Iridium(III) Complexes with Phenyl-tetrazoles as Cyclometalating Ligands

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• 作者：Filippo Monti ; Andrea Baschieri ; Isacco Gualandi ; Juan J. Serrano-P茅rez ; Jos茅 M. Junquera-Hern谩ndez ; Domenica Tonelli ; Andrea Mazzanti ; Sara Muzzioli ; Stefano Stagni ; Cristina Roldan-Carmona ; Antonio Perteg谩s ; Henk J. Bolink ; Enrique Ort铆 ; Letizia Sambri ; Nicola Armaroli
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：July 21, 2014
• 年：2014
• 卷：53
• 期：14
• 页码：7709-7721
• 全文大小：671K
• ISSN：1520-510X

文摘

Ir(III) cationic complexes with cyclometalating tetrazolate ligands were prepared for the first time, following a two-step strategy based on (i) a silver-assisted cyclometalation reaction of a tetrazole derivative with IrCl₃ affording a bis-cyclometalated solvato-complex P ([Ir(ptrz)₂(CH₃CN)₂]⁺, Hptrz = 2-methyl-5-phenyl-2H-tetrazole); (ii) a substitution reaction with five neutral ancillary ligands to get [Ir(ptrz)₂L]⁺, with L = 2,2鈥?bypiridine (1), 4,4鈥?di-tert-butyl-2,2鈥?bipyridine (2), 1,10-phenanthroline (3), and 2-(1-phenyl-1H-1,2,3-triazol-4-yl)pyridine (4), and [Ir(ptrz)₂L₂]⁺, with L = tert-butyl isocyanide (5). X-ray crystal structures of P, 2, and 3 were solved. Electrochemical and photophysical studies, along with density functional theory calculations, allowed a comprehensive rationalization of the electronic properties of 1鈥?b>5. In acetonitrile at 298 K, complexes equipped with bipyridine or phenanthroline ancillary ligands (1鈥?b>3) exhibit intense and structureless emission bands centered at around 540 nm, with metal-to-ligand and ligand-to-ligand charge transfer (MLCT/LLCT) character; their photoluminescence quantum yields (PLQYs) are in the range of 55鈥?0%. By contrast, the luminescence band of 5 is weak, structured, and blue-shifted and is attributed to a ligand-centered (LC) triplet state of the tetrazolate cyclometalated ligand. The PLQY of 4 is extremely low (<0.1%) since its lowest level is a nonemissive triplet metal-centered (³MC) state. In rigid matrix at 77 K, all of the complexes exhibit intense luminescence. Ligands 1鈥?b>3 are also strong emitters in solid matrices at room temperature (1% poly(methyl methacrylate) matrix and neat films), with PLQYs in the range of 27鈥?0%. Good quality films of 2 could be obtained to make light-emitting electrochemical cells that emit bright green light and exhibit a maximum luminance of 310 cd m^鈥?. Tetrazolate cyclometalated ligands push the emission of Ir(III) complexes to the blue, when compared to pyrazolate or triazolate analogues. More generally, among the cationic Ir(III) complexes without fluorine substituents on the cyclometalated ligands, 1鈥?b>3 exhibit the highest-energy MLCT/LLCT emission bands ever reported.