Luminescence And Magnetism Of1,3-propanediamine Salen-type Lanthanide Complexes

The design and synthesis of novel salen type lanthanide complexes with uniqueproperties and study on the correlation between the structure and properties still remainchallenge, which play a crucial role on preparing molecular materials with potentialapplication value. A series of seven-types and twenty-one salen type polynuclearlanthanide complexes have been synthesized and designed by reactions of lanthanideand salen type ligand. All the complexes were have been characterized by a number ofanalytical techniques. Luminescence and magnetic properties of these polynuclearcomplexes were investigated and discussed.Structure and NIR luminescence of ytterbium complexes modulated by anions. Aseries of ytterbium complexes, namely,[Yb（H₂L）₂（CH₃OH）]（ClO₄）₃（1）,[Yb（H₂L）（NO₃）₃]₂·CH₂Cl₂（2）,[Yb（H₂L）₂（NO₃）]₂（PF₆）₄·4H₂O·2CH₂Cl₂（3）,[Yb（H₂L）（OAc）₂]₂（PF₆）₂·4CH₂Cl₂（4）,[Yb₃L′₃（OH）₂Cl（H₂O）5]Cl₃·4H₂O （5）（HL′=2-hydroxy-3-methoxybenzaldehyde）, have been synthesized by reactions ofN,N′-bis（2-hydroxy-3-methoxybenzylidene）-1,3-propanediamine （H₂L） withmultifarious Yb（Ⅲ） salts. The anions dominate the final structures of1–5. For example,counterion （PF₆^–, ClO₄^–）does not involve in the coordination to lanthanide ions. Incontrast, the （NO₃^–, OAc^–） anion is of strong coordination ability so that it is hard tobe displaced by other anions. However, when the Cl–anion was employed, salen typeligand was decomposed. It should be noticed that PF₆^–counterion plays uncanny roleson constructing novel salen type lanthanide complexes with diverse structures. Allcomplexes1–5exhibit NIR luminescence, which can be rationalized on the basis ofdifferent structural effects. The correlation between the structure and lunminscence isconducted.Systematic study on the structures of salen type lanthanide complexes tuned bylanthanide contraction and corresponding luminescence. A family of five N,N′-bis（2-hydroxy-3-methoxybenzylidene）-1,3-propanediamine （H₂L） lanthanidecomplexes, viz.[Ln（H₂L）（OAc）₂]₂（PF₆）₂·2CH₂Cl₂[Ln=Nd （6）, Eu （8） and Tb （10）],[Ln（H₂L）（OAc）₂]₂（PF₆）₂·4CH₂Cl₂[Ln=Sm （7）],[Ln（H₂L）（OAc）₂]₂（PF₆）₂·8H₂O [Ln=Gd （9）] have been isolated by reactions of H₂L with Ln（OAc）₃·6H₂O. X-raycrystallographic analyses reveal that6–10are isostructural exhibiting a discretedinuclear structure with different crystalline solvent molecules. Two types ofN,N′-bis（salicylidene）-1,3-propanediamine （H₂L₁） lanthanide complexes, viz.[Ln（NO₃）₃（H₂L）₂]·0.2CH₃OH [Ln=Ce （11） and Pr （12）] and[Ln（NO₃）₃（H₂L）₂]₂·CH₂Cl₂·CH₃OH [Ln=Nd （13）, Sm （14）, Eu （15）, Tb （16） and Yb（17）], have been isolated by reactions of H₂L with Ln（NO₃）₃·6H₂O. X-raycrystallographic reveal that11–12are isomorphic possessing a novel one-dimensional（1D） ladder-like double-chain structure. Complexes13–17are isostructural exhibiting adiscrete dinuclear structure. the lanthanide contract play essential roles on dominatingthe structures of complexes11–17. The energy gap analysis suggest that theluminescence of Ln（Ⅲ） ion in complexes7,8and10in solid state are dominated by theenergy match between the triplet state of H₂L and the resonance energy level ofcorresponding Ln（Ⅲ） ion. Further, the co-luminescence of Ln（Ⅲ） ion and ligand incomplexes14,15and16in solid state are dominated by the poor energy match betweenthe triplet state of H₂L₁and the resonance energy level of corresponding Ln（Ⅲ） ion.Systematic study on the structures of dinuclear Dy2complexes and correspondingmagneric.[Dy（H₂L）（OAc）₂]₂（PF₆）₂·4CH₂Cl₂（18）,[Dy（H₂L）（NO₃）₃]₂·CH₃OH （19）,[Dy（H₂L）₂（NO₃）]₂（PF₆）₄·4H₂O·2CH₂Cl₂（20） and [Dy（NO₃）₃（H₂L₁）₂]₂·CH₂Cl₂·CH₃OH（21） have been isolated by reactions of salen type ligands （H₂L） and （H₂L₁）withDy（OAc）₃·6H₂O and Dy（NO₃）₃·6H₂O. Magneric studies indicate the ferromagneticcoupling between Dy（Ⅲ） ions in complexes18and20linked by NO₃–and OAc–anions, the interaction is strong enough to compensate the decrease of χMT resultedfrom the depopulated Stark states. The anferromagnetic coupling between Dy（Ⅲ） ions in complexes19and21linked by ligands, the interaction is not strong enough tocompensate the decrease of χMT resulted from the depopulated Stark states. Allcomplexes19–21exhibit different magneric properties, There are two relaxationprocesses in complexes20. The thermally induced relaxation can be fit using theArrhenius law yielding diffirent energy barriers and relaxation time. To some extend,the present research results have oponed up a pathway to achive adustabe SMMS viashorten the distance between both Dy（Ⅲ） ions, Electron-withdrawing effets andaxiality of the Dy（Ⅲ）.