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Title: Lanthanide complexes of the hexadentate N-donor podand tris[3-(2-pyridyl)pyrazolyl]hydroborate: Solid-state and solution properties

Abstract

The hexadentate N{sub 6}-donor podand tris[3-(2-pyridyl)pyrazolyl]hydroborate (Tp{sup Py}) contains 2-pyridyl fragments attached to the pyrazolyl C{sup 3}-positions such that each arm is a bidentate chelate. Three series of lanthanide(III) complexes were prepared: [M(Tp{sup Py})(MeOH){sub 2}F][PF{sub 6}] (series A), [M(Tp{sup Py})(NO{sub 3}){sub 2}] (series B), and [M(Tp{sup Py}){sub 2}]-[BPh{sub 4}] (series C). Crystallographic studies showed that series A and B have a 1:1 metal:Tp{sup Py} ratio, with the metal ion lying within the podand cavity and the remaining coordination sites occupied by solvent molecules and/or counterions to give 9-coordination (A, with one fluoride and two methanol ligands) or 10-coordination (B, with two bidentate nitrate ligands). The C complexes were prepared in the absence of any coordinating anions and have a 1:2 metal:Tp{sup Py} ratio with an unusual icosahedral geometry arising from coordination of the 12 nitrogen donors from two interleaved podands. Conductivity studies on the B complexes show that in water the nitrates dissociate to give [M(Tp{sup Py})(H{sub 2}O){sub q}](NO{sub 3}){sub 2}; the relaxivity of [Gd(Tp{sup Py}(NO{sub 3}){sub 2}] in water is 4.4 s{sup -1} mM{sup -1}, a value comparable to those of clinically useful MRI contrast enhancement agents. Comparison of emission lifetimes of [M(Tp{sup Py})(NO{sub 3}){sub 2}] M = Eu,more » Tb) in H{sub 2}O/d{sub 2}O and CH{sub 3}OH/Cd{sub 3}OD give values for q, the number of coordinated solvent molecules, of 3.6 (water) and 2.6 (methanol). The C complex [Tb(Tp{sup Py}){sub 2}][BPh{sub 4}] also has q = 2.6 in methanol, suggesting that partial ligand dissociation allows access of solvent molecules to the metal coordination sphere.« less

Authors:
; ; ;  [1]
  1. Univ. of Bristol (United Kingdom); and others
Publication Date:
OSTI Identifier:
518389
Resource Type:
Journal Article
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 36; Journal Issue: 1; Other Information: PBD: 1 Jan 1997
Country of Publication:
United States
Language:
English
Subject:
40 CHEMISTRY; GADOLINIUM COMPLEXES; EMISSION SPECTROSCOPY; ELECTRIC CONDUCTIVITY; EUROPIUM COMPLEXES; TERBIUM COMPLEXES; CHELATES; X-RAY DIFFRACTION

Citation Formats

Jones, P L, Amoroso, A J, Jeffery, J C, and Rees, L H. Lanthanide complexes of the hexadentate N-donor podand tris[3-(2-pyridyl)pyrazolyl]hydroborate: Solid-state and solution properties. United States: N. p., 1997. Web. doi:10.1021/ic960621m.
Jones, P L, Amoroso, A J, Jeffery, J C, & Rees, L H. Lanthanide complexes of the hexadentate N-donor podand tris[3-(2-pyridyl)pyrazolyl]hydroborate: Solid-state and solution properties. United States. https://doi.org/10.1021/ic960621m
Jones, P L, Amoroso, A J, Jeffery, J C, and Rees, L H. 1997. "Lanthanide complexes of the hexadentate N-donor podand tris[3-(2-pyridyl)pyrazolyl]hydroborate: Solid-state and solution properties". United States. https://doi.org/10.1021/ic960621m.
@article{osti_518389,
title = {Lanthanide complexes of the hexadentate N-donor podand tris[3-(2-pyridyl)pyrazolyl]hydroborate: Solid-state and solution properties},
author = {Jones, P L and Amoroso, A J and Jeffery, J C and Rees, L H},
abstractNote = {The hexadentate N{sub 6}-donor podand tris[3-(2-pyridyl)pyrazolyl]hydroborate (Tp{sup Py}) contains 2-pyridyl fragments attached to the pyrazolyl C{sup 3}-positions such that each arm is a bidentate chelate. Three series of lanthanide(III) complexes were prepared: [M(Tp{sup Py})(MeOH){sub 2}F][PF{sub 6}] (series A), [M(Tp{sup Py})(NO{sub 3}){sub 2}] (series B), and [M(Tp{sup Py}){sub 2}]-[BPh{sub 4}] (series C). Crystallographic studies showed that series A and B have a 1:1 metal:Tp{sup Py} ratio, with the metal ion lying within the podand cavity and the remaining coordination sites occupied by solvent molecules and/or counterions to give 9-coordination (A, with one fluoride and two methanol ligands) or 10-coordination (B, with two bidentate nitrate ligands). The C complexes were prepared in the absence of any coordinating anions and have a 1:2 metal:Tp{sup Py} ratio with an unusual icosahedral geometry arising from coordination of the 12 nitrogen donors from two interleaved podands. Conductivity studies on the B complexes show that in water the nitrates dissociate to give [M(Tp{sup Py})(H{sub 2}O){sub q}](NO{sub 3}){sub 2}; the relaxivity of [Gd(Tp{sup Py}(NO{sub 3}){sub 2}] in water is 4.4 s{sup -1} mM{sup -1}, a value comparable to those of clinically useful MRI contrast enhancement agents. Comparison of emission lifetimes of [M(Tp{sup Py})(NO{sub 3}){sub 2}] M = Eu, Tb) in H{sub 2}O/d{sub 2}O and CH{sub 3}OH/Cd{sub 3}OD give values for q, the number of coordinated solvent molecules, of 3.6 (water) and 2.6 (methanol). The C complex [Tb(Tp{sup Py}){sub 2}][BPh{sub 4}] also has q = 2.6 in methanol, suggesting that partial ligand dissociation allows access of solvent molecules to the metal coordination sphere.},
doi = {10.1021/ic960621m},
url = {https://www.osti.gov/biblio/518389}, journal = {Inorganic Chemistry},
number = 1,
volume = 36,
place = {United States},
year = {Wed Jan 01 00:00:00 EST 1997},
month = {Wed Jan 01 00:00:00 EST 1997}
}