Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/68651
標題: First stable reduced form of Co-5 (+10): fine tuning of linear pentacobalt(II) complexes containing delocalized metal-metal bonds through ligand modification
作者: Wang, W.Z.
Ismayilov, R.H.
Wang, R.R.
Huang, Y.L.
Yeh, C.Y.
Lee, G.H.
Peng, S.M.
關鍵字: di(2-pyridyl)amide dpa ligands
string complexes
magnetic-properties
structural versatility
trimetallic complexes
tricobalt compounds
stretch isomerism
chain complexes
dft
oxidation
期刊/報告no:: Dalton Transactions, Issue 47, Page(s) 6808-6816.
摘要: Pentacobalt EMACs [Co-5(mu(5)-dpzpda)(4)X-2] (X=Cl- (1), NCS- (2)) with fine-tuning of the supporting ligand based on the tripyridyldiamine ligand, N,N'-di(pyrazin-2-yl) pyridine-2,6-diamine (H(2)dpzpda), and their reduced form (Ph4P)[Co-5(mu(5)-dpzpda)(4)X-2] (X = Cl- (3), NCS- (4)) were first synthesized and structurally characterized. The structures of 1-4 showed direct Co-Co bonds with Co-Co distances in the range 2.2385(7)-2.2888(15) angstrom, and valence electrons delocalized through the whole metal chain with distances of longer than 9.06 angstrom. The distances of the inner Co-Co bonds and the Co-axial ligands became longer after reduction, whereas no significant change was observed in the distances of the outer Co-Co bonds and Co-N (supporting ligand) bonds, which was consistent with the MO analysis. Electrochemical studies on both 1 and 2 showed one reversible oxidation and one reversible reduction at E-1/2 = +0.82 and -0.05 V for 1, and at E-1/2 = +0.89 and +0.02 V for 2, respectively. The redox reactions of the thiocyanate complex 4 happened at higher potentials than the chloride complex 3. A magnetism study of 1-4 revealed anomalous magnetic behaviour similar to that of heptacobalt EMACs, and a deviation from the Curie-Weiss law was observed. The chi T-M value at 300 K is 0.84 and 1.16 emu K mol(-1) for 1 and 2, respectively, suggesting spin-equilibrium or a spin-admixture between doublet and quartet states arising from the Boltzmann distribution over different energy levels. Similar results were obtained for 3 and 4, showing intermediate cMT values between a diamagnetic and a triplet state of 0.15-0.96 emu K mol(-1) in the temperature range 5-300 K. The structural and magnetic results were interpreted through an EHMO study.
URI: http://hdl.handle.net/11455/68651
ISSN: 1477-9226
文章連結: http://dx.doi.org/10.1039/b811520f
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