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Issue 8, 2012
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Luminescent cyanometallates based on phenylpyridine-Ir(iii) units: solvatochromism, metallochromism, and energy-transfer in Ir/Ln and Ir/Re complexes

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Abstract

[Ir(ppy)2(CN)2] (ppy = anion of 2-phenylpyridine) and some substituted derivatives have been investigated for their ability to interact with additional metal cations, both in solution and the solid state, via the externally-directed cyanide lone pairs, and to act as energy-donors in the resulting assemblies. [Ir(ppy)2(CN)2] is slightly solvatochromic, showing a blue-shift of the lowest energy absorption manifold in water compared to organic solvents, and the solubilised tBu-substituted analogue [Ir(tBuppy)2(CN)2] [tBuppy = anion of 2-(4-tBu-phenyl)pyridine] is also metallochromic with coordination of the cyanide lone pairs to two M(II) cations in MeCN (M = Ba, Zn) resulting in blue-shifts of the lowest-energy absorption and emission maxima. These effects are however modest because of (i) the presence of only two cyanide groups, and (ii) the fact that the lowest-energy excited state has a substantial 3LC component and is therefore not purely charge-transfer in nature. Crystallisation of [Ir(ppy)2(CN)2] as its (PPN)+ salt in the presence of excess of lanthanide(III) salts leads to formation of assemblies based on Ir–CN–Ln bonds, which generate in the solid state either Ir2Ln2(μ-CN)4 square assemblies or linear trinuclear species with Ir–CN–Ln–NC–Ir cores. In the Ir2Eu2(μ-CN)4 and Ir2Nd2(μ-CN)4 complexes the Ir-based emission is substantially quenched due to energy-transfer to lower-lying f–f states of these lanthanide ions. In addition reaction of [Ir(F2ppy)2(CN)2] [F2ppy = cyclometallating anion of 2-(2,4-difluorophenyl)pyridine] with [Re(phen)(CO)3(MeCN)][PF6] in solution affords dinuclear IrRe and trinuclear IrRe2 species in which {Re(phen)(CO)3} units are attached to the N-donor termini of one or both of the cyanide groups; these complexes have been structurally characterised and display quantitative Ir→Re energy-transfer, showing luminescence only from the Re(I) terminus on excitation of the Ir(III) unit.

Graphical abstract: Luminescent cyanometallates based on phenylpyridine-Ir(iii) units: solvatochromism, metallochromism, and energy-transfer in Ir/Ln and Ir/Re complexes

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Supplementary files

Article information


Submitted
13 Jul 2011
Accepted
04 Nov 2011
First published
03 Jan 2012

Dalton Trans., 2012,41, 2408-2419
Article type
Paper

Luminescent cyanometallates based on phenylpyridine-Ir(III) units: solvatochromism, metallochromism, and energy-transfer in Ir/Ln and Ir/Re complexes

N. M. Ali, V. L. MacLeod, P. Jennison, I. V. Sazanovich, C. A. Hunter, J. A. Weinstein and M. D. Ward, Dalton Trans., 2012, 41, 2408
DOI: 10.1039/C1DT11328C

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