Carboxylic acid recognition of a tetraamidine having a tetraphenylethylene unit based on aggregation-induced emission

Abstract

A tetraphenylethylene (TPE)-based tetraamidine ( 1a ) for the recognition of dicarboxylic acids has been designed and synthesized. The obtained tetraamidine 1a selectively recognizes α , ω -dicarboxylic acids 2 in a DMSO solution. The improvement of the availability of the single solvent, DMSO, and a higher methylene chain-length selectivity for α , ω -dicarboxylic acids 2 (i.e., selectively recognize 2c - 2f (n = 3–6)) than the TPE-based diamidine 1b which recognizes α , ω -dicarboxylic acids 2c - 2h (n = 3–8) in a DMSO/MeCN mixed solvent was observed. According to the observation of the chain length selectivity and DLS analysis, we proposed the formation of a cyclic aggregate structure (Type A), and the formation of a linear aggregate (Type B) which are supported by the aggregate formation of tetraamdine 1a with the non-flexible terephthalic acid 5 . These fluorescence characteristics of the tetraamidine 1a are applicable for the detection of carboxylic acids. • TPE-based fluorescence sensor for dicarboxylic acids in a polar solvent. • Selective recognition of α , ω -dicarboxylic acids depending on the length of the methylene chain. • Cyclic and linear type aggregates were formed for the recognition of dicarboxylic acids.