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 SM ISO690:2012AROMÍ, Guillem, BELL, Aidan R., HELLIWELL, Madeleine A., RAFTERY, James T., TEAT, Simon J., TIMKO, Grigore, ROUBEAU, Olivier, WINPENNY, Richard E.P.. A systematic exploration of nickel-pyrazolinato chemistry with alkali metals: New cages from serendipitous assembly. In: Chemistry - A European Journal, 2003, vol. 9, pp. 3024-3032. ISSN 0947-6539. DOI: https://doi.org/10.1002/chem.200304939 |
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  Chemistry - A European Journal |
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| Volumul 9 / 2003 / ISSN 0947-6539 | |
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| DOI:https://doi.org/10.1002/chem.200304939 | |
| Pag. 3024-3032 | |
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The preparation and properties of fourteen novel paramagnetic [NiIIx] aggregates bridged by pivalate, pyrazolinolate and in most cases hydroxide are reported. A rich structural diversity has been achieved by changing the nature of the alkali of the base used during the synthesis, leading to the nuclearities [NiII4NaI4] (2, 3, 4), [NiII5-NAI4] (5, 6, 7), [NiII5LiI6] (8), [NiII8MI2] (M = K (9, 10), Rb (11, 12), Cs (13, 14) and [NiII8] (15). All compounds have been characterised by single-crystal X-ray diffraction; however, full crystallographic details are given only for the representative molecules [Ni4Na4- (fpo)4(piv)8(Hpiv)8] (2), [Ni5Na4(OH)2- (mpo)4(piv)8(Hpiv)2(MeCN)2] (5), [Ni5Li6(OH)2 (fpo)2(piv)12(Hpiv)4] (8) [Ni8K2(OH)4(ppo) 4(piv)10(Hppo)2- (Hpiv)2(MeCN)2] (9), [Ni8Rb2(OH)4- (ppo)4(piv)10(Hppo) 2(Hpiv)2(MeCN)2] (11), [Ni8Cs2(OH)4(ppo) 4(piv)10(Hppo)2- (Hpiv)2(MeCN)2] (13) and [Ni8(OH)4-(mpo)2(PhCH 2CO2)10(Hmpo)8] (15). Variable-temperature bulk magnetisation measurements have been performed for each type of complex. The [NiII4NaI4] clusters show intramolecular antiferromagnetic coupling and a spin ground state of S = 0. Complexes of the type [NiII5NaI4] also display antiferromagnetic superexchange, leading to an S=1 spin ground state. The molecule with nuclearity [NiII5LiI6], in contrast, exhibits ferromagnetic interactions, resulting in the presence of low energy states with high multiplicity, and a spin ground state S>1. The [NiII5MI2] and [NiII8] clusters have the same topology of spin carriers, which display predominantly antiferromagnetic interactions to yield a diamagnetic ground state. The coupling within these octanuclear NiII clusters is rationalised in terms of the nature of the Ni-O-Ni angles within the core. |
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| Cuvinte-cheie Alkali metals, Cluster compounds, magnetic properties, nickel, Serendipitious assembly |
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