Photochemistry of [Ru(pytz)(btz)2]2+ and Characterization of a κ1-btz Ligand-Loss Intermediate

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• 作者：Paul A. Scattergood ; Usman Khushnood ; Amina Tariq ; David J. Cooke ; Craig R. Rice ; Paul I. P. Elliott
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：August 1, 2016
• 年：2016
• 卷：55
• 期：15
• 页码：7787-7796
• 全文大小：554K
• 年卷期：0
• ISSN：1520-510X

文摘

We report the synthesis, characterization, and photochemical reactivity of the triazole-containing complex [Ru(pytz)(btz)₂]²⁺ (1, pytz = 1-benzyl-4-(pyrid-2-yl)-1,2,3-triazole, btz = 1,1′-dibenzyl-4,4′-bi-1,2,3-triazolyl). The UV–vis absorption spectrum of 1 exhibits pytz- and btz-centered ¹MLCT bands at 365 and 300 nm, respectively. Upon photoexcitation, acetonitrile solutions of 1 undergo conversion to the ligand-loss intermediate, trans-[Ru(pytz)(κ²-btz)(κ¹-btz)(NCMe)]²⁺ (2, Φ₃₆₃ = 0.013) and ultimately to the ligand-loss product trans-[Ru(pytz)(btz)(NCMe)₂]²⁺ (3), both of which are observed and characterized by ¹H NMR spectroscopy. Time-dependent density functional theory calculations reveal that the S₁ state of the complex has primarily HOMO → LUMO pytz-based ¹MLCT character. Data show that the ³MLCT and ³MC states are in close energetic proximity (≤0.11 eV to 2 d.p.) and that the T₁ state from a single-point triplet state calculation at the S₀ geometry suggests ³MC character. Optimization of the T₁ state of the complex starting from the ground state geometry leads to elongation of the two Ru–N(btz) bonds cis to the pytz ligand to 2.539 and 2.544 Å leading to a pseudo-4-coordinate ³MC state rather than the ³MLCT state. The work therefore provides additional insights into the photophysical and photochemical properties of ruthenium triazole-containing complexes and their excited state dynamics.