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Author  |
Dul, M.C.; Lescouezec, R.; Chamoreau, L.M.; Journaux, Y.; Carrasco, R.; Castellano, M.; Ruiz-Garcia, R.; Cano, J.; Lloret, F.; Julve, M.; Ruiz-Perez, C.; Fabelo, O.; Pardo, E. |
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Title |
Self-assembly, metal binding ability, and magnetic properties of dinickel(II) and dicobalt(II) triple mesocates |
Type |
Journal Article |
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Year |
2012 |
Publication |
CrystEngComm |
Abbreviated Journal |
CrystEngComm |
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Volume |
14 |
Issue |
17 |
Pages |
5639-5648 |
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Abstract |
Two metallacyclic complexes of general formula Na-8[(M2L3)-L-II]center dot xH(2)O [M = Ni (4) and Co (5) with x = 15 (4) and 17 (5)] have been self-assembled in aqueous solution from N,N'-1,3-phenylenebis(oxamic acid) (H4L) and M2+ ions in a ligand/metal molar ratio of 3 : 2 in the presence of NaOH acting as base. X-Ray structural analyses of 4 and 5 show triple-stranded, dinuclear anions of the meso-helicate-type (so-called mesocates) with C-3h molecular symmetry. The two octahedral metal-tris(oxamate) moieties of opposite chiralities (Delta, Lambda form) are connected by three m-phenylene spacers at intermetallic distances of 6.822(2) (4) and 6.868(2) angstrom (5) to give a metallacryptand core. In the crystal lattice, the binding of these heterochiral dinickel(II) and dicobalt(II) triple mesocates to sodium(I) ions leads to oxamato-bridged heterobimetallic three-dimensional open-frameworks with a hexagonal diamond architecture having small pores of 17.566(4) (4) and 17.640(2) angstrom (5) in diameter where the crystallization water molecules and the sodium(I) countercations are hosted. Variable temperature (2.0-300 K) magnetic susceptibility measurements reveal relatively anisotropic S = 2 Ni-2(II) (4) and S = 3 Co-2(II) (5) ground states resulting from the moderate to weak intramolecular ferromagnetic coupling between the two high-spin Ni-II (S-Ni = 1) or Co-II (S-Co = 3/2) ions across the m-phenylenediamidate bridges [J = +3.6 (4) and +1.1 cm(-1) (5); H = -JS(1)center dot S-2]. A simple molecular orbital analysis of the electron exchange interaction identifies the p-type pathways of the meta-substituted phenylene spacers involving the d(z2) and d(x2-y2) pairs of magnetic orbitals of the two trigonally distorted octahedral high-spin M-II ions (M = Ni and Co) as responsible for the overall ferromagnetic coupling observed in 4 and 5 in agreement with a spin polarization mechanism. The decrease of the overall ferromagnetic coupling from 4 to 5 is in turn explained by the additional antiferromagnetic exchange contribution involving the d(xy) pair of magnetic orbitals of the two trigonally distorted octahedral high-spin Co-II ions across the sigma-type pathway of the meta-substituted phenylene spacers. |
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Address |
[Dul, Marie-Claire; Lescouezec, Rodrigue; Chamoreau, Lise-Marie; Journaux, Yves] Univ Paris 06, Inst Parisien Chim Mol, F-75005 Paris, France, Email: rodrigue.lescouezec@upmc.fr; |
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Publisher |
Royal Soc Chemistry |
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Language |
English |
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Original Title |
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Series Volume |
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Edition |
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ISSN |
1466-8033 |
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Notes |
WOS:000306972100041 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1125 |
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