Biomolecules and nanostructures
The Optical Sciences group studies the interaction of light and matter. Our current focus is on detection and sensing/imaging with an emphasis on the development of integrated photonics. We are part of Twente University's Department of Science and Technology and member of the MESA+ institute.
The role of bridging ligands in light-induced hydrogen generation reactivity for Ru/Pd bimetallic assemblies
Photocatalytic hydrogen production has long been targeted as an attractive way to directly convert solar energy into chemical fuel. A simple H2 generation photocatalyst may be comprised of a light-harvesting Ru(II)-polypyridyl center and a catalytic metal (Pd(II)) center, which are connected by a bridging ligand. Based on this design, two different photocatalysts with different bridging ligands were tested (RuPt1 and RuPt2, Figure 1). RuPt1 was found to be photoactive for hydrogen evolution, whereas RuPt2 not.
Figure 1. Structure of complexes RuPt1 (left) and RuPt2 (right).
In this project, the underlying photophysics determining the distinct photocatalytic performance of RuPt1 and RuPt2 are explored by time resolved spectroscopic methods. Ultrafast transient absorption (TA) reveals fast (ca. 30 ps) directional electron transfer from the peripheral bpy ligands towards the bridging 2,5-tpy ligand in RuPt1. This process is likely competed by a bpy-localized cooling process taking place within ca. 10 ps. A long-lived excited state lifetime (>88 ns) was also observed by time-resolved photoluminescence. On the contrary, the inactivity of RuPt2 is explained by a fast recombination (ca. 100 ps) of the excited chromophore, possibly due to a lowered metal-centered (3MC) deactivation state caused by steric encumbrance.