Tuning the Luminescent Properties of Pt(II) Acetylide Complexes through Varying the Electronic Properties of N-Heterocyclic Carbene Ligands

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• 作者：Yuzhen Zhang ; Jessica Clavadetscher ; Michael Bachmann ; Olivier Blacque ; Koushik Venkatesan
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：January 21, 2014
• 年：2014
• 卷：53
• 期：2
• 页码：756-771
• 全文大小：820K
• ISSN：1520-510X

文摘

This Article reports the synthesis, structural characterization, electrochemistry, and photophysical investigations of five groups of luminescent Pt(II) alkynyl complexes bearing N-heterocyclic carbene (NHC) ligands with varying electronic properties. Complexes of the type [Pt(pmdb)(C鈮R)₂] 1a鈥?b>c, [Pt(pm2tz)(C鈮R)₂] 2a鈥?b>d, [Pt(pm3tz)(C鈮R)₂] 3a鈥?b>c, [Pt(ppim)(C鈮R)₂] 4(a, b, e), and [Pt(ppbim)(C鈮R)₂] 5(a, b, e), where pmdb =1,1鈥?dipentyl-3,3鈥?methylene-dibenzimidazoline-2,2鈥?diylidene, pm2tz = 1,1鈥?dipentyl-3,3鈥?methylene-di-1,2,4-triazoline-5,5鈥?diylidene, pm3tz = 1,1鈥?dipentyl-3,3鈥?methylene-di-1,3,4-triazoline-5,5鈥?diylidene, ppim = 3-pentyl-1-picolylimidazoline-2-ylidene, and ppbim = 3-pentyl-1-picolylbenzimidazoline-2-ylidene, and R = 4-C₆H₄F, C₆H₅, 4-C₆H₄OMe, SiMe₃, and 4-C₆H₄N(C₆H₅)₂, were prepared, and the consequences of the electronic properties of the NHC ligands on the phosphorescent emission efficiencies were studied. Moreover, the emission quantum efficiencies of the previously reported complexes [Pt(pmim)(C鈮R)₂] where pmim = 1,1鈥?dipentyl-3,3鈥?methylene-diimidazoline-2,2鈥?diylidene and R = 4-C₆H₄F 6a, C₆H₅ 6b, and 4-C₆H₄OMe 6c were also recorded in neat solid and in 10 wt % PMMA film. The square planar coordination geometry with the alkynyl ligands in cis configuration was corroborated for selected complexes by single crystal X-ray diffraction studies. The observed moderate difference in emission efficiencies of the bis-carbene complexes 6a鈥?b>c, 1a鈥?b>c, 2a鈥?b>c, and 3a鈥?b>c in conjunction with the decreasing electron-donating nature of the NHC ligands, pmim > pmdb > pm2tz 鈮?pm3tz, can be attributed to the slight modification of the triplet emission parentage among the different complexes. The quantum efficiencies of complexes 4(a, b) and 5(a, b) bearing pyridyl-NHC ligand were significantly low in comparison to the bis-carbene complexes owing to the significant change in the charge transfer character of the triplet manifold. Complexes 4e and 5e bearing diarylamine phenylacetylenes display high _em of 27% and 33% in 10 wt % PMMA film, respectively.