A survey of heterocyclic hemithioindigo photoswitches is presented identifying a number of structural motives with outstanding property profiles. The highly sought-after combination of pronounced color change, quantitative switching in both directions, exceptional high quantum yields, and tunable high thermal stability of metastable states can be realized with 4-imidazole, 2-pyrrole, and 3-indole-based derivatives. In the former, an unusual preorganization using isomer selective chalcogen-and hydrogen bonding allows to precisely control geometry changes and tautomerism upon switching. Heterocyclic hemithioindigos thus represent highly promising photoswitches with advanced capabilities that will be of great value to anyone interested in establishing defined and reversible control at the molecular level.
Molecular motors transform external energy input into directional motions and offer exquisite precision for nano‐scale manipulations. To make full use of molecular motor capacities, their directional motions need to be transmitted and used for powering downstream molecular events. Here we present a macrocyclic molecular motor structure able to perform repetitive molecular threading of a flexible tetraethylene glycol chain through the macrocycle. This mechanical threading event is actively powered by the motor and leads to a direct translation of the unidirectional motor rotation into unidirectional translation motion (chain versus ring). The mechanism of the active mechanical threading is elucidated and the actual threading step is identified as a combined helix inversion and threading event. The established molecular machine function resembles the crucial step of macroscopic weaving or sewing processes and therefore offers a first entry point to a “molecular knitting” counterpart.
Transition-metal-mediated reductive coupling of nitric oxide (NO (g) ) to nitrous oxide (N 2 O (g) ) has significance across the fields of industrial chemistry, biochemistry, medicine, and environmental health. Herein, we elucidate a density functional theory (DFT)-supplemented mechanism of NO (g) reductive coupling at a copper-ion center, [(tmpa)Cu I (MeCN)] + (1) {tmpa = tris(2pyridylmethyl)amine}. At −110 °C in EtOH (<−90 °C in MeOH), exposing)] 2+ (OO Xray ) complex. Complementary stopped-flow kinetic analysis of the reaction in MeOH reveals an initial mononitrosyl species [(tmpa)Cu(NO)] + (1-(NO)) that binds a second NO molecule, forming a dinitrosyl species [(tmpa)Cu II (NO) 2 ] (1-(NO) 2 ). The decay of 1-(NO) 2 requires an available starting complex 1 to form a dicopper-dinitrosyl species hypothesized to be [{(tmpa)Cu} 2 (μ-NO) 2 ] 2+ (D) bearing a diamond-core motif, en route to the formation of hyponitrite intermediate 2. In contrast, exposing 1 to NO (g) in 2-MeTHF/THF (v/v 4:1) at <−80 °C leads to the newly observed transient metastable dinitrosyl species [(tmpa)Cu II (NO) 2 ] (1-(NO) 2 ) prior to its disproportionation-mediated transformation to the nitrite product [(tmpa)Cu II (NO 2 )] + . Our study furnishes a near-complete profile of NO (g) activation at a reduced Cu site with tripodal tetradentate ligation in two distinctly different solvents, aided by detailed spectroscopic characterization of metastable intermediates, including resonance Raman characterization of the new dinitrosyl and hyponitrite species detected.
A molecular motor setup that allows harnessing the trajectory of directional motor rotation for an active mechanical threading process is presented by Henry Dube and co‐workers in their Research Article (e202201882). The motor is embedded into a macrocycle and its indane‐based rotor fragment then serves as a “revolving door” in the light‐driven rotation. In this way a process akin to macroscopic threading of a needle is miniaturized to the molecular level, offering a first entry point to mechanical molecular knitting or weaving processes.
Oxidative stress emerged as target in drug discovery due to its diverse role in various diseases, such as cardiovascular, neurodegenerative, and autoimmune diseases. During the last decades, considerable progress was made in the development of compounds with the ability to reduce reactive oxygen species (ROS) like superoxide. However, the dismutation of the latter leads to formation of another harmful ROS, hydrogen peroxide, which can be depleted through peroxidase activity. The [a]
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