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Two mononuclear ferric complexes are reported that respond to a pH change with a 27- and 71-fold jump, respectively, in their capacity to accelerate the longitudinal relaxation rate of water-hydrogen nuclei, and this starting from a negligible base value of only 0.06. This unprecedented performance bodes well for tackling the sensitivity issues hampering the development of Molecular MRI. The two chelates also excel in the fully reversible and fatigue-less nature of this phenomenon. The structural reasons for this performance reside in the macrocyclic nature of the hexa-dentate ligand, as well as the presence of a single pendant arm displaying a five-membered lactam or carbamate which show (perturbed) pK a values of 3.5 in the context of this N6 ⇔ ${ \Leftrightarrow }$ N5O1 coordination motif., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Ammonia, NH 3 , is an essential molecule, being part of fertilizers. It is currently synthesized via the Haber-Bosch process, from the very stable dinitrogen molecule, N 2 and dihydrogen, H 2 . This process requires high temperatures and pressures, thereby generating ca 1.6 % of the global CO 2 emissions. Alternative strategies are needed to realize the functionalization of N 2 to NH 3 under mild conditions. Here, we show that boron-centered radicals provide a means of activating N 2 at room temperature and atmospheric pressure whilst allowing a radical process to occur, leading to the production of borylamines. Subsequent hydrolysis released NH 4 + , the acidic form of NH 3 . EPR spectroscopy supported the intermediacy of radicals in the process, corroborated by DFT calculations, which rationalized the mechanism of the N 2 functionalization by R 2 B radicals., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The activation of SF 6 , a potent greenhouse gas, under metal-free and visible light conditions is reported. Herein, mechanistic investigations including EPR spectroscopy, NMR studies and cyclic voltammetry allowed the rational design of a new fluorinating reagent which was synthesized from the 2-electron activation of SF 6 with commercially available TDAE. This new SF 5 -based reagent was efficiently employed for the deoxyfluorination of CO 2 and the fluorinative desulfurization of CS 2 allowing the formation of useful fluorinated amines. Moreover, for the first time we demonstrated that our SF 5 -based reagent could afford the mild generation of Cl-SF 5 gas. This finding was exploited for the chloro-pentafluorosulfanylation of alkynes and alkenes., (© 2022 Wiley-VCH GmbH.)

The first visible-light-mediated synthesis of trifluoromethylselenolated arenes under metal-free conditions is reported. The use of an organic photocatalyst enables the trifluoromethylselenolation of arene diazonium salts using the shelf-stable reagent trifluoromethyl tolueneselenosulfonate at room temperature. The reaction does not require the presence of any additives and shows high functional-group tolerance, covering a very broad range of starting materials. Mechanistic investigations, including EPR spectroscopy, luminescence investigations, and cyclic voltammetry allow rationalization of the reaction mechanism., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)