Redox‐Switchable Complexes Based on Nanographene‐NHCs

Abstract

A series of rhodium and iridium complexes with a N‐heterocyclic carbene (NHC) ligand decorated with a perylene‐diimide‐pyrene moiety are described. Electrochemical studies reveal that the complexes can undergo two successive one‐electron reduction events, associated to the reduction of the PDI moiety attached to the NHC ligand. The reduction of the ligand produces a significant increase on its electron‐donating character, as observed from the infrared spectroelectrochemical studies. The rhodium complex was tested in the [3+2] cycloaddition of diphenylcyclopropenone and methylphenylacetylene, where it displayed a redox‐switchable behavior. The neutral complex showed moderate activity, which was suppressed when the catalyst was reduced.

A redox-switchable catalyst with an ‘unplugged’ redox tag

“…3 N-Heterocyclic carbenes (NHCs) have been particularly fruitful in the design of redox-switchable ligands, 3,4 mostly because their preparation is relatively simple, and because they can be appended to essentially any functional group. 2 a We recently described two NHC ligands fused to naphtalenediimide (NDI) and perylene-diimide (PDI) moieties that were coordinated to rhodium, iridium 5 and gold. 6 The presence of the NDI or PDI units appended to the NHC ligand allowed toggling between three levels of electronic control of the metal, and this was used for studying the redox-switchable catalytic properties of the complexes in the cycloisomerization of alkynoic acids, 5 a and in the hydroamination of alkynes.…”

Fusing perylene diimide with helicenes

“…[33][34][35] With various molecular designs, PDI- [4]helicenes have shown potential in applications such as organic solar cells, 31,34,36,37 organic field-effect transistors, 27,29,32 organic photodetectors, 15 and switchable catalysis. 38 Despite numerous examples of chiral helicene-based materials, chiroptical studies on [4]helicenes are rare because of the rapid interconversion between two enantiomers 39,40 Typically, crafting configurationally stable [4]helicenes involves steric crowding of large substituents in the terminal rings 41,42 or by symmetry-breaking aggregation. 43 As a result, there is a dearth of studies on chiroptical properties of PDI- [4]helicenes.…”

“…Because of the chemical versatility and stability of PDI molecules, post‐functionalization can then be introduced to synthesize molecules such as polymers, 30,31 macrocycles, 32 and graphene nanoribbons 33–35 . With various molecular designs, PDI‐[4]helicenes have shown potential in applications such as organic solar cells, 31,34,36,37 organic field‐effect transistors, 27,29,32 organic photodetectors, 15 and switchable catalysis 38 …”

Dehydrative Coupling of Alcohols by Iridium(III) Complexes with N-Heterocyclic-Pyridine Chelating Ligands Decorated with Naphthalene-Diimide

“…We recently became interested in the use of NDI and PDI functionalities for the preparation of NHC-based redox-switchable catalysts. The presence of the NDI or PDI moieties appended to the NHC ligands allowed toggling the properties of the metals between three electronic levels, and this was used for exploring the redox-switchable properties of the catalysts in the cycloisomerization of alkynoic acids, the hydroamination of alkynes, and the [3+2] cycloaddition of diphenylcyclopropenone and acetylenes . In the incorporation of the NDI moieties into the NHC ligand, we used two strategies, which included the fusion of the NHC ligand at the core positions of the NDI moiety ,, or the functionalization of the NDI at the imide positions .…”

“…The presence of the NDI or PDI moieties appended to the NHC ligands allowed toggling the properties of the metals between three electronic levels, and this was used for exploring the redox-switchable properties of the catalysts in the cycloisomerization of alkynoic acids, the hydroamination of alkynes, and the [3+2] cycloaddition of diphenylcyclopropenone and acetylenes . In the incorporation of the NDI moieties into the NHC ligand, we used two strategies, which included the fusion of the NHC ligand at the core positions of the NDI moiety ,, or the functionalization of the NDI at the imide positions . This last strategy is a simple and efficient one-step procedure, in which commercially available 1,4,5,8-naphthalenetetracarboxylic acid dianhydride (NDA) is condensed with a primary amine.…”