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Trapping intermediate MLCT states in low-symmetry {Ru(bpy)} complexes

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Abstract

The picosecond excited state dynamics of [Ru(tpm)(bpy)(NCS)]+ (RubNCS+) and [Ru(tpm)(bpy)(CN)]+ (RubCN+) (tpm = tris(1-pyrazolyl)methane, bpy = 2,2′-bipyridine) have been analyzed by means of transient absorption measurements and spectroelectrochemistry. Emissive 3MLCTs with (GS)HOMO(h+)–(GS)LUMO(e) configurations are the lowest triplet excited states regardless of whether 387 or 505 nm photoexcitation is used. 387 nm photoexcitation yields, after a few picoseconds, the emissive 3MLCTs. In contrast, 505 nm photoexcitation populates an intermediate excited state that we assign as a 3MLCT state, in which the hole sits in a metal-centered orbital of different symmetry, prior to its conversion to the emissive 3MLCTs. The disparities in terms of electronic configuration between the intermediate and the emissive 3MLCTs have two important consequences. On one hand, both states feature very different fingerprint absorptions in transient absorption measurements. On the other hand, the reconfiguration is impeded by a kinetic barrier. As such, the conversion is followed spectroscopically and kinetically on the 300 ps timescale.

Graphical abstract: Trapping intermediate MLCT states in low-symmetry {Ru(bpy)} complexes

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Publication details

The article was received on 15 Jun 2017, accepted on 27 Aug 2017 and first published on 29 Aug 2017


Article type: Edge Article
DOI: 10.1039/C7SC02670F
Citation: Chem. Sci., 2017, Advance Article
  • Open access: Creative Commons BY license
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    Trapping intermediate MLCT states in low-symmetry {Ru(bpy)} complexes

    A. Cadranel, P. S. Oviedo, G. E. Pieslinger, S. Yamazaki, V. D. Kleiman, Luis M. Baraldo and D. M. Guldi, Chem. Sci., 2017, Advance Article , DOI: 10.1039/C7SC02670F

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