Synthesis and photochromic studies of η6-mesitylene ruthenium(ii) complexes bearing N-heterocyclic carbene ligands with the dithienylethene moiety

An Isolable, Photoswitchable N‐Heterocyclic Carbene: On‐Demand Reversible Ammonia Activation

“…[2] As the activities and selectivities displayed by such catalysts are intrinsically linked to the electronic properties of the NHCs,t he structural modulation of such moieties has been intensely pursued. [8] All of these catalysts were effectively switched between "off" (inactive) and "on" (active) states by irradiation with UV or visible light, respectively.A lthough other DTE-functionalized NHCs have been reported, [9] the corresponding free carbenes have hitherto not been isolable and required in situ generation. [7] Similarly,aRh catalyst bearing the same NHC was found to catalyze hydroborations.…”

Photoswitchable Nitrogen Superbases: Using Light for Reversible Carbon Dioxide Capture

“…Branda and co‐workers showed that more significant reactivity changes were observed for DTE‐based switchable acids/bases when the central ethene unit is directly involved [15] . An effective system was obtained by incorporating the photochromic DTE unit into the backbone of imidazolium salts [16–20] . The corresponding N‐heterocyclic carbenes (NHCs) [21, 22] function as photoswitchable ligands, [23] organocatalysts [24, 25] or for reversible activation of ammonia [21] …”

“…Accordingly, Lewis base adducts between CO 2 and NHIs with imidazoline backbone are sufficiently stable to be isolable, whereas the complexation of CO 2 with benzimidazoline‐2‐imines is endergonic [27] . We therefore envisaged to synthesize photoswitchable NHIs based on the NHC‐scaffold developed by Yam and Bielawski, [16, 18–20, 25] which will allow switching between these two states and thus enable light‐triggered reversible CO 2 capture (Scheme 1).…”

Enhanced bi-stability in a ruthenium alkynyl spiropyran complex

“…Surprisingly, despite the essentially limitless chemical space, the number of structural motifs that have been established as robust molecular switching elements is relatively sparse; prominent examples of the molecular architectures that are able to undergo structural isomerization between two or more distinct states, and have been investigated as potential molecular switches, include azobenzenes, [5][6][7] stilbenes, [8][9][10] spiropyrans, 5,[11][12][13] diarylethenes, [14][15][16] and fulgides. 5,[17][18][19] Although the great majority of photochemically controlled molecular switches explored to date have been based on organic structures, the incorporation of photochromic entities into metal complexes can provide a number of advantages, allowing the combination of magnetic, electrochemical, and optical properties of the metal complexes with the photochromic reaction, [20][21][22][23][24][25] providing access to a broader diversity of molecular architectures and permitting an element of control over the switching characteristics. 26 For example, diarylethene moieties, specifically 5,5′-dithienylperfluorocyclopentene (DTE), which represents perhaps the archetypal molecular switch, has been incorporated into metal alkynyl complexes.…”