Insights into the different mechanistic stages of light-induced hydrogen evolution of a 5,5′-bisphenanthroline linked RuPt complex

Abstract

Herein, the synthesis in conjunction with the structural, electrochemical, and photophysical characterization of a 5,5´-bisphenanthroline (phenphen) linked heterodinuclear RuPt complex (Ru(phenphen)Pt) as well as its light-driven hydrogen formation activity is...

Stability of Catalytic Centres in Light‐Driven Hydrogen Evolution by Di‐ and Oligonuclear Photocatalysts

“…However, this catalysis is mainly driven by Pt(0) particles, while the tpphzsystem which provides an electron deficient BL and thus acts as molecular catalyst in case of PtCl 2 as CC. [81] Also, the tetranuclear complexes (Figure 11) investigated by Brewer et al possessing electron-poor ligand environments at the CC are stable during catalysis and act as molecular photocatalysts, as proven by the Hg test. [106][107][108] Interestingly, in these systems, three Ru-PS cores significantly lowered catalytic activity compared to the same system based on two Ru-cores, as the TON was decreased by a factor of four.…”

“…A recent report on a related Ru−Pt‐based photocatalyst, [(tbbpy) 2 Ru(phenphen)PtCl 2 ] 2+ (phenphen=5,5’‐bis(1,10‐phenanthroline), see Figure 12), an intramolecular photocatalyst without a reservoir and an electron rich ligand moiety at the CC, showed light‐driven hydrogen evolution. However, this catalysis is mainly driven by Pt(0) particles, while the tpphz‐system which provides an electron deficient BL and thus acts as molecular catalyst in case of PtCl 2 as CC [81] …”

“…[67] Changing the chloride ligands in [(tbbpy) 2 Ru(tpphz)PtX 2 ] 2 + for iodide ligands is not as facile as described for [(tbbpy) 2 Ru-(bbip)PtCl 2 ], where simple addition of excess iodide causes chloride-iodide exchange at the CC (see Figure 13). [58,81] For the tpphz system, a different synthesis strategy has to be employed to introduce iodide ligands, as dynamic exchange of the halide ligands in [(tbbpy) 2 Ru(tpphz)PtX 2 ] 2 + is not possible.…”

“…Exchange of chlorido-to iodido-ligands leads to an enhancement of the catalytic activity by almost a factor of 40 for the tpphz-based system (TON PtCl2 = 7 to TON PtI2 = 276). [61] The addition of TBACl to the very active [(tbbpy) 2 Ru- [49,[59][60][61]81] Chemistry-A European Journal (tpphz)PtI 2 ] 2 + does not lead to any change in catalytic activity, highlighting the very high stability of the PtÀ I bond. However, it was also shown that [(bpy) 2 Ru(tpy)PtI 2 ] 2 + (tpy = 2,2':5',2''-terpyridine) can form pentanuclear structures in the solid state by PtÀ IÀ PtÀ IÀ Pt bridges, highlighting that more than one CC species might be present during catalysis.…”

“…It should be noted that it is very important to exclude direct deactivation of the catalyst by Hg(0). [75,79,80] The following effects of elemental Hg on a PS-BL-CC system, such as i) loss of ligand environment at the CC [81] and ii) loss of the whole CC [60] have already been observed. Furthermore, Hg(0) may for instance reduce the photo-oxidized [Ru(III)(bpy) 3 ] 3 + (bpy = 2,2'-bipyridine) complex under formation of Hg + and [Ru(II)(bpy) 3 ] 2 + , thus acting as a reductive quencher and an electron donor.…”