NDLI: Red emitting $[Ir(C\^N)_{2}(N\^N)]^{+}$ complexes employing bidentate 2,2′:6′,2′′-terpyridine ligands for light-emitting electrochemical cells

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Constable, Edwin C. Schneider, Gabriel E. Housecroft, Catherine E. Bolink, Henk J. Pertegás, Antonio Roldan-carmona, Cristina Zampese, Jennifer A.
Description	Author Affiliation: Constable EC ( Department of Chemistry, University of Basel, Spitalstrasse 51, CH-4056 Basel, Switzerland. catherine.housecroft@unibas.ch.)
Abstract	2,2′:6′,2′′-Terpyridine (tpy), $4′-(4-HOC_{6}H_{4})-2,2′:6′,2′′-terpyridine$ (1), $4′-(4-MeOC_{6}H_{4})-2,2′:6′,2′′-terpyridine$ (2), $4′-(4-MeSC_{6}H_{4})-2,2′:6′,2′′-terpyridine$ (3), $4′-(4-H_{2}NC_{6}H_{4})-2,2′:6′,2′′-terpyridine$ (4) and 4′-(4-pyridyl)-2,2′:6′,2′′-terpyridine (4) act as N^N chelates in complexes of the type $[Ir(C\^N)_{2}(N\^N)][PF_{6}]$ in which the cyclometallating ligand, C^N, is derived from 2-phenylpyridine (Hppy) or 3,5-dimethyl-1-phenyl-1H-pyrazole (Hdmppz). The single crystal structures of eight complexes have been determined, and in each iridium(III) complex cation, the non-coordinated pyridine ring of the tpy unit is involved in a face-to-face π-stacking interaction with the cyclometallated ring of an adjacent ligand. Solution NMR spectra of the $[Ir(ppy)_{2}(N\^N)]^{+}$ complexes are consistent with the presence of a non-classical hydrogen bond between the non-coordinated N-donor of the tpy domain and a CH unit of one pyridine ring of an adjacent $ppy^{−}$ ligand; the presence of the N⋯HC interaction was confirmed in one of the solid-state structures. The pendant pyridine ring of the coordinated tpy undergoes hindered rotation on the NMR timescale at 295 K. In $CH_{2}Cl_{2},$ the complexes are orange or red emitters, with $λ^{em}_{max}$ in the range 580 to 642 nm; photoluminescence quantum yields (PLQY) are <10%, and lifetimes range from 54 to 136 ns. N-Methylation of the pendant 4′-(4-pyridyl) group in $[Ir(dmppz)_{2}(pytpy)][PF_{6}]$ essentially quenches the emission. Light-emitting electrochemical cells (LECs) have been fabricated in a thin film configuration; the emission spectra of the LECs are red-shifted with respect to the PL spectra of the corresponding complex in thin film configuration. For the device incorporating $[Ir(ppy)_{2}(pytpy)][PF_{6}],$ the PL to EL red-shift is extremely large and this is indicative of a different emitting state being involved. The most efficient devices used $[Ir(ppy)_{2}(1)][PF_{6}],$ $[Ir(ppy)_{2}(2)][PF_{6}]$ or $[Ir(ppy)_{2}(3)][PF_{6}]$ in the emissive layer; the devices exhibited rapid turn-on times, but showed relatively low efficiencies in accordance with the solid state photoluminescence quantum yields.
ISSN	14779226
Issue Number	12
Journal	Dalton Trans.
Volume Number	43
e-ISSN	13645447
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2014-03-28
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Chemistry
Content Type	Text
Resource Type	Article
Subject	Inorganic Chemistry

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