N-heterocyclic olefin-functionalized bipyridine introduces intraligand charge-transfer and proton-responsive photophysics into an Ir( <scp>iii</scp> ) complex

Lempereur, Sven;Glaser, Felix;Pižl, Martin;Schöndorf, Leon;Troian-Gautier, Ludovic;et.al.
(2026) Dalton Transactions — Vol. 55, n° 31, p. 11561-11574 (2026)

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  • Lempereur, SvenInstitut de la Matière Condensée et des Nanosciences (IMCN), Molecular Chemistry, Materials and Catalysis (MOST), Université catholique de Louvain (UCLouvain), Place Louis Pasteur 1, bte L4.01.02, 1348 Louvain-la-Neuve, Belgium
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  • Glaser, Felixorcid-logoInstitut de la Matière Condensée et des Nanosciences (IMCN), Molecular Chemistry, Materials and Catalysis (MOST), Université catholique de Louvain (UCLouvain), Place Louis Pasteur 1, bte L4.01.02, 1348 Louvain-la-Neuve, Belgium
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  • Pižl, Martinorcid-logoDepartment of Inorganic Chemistry, University of Chemistry and Technology Prague, Technická 5, 166 28 Prague 6, Czech Republic
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  • Schöndorf, LeonInstitute of General, Inorganic and Theoretical Chemistry, Universität Innsbruck, Innrain 80-82, 6020 Innsbruck, Austria
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  • Troian-Gautier, Ludovicorcid-logoInstitut de la Matière Condensée et des Nanosciences (IMCN), Molecular Chemistry, Materials and Catalysis (MOST), Université catholique de Louvain (UCLouvain), Place Louis Pasteur 1, bte L4.01.02, 1348 Louvain-la-Neuve, Belgium
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Abstract
The development of efficient photosensitizers is central to advancing solar fuel technologies and photo-induced chemical transformations. Herein, we report the synthesis and detailed photophysical investigation of a novel heteroleptic Ir(III) complex, [Ir(ppy) 2 (bpyNHO)] + (Ir-NHO), featuring a 2,2'-bipyridine ligand functionalized with two N-heterocyclic olefin (NHO) moieties. The strong σ-and π-donating character of the NHO groups significantly alters the electronic structure of the complex, while simultaneously introducing proton-responsive sites within the second coordination sphere. Steady-state and time-resolved spectroscopic studies, supported by theoretical calculations, reveal that coplanarity between the NHO fragments and the bipyridine core promotes transition via an intense intraligand charge transfer (ILCT). In comparison with the parent Ir-bpy analogue, Ir-NHO exhibits a pronounced emission blue shift of 60 nm (0.23 eV), arising from destabilization of the HOMO localized on the bpy-NHO ligand. Protonation reversibly suppresses these electronic effects, yielding photophysical properties closely resembling those of the parent complex. These findings highlight the potential of NHO-functionalized ligands for the design of switchable photosensitizers and multifunctional photoactive systems.
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Lempereur, S., Glaser, F., Pižl, M., Schöndorf, L., Seidl, M., Dielmann, F., & Troian-Gautier, L. (2026). N-heterocyclic olefin-functionalized bipyridine introduces intraligand charge-transfer and proton-responsive photophysics into an Ir( <scp>iii</scp> ) complex. Dalton Transactions, 55(31), 11561-11574. https://doi.org/10.1039/d6dt01458e (Original work published 2026)