Synthesis of two tetra-azolium salts and the recognition performance for guests

One open tetra-benzimidazolium salt ( 1 ) and one cyclic tetra-imidazolium salt ( 2 ) based on tetramethylbenzene were synthesized and characterized. The single crystal structure of 1 was determined by X-ray diffraction. The recognition performance of compounds 1 and 2 for guests ( 1 for o -phenylenediamine (OPD) and 2 for F − ) was investigated via fluorescent spectra, UV/vis spectra, 1 H NMR, HRMS and IR spectra. In particular, a remarkable color change (from colorless to pale brown) was observed in the recognition process of 2 for F − , which indicated that this recognition can not only be carried out by using an instrument but also by the naked eye, and this had great convenience in practice. Two tetra-azolium salts 1 and 2 were synthesized and characterized, and their selective recognition of guests ( o -phenylenediamine and F − ) was investigated.