Quadruple Functionalization of a Tetraphenylethylene Aromatic Scaffold with Ynamides or Tetracyanobutadienes: Synthesis and Optical Properties

Abstract

Ynamides are useful and versatile building blocks in organic synthesis, from which 1,1,4,4‐tetracyanobutadienes (TCBD) can be prepared for application in molecular electronics. However, their insertion onto multi‐functional molecular scaffold remains a synthetic challenge. In this work, we report the two‐steps synthesis in good isolated yield (64 % overall, 89 % stepwise) of a tetraphenylethylene (TPE) bearing four ynamides, and its further one‐step conversion into the tetra‐TCBD derivative through a [2+2] cycloaddition‐retroelectrocyclization sequence. The concomitant formation of the four ynamides required a specific optimisation of the reaction conditions. Although a poor fluorescent emitter in solution, the tetra‐TCBD compound displayed near‐infrared luminescence in the solid state, which is an attractive optoelectronic feature when considering future applications in molecular electronic devices.

Star-Shaped Triphenylamine–Tetracyanobutadiene–Phenothiazine Push–Pull Systems: Role of Terminal Phenothiazine in Improving Charge Transfer

“…The strong push–pull effects result in electron polarization (also often termed as ground-state charge transfer), resulting in a new low-energy optical transition extending the optical coverage. Making use of the facile reaction and optical properties, they have extensively explored building TCBD-substituted push–pull systems − and polymers as promising materials for photovoltaic applications. − Our groups have explored a wide variety of donor-functionalized TCBD-based molecular systems exhibiting novel optical and excited-state properties including ultrafast charge transfer and intervalence charge transfer properties. − …”

π-Extended indoloquinoxaline functionalized triarylamines with ethynyl and tetracyanobutadiene bridges for p-channel and ambipolar OFETs

“…The easy synthetic methods also led to the formation of a variety of molecules for a wide range of applications. 45,46 These properties encouraged us to use TCBD for transistor applications. TCBD and TAA are strong electron-accepting and donating units; IQ is considered as a weak acceptor or π-terminal unit.…”

Superior Photophysical and Photosensitizing Properties of Nanoaggregates of Weakly Emissive Dyes for Use in Bioimaging and Photodynamic Therapy

“…These chromophores have been widely considered as suitable small molecules for organic electronics, since their orbital energy levels can be easily controlled by judiciously choosing donors and acceptors . However, the synthesized 1,1,4,4-tetracyanobuta-1,3-dienes (TCBDs) have largely been found to be nonemissive/negligible due to radiation-less decay pathways mediated by photoinduced electron transfer/twisted ICT phenomena or charge separation. − Despite the fact that emissive TCBD chromophores have been rarely reported, − their numerous applications continue to demand their synthesis. Nevertheless, Li and co-workers have observed aggregation-induced emission (AIE) with a quantum yield (Φ F ) of 8.5% in hexane during the morphological transition into vesicle/nanotube nanostructures in the aggregate-friendly designed (TCBD) 2 OPV 3 molecule .…”

“…To obtain emissive TCBDs, another approach was made by several groups, i.e., fluorophore conjugation with TCBDs; however, only a few reports have successfully shown luminescence behavior. For example, Trolez and co-workers demonstrated that the ynamide- based TCBD conjugated with fluorophores achieved notable photoluminescence (PL), including an NIR emission in organic apolar solvents, e.g., cyclohexane, with a remarkable quantum yield of 7.6% , and a weak NIR emission in the solid state due to the AIE synthon of tetraphenylethene . Using a similar approach and varying polyaromatics, a significant increase of the luminescence lifetime was demonstrated in the solid state in comparison to that in solution .…”