A Metal–Organic Tetrahedron as a Redox Vehicle to Encapsulate Organic Dyes for Photocatalytic Proton Reduction

Abstract

The design of artificial systems that mimic highly evolved and finely tuned natural photosynthetic systems is a subject of intensive research. We report herein a new approach to constructing supramolecular systems for the photocatalytic generation of hydrogen from water by encapsulating an organic dye molecule into the pocket of a redox-active metal-organic polyhedron. The assembled neutral Co4L4 tetrahedron consists of four ligands and four cobalt ions that connect together in alternating fashion. The cobalt ions are coordinated by three thiosemicarbazone NS chelators and exhibit a redox potential suitable for electrochemical proton reduction. The close proximity between the redox site and the photosensitizer encapsulated in the pocket enables photoinduced electron transfer from the excited state of the photosensitizer to the cobalt-based catalytic sites via a powerful pseudo-intramolecular pathway. The modified supramolecular system exhibits TON values comparable to the highest values reported for related cobalt/fluorescein systems. Control experiments based on a smaller tetrahedral analogue of the vehicle with a filled pocket and a mononuclear compound resembling the cobalt corner of the tetrahedron suggest an enzymatic dynamics behavior. The new, well-elucidated reaction pathways and the increased molarity of the reaction within the confined space render these supramolecular systems superior to other relevant systems.

Supramolecular Photoinduced Electron Transfer between a Redox‐Active Hexanuclear Metal–Organic Cylinder and an Encapsulated Ruthenium(II) Complex

“…The fact that the decay behavior approximates well to a typical exponential function suggests that the complexation species exhibits an ignored emission. The titration profile of [Ru(dcbpy) 3 ] (10.0 μ m ) upon addition of Ni‐YL up to 50.0 μ m is consistent with a Hill plot . The best fitting of the titration profile suggests a 1:1 host–guest behavior with an association constant ( K ass ) of (6.46±0.13)×10 4 m −1 .…”

A metal-organic cage incorporating multiple light harvesting and catalytic centres for photochemical hydrogen production

“…The photocatalytic H 2 production tests reveal a high TON of 635 in 48 h and prolonged photocatalytic robustness. To the best of our knowledge, such a self-assembled MOC as the single hydrogen-evolving PMD made up of multiple photo- and catalytic metal centres has not been reported yet, although Duan et al 40. have utilized MOCs for photocatalytic H 2 generation via encapsulation of organic dyes.…”

Encapsulation of Organic Dyes within an Electron‐Deficient Redox Metal‐Organic Tetrahedron for Photocatalytic Proton Reduction

“…Irradiation of a solution containing Fl (2.0 mM), Ni‐AFP (10.0 μM), and Et 3 N (10 % in volume) in an EtOH/H 2 O (1 : 1 in volume) solution at 298 K resulted in direct hydrogen generation ,. A high‐efficient way of hydrogen production was achieved at pH=10.5 with Et 3 N (12 % in volume) (Supporting information, Figure S10).…”