878269-61-5Relevant articles and documents
CF3 Substitution of [Cu(P^P)(bpy)][PF6] Complexes: Effects on Photophysical Properties and Light-Emitting Electrochemical Cell Performance
Keller, Sarah,Brunner, Fabian,Junquera-Hernández, José M.,Pertegás, Antonio,La-Placa, Maria-Grazia,Prescimone, Alessandro,Constable, Edwin C.,Bolink, Henk J.,Ortí, Enrique,Housecroft, Catherine E.
, p. 217 - 229 (2018)
Herein, [Cu(P^P)(N^N)][PF6] complexes (P^P=bis[2-(diphenylphosphino)phenyl]ether (POP) or 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (xantphos); N^N=CF3-substituted 2,2′-bipyridines (6,6′-(CF3)2bpy, 6-CF3bpy, 5,5′-(CF3)2bpy, 4,4′-(CF3)2bpy, 6,6′-Me2-4,4′-(CF3)2bpy)) are reported. The effects of CF3 substitution on their structure as well as their electrochemical and photophysical properties are also presented. The HOMO–LUMO gap was tuned by the N^N ligand; the largest redshift in the metal-to-ligand charge transfer (MLCT) band was for [Cu(P^P){5,5′-(CF3)2bpy}][PF6]. In solution, the compounds are weak yellow to red emitters. The emission properties depend on the substitution pattern, but this cannot be explained by simple electronic arguments. Among powders, [Cu(xantphos){4,4′-(CF3)2bpy}][PF6] has the highest photoluminescence quantum yield (PLQY; 50.3 %) with an emission lifetime of 12 μs. Compared to 298 K solution behavior, excited-state lifetimes became longer in frozen Me-THF (77 K; THF=tetrahydrofuran), thus indicating thermally activated delayed fluorescence (TADF). Time-dependent (TD)-DFT calculations show that the energy gap between the lowest-energy singlet and triplet excited states (0.12–0.20 eV) permits TADF. Light-emitting electrochemical cells (LECs) with [Cu(POP)+(6-CF3bpy)][PF6], [Cu(xantphos)(6-CF3bpy)][PF6], or [Cu(xantphos){6,6′-Me2-4,4′-(CF3)2bpy}][PF6] emit yellow electroluminescence. The LEC with [Cu(xantphos){6,6′-Me2-4,4′-(CF3)2bpy}][PF6] had the fastest turn-on time (8 min), and the LEC with the longest lifetime (t1/2=31 h) contained [Cu(xantphos)(6-CF3bpy)][PF6]; these LECs reached maximum luminances of 131 and 109 cd m?2, respectively.
Synthesis, structure, and excited state kinetics of heteroleptic Cu(i) complexes with a new sterically demanding phenanthroline ligand
Kohler, Lars,Hadt, Ryan G.,Hayes, Dugan,Chen, Lin X.,Mulfort, Karen L.
, p. 13088 - 13100 (2017)
In this report we describe the synthesis of a new phenanthroline ligand, 2,9-di(2,4,6-tri-isopropyl-phenyl)-1,10-phenanthroline (bL2) and its use as the blocking ligand in the preparation of two new heteroleptic Cu(i)diimine complexes. Analysis of the CuHETPHEN single crystal structures shows a distinct distortion from an ideal tetrahedral geometry around the Cu(i) center, forced by the secondary phenanthroline ligand rotating to accommodate the isopropyl groups of bL2. The increased steric bulk of bL2 as compared to the more commonly used 2,9-dimesityl-1,10-phenanthroline blocking ligand prohibits intramolecular ligand-ligand interaction, which is unique among CuHETPHEN complexes. The ground state optical and redox properties of CuHETPHEN complexes are responsive to the substitution on the blocking ligand even though the differences in structure are far removed from the Cu(i) center. Transient optical spectroscopy was used to understand the excited state kinetics in both coordinating and non-coordinating solvents following visible excitation. Substitution of the blocking phenanthroline ligand has a significant impact on the 3MLCT decay and can be used to increase the excited state lifetime by 50%. Electronic structure calculations established relationships between ground and excited state properties, and general entatic state concepts are discussed for copper photosensitizers. This work contributes to the growing library of CuHETPHEN complexes and broadens the fundamental understanding of their ground and excited state properties.
The shiny side of copper: Bringing copper(i) light-emitting electrochemical cells closer to application
Bolink, Henk J.,Constable, Edwin C.,Housecroft, Catherine E.,Junquera-Hernández, José M.,Keller, Sarah,La Placa, Maria-Grazia,Ortí, Enrique,Prescimone, Alessandro,Sessolo, Michele
, p. 22631 - 22644 (2020/07/03)
Heteroleptic [Cu(P^P)(N^N)][PF6] complexes, where N^N is 5,5′-dimethyl-2,2′-bipyridine (5,5′-Me2bpy), 4,5,6-trimethyl-2,2′-bipyridine (4,5,6-Me3bpy), 6-(tert-butyl)-2,2′-bipyridine (6-tBubpy) and 2-ethyl-1,10-phenanthroline (2-Etphen) and P^P is either bis(2-(diphenylphosphino)phenyl)ether (POP, PIN [oxydi(2,1-phenylene)]bis(diphenylphosphane)) or 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (xantphos, PIN (9,9-dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphane)) have been synthesized and their NMR spectroscopic, mass spectrometric, structural, electrochemical and photophysical properties were investigated. The single-crystal structures of [Cu(POP)(5,5′-Me2bpy)][PF6], [Cu(xantphos)(5,5′-Me2bpy)][PF6], [Cu(POP)(6-tBubpy)][PF6], [Cu(POP)(4,5,6-Me3bpy)][PF6]·1.5Et2O, [Cu(xantphos)(4,5,6-Me3bpy)][PF6]·2.33CH2Cl2, [Cu(POP)(2-Etphen)][PF6] and [Cu(xantphos)(2-Etphen)][PF6] are described. While alkyl substituents in general exhibit electron-donating properties, variation in the nature and substitution-position of the alkyl group in the N^N chelate leads to different effects in the photophysical properties of the [Cu(P^P)(N^N)][PF6] complexes. In the solid state, the complexes are yellow to green emitters with emission maxima between 518 and 602 nm, and photoluminescence quantum yields (PLQYs) ranging from 1.1 to 58.8percent. All complexes show thermally activated delayed fluorescence (TADF). The complexes were employed in the active layer of light-emitting electrochemical cells (LECs). The device performance properties are among the best reported for copper-based LECs, with maximum luminance values of up to 462 cd m-2 and device half-lifetimes of up to 98 hours.
Synthesis, structure, ultrafast kinetics, and light-induced dynamics of CuHETPHEN chromophores
Kohler, Lars,Hayes, Dugan,Hong, Jiyun,Carter, Tyler J.,Shelby, Megan L.,Fransted, Kelly A.,Chen, Lin X.,Mulfort, Karen L.
, p. 9871 - 9883 (2016/07/06)
Five heteroleptic Cu(i)bis(phenanthroline) chromophores with distinct variation in the steric bulk at the 2,9-phenanthroline position were synthesized using the HETPHEN method, and their ground and excited state properties are described. Analysis of the crystal structures reveals a significant distortion from tetrahedral geometry around the Cu(i) centre which is attributed to favourable aromatic interactions between the two phenanthroline ligands. Ultrafast and nanosecond transient optical spectroscopies reveal that the excited state lifetime can be tuned across two orders of magnitude up to 74 nanoseconds in acetonitrile by changing the 2,9-substituent from hydrogen to sec-butyl. X-ray transient absorption spectroscopy at the Cu K-edge confirmed Cu(i) oxidation to Cu(ii) and revealed a decrease of the Cu-N bond lengths in the excited state. The ground and excited state characterization presented here will guide the integration of CuHETPHEN chromophores into complex electron donor-acceptor architectures.
