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Rapid and efficient analysis of fluoride ion is crucial to providing key information for fluoride ion hazard assessment and pollution management. In this study, we synthesized one symmetrical structure called 1,4-bis(4,5-diphenyl-1H-imidazol-2-yl)benzene (1a) and two asymmetrical structures, namely 2-(4-(4,5-diphenyl-1H-imidazol-2-yl)phenyl)-1H-phenanthro(9,10-d)imidazole (1b) and 2-(4-(4,5-diphenyl-1H-imidazol-2-yl)phenyl)-1H-imidazo(4,5-f)(1,10)phenanthroline (1c), which served as an efficient anion sensor for fluoride ion over a wide range of other anions (Cl-, Br-, I-, NO3-, ClO4-, HSO4-, BF4-, and PF6-) owing to imidazole group in the main backbone. The absorption intensity of compound 1a at λmax 358 nm slightly decreased; however, a new band at λmax 414 nm appeared upon the addition of fluoride ion, while no evident change occurred upon the addition of eight other anions. The photoluminescence intensity of compound 1a at λmax 426 nm was nearly quenched and fluorescence emission spectra were broadened when fluoride ion was added into dimethyl sulfoxide (DMSO) solution of compound 1a. Compared with the optical behaviors of the DMSO solution of compound 1a in the presence of Bu4N+F-, compounds 1b and 1c exhibited considerable sensitivity to fluoride ion due to the increase in coplanarity. Furthermore, compared with the fluorescence emission behaviors of the DMSO solutions of compounds 1a and 1b in the presence of Bu4N+F-, compound 1c exhibited the most significant sensitivity to fluoride ion due to the charge transfer enhancement. Consequently, the detection limits of compounds 1a--1c increased from 5.47 x 10-6 M to 4.21 x 10-6 M to 9.12 x 10-7 M. Furthermore, the largest red shift (75 nm) of the DMSO solution compound 1c in the presence of fluoride ion can be observed. Our results suggest that the increase in coplanarity and the introduction of electron-withdrawing groups to the imidazole backbone can improve the performance in detecting fluoride ion. [ABSTRACT FROM AUTHOR]

A novelseries of donor–acceptor star-shaped conjugatedmacroelectrolytes (CMEs), denoted as 4FTs, including anionic carboxylicacid sodium groups (4FNaT), neutral diethanolamine groups (4FNOHT),and cationic ammonium groups (4FNBrT), were designed, synthesized,and explored as an excellent platform to investigate the impact ofvarious polar pendent groups on self-assembly behaviors. The resultingCMEs with donor–acceptor star-shaped architectures exhibiteddistinct light-harvesting properties. The interactions between 4FTsand TrNBr, a star-shaped monodisperse CME grafted with cationic quaternaryammonium side chains, were investigated in H2O and CH3OH using steady-state, time-resolved fluorescence, dynamiclight scattering (DLS), and transmission electron microscopy (TEM).Highly favored energy transfer has been proven by the excellent spectraloverlap between TrNBr fluorescence and 4FTs absorptions which canbe tuned by adjusting the pendent polar groups and solvents. It issuggested that self-assembled structures are formed between TrNBrand 4FNaT, while there is no obvious change for TrNBr/4FNOHT and TrNBr/4FNBrTin both H2O and CH3OH at low concentrations(<10–6M). This result is confirmed by the changeof the TrNBr and 4FTs fluorescence properties and the time-resolvedfluorescence data. The overall results manifest that at low concentrationsthe self-assembly between TrNBr and 4FTs is dominated by the electrostaticinteractions. This study suggests that the functionalization of pendentpolar groups of star-shaped CMEs has proven to be effective to modulatethe self-assembly behaviors in dilute solutions and thus provide astrategy to further manage the optoelectronic properties. [ABSTRACT FROM AUTHOR]