Encapsulation of a Quinhydrone Cofactor in the Inner Pocket of Cobalt Triangular Prisms: Combined Light‐Driven Reduction of Protons and Hydrogenation of Nitrobenzene

Abstract

The design of artificial systems that mimic highly evolved and finely tuned natural photosynthetic systems has attracted intensive research interest. A new system was formulated that encapsulates a quinhydrone (QHQ) cofactor in metal-organic hosts based on inspiration from the redox relays of photosystem II. The M L triangular prism hosts provided a special redox-modulated environment for the cofactor localized within the pocket, and the proximity effects of the host-guest interactions facilitated the formation of charge-transfer complexes that are typically very difficult to form in normal homogeneous systems. Extensive electron delocalization and well-controlled redox potential were induced to decrease the overpotential of the metal sites for proton reduction. The excellent activity and stability of the supramolecular systems allow the tandem reductions being combined to efficiently reduce nitrobenzene using active H-sources from the light activation of water.

The Redox Coupling Effect in a Photocatalytic RuII‐PdII Cage with TTF Guest as Electron Relay Mediator for Visible‐Light Hydrogen‐Evolving Promotion

“…Along this line,synthetic strategies have been reported to engineer functional coordination innerspace of nanocages via incorporation of either redox-active or photoactive centers, [31][32][33][34] thus generating MOC-based photocatalytic hostguest systems to imitate natural photosynthesis, [9,[35][36][37][38][39] where the spatially separated electron and/or energy transfer processes can facilitate photocatalytic water/H 2 Ss plitting, as well as other chemical transformations.T oa chieve efficient conversion from solar energy to chemical energy in such hostguest systems,one of the fundamental factors is to control the photo-induced redox events in the confined chemical nanospace. [39,40] So far, many research efforts have been devoted to the exploration of electron and energy transfer processes between host and guest molecules,e ither depending on construction of photoactive hosts or resorting to encapsulation of dye guests,r espectively.…”

Nature is the Cure: Engineering Natural Redox Cofactors for Biomimetic and Bioinspired Catalysis

“…Photosystem II (PS II) couples oxidation of water to the reduction of plastoquinone using a complex array of redox relays. The combination of two chemical reactivities, namely light‐driven proton reduction and hydrogenation of nitrobenzene, was achieved by encapsulating a quinhydrone (QHQ) cofactor inside cobalt triangular prismatic structures . The system features ditopic tridentate amide‐based ligands TPC (Scheme ), which form a M 6 L 3 prismatic host cavity (Co−TPC) upon complexation with cobalt ions.…”

“…The combination of two chemical reactivities, namely light-driven proton reduction and hydrogenation of nitro-benzene, was achieved by encapsulating a quinhydrone (QHQ) cofactor inside cobalt triangular prismatic structures. [19] The system features ditopic tridentate amide-based ligands TPC (Scheme 3), which form a M 6 L 3 prismatic host cavity (CoÀ TPC) upon complexation with cobalt ions. Encapsulation of a QHQ cofactor acting as proton source, inside the hydrophobic cavity of the CoÀ TPC host generates a host-guest charge-transfer system that can efficiently perform light-induced reduction of protons in conjunction with photoredox catalyst Ru(bpy) 3 2 + .…”

Encapsulation of a Quinhydrone Cofactor in the Inner Pocket of Cobalt Triangular Prisms: Combined Light‐Driven Reduction of Protons and Hydrogenation of Nitrobenzene

“…formation of aM 6 L 3 triangular prism consisting of six cobalt ions and three ligands ( Figure 1). [24] Thes ix cobalt ions were situated at the vertices,whereas the three ligands acted as the three quadrangular sides of the triangular prism to form apocket with acalculated height of approximately 9.0 and aC o···Co separation between the top and bottom triangle faces was in an average of 9.4 .T he central CH 2 groups of the three ligands bent outward from the prism, which offer ah ydrophobic cavity for the recognition and localization of the bio-inspired QHQ cofactor [3a, 12] in the host.…”

“…Crystal structure of the molecular triangular prism Co-TPC showing the coordination geometry of the cobalt ions and the pocket, with top and side views of the triangularp rism showing the resulting confined space with open windows. Co green, Ored, Nblue, Cgray and other colors [24]. …”