto-structural relationships of 4 and 5 are investigated as well.Moreover,DFT calculations have been performed on both compounds to provide the qualitatively and quantitatively theoretical explanation of the magnetic behaviors.