Structural and Electronic Tuning of Luminescent Zn^II Complexes Based on an o-Terphenyl Ligand Motif

Journal Article · Wed Jul 30 00:00:00 EDT 2025 · Journal of the American Chemical Society

DOI:https://doi.org/10.1021/jacs.5c07162· OSTI ID:3012418

Shariaty, Darius A. ^[1]; Djurovich, Peter I. ^[1]; Thompson, Mark E. ^[1]

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1. Univ. of Southern California, Los Angeles, CA (United States)

Here, the structural and photophysical properties of five chiral Zn complexes incorporating a carbazolate (Cz) donor that is electronically decoupled from a pyridyl acceptor by an ortho-connection to a bridging phenylene group are presented. The bidentate ligand in the unsubstituted bis-ligated parent complex was methylated at key positions to constrain the torsional freedom of the donor/acceptor moieties, resulting in three structurally modified bis-ligated derivatives, all exhibiting energy gaps between the singlet and triplet excited states (ΔE_ST) between 22 and 27 meV. Methylation improves the photoluminescence quantum yield (up to 30% in solution), while the low ΔE_ST of these complexes allows for dual-emission properties in all of the bis-ligated derivatives. Structural modification of the Cz/pyridyl ligand was also investigated by linking the unsubstituted bidentate ligand to generate a tetradentate, tetrapodal ligand. The solution-state structure of the tetradentate ligand is similar in its free and ligated forms, featuring a binding site reminiscent of enzymes and metal-sequestering ligands. The resulting tetradentate complex [Zn(N₂R₂)] shows enhanced through-bond conjugation, increasing the ΔE_ST to 89 meV, thereby eliminating the dual-emission characteristics of the bis-ligated complexes. Furthermore, this complex shows a 50-fold improvement in hydrolytic stability in organic solution relative to the parent complex. These compounds and their analyses are intended to enrich the understanding of compounds exhibiting through-space charge transfer and guide the search for earth-abundant metal complexes for applications in photosensitization and luminescence.

• Research Organization: Univ. of Southern California, Los Angeles, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: SC0016450
• OSTI ID: 3012418
• Journal Information: Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 32 Vol. 147; ISSN 0002-7863; ISSN 1520-5126
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

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