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Acid/Base‐Triggered Switching of Circularly Polarized Luminescence and Electronic Circular Dichroism in Organic and Organometallic Helicenes |
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| Authors: | Nidal Saleh Barry Moore II Monika Srebro Nicolas Vanthuyne Loïc Toupet J A Gareth Williams Christian Roussel Kirandeep K Deol Gilles Muller Jochen Autschbach Jeanne Crassous |
| Institution: | 1. Institut des Sciences Chimiques de Rennes, UMR 6226, Institut de Physique de Rennes, UMR 6251, Campus de Beaulieu, CNRS‐Université de Rennes 1, 35042 Rennes Cedex (France);2. Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY 14260 (USA);3. Faculty of Chemistry, Jagiellonian University, 30‐060 Krakow (Poland);4. Aix Marseille Université, Centrale Marseille, CNRS, iSm2 UMR 7313, 13397, Marseille (France);5. Department of Chemistry, University of Durham, Durham, DH1 3LE (UK);6. Department of Chemistry, San José State University, San José, CA 95192‐0101 (USA) |
| Abstract: | Electronic circular dichroism and circularly polarized luminescence acid/base switching activity has been demonstrated in helicene‐bipyridine proligand 1 a and in its “rollover” cycloplatinated derivative 2 a . Whereas proligand 1 a displays a strong bathochromic shift (>160 nm) of the nonpolarized and circularly polarized luminescence upon protonation, complex 2 a displays slightly stronger emission. This strikingly different behavior between singlet emission in the organic helicene and triplet emission in the organometallic derivative has been rationalized by using quantum‐chemical calculations. The very large bathochromic shift of the emission observed upon protonation of azahelicene‐bipyridine 1 a has been attributed to the decrease in aromaticity (promoting a charge‐transfer‐type transition rather than a π–π* transition) as well as an increase in the HOMO–LUMO character of the transition and stabilization of the LUMO level upon protonation. |
| Keywords: | circular dichroism density functional calculations helicenes luminescence switches |