Mechanical Modulation of the Solid-State Luminescence of Tricarbonyl Rhenium(I) Complexes through the Interplay between Two Triplet Excited States |
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Authors: | Dr Jan Patrick Calupitan Alexandre Poirot Dr Jinhui Wang Dr Béatrice Delavaux-Nicot Dr Mariusz Wolff Dr Maria Jaworska Dr Rémi Métivier Prof Eric Benoist Dr Clémence Allain Dr Suzanne Fery-Forgues |
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Institution: | 1. Laboratoire PPSM, CNRS UMR 8531, ENS Paris-Saclay, Université Paris-Saclay, 91190 Gif-sur-Yvette, France;2. SPCMIB, CNRS UMR5068, Université Toulouse III-Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex 9, France;3. Laboratoire de Chimie de Coordination, CNRS (UPR 8241), Université de Toulouse (UPS, INPT), 205 route de Narbonne, 31077 Toulouse Cedex 4, France;4. Institut für Chemische Katalyse, Universität Wien, Währinger Strasse 38, 1090 Wien, Austria;5. Institute of Chemistry, University of Silesia in Katowice, 9th Szkolna St., 40-006 Katowice, Poland |
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Abstract: | Mechanoresponsive luminescence (MRL) materials promise smart devices for sensing, optoelectronics and security. We present here the first report on the MRL activity of two ReI complexes, opening up new opportunities for applications in these fields. Both complexes exhibit marked solid-state luminescence enhancement (SLE). Furthermore, the pristine microcrystalline powders emit in the yellow-green region, and grinding led to an amorphous phase with concomitant emission redshift and shrinking of the photoluminescence (PL) quantum yields and lifetimes. Quantum chemical calculations revealed the existence of two low-lying triplet excited states with very similar energy levels, that is, 3IL and 3MLCT, having, respectively, almost pure intraligand (IL) and metal-to-ligand charge-transfer (MLCT) character. Transition between these states could be promoted by rotation around the pyridyltriazole−phenylbenzoxazole bond. In the microcrystals, in which rotations are hindered, the 3IL state induces the prominent PL emission at short wavelengths. Upon grinding, rotation is facilitated and the transition to the 3MLCT state results in a larger proportion of long-wavelength PL. FTIR and variable-temperature PL spectroscopy showed that the opening of the vibrational modes favours non-radiative deactivation of the triplet states in the amorphous phase. In solution, PL only arises from the 3MLCT state. The same mechanism accounts for the spectroscopic differences observed when passing from crystals to amorphous powders, and then to solutions, thereby clarifying the link between SLE and MRL for these complexes. |
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Keywords: | density functional calculations luminescence mechanochromism rhenium |
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