Highly Luminescent Dinuclear Platinum(II) Complexes Incorporating Bis-Cyclometallating Pyrazine-Based Ligands: A Versatile Approach to Efficient Red Phosphors
Highly Luminescent Dinuclear Platinum(II) Complexes Incorporating Bis-Cyclometallating Pyrazine-Based Ligands: A Versatile Approach to Efficient Red Phosphors
复制标题
DOI：
10.1021/ic401131x
复制
发表时间：
2013-10-07
影响因子：
4.6
通讯作者：
Kozhevnikov, Valery N.
中科院分区：
文献类型：
--
作者：
Culham, Stacey;Lanoe, Pierre-Henri;Kozhevnikov, Valery N.
合成了一系列含二苯基吡嗪桥联配体（（LH 2）-H-n）的双核铂（II）配合物。2，5-二苯基吡嗪（（LH 2）-H-2）和2，3-二苯基吡嗪（（LH 2）-H-3）都能进行两个苯环的环化，每个金属离子与中心杂环的两个氮原子结合，在用二新戊酰基甲烷（dpm）的阴离子处理后，得到式{Pt（dpm）}（2）L-n的络合物。这些化合物是4，6-二苯基嘧啶（（LH 2）-H-1）的类似络合物的异构体。还制备了二苯并-（f，h）喹喔啉（（LH 2）-H-4）、2，3-二苯基-喹喔啉（（LH 2）-H-5）和二苯并[3，2-a：2 '，3'-c]吩嗪（（LH 2）-H-6）的相关配合物，从而研究了苯环捆绑在一起（（LH 2）-H-4和（LH 2）-H-6）和/或从吡嗪到喹喔啉的缀合延伸（（LH 2）-H-5和（LH 2）-H-6）的效果。在所有情况下，相应的单核配合物，Pt（dpm）（LH）-H-n，已被分离出来。所有12种配合物在室温下在溶液中都是磷光的。双核配合物的发射光谱一致红移相比，其单核类似物，是最低的能量吸收带。电化学数据和TD-DFT计算表明，这种效果主要来自稳定的LUMO。第二金属离子的引入还具有显著增加摩尔吸光率的效果，并且在大多数情况下，具有显著增加辐射速率常数的效果。同时，（LH 2）-H-5和（LH 2）-H-6的杂环中共轭的扩展以及（LH 2）-H-4和（LH 2）-H-6中环间键形成所促进的芳香体系的平面化导致吸收和发射光谱进一步红移到对于环化铂（II）络合物来说异常长的波长。这些结果可以为调节和优化d区金属配合物的光学性质提供一种通用的设计策略。
A series of luminescent dinuclear platinum(II) complexes incorporating diphenylpyrazine-based bridging ligands ((LH2)-H-n) has been prepared. Both 2,5-diphenylpyrazine ((LH2)-H-2) and 2,3-diphenylpyrazine ((LH2)-H-3) are able to undergo cyclometalation of the two phenyl rings, with each metal ion binding to the two nitrogen atoms of the central heterocycle, giving, after treatment with the anion of dipivaloyl methane (dpm), complexes of formula {Pt(dpm)}(2)L-n. These compounds are isomers of the analogous complex of 4,6-diphenylpyrimidine ((LH2)-H-1). Related complexes of dibenzo-(f,h)quinoxaline ((LH2)-H-4), 2,3-diphenyl-quinoxaline ((LH2)-H-5), and dibenzo[3,2-a:2',3'-c]phenazine ((LH2)-H-6) have also been prepared, allowing the effects of strapping together the phenyl rings ((LH2)-H-4 and (LH2)-H-6) and/or extension of the conjugation from pyrazine to quinoxaline ((LH2)-H-5 and (LH2)-H-6) to be investigated. In all cases, the corresponding mononuclear complexes, Pt(dpm)(LH)-H-n, have been isolated too. All 12 complexes are phosphorescent in solution at ambient temperature. Emission spectra of the dinuclear complexes are consistently red shifted compared to their mononuclear analogues, as are the lowest energy absorption bands. Electrochemical data and TD-DFT calculations suggest that this effect arises primarily from stabilization of the LUMO. Introduction of the second metal ion also has the effect of substantially increasing the molar absorptivity and, in most cases, the radiative rate constants. Meanwhile, extension of conjugation in the heterocycle of (LH2)-H-5 and (LH2)-H-6 and planarization of the aromatic system favored by interannular bond formation in (LH2)-H-4 and (LH2)-H-6 leads to further red shifts of the absorption and emission spectra to wavelengths that are unusually long for cyclometalated platinum(II) complexes. The results may offer a versatile design strategy for tuning and optimizing the optical properties of d-block metal complexes for contemporary applications.