Zhang Yuzhen, Clavadetscher Jessica, Bachmann Michael, Blacque Olivier, Venkatesan Koushik
Institute of Inorganic Chemistry, University of Zürich , Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
Inorg Chem. 2014 Jan 21;53(2):756-71. doi: 10.1021/ic401841n. Epub 2014 Jan 6.
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≡CR)2] 1a-c, [Pt(pm2tz)(C≡CR)2] 2a-d, [Pt(pm3tz)(C≡CR)2] 3a-c, [Pt(ppim)(C≡CR)2] 4(a, b, e), and [Pt(ppbim)(C≡CR)2] 5(a, b, e), where pmdb =1,1'-dipentyl-3,3'-methylene-dibenzimidazoline-2,2'-diylidene, pm2tz = 1,1'-dipentyl-3,3'-methylene-di-1,2,4-triazoline-5,5'-diylidene, pm3tz = 1,1'-dipentyl-3,3'-methylene-di-1,3,4-triazoline-5,5'-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≡CR)2] where pmim = 1,1'-dipentyl-3,3'-methylene-diimidazoline-2,2'-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-c, 1a-c, 2a-c, and 3a-c in conjunction with the decreasing electron-donating nature of the NHC ligands, pmim > pmdb > pm2tz ≈ 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 ϕem of 27% and 33% in 10 wt % PMMA film, respectively.
本文报道了五组带有具有不同电子性质的N-杂环卡宾（NHC）配体的发光Pt（II）炔基配合物的合成、结构表征、电化学和光物理研究。制备了[Pt（pmdb）（C≡CR）2] 1a - c、[Pt（pm2tz）（C≡CR）2] 2a - d、[Pt（pm3tz）（C≡CR）2] 3a - c、[Pt（ppim）（C≡CR）2] 4（a，b，e）和[Pt（ppbim）（C≡CR）2] 5（a，b，e）类型的配合物，其中pmdb = 1,1'-二戊基-3,3'-亚甲基-二苯并咪唑啉-2,2'-二亚基，pm2tz = 1,1'-二戊基-3,3'-亚甲基-二-1,2,4-三唑啉-5,5'-二亚基，pm3tz = 1,1'-二戊基-3,3'-亚甲基-二-1,3,4-三唑啉-5,5'-二亚基，ppim = 3-戊基-1-吡啶基咪唑啉-2-亚基，ppbim = 3-戊基-1-吡啶基苯并咪唑啉-2-亚基，且R = 4-C6H4F、C6H5、4-C6H4OMe、SiMe3和4-C6H4N（C6H5）2，并研究了NHC配体的电子性质对磷光发射效率的影响。此外，还记录了先前报道的配合物[Pt（pmim）（C≡CR）2]（其中pmim = 1,1'-二戊基-3,3'-亚甲基-二咪唑啉-2,2'-二亚基且R = 4-C6H4F 6a、C6H5 6b和4-C6H4OMe 6c）在纯固体和10 wt% PMMA薄膜中的发射量子效率。通过单晶X射线衍射研究证实了所选配合物具有顺式构型的炔基配体的平面正方形配位几何结构。双卡宾配合物6a - c、1a - c、2a - c和3a - c在发射效率上观察到的适度差异，以及NHC配体给电子性质的降低，pmim > pmdb > pm2tz ≈ pm3tz，可归因于不同配合物之间三重态发射起源的轻微改变。与双卡宾配合物相比，带有吡啶基-NHC配体的配合物4（a，b）和5（a，b）的量子效率显著较低，这是由于三重态多重态的电荷转移特性发生了显著变化。带有二芳基胺苯乙炔的配合物4e和5e在10 wt% PMMA薄膜中的发射量子效率分别高达27%和33%。
