Dierks Philipp, Päpcke Ayla, Bokareva Olga S, Altenburger Björn, Reuter Thomas, Heinze Katja, Kühn Oliver, Lochbrunner Stefan, Bauer Matthias
Faculty of Science, Chemistry Department and Center for Sustainable Systems Design, Paderborn University, Warburger Strasse 100, 33098 Paderborn, Germany.
Institute of Physics, University of Rostock, Albert-Einstein-Strasse 23-24, 18059 Rostock, Germany.
Inorg Chem. 2020 Oct 19;59(20):14746-14761. doi: 10.1021/acs.inorgchem.0c02039. Epub 2020 Sep 16.
Two new bichromophoric complexes, [Fe(bim-ant)] and [Fe(bim-pyr)] ([H-bim] = 1,1'-(pyridine-2,6-diyl)bis(3-methyl-1-imidazol-3-ium); ant = 9-anthracenyl; pyr = 1-pyrenyl), are investigated to explore the possibility of tuning the excited-state behavior in photoactive iron(II) complexes to design substitutes for noble-metal compounds. The ground-state properties of both complexes are characterized thoroughly by electrochemical methods and optical absorption spectroscopy, complemented by time-dependent density functional theory calculations. The excited states are investigated by static and time-resolved luminescence and femtosecond transient absorption spectroscopy. Both complexes exhibit room temperature luminescence, which originates from singlet states dominated by the chromophore (Chrom). In the cationic pro-ligands and in the iron(II) complexes, the emission is shifted to red by up to 110 nm (5780 cm). This offers the possibility of tuning the organic chromophore emission by metal-ion coordination. The fluorescence lifetimes of the complexes are in the nanosecond range, while triplet metal-to-ligand charge-transfer (MLCT) lifetimes are around 14 ps. An antenna effect as in ruthenium(II) polypyridine complexes connected to an organic chromophore is found in the form of an internal conversion within 3.4 ns from the Chrom to the MLCT states. Because no singlet oxygen forms from triplet oxygen in the presence of the iron(II) complexes and light, efficient intersystem crossing to the triplet state of the organic chromophore (Chrom) is not promoted in the iron(II) complexes.
研究了两种新型双色团配合物[Fe(bim-ant)]和[Fe(bim-pyr)]（[H-bim]=1,1'-(吡啶-2,6-二基)双(3-甲基-1-咪唑-3-鎓)；ant=9-蒽基；pyr=1-芘基），以探索调节光活性铁(II)配合物中激发态行为的可能性，从而设计贵金属化合物的替代品。通过电化学方法和光吸收光谱对这两种配合物的基态性质进行了全面表征，并辅以含时密度泛函理论计算。通过静态和时间分辨发光以及飞秒瞬态吸收光谱对激发态进行了研究。两种配合物在室温下均有发光，其源于以发色团（Chrom）为主的单重态。在阳离子前体配体和铁(II)配合物中，发射波长红移高达110 nm（5780 cm）。这提供了通过金属离子配位调节有机发色团发射的可能性。配合物的荧光寿命在纳秒范围内，而三重态金属到配体电荷转移（MLCT）寿命约为14 ps。在与有机发色团相连的钌(II)多吡啶配合物中发现的天线效应，以在3.4 ns内从Chrom到MLCT态的内转换形式出现。由于在铁(II)配合物和光存在的情况下，三重态氧不会形成单线态氧，因此铁(II)配合物中不会促进有效地系间窜越到有机发色团（Chrom）的三重态。
