Coordination chemistry of tetradentate N-donor ligands containing two pyrazolyl-pyridine units separated by a 1,8-naphthyl spacer: Dodecanuclear and tetranuclear coordination cages and cyclic helicates

S.P. Argent, H. Adams, T. Riis-Johannessen, J.C. Jeffery, L.P. Harding, O. Mamula, M.D. Ward

Research output: Contribution to journalArticle

106 Citations (Scopus)

Abstract

The tetradentate ligand Lnaph contains two N-donor bidentate pyrazolyl−pyridine units connected to a 1,8-naphthyl core via methylene spacers; L*45 and L*56 are chiral ligands with a structure similar to that of Lnaph but bearing pinene groups fused to either C4 and C5 or C5 and C6 of the terminal pyridyl rings. The complexes [Cu(Lnaph)](OTf) and [Ag(Lnaph)](BF4) have unremarkable mononuclear structures, with CuI being four-coordinate and AgI being two-coordinate with two additional weak interactions (i.e., “2 + 2” coordinate). In contrast, [Cu4(Lnaph)4][BF4]4 is a cyclic tetranuclear helicate with a tetrafluoroborate anion in the central cavity, formed by an anion-templating effect; electrospray mass spectrometry (ESMS) spectra show the presence of other cyclic oligomers in solution. The chiral ligands show comparable behavior, with [Cu(L*45)](BF4) and [Ag(L*45)](ClO4) having similar mononuclear crystal structures and with the ligands being tetradentate chelates. In contrast, [Ag4(L*56)4](BF4)4 is a cyclic tetranuclear helicate in which both diastereomers of the complex are present in the crystal; the two diastereomers have similar gross geometries but are significantly different in detail. Despite their different crystal structures, [Ag(L*45)](ClO4) and [Ag4(L*56)4](BF4)4 behave similarly in solution according to ESMS studies, with a range of cyclic oligomers (up to Ag9L9) forming. With transition-metal dications CoII, CuII, and CdII, Lnaph generates a series of unusual dodecanuclear coordination cages [M12(Lnaph)18]X24 (X- = ClO4- or BF4-) in which the 12 metal ions occupy the vertices of a truncated tetrahedron and a bridging ligand spans each of the 18 edges. The central cavity of each cage can accommodate four counterions, and each cage molecule is chiral, with all 12 metal trischelates being homochiral; the crystals are racemic. Extensive aromatic stacking between ligands around the periphery of the cages appears to be a significant factor in their assembly. The chiral analogue L*45 forms the simpler tetranuclear, tetrahedral coordination cage [Zn4(L*45)6](ClO4)8, with one anion in the central cavity; the steric bulk of the pinene chiral auxiliaries prevents the formation of a dodecanuclear cage, although trace amounts of [Zn12(L*45)18](ClO4)24 can be detected in solution by ESMS. Formation of [Zn4(L*45)6](ClO4)8 is diastereoselective, with the chirality of the pinene groups controlling the chirality of the tetranuclear cage.
LanguageEnglish
Pages3905-3919
Number of pages15
JournalInorganic Chemistry
Volume45
Issue number10
DOIs
Publication statusPublished - 11 Apr 2006

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spacers
pyridines
chemistry
Ligands
ligands
Anions
Mass spectrometry
mass spectroscopy
Chirality
anions
oligomers
chirality
Oligomers
cavities
Bearings (structural)
Crystal structure
Crystals
crystal structure
chelates
methylene

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@article{a46bfafb83a94651be8b5cc984de56b9,
title = "Coordination chemistry of tetradentate N-donor ligands containing two pyrazolyl-pyridine units separated by a 1,8-naphthyl spacer: Dodecanuclear and tetranuclear coordination cages and cyclic helicates",
abstract = "The tetradentate ligand Lnaph contains two N-donor bidentate pyrazolyl−pyridine units connected to a 1,8-naphthyl core via methylene spacers; L*45 and L*56 are chiral ligands with a structure similar to that of Lnaph but bearing pinene groups fused to either C4 and C5 or C5 and C6 of the terminal pyridyl rings. The complexes [Cu(Lnaph)](OTf) and [Ag(Lnaph)](BF4) have unremarkable mononuclear structures, with CuI being four-coordinate and AgI being two-coordinate with two additional weak interactions (i.e., “2 + 2” coordinate). In contrast, [Cu4(Lnaph)4][BF4]4 is a cyclic tetranuclear helicate with a tetrafluoroborate anion in the central cavity, formed by an anion-templating effect; electrospray mass spectrometry (ESMS) spectra show the presence of other cyclic oligomers in solution. The chiral ligands show comparable behavior, with [Cu(L*45)](BF4) and [Ag(L*45)](ClO4) having similar mononuclear crystal structures and with the ligands being tetradentate chelates. In contrast, [Ag4(L*56)4](BF4)4 is a cyclic tetranuclear helicate in which both diastereomers of the complex are present in the crystal; the two diastereomers have similar gross geometries but are significantly different in detail. Despite their different crystal structures, [Ag(L*45)](ClO4) and [Ag4(L*56)4](BF4)4 behave similarly in solution according to ESMS studies, with a range of cyclic oligomers (up to Ag9L9) forming. With transition-metal dications CoII, CuII, and CdII, Lnaph generates a series of unusual dodecanuclear coordination cages [M12(Lnaph)18]X24 (X- = ClO4- or BF4-) in which the 12 metal ions occupy the vertices of a truncated tetrahedron and a bridging ligand spans each of the 18 edges. The central cavity of each cage can accommodate four counterions, and each cage molecule is chiral, with all 12 metal trischelates being homochiral; the crystals are racemic. Extensive aromatic stacking between ligands around the periphery of the cages appears to be a significant factor in their assembly. The chiral analogue L*45 forms the simpler tetranuclear, tetrahedral coordination cage [Zn4(L*45)6](ClO4)8, with one anion in the central cavity; the steric bulk of the pinene chiral auxiliaries prevents the formation of a dodecanuclear cage, although trace amounts of [Zn12(L*45)18](ClO4)24 can be detected in solution by ESMS. Formation of [Zn4(L*45)6](ClO4)8 is diastereoselective, with the chirality of the pinene groups controlling the chirality of the tetranuclear cage.",
author = "S.P. Argent and H. Adams and T. Riis-Johannessen and J.C. Jeffery and L.P. Harding and O. Mamula and M.D. Ward",
note = "cited By 99",
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language = "English",
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Coordination chemistry of tetradentate N-donor ligands containing two pyrazolyl-pyridine units separated by a 1,8-naphthyl spacer: Dodecanuclear and tetranuclear coordination cages and cyclic helicates. / Argent, S.P.; Adams, H.; Riis-Johannessen, T.; Jeffery, J.C.; Harding, L.P.; Mamula, O.; Ward, M.D.

In: Inorganic Chemistry, Vol. 45, No. 10, 11.04.2006, p. 3905-3919.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Coordination chemistry of tetradentate N-donor ligands containing two pyrazolyl-pyridine units separated by a 1,8-naphthyl spacer: Dodecanuclear and tetranuclear coordination cages and cyclic helicates

AU - Argent, S.P.

AU - Adams, H.

AU - Riis-Johannessen, T.

AU - Jeffery, J.C.

AU - Harding, L.P.

AU - Mamula, O.

AU - Ward, M.D.

N1 - cited By 99

PY - 2006/4/11

Y1 - 2006/4/11

N2 - The tetradentate ligand Lnaph contains two N-donor bidentate pyrazolyl−pyridine units connected to a 1,8-naphthyl core via methylene spacers; L*45 and L*56 are chiral ligands with a structure similar to that of Lnaph but bearing pinene groups fused to either C4 and C5 or C5 and C6 of the terminal pyridyl rings. The complexes [Cu(Lnaph)](OTf) and [Ag(Lnaph)](BF4) have unremarkable mononuclear structures, with CuI being four-coordinate and AgI being two-coordinate with two additional weak interactions (i.e., “2 + 2” coordinate). In contrast, [Cu4(Lnaph)4][BF4]4 is a cyclic tetranuclear helicate with a tetrafluoroborate anion in the central cavity, formed by an anion-templating effect; electrospray mass spectrometry (ESMS) spectra show the presence of other cyclic oligomers in solution. The chiral ligands show comparable behavior, with [Cu(L*45)](BF4) and [Ag(L*45)](ClO4) having similar mononuclear crystal structures and with the ligands being tetradentate chelates. In contrast, [Ag4(L*56)4](BF4)4 is a cyclic tetranuclear helicate in which both diastereomers of the complex are present in the crystal; the two diastereomers have similar gross geometries but are significantly different in detail. Despite their different crystal structures, [Ag(L*45)](ClO4) and [Ag4(L*56)4](BF4)4 behave similarly in solution according to ESMS studies, with a range of cyclic oligomers (up to Ag9L9) forming. With transition-metal dications CoII, CuII, and CdII, Lnaph generates a series of unusual dodecanuclear coordination cages [M12(Lnaph)18]X24 (X- = ClO4- or BF4-) in which the 12 metal ions occupy the vertices of a truncated tetrahedron and a bridging ligand spans each of the 18 edges. The central cavity of each cage can accommodate four counterions, and each cage molecule is chiral, with all 12 metal trischelates being homochiral; the crystals are racemic. Extensive aromatic stacking between ligands around the periphery of the cages appears to be a significant factor in their assembly. The chiral analogue L*45 forms the simpler tetranuclear, tetrahedral coordination cage [Zn4(L*45)6](ClO4)8, with one anion in the central cavity; the steric bulk of the pinene chiral auxiliaries prevents the formation of a dodecanuclear cage, although trace amounts of [Zn12(L*45)18](ClO4)24 can be detected in solution by ESMS. Formation of [Zn4(L*45)6](ClO4)8 is diastereoselective, with the chirality of the pinene groups controlling the chirality of the tetranuclear cage.

AB - The tetradentate ligand Lnaph contains two N-donor bidentate pyrazolyl−pyridine units connected to a 1,8-naphthyl core via methylene spacers; L*45 and L*56 are chiral ligands with a structure similar to that of Lnaph but bearing pinene groups fused to either C4 and C5 or C5 and C6 of the terminal pyridyl rings. The complexes [Cu(Lnaph)](OTf) and [Ag(Lnaph)](BF4) have unremarkable mononuclear structures, with CuI being four-coordinate and AgI being two-coordinate with two additional weak interactions (i.e., “2 + 2” coordinate). In contrast, [Cu4(Lnaph)4][BF4]4 is a cyclic tetranuclear helicate with a tetrafluoroborate anion in the central cavity, formed by an anion-templating effect; electrospray mass spectrometry (ESMS) spectra show the presence of other cyclic oligomers in solution. The chiral ligands show comparable behavior, with [Cu(L*45)](BF4) and [Ag(L*45)](ClO4) having similar mononuclear crystal structures and with the ligands being tetradentate chelates. In contrast, [Ag4(L*56)4](BF4)4 is a cyclic tetranuclear helicate in which both diastereomers of the complex are present in the crystal; the two diastereomers have similar gross geometries but are significantly different in detail. Despite their different crystal structures, [Ag(L*45)](ClO4) and [Ag4(L*56)4](BF4)4 behave similarly in solution according to ESMS studies, with a range of cyclic oligomers (up to Ag9L9) forming. With transition-metal dications CoII, CuII, and CdII, Lnaph generates a series of unusual dodecanuclear coordination cages [M12(Lnaph)18]X24 (X- = ClO4- or BF4-) in which the 12 metal ions occupy the vertices of a truncated tetrahedron and a bridging ligand spans each of the 18 edges. The central cavity of each cage can accommodate four counterions, and each cage molecule is chiral, with all 12 metal trischelates being homochiral; the crystals are racemic. Extensive aromatic stacking between ligands around the periphery of the cages appears to be a significant factor in their assembly. The chiral analogue L*45 forms the simpler tetranuclear, tetrahedral coordination cage [Zn4(L*45)6](ClO4)8, with one anion in the central cavity; the steric bulk of the pinene chiral auxiliaries prevents the formation of a dodecanuclear cage, although trace amounts of [Zn12(L*45)18](ClO4)24 can be detected in solution by ESMS. Formation of [Zn4(L*45)6](ClO4)8 is diastereoselective, with the chirality of the pinene groups controlling the chirality of the tetranuclear cage.

U2 - 10.1021/ic060157d

DO - 10.1021/ic060157d

M3 - Article

VL - 45

SP - 3905

EP - 3919

JO - Inorganic Chemistry

T2 - Inorganic Chemistry

JF - Inorganic Chemistry

SN - 0020-1669

IS - 10

ER -