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A kinetically inert and optically active CrIII partner in thermodynamically self-assembled heterodimetallic non-covalent d–f podates

Imbert, Daniel
Bünzli, Jean-Claude G.
Published in Journal of the Chemical Society. Dalton Transactions. 2002, vol. 9, p. 1929-1940
Abstract Stoichiometric mixing of the segmental ligand 2-{6-[N,N-diethylcarboxamido]pyridin-2-yl}-1,1'-dimethyl-5,5'-methylene-2'-(5-methylpyridin-2-yl)bis[1H-benzimidazole] (L) with Ln(CF3SO3)3 (Ln = La-Lu) and Cr(CF3SO3)2 under an inert atm. produces quant. the self-assembled triple-stranded noncovalent podates (HHH)-[LnCrIIL3]5+. Air oxidn. of the low-spin CrII complexes gives selectively the head-to-head-to-head podates (HHH)-[LnCrIIIL3]6+ into which inert CrIII was incorporated. The x-ray crystal structures of [LnCrIII(L)3](CF3SO3)6(MeCN)4 (Ln = Eu, 7; Ln = Lu, 8) confirm the formation of regular triple-helical cations (HHH)-[LnCrIIIL3]6+ whose structure is maintained in MeCN according to ESI-MS, spectrophotometry and NMR data. Photophys. studies evidence efficient sensitization of both EuIII and CrIII through ligand excitation at low temp., while a subsequent intramol. EuIII CrIII energy transfer (.eta. = 70%) limits Eu-centered luminescence and induces directional light-conversion along the 3-fold axis, resulting in CrIII emission. For (HHH)-[TbCrIIIL3]6+, the better spectral overlap between the emission spectrum of TbIII (5D4 7FJ) and the absorption spectrum of CrIII (4A2 4T2) provides a quant. TbIII CrIII energy transfer (.eta..gtoreq. 99%) and long-range intermetallic communication. De-complexation of LnIII with H2O or EDTA4- gives the 1st inert and optically active-CrIII-contg. triple-helical nonadentate receptor (HHH)-[CrIIIL3]3+.
Keywords Chromium rare earth carboxamidopyridinylbenzimidizolemethane helical prepn UV luminescenceCrystal structure chromium europium lutetium carboxamidopyridinylbenzimidizole triple helicatePhotophys property chromium rare earth carboxamidopyridinylbenzimidizole triple helicateIntermetallic energy transfer intramol chromium rare earth carboxamidopyridinylbenzimidizole
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Other version: http://www.rsc.org/ej/DT/2002/b200011c.pdf
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CANTUEL, Martine et al. A kinetically inert and optically active CrIII partner in thermodynamically self-assembled heterodimetallic non-covalent d–f podates. In: Journal of the Chemical Society. Dalton Transactions, 2002, vol. 9, p. 1929-1940. doi: 10.1039/b200011c https://archive-ouverte.unige.ch/unige:2355

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Deposited on : 2009-08-07

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