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Author: Dietzek, Benjamin × Author: Wächtler, Maria × Type: article × WGL Institute: IPHT ×

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Now showing 1 - 3 of 3
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    Photophysics of BODIPY dyes as readily designable photosensitisers in light-driven proton reduction
    (Basel : MDPI, 2017) Dura, Laura; Wächtler, Maria; Kupfer, Stephan; Kübel, Joachim; Ahrens, Johannes; Höfler, Sebastian; Bröring, Martin; Dietzek, Benjamin; Beweries, Torsten
    A series of boron dipyrromethene (BODIPY) dyes was tested as photosensitisers for light-driven hydrogen evolution in combination with the complex [Pd(PPh3)Cl2]2 as a source for catalytically-active Pd nanoparticles and triethylamine as a sacrificial electron donor. In line with earlier reports, halogenated dyes showed significantly higher hydrogen production activity. All BODIPYs were fully characterised using stationary absorption and emission spectroscopy. Time-resolved spectroscopic investigations on meso-mesityl substituted compounds revealed that reduction of the photo-excited BODIPY by the sacrificial agent occurs from an excited singlet state, while, in halogenated species, long-lived triplet states are present, determining electron transfer processes from the sacrificial agent. Quantum chemical calculations performed at the time-dependent density functional level of theory indicate that the differences in the photocatalytic performance of the present series of dyes can be correlated to the varying efficiency of intersystem crossing in non-halogenated and halogenated species and not to alterations in the energy levels introduced upon substitution.
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    Energy transfer and formation of long-lived 3MLCT states in multimetallic complexes with extended highly conjugated bis-terpyridyl ligands
    (Cambridge : RSC Publ., 2015) Wächtler, Maria; Kübel, Joachim; Barthelmes, Kevin; Winter, Andreas; Schmiedel, Alexander; Pascher, Torbjörn; Lambert, Christoph; Schubert, Ulrich S.; Dietzek, Benjamin
    Multimetallic complexes with extended and highly conjugated bis-2,2′:6′,2′′-terpyridyl bridging ligands, which present building blocks for coordination polymers, are investigated with respect to their ability to act as light-harvesting antennae. The investigated species combine Ru(II)- with Os(II)- and Fe(II)-terpyridyl chromophores, the latter acting as energy sinks. Due to the extended conjugated system the ligands are able to prolong the lifetime of the 3MLCT states compared to unsubstituted terpyridyl species by delocalization and energetic stabilization of the 3MLCT states. This concept is applied for the first time to Fe(II) terpyridyl species and results in an exceptionally long lifetime of 23 ps for the Fe(II) 3MLCT state. While partial energy (>80%) transfer is observed between the Ru(II) and Fe(II) centers with a time-constant of 15 ps, excitation energy is transferred completely from the Ru(II) to the Os(II) center within the first 200 fs after excitation.
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    Determination of side products in the photocatalytic generation of hydrogen with copper photosensitizers by resonance Raman spectroelectrochemistry
    (London : RSC Publishing, 2016) Zhang, Ying; Heberle, Martin; Wächtler, Maria; Karnahl, Michael; Dietzek, Benjamin
    A combination of UV-Vis and resonance Raman spectroscopy in conjunction with electrochemistry is employed to reveal the nature of a side product formed when using heteroleptic Cu(I)-photosensitizers [(P^P)Cu(N^N)]+ for photocatalytic hydrogen generation. It is shown that homoleptic [Cu(N^N)2]+ complexes are formed under oxidative conditions confirming a proposed deactivation pathway.