Fabrication Of A Supramolecular Artificial Light-harvesting System Based On Pillar[5]arene And Its Application For Organic Photocatalysis

Supramolecular self-assembly refers to the process by which multiple molecular units spontaneously associate into highly ordered molecular aggregates through intermolecular interactions.It can improve assembly efficiency as well as avoid tedious and complex synthesis.What's more,by adjusting the structure of a single molecular unit and non-covalent bonding,the structure and performance of the assembly can be accurately controlled.Therefore,this "bottom-up" supramolecular self-assembly strategy is more beneficial to the construction of multi-dimensional functional nanomaterials,which have played an increasingly important role in many fields such as drug delivery systems,chemical sensing,liquid crystal materials,smart window materials and photocatalysis.With the development of a new generation of host macrocyclic molecules,supramolecular assemblies based on water-soluble pillar[5]arene through host-guest interaction have attracted increasingly interests in recent years.In this paper,an artificial light-harvesting system is constructed based on the host-guest recognition of the water-soluble pillar[5]arene,and the captured energy is applied to the field of organic photocatalysis,which is of great significance for in-depth understanding and mimicking natural photosynthesis.The research includes the following two parts:In the first part,we report the fabrication of a novel artificial light-harvesting system based on the noncovalent supramolecular assembly between a water-soluble pillar[5]arene(WP5)and a bola-type tetraphenylethylene-functionalized dialkyl ammonium derivative(TPEDA),which could realize two-step sequential energy-transfer process in aqueous environment.Due to the unique property of aggregation-induced emission(AIE)effect,TPE analogues in the aggregated form can exhibit strong emission,which makes TPEDA a remarkable donor in water.Meanwhile,WP5 could function as an ideal host towards TPEDA to lower its critical aggregation concentration as well as strengthen the AIE effect.When WP5 was added into the aqueous solution of TPEDA,stable host-guest inclusion complex could be formed and further self-assemble into supramolecular nanoparticles.Driven by the noncovalent interaction,an energy acceptor,the hydrophobic fluorescent dye Eosin Y(ESY),could be successfully entrapped into the hydrophobic core of the formed WP5?TPEDA vesicles.Because of the well overlap between the emission band of the WP5?TPEDA complex and the absorption band of ESY,efficient one-step energy-transfer process could take place from WP5?TPEDA vesicles to ESY.Furthermore,a two-step sequential energy-transfer process could also be realized by the simultaneous encapsulation of the hydrophobic dye Nile Red(Ni R)as the second energy acceptor.Thus,this two-step energy-transfer process could initially take place from WP5?TPEDA vesicles to ESY and then to Ni R at a relatively high energy-transfer efficiency with the donor/acceptor ratio [TPEDA]/[ESY]/[Ni R] = 200:1:1.In the second part,by adjusting the donor / acceptor ratio,under the condition of [TPEDA]/[ESY]/[Ni R] = 100:5:2,the WP5?TPEDA-ESY-Ni R system can realize strong white light emission,with the coordinates in the chromaticity diagram of(0.33,0.33),which has potential applications in the field of white light emitting materials.More importantly,because the AIE effect effectively avoids the phenomenon of fluorescence quenching and promotes energy transfer process efficiently,the constructed artificial light-harvesting system can be utilized as a nanoreactor and a high-efficiency catalyst for the dehalogenation of ?-bromoacetophenone.By optimizing the reaction conditions,the reaction can reach a yield of 96% in the water medium.This work provides a theoretical basis for understanding and mimicking natural photosynthesis process deeply.In summary,we have constructed an artificial light-harvesting system with a two-step sequential energy transfer process based on a supramolecular self-assembly strategy and host-guest recognition interaction of water-soluble pillar[5]arene.Futhermore,the captured energy could initially utilized in the filed of white light emission and organic photocatalysis.In the future,we will continue to develop new functional nanomaterials based on water-soluble pillar[5]arene for application in the field of chiral catalysis,and further strengthen the interdisciplinary nature of supramolecular chemistry with physics and biology,which provides a new direction and perspective for understanding and mimicking the internal mechanism of life.