Fluorescence quenched and boosted by a-PET effect and host−guest complexation respectively in BODIPY-functionalized pillar[5]arene

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A BODIPY -functionalized ethoxypillar[5]arene ( EtP5-BDP ) and a guest compound G containing both of the cyano and triazole moieties were synthesized. The a-PET process between ethoxypillar[5]arene ( EtP5 ) moiety and BODIPY moiety in EtP5-BDP was predicted by DFT/TDDFT calculations before experiment research. It was easier to occur for the a-PET process in polar solvents (e.g. acetone and CH 3 CN). The fluorescence of BODIPY moiety in EtP5-BDP was quenched to varying degrees in toluene, CHCl 3 , acetone and CH 3 CN. Due to the stronger interactions between EtP5 and G in toluene and CHCl 3 , when guest G was added, the fluorescence emissions of BODIPY moiety in EtP5-BDP in these two solvents were boosted but they still not recovered to the original emission level of BODIPY . Therefore, the electron transfer between EtP5 moiety and BODIPY moiety could be weakened but not inhibited completely by the host−guest complexation of EtP5-BDP and G . The Δ G CS was −0.01, −0.23, −0.40 and −0.42 eV for the PET process from EtP5 moiety to BODIPY moiety in toluene, CHCl 3 , acetone and CH 3 CN, respectively. The E C S of EtP5-BDP was lower than S 1 energy state of BODIPY in various solvents. The charge transfer efficiencies (Φ CT ) from EtP5 moiety to BODIPY moiety in toluene, CHCl 3 , acetone and CH 3 CN were 21%, 46%, 64% and 68%, respectively. All the results proved the a-PET process from EtP5 moiety to BODIPY moiety in EtP5-BDP . Compared with pure BODIPY , the fluorescence of EtP5-BDP was quenched by the a-PET process with pillar[5]arene moiety as an electron donor; however, it became stronger when guest G was added due to the electron transfer from pillar[5]arene moiety to G as a result of the host−guest complexation which could weaken the a-PET effect between tP5 and ODIPY moieties. • The a-PET process between EtP5 moiety and BODIPY moiety in EtP5-BDP was predicted by DFT/TDDFT calculations. • The fluorescence of BODIPY moiety in EtP5-BDP was quenched to varying degrees in toluene, CHCl 3 , acetone and CH 3 CN. • The fluorescence emissions of BODIPY moiety in EtP5-BDP in toluene and CHCl 3 were boosted when guest G was added. • The a-PET process in EtP5-BDP was verified by the calculations of Δ G CS , E C S and Φ CT .