Synthesis and Fluorescent Properties of Multi-Functionalized C<sub>70</sub> Derivatives of C<sub>70</sub>(OCH<sub>3</sub>)<sub>10</sub>[C(COOEt)<sub>2</sub>] and C<sub>70</sub>(OCH<sub>3</sub>)<sub>10</sub>[C(COOEt)<sub>2</sub>]<sub>2</sub>

oleh: Ke Luan, Lu Wang, Fang-Fang Xie, Bin-Wen Chen, Zuo-Chang Chen, Lin-Long Deng, Su-Yuan Xie, Lan-Sun Zheng

Format: Article
Diterbitkan: MDPI AG 2022-04-01

Deskripsi

Due to the partially reduced π-conjugation of the fullerene cage, multi-functionalized fullerene derivatives exhibit remarkable fluorescent properties compared to pristine fullerenes, which have high potential for application in organic light-emitting diodes (OLEDs). In this study two multi-functionalized C<sub>70</sub> derivatives, C<sub>70</sub>(OCH<sub>3</sub>)<sub>10</sub>[C(COOEt)<sub>2</sub>] and C<sub>70</sub>(OCH<sub>3</sub>)<sub>10</sub>[C(COOEt)<sub>2</sub>]<sub>2</sub>, with excellent fluorescence properties, were designed and synthesized. Compared with C<sub>70</sub>(OCH<sub>3</sub>)<sub>10</sub> containing a single kind of functional group, both the C<sub>70</sub>(OCH<sub>3</sub>)<sub>10</sub>[C(COOEt)<sub>2</sub>] and C<sub>70</sub>(OCH<sub>3</sub>)<sub>10</sub>[C(COOEt)<sub>2</sub>]<sub>2</sub> exhibited enhanced fluorescence properties with blue fluorescence emission. The fluorescence quantum yields of the C<sub>70</sub>(OCH<sub>3</sub>)<sub>10</sub>[C(COOEt)<sub>2</sub>] and C<sub>70</sub>(OCH<sub>3</sub>)<sub>10</sub>[C(COOEt)<sub>2</sub>]<sub>2</sub> were 1.94% and 2.30%, respectively, which were about ten times higher than that of C<sub>70</sub>(OCH<sub>3</sub>)<sub>10</sub>. The theoretical calculations revealed that the multi-functionalization of the C<sub>70</sub> increased the S<sub>1</sub>–T<sub>1</sub> energy gap, reducing the intersystem crossing efficiency, resulting in the higher fluorescence quantum yield of the C<sub>70</sub> derivatives. The results indicate that multi-functionalization is a viable strategy to improve the fluorescence of fullerene derivatives.