On the role of ligand-field states for the photophysical properties of ruthenium(II) polypyridyl complexes

Article Article scientifique Article On the role of ligand-field states for the photophysical properties of ruthenium(II) polypyridyl complexes eng 2015 author Sun Qinchao 788543 author Mosquera Vazquez Sandra 763900 author Suffren Yan Jonathan Mathieu 784690 author Hankache Jihane 686575 author Jeddi Nahid 23520 author Lawson Daku Latevi Max 530149 author Vauthey Eric 0000-0002-9580-9683 133895 author Hauser Andreas 111359 87-99 10.1016/j.ccr.2014.07.004 0010-8545 http://linkinghub.elsevier.com/retrieve/pii/S0010854514001908 The role of ligand-field states for the photophysical properties of d6 systems has been discussed in a large number of publications over the past decades. Since the seminal paper by Houten and Watts, for instance, the quenching of the 3MLCT luminescence in ruthenium(II) polypyridyl complexes is attributed to the presence of the first excited ligand-field state, namely a component of the 3T1(t2g5eg1) state, at similar energies. If this state lies above the 3MLCT state, the luminescence is quenched via thermal population at elevated temperatures only. If it lies well below, then the luminescence is quenched down to cryogenic temperatures. In this contribution we present transient absorption spectra on non-luminescent ruthenium polypyridyl complexes such as [Ru(m-bpy)3]2+, m-bpy = 6-methyl-2,2'-bipyridine, in acetonitrile at room temperature, which reveal an ultra-rapid depopulation of the 3MLCT state but a much slower ground state recovery. We propose that in this and related complexes the methyl groups force longer metal-ligand bond lengths, thus resulting in a lowering of the ligand-field strength such that the 3dd state drops to below the 3MLCT state, and that furthermore the population of this state from the 3MLCT state occurs faster than its decay to the ground state. In addition we demonstrate that in this complex the luminescence can be switched on by external pressure, which we attribute to a destabilisation of the ligand-field state by the pressure due to its larger molecular volume compared to the ground state as well as the 3MLCT state. Ruthenium(II) polypyridyl complexes Ligand-field states Luminescence quenching Photophysical properties High-pressure Dewey 540 38 Département de chimie physique 142 false 687 Groupe Hauser 686 Groupe Vauthey Coordination chemistry reviews 282-283 839ba7b9-edf9-4110-bf10-4933e38616c4 Article (Published version) Restricted ref01426.pdf 3284903 application/pdf restrictedAccess Faculté des sciences / Section de chimie et biochimie / Département de chimie physique

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On the role of ligand-field states for the photophysical properties of ruthenium(II) polypyridyl complexes	Coordination chemistry reviews			2015	874	0

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