Luminescent Iridium–Terpyridine Complexes with Various Bis-Cyclometalated Ligands

Luminescent Iridium–Terpyridine Complexes with Various Bis-Cyclometalated Ligands

A series of luminescent bis-cyclometalated iridium complexes with 2,2′:6′,2″-terpyridine (tpy), [Ir(<i>C^N</i>)<sub>2</sub>(tpy)]PF<sub>6</sub> (<i>C^N</i> = 2-phenylpyridinate (ppy) for <b>1</b>; benzo[h]quinolinate (bzq) for <b>2<...

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Bibliographic Details
Main Authors: Ko Ikeda, Natsumi Yano, Makoto Handa, Yusuke Kataoka
Format: Article
Language:English
Published: MDPI AG 2025-01-01
Series:Molecules
Subjects:
cyclometalated iridium complexes
luminescent properties
crystal structures
photophysical properties
terpyridine ligands
supramolecular interactions
Online Access:https://www.mdpi.com/1420-3049/30/1/193
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Summary:A series of luminescent bis-cyclometalated iridium complexes with 2,2′:6′,2″-terpyridine (tpy), [Ir(<i>C^N</i>)<sub>2</sub>(tpy)]PF<sub>6</sub> (<i>C^N</i> = 2-phenylpyridinate (ppy) for <b>1</b>; benzo[h]quinolinate (bzq) for <b>2</b>; 1-phenylisoquinolinate (piq) for <b>3</b>; and 2-phenylbenzothiazolate (pbt) for <b>4</b>), have been synthesized and structurally characterized. Single-crystal X-ray diffraction analyses reveal that the tpy ligands of <b>1</b>–<b>4</b> are coordinated to the iridium center in a bidentate fashion, and the uncoordinated pendant pyridine rings in the tpy ligands of <b>1</b>–<b>4</b> form intramolecular π-π stacking interactions with a phenyl moiety of <i>C^N</i> ligands. In addition, the pendant pyridine ring in the tpy ligand of <b>1</b> forms an intramolecular hydrogen bonding interaction, unlike in <b>2</b>–<b>4</b>. Of interest, the photophysical properties of <b>1</b>–<b>4</b> are strongly influenced by the <i>C^N</i> ligands; <b>1</b> shows a luminescence band at 572 nm, with a short lifetime (τ) value of 80 nsec and a lower absolute luminescence quantum yield (Φ) of 3.72%, whereas <b>3</b> exhibits an intense luminescence band at 588 nm with a long τ value of 1965 nsec and a moderate Φ value of 9.57%. The density functional theory calculations revealed that the luminescence originates from the triplet metal–ligand to ligand charge transfer (<sup>3</sup>MLL′CT) excited state.
ISSN:1420-3049

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