Optimization of Hydrogen‐Evolving Photochemical Molecular Devices

Abstract

A molecular photocatalyst consisting of a Ru(II) photocenter, a tetrapyridophenazine bridging ligand, and a PtX2 (X=Cl or I) moiety as the catalytic center functions as a stable system for light-driven hydrogen production. The catalytic activity of this photochemical molecular device (PMD) is significantly enhanced by exchanging the terminal chlorides at the Pt center for iodide ligands. Ultrafast transient absorption spectroscopy shows that the intramolecular photophysics are not affected by this change. Additionally, the general catalytic behavior, that is, instant hydrogen formation, a constant turnover frequency, and stability are maintained. Unlike as observed for the Pd analogue, the presence of excess halide does not affect the hydrogen generation capacity of the PMD. The highly improved catalytic efficiency is explained by an increased electron density at the Pt catalytic center, this is confirmed by DFT studies.

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

“…Moreover, integrating six catalytic Pd centres in a whole cage may endow them with synergistic durability on structural deformation during catalysis on a Pd-centre, where dissociation of Pd–N bond and formation of hydride intermediate may occur1221232425. The stability of MOC-16 is also confirmed by an Hg-test, where the 1 H NMR spectra of MOC-16 recorded before and after the treatment with excess Hg in DMSO for 9 h shows no destruction of MOC-16 (Supplementary Fig.…”

“…To date, many active bimetallic PMDs, such as Ru–Pt121421, Ru–Pd13232425, Ru–Rh26, Ru–Co15 and Ir–Co27 complexes, have been developed for homogenous catalysis. Considering the multiple electrons transfer and accumulation required for H 2 evolution, many efforts are made to improve the effective and directional electron transfer from light absorbing centres to catalytic metal centres282930.…”

Functional Dimming of Pincer‐Shaped Bibenzimidazole‐Ruthenium(II) Complexes with Improved Anion‐Sensitive Luminescence

“…[7,8] On the one hand, polypyridyl-ruthenium(II) complexes are widely applicable molecular tools for the introduction of light in technological and biological applications [9][10][11][12] because of their well-known photophysical properties and generally long-lived excited states, in which light energy is absorbed and provided for chemical conversions. [13,14] On the other hand, the vast synthetic variability of the general tris(diimine) framework allows the adjustment of a chromophore for a distinct application. [15][16][17] For example, 2,2′-bibenzimidazole ligands provide an elegant direct connection between a cisdiimine function for coordination to a ruthenium center with and XRD studies.…”

Ruthenium Imidazophenanthrolinium Complexes with Prolonged Excited‐State Lifetimes

“…Therefore, another requirement for new polypyridyl ruthenium chromophores arises, that is, (5) the excited state should be stable to quenching by oxygen. [24] For detailed mechanistic investigations of the underlying principles of light-induced catalysis, photochemical molecular devices (PMDs) consisting of a photocenter, a bridging ligand, and a coordinated catalytic center have great potential. [25] We recently reported the synthesis of the new ruthenium complex [(tbbpy) 2 Ru(bbip)][PF 6 ] 3 {1; tbbpy = 4,4Ј-di-tertbutyl-2,2Ј-bipyridine, bbip = 1,3-(bisbenzyl)-1H-imidazo [4,5-f] [1,10]phenanthrolinium; Figure 1}, which already satisfies requirements (1)- (4).…”