A family of rare-earth derivant mixed-polyoxoniobate clusters K_(12)(NH_(4))10[{Nb_(12)P_(4)W_(24)O_(122)}_(2){Ln(H_(2)O)_(5)}_(4){Nb_(4)O_(4)(OH)_(6)}]·xH_(2)O(Ln=Sm,Eu,Tb,Dy,Er,Tm and Yb for 1–7,abbreviated as...A family of rare-earth derivant mixed-polyoxoniobate clusters K_(12)(NH_(4))10[{Nb_(12)P_(4)W_(24)O_(122)}_(2){Ln(H_(2)O)_(5)}_(4){Nb_(4)O_(4)(OH)_(6)}]·xH_(2)O(Ln=Sm,Eu,Tb,Dy,Er,Tm and Yb for 1–7,abbreviated as{Ln_(4)Nb_(28)})were synthesized and structurally characterized by single-crystal X-ray diffraction,elemental analyses,IR spectroscopy and TG analyses.Containing four Wells–Dawson[Nb_(6)P_(2)W_(12)O_(62)]^(12)−,a{Nb_(4)O_(6)}core,and four Ln^(Ⅲ) ions,the polyanions in 1–7 are a group of rare-earth derivants of phosphoniobotungstates.These water-soluble clusters behave as weak acids with good stability and high proton release capacity depending on the pH.Each cluster carries~22 negative charges in the aqueous solution without any deprotonation with the pH the same as that used for deionized water.Upon the introduction of bases,they get deprotonated gradually and each anion cluster can release up to 20 protons from its 20 coordinated water ligands.The pKa values of these acidic clusters with different degrees of deprotonation range from~8.3 to~10.5.Moreover,these clusters demonstrate an increasing deprotonation efficiency with the decreasing ionic radius of incorporated Ln^(Ⅲ) ions,which could be attributed to the lanthanide contraction.In other words,the{Ln_(4)Nb_(28)}macroanion clusters with smaller Ln^(Ⅲ) centers are easier to deprotonate due to their shorter and stronger Ln–O bonds.This is the first study that focuses on the effect of lanthanide contraction on proton release in polyoxometalate chemistry.The{Ln_(4)Nb_(28)}clusters with good stability,high proton release capacity,and controllable deprotonation efficiency provide models for the understanding of protonated polyelectrolyte solutions,and the design and applications of polyoxometalatebased protonated materials.展开更多
基金supported by the National Natural Science Foundation of China(21671056 and 22071045)the Excellent Youth Science Fund Project of Henan Province(202300410042)+2 种基金Henan Universitysupport from the National Science Foundation(CHE2132178)The University of Akron.
文摘A family of rare-earth derivant mixed-polyoxoniobate clusters K_(12)(NH_(4))10[{Nb_(12)P_(4)W_(24)O_(122)}_(2){Ln(H_(2)O)_(5)}_(4){Nb_(4)O_(4)(OH)_(6)}]·xH_(2)O(Ln=Sm,Eu,Tb,Dy,Er,Tm and Yb for 1–7,abbreviated as{Ln_(4)Nb_(28)})were synthesized and structurally characterized by single-crystal X-ray diffraction,elemental analyses,IR spectroscopy and TG analyses.Containing four Wells–Dawson[Nb_(6)P_(2)W_(12)O_(62)]^(12)−,a{Nb_(4)O_(6)}core,and four Ln^(Ⅲ) ions,the polyanions in 1–7 are a group of rare-earth derivants of phosphoniobotungstates.These water-soluble clusters behave as weak acids with good stability and high proton release capacity depending on the pH.Each cluster carries~22 negative charges in the aqueous solution without any deprotonation with the pH the same as that used for deionized water.Upon the introduction of bases,they get deprotonated gradually and each anion cluster can release up to 20 protons from its 20 coordinated water ligands.The pKa values of these acidic clusters with different degrees of deprotonation range from~8.3 to~10.5.Moreover,these clusters demonstrate an increasing deprotonation efficiency with the decreasing ionic radius of incorporated Ln^(Ⅲ) ions,which could be attributed to the lanthanide contraction.In other words,the{Ln_(4)Nb_(28)}macroanion clusters with smaller Ln^(Ⅲ) centers are easier to deprotonate due to their shorter and stronger Ln–O bonds.This is the first study that focuses on the effect of lanthanide contraction on proton release in polyoxometalate chemistry.The{Ln_(4)Nb_(28)}clusters with good stability,high proton release capacity,and controllable deprotonation efficiency provide models for the understanding of protonated polyelectrolyte solutions,and the design and applications of polyoxometalatebased protonated materials.
