Alkali metal complexes of an enantiopure iminophosphonamide bearing chiral centers at both nitrogen atoms are described. They show bright phosphorescence and thermally activated delayed fluorescence (TADF).

Seeking a sustainable and selective approach for terpene modification, a catalyst deconvolution approach was applied to the Meinwald rearrangement of (+)-limonene oxide as a model substrate to yield dihydrocarvone. In order to identify the most suitable catalyst and reaction conditions, different Lewis acids were evaluated. Bismuth triflate proved to be the most active catalyst under mild reaction conditions, with a low catalyst loading (1 mol%) and a relatively short reaction time (3 h). The optimized reaction conditions were subsequently transferred to other terpene-based epoxides, yielding different bio-based biscarbonyl structures, which constitute interesting and valuable substances, e.g. for polymer synthesis or as fragrances. Monoepoxides derived from ( R )-(−)-carvone and (+)-dihydrocarvone rearranged to the desired products with high selectivities and yields. γ-Terpinene dioxide could be transformed in a double rearrangement to the respective biscarbonyl in moderate yields. A better result was achieved for limonene dioxide after further adjustment of the protocol to reach acceptable yields with a low catalyst loading of 0.1 mol% using 2-methyl tetrahydrofuran as a sustainable solvent. Compared to many procedures described in the literature, this procedure represents a step towards an increased sustainability in terpene modification by considering several principles of Green Chemistry, such as renewable resources, catalysis and mild reaction conditions for elementary chemical transformations. This article is part of a discussion meeting issue ‘Science to enable the circular economy’.

A coumarin functionalized aminodiphosphine has been introduced as a bidentate ligand in coinage metal chemistry. Mono-, di-, and trimetallic copper and silver complexes were synthesized with this ligand. The hybrid character of the ligand led to compounds with rich luminescence properties. These include coumarin-based blue fluorescence, observed as a sole emission in solution at room temperature, and green phosphorescence, which is efficient at low temperatures and dominates the spectra of the metal complexes. In the rigid environment of frozen solutions, the green phosphorescence shows an unusually long (for metal complexes) decay on the seconds timescale in high quantum yield. In addition, a red phosphorescence, which may be assigned to the triplet state localized in the phosphine-M 3 Cl 2 (M=Cu, Ag), is observed for the trinuclear complexes at low temperature. Neither the second-long phosphorescence nor the red emission is observed for the coumarin ligand, thus they must be a result of the coordination to coinage metal clusters. The excited states in these compounds were also investigated by femtosecond transient absorption spectroscopy and quantum chemical calculations.

Highly efficient chemical ligations that operate in water under mild conditions are the foundation of bioorthogonal chemistry. However, the toolbox of suitable reactions is limited. Conventional approaches to expand this toolbox aim at altering the inherent reactivity of functional groups to design new reactions that meet the required benchmarks. Inspired by controlled reaction environments that enzymes provide, we report a fundamentally different approach that makes inefficient reactions highly efficient within defined local environments. Contrasting enzymatically catalyzed reactions, the reactivity controlling self-assembled environment is brought about by the ligation targets themselves�avoiding the use of a catalyst. Targeting [2 + 2] photocycloadditions, which are inefficient at low concentrations and readily quenched by oxygen, short β-sheet encoded peptide sequences are inserted between a hydrophobic photoreactive styrylpyrene unit and a hydrophilic polymer. In water, electrostatic repulsion of deprotonated amino acid residues governs the formation of small selfassembled structures, which enable a highly efficient photoligation of the polymer, reaching ∼90% ligation within 2 min (0.034 mM). Upon protonation at low pH, the self-assembly changes into 1D fibers, altering photophysical properties and shutting down the photocycloaddition reaction. Using the reversible morphology change, it is possible to switch the photoligation "ON" or "OFF" under constant irradiation simply by varying the pH. Importantly, in dimethylformamide, the photoligation reaction did not occur even at 10-fold higher concentrations (0.34 mM). The self-assembly into a specific architecture, encoded into the polymer ligation target, enables a highly efficient ligation that overcomes the concentration limitations and high oxygen sensitivity of [2 + 2] photocycloadditions.