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Heteroleptic Ter–Bidentate Cr(III) Complexes as Tunable Optical Sensitizers

Published in Inorganic Chemistry. 2018, vol. 57, no. 22, p. 14362-14373
Abstract In order to exploit Cr(III) coordination complexes as sensitizers in supramolecular energy-converting devices, the latter optical relays should display long-lived excited states, broad emission bands and tunable spatial and electronic connections to activator units. An ad-hoc versatile strategy has been therefore developed for the preparation of a family of luminescent pseudo-octahedral [CrN6] chromophores made up of ter-bidentate heteroleptic [Cr(phen)2(N-N')]3+ complexes, where phen is 1,10-phenanthroline and N-N' stands for ,'-diimine ligands possessing peripheral substituents compatible with both electronic tuning and structure extensions. As long as the ligand field in these [CrN6] chromophores remains sufficiently strong to avoid back intersystem crossing, photophysical studies indicate that the lifetime of the near-infrared emissive Cr(2E) excited state is poorly sensitive to 2 ligand-based electronic effects. On the contrary, a drop in symmetry, the coupling with high frequency oscillators and the implementation of sterical constraints in heteroleptic [Cr(phen)2(N-N')]3+ complexes affect both Cr(2E4A2) energies and Cr(2E) lifetimes. Altogether, [Cr(phen)2(phenAlkyn)]3+ (phenAlkyn = 5-ethynyl-1,10-phenanthroline) and [Cr(phen)2(dpma)]3+ (dpma = di(pyrid-2- yl)(methyl)amine) complexes mirror the favorable photophysical properties of homoleptic [Cr(phen)3]3+ and thus emerge as the best heteroleptic candidates for acting as sensitizers at room temperature, and below 100 K, respectively, in more complicated architectures.
Keywords Chromium(III)ComplexHeterolepticLifetimeSensitizerSymmetry
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Research group Groupe Piguet
Project FNS: 200020_178758
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DOISTAU, Benjamin et al. Heteroleptic Ter–Bidentate Cr(III) Complexes as Tunable Optical Sensitizers. In: Inorganic Chemistry, 2018, vol. 57, n° 22, p. 14362-14373. https://archive-ouverte.unige.ch/unige:111465

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Deposited on : 2018-11-27

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