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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >The photochemistry of rhenium(i) tricarbonyl N-heterocyclic carbene complexes
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The photochemistry of rhenium(i) tricarbonyl N-heterocyclic carbene complexes

机译：carbonyl（i）三羰基N-杂环卡宾配合物的光化学

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摘要

The photophysical and photochemical properties of the new tricarbonyl rhenium(i) complexes bound to N-heterocyclic carbene ligands (NHC), fac-[Re(CO)_3(N^C)X] (N^C = 1-phenyl-3-(2-pyridyl)imidazole or 1-quinolinyl-3-(2-pyridyl)imidazole; X = Cl or Br), are reported. The photophysics of these complexes highlight phosphorescent emission from triplet metal-to-ligand (~3MLCT) excited states, typical of tricarbonyl rhenium(i) complexes, with the pyridyl-bound species displaying a ten-fold shorter excited state lifetime. On the other hand, these pyridyl-bound species display solvent-dependent photochemical CO dissociation following what appear to be two different mechanisms, with a key step being the formation of cationic tricarbonyl solvato-complexes, being themselves photochemically active. The photochemical mechanisms are illustrated with a combination of NMR, IR, UV-Vis, emission and X-ray structural characterization techniques, clearly demonstrating that the presence of the NHC ligand is responsible for the previously unobserved photochemical behavior in other photoactive tricarbonyl rhenium(i) species. The complexes bound to the quinolinyl-NHC ligand (which possess a lower-energy ~3MLCT) are photostable, suggesting that the photoreactive excited state is not any longer thermally accessible. The photochemistry of the pyridyl complexes was investigated in acetonitrile solutions and also in the presence of triethylphosphite, showing a competing and bifurcated photoreactivity promoted by the trans effect of both the NHC and phosphite ligands.
机译：与N-杂环卡宾配体（NHC），fac- [Re（CO）_3（N ^ C）X]（N ^ C = 1-phenyl-3）结合的新型三羰基rh（i）配合物的光物理和光化学性质报道了-（2-吡啶基）咪唑或1-喹啉基-3-（2-吡啶基）咪唑; X ＝ Cl或Br）。这些配合物的光物理特性突出了三重金属到配体（〜3MLCT）激发态的磷光发射，这是三羰基rh（i）配合物的典型特征，吡啶基结合的物种显示出的激发态寿命缩短了十倍。另一方面，这些吡啶基结合的物质按照似乎是两种不同的机理显示出溶剂依赖性的光化学CO解离，其中关键步骤是形成阳离子三羰基溶剂合物，它们本身具有光化学活性。结合NMR，IR，UV-Vis，发射和X射线结构表征技术对光化学机理进行了说明，清楚地表明了NHC配体的存在是其他光敏三羰基rh（i ）的物种。与喹啉基-NHC配体（具有较低的〜3MLCT能量）结合的配合物是光稳定的，这表明光反应性的激发态不再是热可及的。在乙腈溶液中以及在亚磷酸三乙酯存在下，对吡啶基配合物的光化学进行了研究，显示了NHC和亚磷酸酯配体的反式促进了竞争性和分叉的光反应性。

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