Solvated iron metallogrid complex exhibits reversible photocycle

Photoinduced spin switching in metallogrid complexes containing d4-d7 transition metal ion centers has shown promise in molecular electronics for driving information storage and manipulation. Recently, this phenomenon has been introduced in photochemistry for producing stable photoreactants.

Compared to their mononuclear counterparts, however, relatively little is known about the photophysical properties of such polynuclear complexes in solution. New work looks to provide a step forward for their wider use in advanced light-driven reactions.

Naumova et al. report experimental findings describing the ultrafast photoinduced dynamics of a solvated [2x2] iron(II) metallogrid complex. By analyzing transient optical infrared absorption and X-ray emission spectroscopic measurements down to the femtosecond timescale, with the support of density functional theory calculations, the group found that the material exhibits a reversible photocycle, which can be described in terms of independent intra-site transitions.

The Franck-Condon state decays by the formation of a vibrationally-hot high-spin state with coherent behavior within a few picoseconds and thermalizes within tens of picoseconds to yield a metastable high-spin state that lives for hundreds of nanoseconds.

“We were very surprised to realize that the photoexcited metallogrids present this particular combination of photophysical properties, which mononuclear complexes do not. This will greatly widen the scope of practical applications for polynuclear complexes,” said author Sophie Canton.

Canton hopes that their work will spur further scientific interest in designing new ways of binding several metal ions in a single assembly so as to fully control the formation of the metastable state.

In future experiments, they will incorporate other types of measurements based on the ultrafast X-ray absorption and scattering techniques to investigate the role of the surrounding solvent and intramolecular cooperativity.

Source: “Exploring the light-induced dynamics in solvated metallogrid complexes with femtosecond pulses across the electromagnetic spectrum,” by Maria Naumova, Aleksandr Kalinko, Joanne W. L. Wong, Sol Alvarez Gutierrez, Jie Meng, Mingli Liang, Mohamed Abdellah, Huifang Geng, Weihua Lin, Katharina Kubicek, Mykola Biednov, Frederico Lima, Andreas Galler, Peter Zalden, Stefano Checchia, Pierre-Adrien Mante, Jennifer Zimara, Dirk Schwarzer, Serhiy Demeshko, Vadim Murzin, David Gosztola, Martin Jarenmark, Jianxin Zhang, Matthias Bauer, Max Latevi Lawson Daku, Dmitry Khakhulin, Wojciech Gawelda, Christian Bressler, Franc Meyer, Kaibo Zheng, and Sophie E. Canton, Journal of Chemical Physics (2020). The article can be accessed at https://doi.org/10.1063/1.5138641 .