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...

A review. In recent decades, mimicking natural photosynthesis by artificial photocatalysis represented a major research direction with the ultimate goal of reducing fossil fuel consumption through efficient solar energy harvesting. To transfer molecular photocatalysis from the lab scale to an industrially relevant process, it is important to overcome instability problems of the catalysts during light‐driven operation. As it is well‐known that many of the typically utilized noble metal‐based catalytic centres (e. g. Pt and Pd) undergo particle formation during (photo)catalysis and thus switch the whole process from a homogeneous into a heterogeneous one, an understanding of the factors governing particle formation is crucially needed. The review therefore focuses on di‐ and oligonuclear photocatalysts bearing a range of different bridging ligand architectures for drawing structure‐catalyst‐stability relationships in light‐driven intramolecular reductive catalysis. In addition, ligand effects at the catalytic centre and their implications for catalytic activity in intermolecular systems will be discussed, as will important insights into the future design of operationally stable catalysts.

The applicability of RuII polypyridyl complexes with appropriate functionalities as substrates for biorthogonal coupling reactions is investigated. In detail, copper(I)‐catalyzed azide–alkyne cycloadditions (CuAAC), strain‐promoted azide–alkyne cycloadditions (SPAAC), and maleimide–thiol coupling reactions of ruthenium complexes are examined. The first examples of SPAAC in which the organic azide is provided by the metal complex are presented. All of the chromophores belong to one easy‐to‐synthesize scaffold, which has proven to be convenient for the application of metal chromophores. The fundamental photophysical properties of the examined compounds do not change with substitution, which is important for the design of chromophore conjugates. Furthermore, the limitations of CuAAC reactions will be discussed with regard to copper impurities in the products formed.

Herein, we present the synthesis, characterization, and light-driven hydrogen evolution activity of two dinuclear Ru-Pt complexes, Rup(ph)pPtX2 (X = Cl, I), comprising a new phenyl-spaced 5,5′-bis-phenanthroline p(ph)p bridging ligand. The two complexes only differ in the nature of the halide ligand at the catalytic center. Structural, photophysical, electrochemical, as well as photochemical characterization techniques revealed that the variations of single components of the intramolecular system provide a strong influence on the stability even in non-catalytic conditions. Interestingly, varying electron density at the catalytic center, mainly influenced by the coordinating halide at the catalytic center, as shown by 195Pt NMR spectroscopy, strongly influences the photocatalytic efficiency. Furthermore, intensive investigations on the potential catalytic mechanism showed that small structural variations (e.g., halide exchange) not only affect catalytic activity but can also switch the main catalytic mechanism from an initially molecular one to a fully heterogeneous, colloid-driven hydrogen evolution.

Six different monoarylated N‐aryl‐1H‐imidazo[4,5‐f][1,10]phenanthroline (Rip) ligands and their corresponding ruthenium complexes [(tbbpy)2Ru(Rip)]2+ Ru(Rip) have been synthesized bearing different aryl substituents on the imidazole unit including electron donating and accepting groups. N,N’‐disubstitution on the imidazole unit yielded five new 1‐aryl‐3‐benzyl‐1H‐imidazo[4,5‐f][1,10]phenanthrolinium bromide (RR'ip)+ ligands and the corresponding ruthenium complexes [(tbbpy)2Ru(RR'ip)]3+ Ru(RR'ip). All complexes were characterized in terms of their structural, photophysical, photochemical and electrochemical properties. The photophysical data revealed a high luminescence quantum yield (21.6–22.8 %) for monoarylated Ru(Rip) complexes compared to [Ru(bpy)3]2+ (9.5 %) under inert conditions. Generating the imidazolium unit, yielding Ru(RR'ip)‐complexes lead to notable loss of quantum yields. Furthermore, we observed an enhanced photostability of Ru(RR'ip) complexes in the case of ortho substituted aryl groups.