Influence of the Diphosphine Coordination Mode on the Structural and Optical Properties of Cyclometalated Platinum(II) Complexes: An Experimental and Theoretical Study on Intramolecular Pt•••Pt and π•••π Interactions
Influence of the Diphosphine Coordination Mode on the Structural and Optical Properties of Cyclometalated Platinum(II) Complexes: An Experimental and Theoretical Study on Intramolecular Pt•••Pt and π•••π Interactions
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DOI：
10.1021/acs.inorgchem.8b00137
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发表时间：
2018-05-07
影响因子：
4.6
通讯作者：
Notash, Behrouz
中科院分区：
文献类型：
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作者：
Barzegar-Kiadehi, S. Reza;Haghighi, Mohsen Golbon;Notash, Behrouz
在[Pt(CN)(CF3CO2)(SMe2)](1)的反应中，CAN是苯并[h]喹啉酸酯（bhq）， 1a或2-苯基吡啶酸酯（ppy）， 1b，与1等量的二（二苯基膦）甲烷（dppm）反应得到双螯合物[Pt(CN)dppm]CF3CO2(2)。采用不同寻常的反应途径，通过dppm配体的开环和CF3CO2阴离子在铂中心的配位，加入等摩尔量的配合物1和2，制备了双核配合物[Pt-2(CN)(2)(CF3CO2)(2)(mu-dppm)](3)。采用密度泛函理论（DFT）对反应途径和溶剂极性的影响进行了研究。3a的晶体结构表现出相当大的分子内Pt中心点、Pt中心点、Pt中心点和pi中心点、pi中心点的相互作用。将3的晶体结构和形成途径与类似的类似物[Pt-2(bhq)(2)(Cl)(2)(mu-dppm)](5)进行了比较。所有配合物均通过多核磁共振波谱和元素分析进行了全面表征。此外，用x射线晶体学证实了配合物1b、2a、2b、3a和5的晶体结构。二聚化通过改变dppm的配位模式，从配合物2的螯合模式到配合物3和5的桥式模式，对所研究化合物的激发态的影响进行了研究。在3的吸收光谱中出现了一个非常低的能带，该能带被分配给金属金属到配体的电荷转移[MMLCT]；d σ *(Pt-2) -> pi*(CN)]跃迁呈现负溶剂变色，是Pt中心点中心点Pt分子内相互作用的重要证据。在77 K和300 K下，聚甲基丙烯酸甲酯介质和粉末状态下，2a的振动分辨和长寿命发射，以及随时间变化的DFT计算表明，三态配体中心（(LC)-L-3）发射混合了一些MMLCT特征。3中的非结构化短寿命发射是指磷光(MMLCT)- m -3 [d sigma*(Pt-2) -> pi*(CN)]跃迁。配合物5虽然是双核化合物，但由于Pt中心点中心点中心点Pt相互作用距离较远，导致(MLCT)-M-3跃迁的发生逐渐减弱，成为单核单元，发射主要来源于(MLCT)-M-3跃迁。因此，更多的金属参与导致所研究的配合物从LC到MLCT再到MMLCT跃迁时（lambda（abs）和lambda(em): 3a > 3b > 5 > 2a > 2b）的吸收和发射光谱发生更多的红移。
The reaction of [Pt(CN)(CF3CO2)(SMe2)] (1), in which CAN is either benzo[h]quinolinate (bhq), 1a, or 2-phenylpyridinate (ppy), 1b, with 1 equiv of bis(diphenylphosphino)methane (dppm) gave the bischelate complexes [Pt(CN)dppm]CF3CO2 (2). The binuclear complexes [Pt-2(CN)(2)(CF3CO2)(2)(mu-dppm)] (3) were prepared, using an unusual reaction pathway, by the addition of equimolar amount of complexes 1 and 2, through the ring opening of the chelating dppm ligand and coordination of the CF3CO2 anion to the platinum center. The proposed reaction pathway and effect of the solvent polarity were investigated by density functional theory (DFT) calculations. The crystal structure of 3a shows considerable intramolecular Pt center dot center dot center dot Pt and pi center dot center dot center dot pi interactions. The crystal structure and formation pathway toward 3 were compared with the similar analogue [Pt-2(bhq)(2)(Cl)(2)(mu-dppm)] (5). All complexes were fully characterized using multinuclear NMR spectroscopy and elemental analysis. Furthermore, the crystal structures of some complexes including 1b, 2a, 2b, 3a, and 5 were confirmed by X-ray crystallography. The effect of dimerization via a change in the coordination mode of dppm, from a chelate mode in complex 2 to a bridge mode in complexes 3 and 5, upon the excited states of the studied compounds was investigated in their distinguished absorption and emission profiles. The appearance of a remarkably low energy band in the absorption spectra of 3, which was assigned to a metal metal to ligand charge transfer [MMLCT; d sigma*(Pt-2) -> pi*(CN)] transition showing negative solvatochromism, is important evidence for the Pt center dot center dot center dot Pt intramolecular interaction. The vibronically resolved and long-lifetime emission of 2a in poly(methyl methacrylate) media and powder states at 77 and 300 K, along with time-dependent DFT calculations, suggested that the triplet ligand-centered ((LC)-L-3) emission was mixed with some MMLCT character. Unstructured and short-lifetime emission in 3 refers to the phosphorescence (MMLCT)-M-3 [d sigma*(Pt-2) -> pi*(CN)] transition. Although complex 5 is a binuclear compound, the long distance of the Pt center dot center dot center dot Pt interaction caused the occurrence of the (MMLCT)-M-3 transition to fade and act as a mononuclear unit, and the emission originated mostly from the (MLCT)-M-3 transition. As a result, more metal participation leads to more red-shifted absorption and emission spectra of the studied complexes upon going from LC to MLCT to MMLCT transitions (lambda(abs) and lambda(em): 3a > 3b > 5 > 2a > 2b).