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Ligand-field excited states of hexacyanochromate and hexacyanocobaltate as sensitisers for near-infrared luminescence from Nd(III) and Yb(III) in cyanide-bridged d–f assemblies

Lazarides, Theodore, Davies, Graham M., Adams, Harry, Sabatini, Cristiana, Barigelletti, Francesco, Barbieri, Andrea, Pope, Simon J. A., Faulkner, Stephen and Ward, Michael D. 2007. Ligand-field excited states of hexacyanochromate and hexacyanocobaltate as sensitisers for near-infrared luminescence from Nd(III) and Yb(III) in cyanide-bridged d–f assemblies. Photochemical & Photobiological Sciences 6 (11) , pp. 1152-1157. 10.1039/b708683k

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Abstract

Crystallisation of [Co(CN)6]3− or [Cr(CN)6]3− with Ln(III) salts (Ln = Nd, Gd, Yb) from aqueous dmf afforded the cyanide-bridged d/f systems [Ln(dmf)4(H2O)3(μ-CN)Co(CN)5] (Co–Ln, discrete dinuclear species) and {[Cr(CN)4(μ-CN)2Ln(H2O)2(dmf)4]}∞ (Cr–Ln, infinite cyanide-bridged chains with alternating Cr and Ln centres). With Ln = Gd the characteristic long-lived phosphorescence from d–d excited states of the [M(CN)6]3− units was apparent in the red region of the spectrum, with lifetimes of the order of 1 μs, since the heavy atom effect of the Gd(III) promotes inter-system crossing at the [M(CN)6]3− units to generate the phosphorescent spin-forbidden excited states. With Ln = Yb or Nd however, the d-block luminescence was completely quenched due to fast (>108 s−1) energy-transfer to the Ln(III) centre, resulting in the characteristic sensitised emission from Yb(III) and Nd(III) in the near-IR region. For both Co–Nd and Co–Yb, calculations based on spectroscopic overlap between emission of the donor (Co) and absorption of the acceptor (Ln) suggest that the Dexter energy-transfer mechanism is responsible for the complete quenching that we observe.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Subjects: Q Science > QD Chemistry
Publisher: Royal Society of Chemistry
ISSN: 1474-905X
Last Modified: 04 Jun 2017 04:37
URI: http://orca.cf.ac.uk/id/eprint/41625

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