Rationally Designed Blue Triplet Emitting Gold(III) Complexes Based on a Phenylpyridine‐Derived Framework

Abstract

A series of blue-emitting phosphorescent mono-cyclometalated Au complexes have been successfully synthesized. Tailoring the substitutions on the phenylpyridine (ppy) ligand scaffold with electron-withdrawing fluorine groups on the phenyl ring to achieve stabilization of the HOMO and an electron-donating dimethylamino group on the pyridine ring to destabilize the LUMO resulted in a large energy gap and bestowed on the gold(III) complexes high-energy emission and high quantum efficiencies. The results of cyclic voltammetry studies suggested a predominantly redox event localized on the cyclometalated ligand. Thermogravimetric analysis of selected complexes revealed a high stability up to 280 °C, thus the complexes are suitable for device fabrication through vacuum-deposition. Photophysical investigations performed on all the derivatives revealed phosphorescence emission in neat solid, solution, doped in poly(methyl methacrylate) (PMMA) films at room temperature as well as in rigidified glass media (2-MeTHF) at 77 K. A high photoluminescent quantum efficiency of 28 % was obtained for a complex in PMMA, the highest quantum yield reported for a blue-emitting gold(III) complex.

Thermally Robust and Tuneable Phosphorescent Gold(III) Complexes Bearing (N^N)‐Type Bidentate Ligands as Ancillary Chelates

“…The substitution of an NMe 2 ‐group on the para ‐position of the pyridine ring of complex 4 b resulted in a hypsochromic shift of the lowest energy peak. This is due to the π‐donating effect of the NMe 2 group, which destabilises the LUMO of the complex . Overall, the following trend is observed for the absorption maxima for the complexes 6 b > 3 b ≈ 4 b > 2 b > 5 b .…”

“…The onset of degradation ( T d ) for the samples are provided in the Supporting Information (Table S1 and Figures S2–S6) and show similar temperature ranges between 340–365 °C for the complexes bearing 2 ‐ppy as the ligand. Compared with previously investigated mono‐cyclometalated gold(III) complexes bearing two perfluorinated aryls as ancillary ligands, the studied compounds exhibit a thermal stability that was significantly increased by about 70–100 °C.…”

“…The target complexes 1 a – 6 b were synthesised in 15–85 % yield starting from the corresponding gold(III)‐dichloride precursors I – VI and the successive ligation of the (N^N)‐type ligands bipzH 2 ( a ) or mepzH 2 ( b ) according to the synthetic strategy shown in Scheme . Precursors were synthesised by slight modification of the reported procedures . The final complexes were characterised by 1 H, 13 C and 19 F NMR spectroscopy; HR‐ESI‐MS and elemental analysis.…”

“…The ligands 5,5′‐bis(trifluoromethyl)‐2 H ,2′ H ‐3,3′‐bipyrazole (bipzH 2 , a ), 5,5′‐(1‐methylethylidene)bis(3‐trifluoromethyl)‐1 H ‐pyrazole (mepzH 2 , b ), 2‐(9,9′‐dimethylfluorenyl)pyridine (dmfpy, L2 ), 2‐(dibenzofuran‐4‐yl)pyridine (dbfpy, L3 ), 2‐(9,9′‐dimethylfluorenyl)‐4‐dimethylaminopyridine (dmfapy, L4 ), 2‐(dibenzofuran‐2‐yl)‐4‐(dimethylamino)pyridine (dbfapy, L6 ) and precursors [Au(ppy)Cl 2 ] ( I ), [Au(dmfpy)Cl 2 ] ( II ), [Au(dbfpy)Cl 2 ] ( III ), [Au(dmfapy)Cl 2 ] ( IV ), [Au(btph)Cl 2 ] ( V ), and [Au(dbfapy)Cl 2 ] ( VI ) were synthesised by slight modifications of the reported procedures ,…”

Strongly Luminescent Cyclometalated Gold(III) Complexes Supported by Bidentate Ligands Displaying Intermolecular Interactions and Tunable Emission Energy

“…Many reported bidentate Au III complexes easily undergo decomposition by means of reductive elimination to form homocoupled butadiynes or biaryl species ,. Incorporation of an electron‐withdrawing fluorine atom or fluorine‐containing substituent was suggested to be a possible means to improve the complex stability ,,. This present work also demonstrates that bidentate β‐diketonate‐type ancillary ligands can stabilize [Au III (C^C)] complexes.…”