| Single-molecule magnets?SMMs?that behave magnetic bistability and slow relaxation process have unique potential in ultrahigh-density memory components and spintronic devices.Numerous single-molecule magnets with novel structures and interesting magnetic behaviors have been reported along with the development of experimental techniques and magnetic theory.Remarkably,a new benchmark in molecular magnetism with a record anisotropy barrier of 1837 K and record magnetic blocking up to 60 K,have recently been established,pushing the blocking temperature?TB?much closer to the liquid nitrogen temperature.As is well-known,magnetic relaxation behavior can be affected sensitively by the subtle changes in the ligand field and coordination environment around paramagnetic ions.In addition,constructing multi-functional molecular magnetic materials has sparked increasing interest by combining molecular magnetic materials with other physical or chemical functions,such as optical activity,electrical conductivity,porous properties,and ferroelectric properties.In this paper,In order to further explore their magnetic structure relationship,single-molecule magnets with special structures and functions have been designed and synthesized.In addition,relevant research results provide ideas for constructing new multifunctional molecular magnetic materials with chirality or sensing properties.The main works of this paper are as follows:?1?A series of hexa-nulcear lanthanide?III?clusters,{Gd6?H3L?6?benzoate?6}·2H2O·C7H8?1?,{Tb6?H3L?6?benzoate?6}·2H2O·C7H8?2?and{Dy6?H3L?6?benzoate?6}·2H2O?3?,had been constructed with the pentol ligand,2,2-bis?hydroxymethyl?-2,2',2''-nitrilotrieth-anol?H5L?by utilizing solvothermal method.Single-crystal X-ray diffraction analyses reveal that they are characterized similar six-member cyclic structures.In addition,magnetization studies indicate that Gd6 displays a large magnetic entropy changes at low temperature regions.Of particular interest of this ring is the presence of slow magnetic relaxation behavior under zero-dc field,indicating a non-magnetic ground state with a net toroidal magnetic moment.Compared to the other reported Dy6 clusters,the modulation of the ligand fields,the presence of the amine function coordinating sites and the subsequent electron density of Dy centers along with the utilized pentol ligand might be indeed responsible for the improved barrier to magnetic relaxation.?2?Two pairs of new 4f clusters were successfully synthesized with different structures by slightly changing the synthesis conditions.The four complexes of formula{Ln2?NO3?4?H2O?2?L?2}·2?C2H3N??Ln=Dy?4?,Gd?5??,{Ln9??4-OH?2??3-OH?8??2-OCH3?4?NO3?8?H2O?8?L?4}?OH?·10H2O?Ln=Dy?6?,Gd?7??have been structurally and magnetically characterized.X-ray single crystal and powder diffraction experiments show that Ln2 and Ln9 complexs can transform from single crystal to single crystal reversibly under certain conditions.The Ln2 molecules are a symmetrical dinuclear structure with 9-coordinated 4f ions,while the Ln9 ones are an hourglass-like configuration with 8-coordinated 4f ions.Magnetic studies reveal that the two Dy derivative displays different slow magnetic relaxation behavior with the effective energy barrier of 217.87 K and 9.24 K,respectively.Theoretical calculations further elucidate their different magnetic behaviors.The two Gd analogue complexes exhibit large magnetocaloric effect with 27.3 J kg-1 K-1 and 40.6 J kg-1 K-1,respectively.?3?Two enantiomeric pairs of new 3d-4f heterometallic complexes were synthesized from two enantiomer Schiff base ligands R-/S-H2L in situ generated from the condensation of o-vanillin with R-or S-2-phenylglycinol.The complexes of formula[Mn6Ln2??3-OH?4??4-O??Ac?4?H2O?2?R-L?6]·NO3·OH?Ln=Dy?8R?,Gd?9R??,[Mn6Ln2??3-OH?4??4-O??Ac?4?H2O?2?S-L?6]·NO3·OH?Ln=Dy?8S?,Gd?9S??have been structurally and magnetically characterized.Single-crystal X-ray diffraction analyses reveal that the above complexes consisted of a[Mn6Ln2]core,featuring a sandwich configuration.Magnetic studies reveal that the Dy derivative displays slow magnetic relaxation under a zero-dc field with an effective energy barrier of 14.85 K,and the significant magnetocaloric effect of Gd analogue is found in a wide temperature range.?4?Two enantiomeric pairs of new 3d-4f heterometallic complexes were synthesized from two enantiomer Schiff base ligands.The four complexes of formula Co3Ln?R-L?6?Ln=Dy?10R?,Gd?11R??,Co3Ln?S-L?6?Ln=Dy?10S?,Gd?11S??,have been structurally and magnetically characterized.Single-crystal X-ray diffraction analyses reveal that the above complexes consisted of a[Co3Ln]core with six-coordinated 4f ion,featuring an impeller configuration.Circular dichroism?CD?spectroscopy also confirmed they are enantiomers.Magnetic studies indicate that the Dy derivative displays slow magnetic relaxation under a zero-dc field with an effective energy barrier of 22.33 K.?5?By utilizing a flexible tetrapyridinate ligand,tetrakis?4-pyridyloxymethylene?methane?L?,a novel multi-functional soft porous magnetic framework,[Co?NCS?2?L?]·2H2O·CH3OH?12?,was constructed.This framework exhibits quick and selective solvatochromic and vapochromic behavior during a reversible crystal-to-amorphous-to-crystal?CAC?transformation.Importantly,the rapid CAC transition can selectively be triggered by methanol molecules,even at low concentrations of liquid or gaseous methanol.This reproducible transition can be monitored by single-crystal and power X-ray analysis,IR and UV-Vis,which all powerfully illustrate the selectivity and sensitivity of this system.In addition,the typical magnetic behavior of Single Ion Magnets?SIMs?have been successfully introduced into this 3D framework,and the modified dynamic relaxations have been investigated via experimental and theoretical analysis.The consistent observations of both experimental and theoretical results support unambiguously that the distortions in the metal environments are responsible for the finely-tuned SIM behavior. |
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