Effective Light-Harvesting Antennae Based on BODIPY-Tethered Cardo Polyfluorenes via Rapid Energy Transferring and Low Concentration Quenching

Abstract

Light-harvesting antennae (LHA) were demonstrated using polyfluorenes (PFs) modified with borondipyrromethene (BODIPY) dyes tethered to the cardo structures. PFs work as a light absorber and an energy donor to the BODIPY units. The series of BODIPY-tethering PFs via the cardo carbon including homocardo PFs and alternative polymers with fluorene and the cardo fluorene were synthesized, and their optical properties were investigated. Initially, highly efficient energy transferring was observed from the PF main chains to the BODIPY unit (99%). It was found that PFs can work as an efficient light absorber because of the large molar extinction coefficient and cause the rapid energy transfer through the cardo structure. Next, from the comparison with the emission efficiency of the BODIPY units in the series of the synthetic polymers, the favorable position of the BODIPY units was obtained to avoid the concentration quenching: The alternative polymer with cardo fluorene and dialkyl-substituted fluorene showed the largest emission efficiency in this study. Finally, we received the effective LHA with the 9 times larger amplification efficiency compared to that of the unimolar BODIPY unit. The results from the computer modeling suggest that the positions of the BODIPY units via the cardo structure could play a significant role in the inhibition of aggregation and electronic coupling with the BODIPY units, leading to the suppression of concentration quenching. Here is presented the feasibility of the cardo structure in fluorene as a scaffold for designing advanced optical materials.

Synthesis of dual-emissive polymers based on ineffective energy transfer through cardo fluorene-containing conjugated polymers

“…The design and synthesis of the polymers is outlined in Scheme 1. The dibromo fluorene monomers with the BODIPY units were synthesized according to the literature [5]. All monomers were characterized by 1 H, 13 C and 11 B NMR spectroscopies and mass measurements, and it was concluded that pure monomers with the desired structures were obtained.…”

“…2,7-Dibromo-9,9-didodecylfluorene was obtained commercially, and used without further purification. 4,7-Bis-(3-hexylthiophen-2-yl) benzo[1,2,5]thiadiazole, monomers 1 and 2 were prepared according to the literature [5]. All reaction was performed under argon atmosphere.…”

“…Therefore, the pure blue emissions were observed from a series of the modified polyfluorenes with various electron-positive and negative units. In addition, it was also presented that by tethering the fluorophores to polyfluorene via the cardo carbon, the concentration quenching can be avoided [5]. Therefore, there is large possibility to realize the multi-functional emissive polymers based on the preprogrammed design without loss of intrinsic optical properties of the components by undesired energy transfer or electronic interaction.…”

Recent progress in the development of advanced element-block materials

“…As we mentioned above, although organoboron complex-containing conjugated polymers have been studied as a versatile substance for fabricating advanced organic opto-electronic devices because of their superior optical properties and carrier-transport abilities, [73][74][75][76][77][78][79][80][81][82][83][84] ACQ problems remain as critical limitations to the practical use of these materials. In 2001, an AIE-active molecule was first reported.…”

Recent Advances in the Synthesis and Applications of Organoborane Polymers

“…For example, a water-soluble conjugated copolymer (20) was obtained by Suzuki-Miyaura coupling copolymerization of a dibrominated diazaborole (Scheme 4c) [83]. Finally, Chujo and coworkers incorporated BODIPY chromophores as pendant groups to polyfluorenes by Ni-catalyzed Yamamoto or Suzuki-Miyaura coupling methods [84]. The polymers exhibited interesting energy transfer from the BODIPY side chains to the polyfluorene main chain.…”