Luminescent copper(i) complexes with bisphosphane and halogen-substituted 2,2′-bipyridine ligands

Sarah Keller, Alessandro Prescimone, Henk Bolink, Michele Sessolo, Giulia Longo, Laura Martínez-Sarti, José M. Junquera-Hernández, Edwin C. Constable, Enrique Ortí*, Catherine E. Housecroft

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)
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Abstract

Heteroleptic [Cu(P∧P)(N∧N)][PF6] complexes, where N∧N is a halo-substituted 2,2′-bipyridine (bpy) and P∧P is either bis(2-(diphenylphosphino)phenyl)ether (POP) or 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (xantphos) have been synthesized and investigated. To stabilize the tetrahedral geometry of the copper(i) complexes, the steric demands of the bpy ligands have been increased by introducing 6- or 6,6′-halo-substituents in 6,6′-dichloro-2,2′-bipyridine (6,6′-Cl2bpy), 6-bromo-2,2′-bipyridine (6-Brbpy) and 6,6′-dibromo-2,2′-bipyridine (6,6′-Br2bpy). The solid-state structures of [Cu(POP)(6,6′-Cl2bpy)][PF6], [Cu(xantphos)(6,6′-Cl2bpy)][PF6]·CH2Cl2, [Cu(POP)(6-Brbpy)][PF6] and [Cu(xantphos)(6-Brbpy)][PF6]·0.7Et2O obtained from single crystal X-ray diffraction are described including the pressure dependence of the structure of [Cu(POP)(6-Brbpy)][PF6]. The copper(i) complexes with either POP or xantphos and 6,6′-Cl2bpy, 6-Brbpy and 6,6′-Br2bpy are orange-to-red emitters in solution and yellow-to-orange emitters in the solid state, and their electrochemical and photophysical properties have been evaluated with the help of density functional theory (DFT) calculations. The emission properties are strongly influenced by the substitution pattern that largely affects the geometry of the emitting triplet state. [Cu(POP)(6,6′-Cl2bpy)][PF6] and [Cu(xantphos)(6,6′-Cl2bpy)][PF6] show photoluminescence quantum yields of 15 and 17%, respectively, in the solid state, and these compounds were tested as luminophores in light-emitting electrochemical cells (LECs). The devices exhibit orange electroluminescence and very short turn-on times (<5 to 12 s). Maximum luminance values of 121 and 259 cd m-2 for [Cu(POP)(6,6′-Cl2bpy)][PF6] and [Cu(xantphos)(6,6′-Cl2bpy)][PF6], respectively, were achieved at an average current density of 100 A m-2. External quantum efficiencies of 1.2% were recorded for both complexes.

Original languageEnglish
Pages (from-to)14263-14276
Number of pages14
JournalDalton Transactions
Volume47
Issue number40
Early online date17 May 2018
DOIs
Publication statusPublished - 28 Oct 2018
Externally publishedYes

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