Fast and Tunable Phosphorescence from Organic Ionic Crystals

Thumbnail Image
Access rights
Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Degree programme
Angewandte Chemie - International Edition, Volume 62, issue 36
Crystalline diphosphonium iodides [MeR2P-spacer-R2Me]I with phenylene (1, 2), naphthalene (3, 4), biphenyl (5) and anthracene (6) as aromatic spacers, are photoemissive under ambient conditions. The emission colors (λem values from 550 to 880 nm) and intensities (Φem reaching 0.75) are defined by the composition and substitution geometry of the central conjugated chromophore motif, and the anion-π interactions. Time-resolved and variable-temperature luminescence studies suggest phosphorescence for all the titled compounds, which demonstrate observed lifetimes of 0.46–92.23 μs at 297 K. Radiative rate constants kr as high as 2.8×105 s−1 deduced for salts 1–3 were assigned to strong spin-orbit coupling enhanced by an external heavy atom effect arising from the anion-π charge-transfer character of the triplet excited state. These rates of anomalously fast metal-free phosphorescence are comparable to those of transition metal complexes and organic luminophores that utilize triplet excitons via a thermally activated delayed fluorescence mechanism, making such ionic luminophores a new paradigm for the design of photofunctional and responsive molecular materials.
Funding Information: Financial support from the Academy of Finland (decision 351618, I.O.K.; decision 340584, T.E. and A.J.K.; decision 339544, J.J.S.; Flagship Programme, Photonics Research and Innovation PREIN, decision 320166), Alexander von Humboldt and Otto A. Malm Foundations (A.B.), and the National Science and Technology Council (NSTC), Taiwan, are gratefully acknowledged. Publisher Copyright: © 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.
Anion-π Interactions, Charge Transfer, Crystal Engineering, Phosphonium Salt, Phosphorescence
Other note
Partanen, I, Al-Saedy, O, Eskelinen, T, Karttunen, A J, Saarinen, J J, Mrózek, O, Steffen, A, Belyaev, A, Chou, P-T & Koshevoy, I O 2023, ' Fast and Tunable Phosphorescence from Organic Ionic Crystals ', Angewandte Chemie - International Edition, vol. 62, no. 36, e202305108 .