Experimental and DFT Characterization of Metal-to-Ligand Charge-Transfer Excited States of (Rutheniumammine)(Monodentate Aromatic Ligand) Chromophores

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• 作者：Chia Nung Tsai ; Yi-Han Tian ; Xuetao Shi ; Richard L. Lord ; H. Bernhard Schlegel ; Yuan Jang Chen ; John F. Endicott
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：September 3, 2013
• 年：2013
• 卷：52
• 期：17
• 页码：9774-9790
• 全文大小：898K
• 年卷期：v.52,no.17(September 3, 2013)
• ISSN：1520-510X

文摘

The heretofore unknown emission properties of the metal-to-ligand charge-transfer (MLCT) excited states of several complexes with (ruthenium)(monodentate aromatic ligand, MDA) chromophores are given. Emission spectra and lifetimes in 77 K glasses are reported for several monometallic complexes of the type [Ru(NH₃)_5鈥?i>n(L)_n(MDA)]²⁺ and two bimetallic pyrazine (pz)-bridged [{Ru(NH₃)_4鈥?i>n(L)_n}₂pz]⁴⁺ complexes (L = pz, pyridine, or a multipyridine ligand; MDA = pz or a substituted pyridine, Y-py). The emission maxima occur in the visible and near-IR spectral regions and have much more poorly resolved vibronic sidebands than do related complexes with Ru-bpy chromophores, and the excited-state lifetimes are characteristic of Ru-bpy MLCT excited states in this energy range. The emission yields of trans-[Ru(NH₃)₄(MDA)(pz)]²⁺ (MDA = py or pz) are less than 0.2%, and combined with the other observations, this implies that most of the excited-state quenching occurs in high-energy excited states whose population precedes that of the lowest-energy ³MLCT excited state. The pz-bridged, bimetallic complexes have mixed-valence excited states, and they absorb and emit at lower energies than their monometallic analogues do.