We rationalize the behaviour of protonated merocyanines in water through cross-validation of 1H NMR, UV-Vis and pH measurements, and show their capability to act as reversible photoacids along light/dark cycles can be described by a four-state model.

Out of the 14 lanthanide (Ln) ions, molecular complexes of Ln(IV) were known only for cerium and more recently terbium. Here we demonstrate that the +IV oxidation state is also accessible for the large praseodymium (Pr) cation. The oxidation of the tetrakis(triphenysiloxide) Pr(III) ate complex, [KPr(OSiPh 3 ) 4 (THF) 3 ], 1-Pr Ph , with [N(C 6 H 4 Br) 3 ][SbCl 6 ], affords the Pr(IV) complex [Pr(OSiPh 3 ) 4 (MeCN) 2 ], 2-Pr Ph , which is stable once isolated. The solid state structure, UV−visible spectroscopy, magnetometry, and cyclic voltammetry data along with the DFT computations of the 2-Pr Ph complex unambiguously confirm the presence of Pr(IV).

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Functionalized imidazolium iodide salts (ionic liquids) modified with CH CHCH , CH CCH, or CH CN groups are applied as dopants in the synthesis of CH NH PbI -type perovskites together with a fumigation step. Notably, a solar cell device prepared from the perovskite film doped with the salt containing the CH CHCH side-chain has a power conversion efficiency of 19.21%, which is the highest efficiency reported for perovskite solar cells involving a fumigation step. However, doping with the imidazolium salts with the CH CCH and CH CN groups result in perovskite layers that lead to solar cell devices with similar or lower power conversion efficiencies than the dopant-free cell.

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Four novel polypyridine cobalt(II) complexes were developed based on a hexadentate ligand scaffold bearing either electron‐withdrawing (−CF3) or electron‐donating (−OCH3) groups in different positions of the ligand. Experiments and theoretical calculations were combined to perform a systematic investigation of the effect of the ligand modification on the hydrogen evolution reaction. The results indicated that the position, rather than the type of substituent, was the dominating factor in promoting catalysis. The best performances were observed upon introduction of substituents on the pyridine moiety of the hexadentate ligand, which promoted the formation of the Co(II)H intermediate via intramolecular proton transfer reactions with low activation energy. Quantum yields of 11.3 and 10.1 %, maximum turnover frequencies of 86.1 and 76.6 min−1, and maximum turnover numbers of 5520 and 4043 were obtained, respectively, with a −OCH3 and a −CF3 substituent.

Nature carefully selects specific metal ions for incorporation into the enzymes that catalyze the chemical reactions necessary for life. Hydrogenases, enzymes that activate molecular H2, exclusively utilize Ni and Fe in [NiFe]-, [FeFe]-, and [Fe]-hydrogeanses. However, other transition metals are known to activate or catalyze the production of hydrogen in synthetic systems. Here, we report the development of a biomimetic model complex of [Fe]-hydrogenase that incorporates a Mn, as opposed to a Fe, metal center. This Mn complex is able to heterolytically cleave H2 as well as catalyze hydrogenation reactions. Incorporation of the model into an apoenzyme of [Fe]-hydrogenase results in a [Mn]-hydrogenase with enhanced occupancy-normalized activity over an analogous semi-synthetic [Fe]-hydrogenase. These findings represent the first instance of a non-native metal hydrogenase showing catalytic functionality and demonstrate that hydrogenases based on a manganese active site are viable.