LAUSR

Abstract Two tetra-benzimidazolium salts with bridging 9,10-anthraquinone (1 and 2) were synthesized. The crystal structure of 1 was determined by X-ray analysis. One 38-membered macrocycle in 1 was formed by two 9,10-anthraquinone, four benzimidazoliums and six alkylene groups, in which π···π interactions between two anthraquinone were observed. By contrast, compound 2 adopted an open structure, and it was formed by one 9,10-anthraquinone and four benzimidazolium groups, four alkylene groups and two propyl groups. Additionally, the recognition of anions was investigated using 1 (or 2) as chemosensors via fluorescence spectra, UV/vis spectra, HRMS, 1H NMR and IR spectra. The results indicated that compound 1 can distinguish H2PO4− from other anions by the naked eyes (from colorless to yellow under visible light) or by instruments, and compound 2 was able to differentiate H2PO4− from other anions by instruments.