Monocyclometalated Gold(III) Monoaryl Complexes—A New Class of Triplet Phosphors with Highly Tunable and Efficient Emission Properties. Issue 9 (30th January 2014)

• Record Type: Journal Article
• Authors: Szentkuti, Alexander; Bachmann, Michael; Garg, Jai Anand; Blacque, Olivier; Venkatesan, Koushik
• Is Part Of: Chemistry. Volume 20:Issue 9(2014)
• Page Start: 2585
• Page End: 2596
• Publication Date: 2014-01-30
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201303673
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Highly tunable and rich phosphorescent emission properties based on the stable monocyclometalated gold(III) monoaryl structural motif are reported. Monochloro complexes of the type <italic>cis</italic>‐[(N^C)Au(C<sub>6</sub>H<sub>2</sub>(CF<sub>3</sub>)<sub>3</sub>)(Cl)] N^C=2‐phenylpyridine (ppy)] (<bold>1</bold>), [N^C=benzo[<italic>h</italic>]quinoline (bzq)] (<bold>2</bold>), [N^C=2‐(5‐Methyl‐2‐thienyl)pyridine (5m‐thpy)] (<bold>3</bold>) were successfully prepared in modest to good yields by reacting an excess of 2, 4, 6‐tris(trifluoromethyl)phenyl lithium (LiFmes) with the corresponding dichloride complexes <italic>cis</italic>‐[(N^C)AuCl<sub>2</sub>]. Subsequent replacement of the chloride ligand in <bold>1</bold> with strong ligand field strength such as cyanide and terminal alkynes resulted in complexes of the type <italic>cis</italic>‐[(ppy)Au(Fmes)(R)] R=CN (<bold>4</bold>), I (<bold>5</bold>), CCC<sub>6</sub>H<sub>5</sub> (<bold>6</bold>) and CCC<sub>6</sub>H<sub>4</sub>N(C<sub>6</sub>H<sub>5</sub>)‐<italic>p</italic> (<bold>7</bold>). Single crystal X‐ray diffraction studies of all the complexes except <bold>7</bold> were performed to further corroborate their chemical identity. Thermogravimetric analysis (TGA) studies of the uncommon <italic>cis</italic> configured aryl alkyne complex <bold>7</bold> confirmed the high stability of this complex. Detailed photophysical investigations carried out in solution at room temperature, at 77 K (2‐MeTHF) in rigidified media, solid state and 5 wt % PMMA revealed the phosphorescent nature of emission in these complexes. Additionally, their behavior was found to be governed based on both the nature of the cyclometalated ligand and the electronic properties of the ancillary ligands. Highly efficient interligand charge transfer in complex <bold>7</bold> provides access to a wide range of emission colors (solvent‐dependent) from deep blue to red with phosphorescence emission quantum yield of 30 % (441 nm) and 39 % (622 nm) in solution and solid state, respectively, and is the highest reported for any Au<sup>III</sup> complexes. DFT and TDDFT calculations carried out further validated the observations and assignments based on the photophysical experimental findings.</p> </abstract>