Lanthanide Complexes of the Hexadentate N-Donor Podand Tris[3-(2-pyridyl)pyrazolyl]hydroborate: Solid-State and Solution Properties

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• 作者：Peter L. Jones ; Angelo J. Amoroso ; John C. Jeffery ; Jon A. McCleverty ; Elefteria Psillakis ; Leigh H. Rees ; and Michael D. Ward
• 刊名：Inorganic Chemistry
• 出版年：1997
• 出版时间：January 1, 1997
• 年：1997
• 卷：36
• 期：1
• 页码：10 - 18
• 全文大小：326K
• 年卷期：v.36,no.1(January 1, 1997)
• ISSN：1520-510X

文摘

The hexadentate N₆-donor podandtris[3-(2-pyridyl)pyrazolyl]hydroborate(Tp^Py) contains 2-pyridyl fragmentsattached to the pyrazolyl C³-positions such that each armis a bidentate chelate. Three series oflanthanide(III)complexes were prepared:[M(Tp^Py)(MeOH)₂F][PF₆](series A),[M(Tp^Py)(NO₃)₂] (seriesB), and[M(Tp^Py)₂][BPh₄] (series C). Crystallographicstudies showed that series A and B have a 1:1metal:Tp^Py ratio, with themetal ion lying within the podand cavity and the remaining coordinationsites occupied by solvent moleculesand/or counterions to give 9-coordination (A, with onefluoride and two methanol ligands) or 10-coordination(B,with two bidentate nitrate ligands). The C complexeswere prepared in the absence of any coordinating anionsand have a 1:2 metal:Tp^Py ratio with an unusual icosahedralgeometry arising from coordination of the 12 nitrogendonors from two interleaved podands. Conductivity studies on theB complexes show that in water the nitratesdissociate to give[M(Tp^Py)(H₂O)_q](NO₃)₂;the relaxivity of[Gd(Tp^Py)(NO₃)₂] inwater is 4.4 s^-1mM^-1, a valuecomparable to those of clinically useful MRI contrast enhancementagents. Comparison of emission lifetimes of[M(Tp^Py)(NO₃)₂] (M = Eu,Tb) in H₂O/D₂O andCH₃OH/CD₃OD give values forq, the number of coordinatedsolvent molecules, of 3.6 (water) and 2.6 (methanol). TheC complex[Tb(Tp^Py)₂][BPh₄]also has q = 2.6 inmethanol, suggesting that partial ligand dissociation allows access ofsolvent molecules to the metal coordinationsphere.