| In this paper,the ligands 2,2:6',2"-terpyridine,5,5'-dimethyl-2,2'-bipyridine and2,4-dimethylbenzoic acid,2,6-dimethylbenzoic acid,2,3-dimethoxybenzoic acid were selected to react with Ln?NO3?36H2O,respectively,and 27 kinds of complexes were synthesized.[Ln?2,4-DMBA?3?terpy??H2O?]2?Ln=Eu?1?,La?2?,Pr?3?,Nd?4?,Sm?5?,Gd?6??and[Ln?2,4-DMBA?3?terpy??H2O?]?Ln=Dy?7?,Ho?8?,Er?9?,Tb?10??;[Ln?2,6-DMBA?3?5,5'-DM-2,2'-bipy??H2O?]2?Ln=La?11??and[Ln?2,6-DMBA?3?5,5'-DM-2,2'-bipy?]2?Ln=Tb?12?,Dy?13?,Ho?14?,Pr?15?,Nd?16?,Eu?17?,Sm?18??;[Ln?2,3-DMOBA?3?5,5'-DM-2,2'-bipy?]2C2H5OH?Ln=Eu?19?,Sm?20?,Gd?21?,Ho?22?,Er?23?,Pr?24?,Nd?25?,Tb?26?,Dy?27?.2,4-DMBA=2,4-dimethylbenzoic acid;2,6-DMBA=2,6-dimethylbenzoic acid;2,3-DMOBA=2,3-dimethoxybenzoic acid;terpy=2,2:6',2"-terpyridine;5,5'-DM-2,2'-bipy=5,5'-dimethyl-2,2'-bipyridine?.Among them,the first series adopts the solvent thermal synthesis method,and the second and third series adopt the normal temperature solution synthesis method.These complexes have been characterized by elemental analysis,X-ray single crystal diffraction,X-ray powder diffraction,and TG-DSC/FTIR,and further studied by molar heat capacity,fluorescence,and magnetic properties.X-ray single crystal diffraction data show that complexes 1-10 all have coordination water,complexes 1-6 are binuclear structures and crystallizes in the monoclinic with system P2?1?/c space group,and each central ion is nine-coordinated.Compared with previous complexes,the novel feature is that the two central ions in the binuclear structure are connected only by two 2,4-DMBA ligands.The complexes7-10 are mononuclear structures and crystallizes in the triclinic P?space group.The central ion is eight-coordinated.In the mononuclear structure,only one 2,4-DMBA ligand adopts chelating bidentate coordination mode,and the other two adopt monodentate coordination mode to coordinate with the central ion.Complexes 11-18are all binuclear structures,but they are divided into three different types.Complex 11contains two water complexes and the central ion is eight-coordinated,forming a distorted square antiprism geometry.Of the six 2,6-DMBA ligand coordinated,two are monodentate coordination,four are bridging bidentate coordination.Complexes12-14 do not contain coordination water,but the coordination number and coordination environment of the central ion are the same as that of complex 11.Of the six 2,6-DMBA ligand coordinated,two are chelating bidentate coordination,four are bridging bidentate coordination,and two central ions are coordinated via four bridging bidentate 2,6-DMBA ligands.Complexes 15-18 also do not contain coordination water,the central ions coordination number is nine and adopts a distorted monocapped square anti-prismatic coordination geometry.Of the six2,6-dimethylbenzoic acids coordinated,two are chelating bidentate coordination,two are bridging bidentate coordination,and the remaining two are bridging-chelating coordination.It is because of the different coordination modes of ligands that the complexes present different coordination environments.Complexes 12-14 and 15-18have completely different crystal structures and central ion coordination environments,but they have the same general formula and are in the same crystal system and space group.Not only this time,the one-dimensional supramolecular chain structure and two-dimensional supramolecular planar structure they formed are also same,which is novel.Complexes 19-27 are binuclear complexes,each containing a free ethanol molecule.The coordinated 2,3-dimethoxybenzoic acid ligands mainly adopt three coordination modes:chelate bidentate,bridged bidentate and bridging-chelating.Both central ions are nine-coordinated and are connected by two bridged bidentate2,3-dimethoxybenzoic acid and two bridging-chelating 2,3-dimethoxybenzoic acid.Complexes 1-27 can be composed of one-dimensional chains and two-dimensional surface structures by C-HO hydrogen bonding interactions or??stacking interactions.The results of TG-DSC/FTIR show that in the process of thermal decomposition,the complexes containing water and free ethanol will lose water and ethanol first,and then lose the nitrogen-containing ligand?terpy and 5,5'-DM-2,2'-bipy?,and finally lost the acidic ligand.These decomposition processes also correspond to the three-dimensional infrared spectrum of gaseous products.At the same time,the molar heat capacities of complexes 17-18 and 26-27 are studied.The results show that the molar heat capacity of the complexes increases with the increase of temperature.By using the least square method,the average molar heat capacities are fitted to polynomial equations with the reduced temperature.At the same time,calculate the thermodynamic function value and smooth thermal capacity of the complexes.The fluorescence properties of complexes 1,10,12,17,19 and 26 are studied.Europium complexes show the red light,and terbium complexes show the green light.Moreover,the fluorescence lifetime and intrinsic quantum yield of the complexes are obtained.The magnetic properties of complexes 12,13,14,21 and 23 are studied and fitted.The results show that there may be antiferromagnetic interaction in complexes12,14,22 and 23.However,complexes 13 and 21 may have ferromagnetic interaction. |
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