Environment-sensitive indolenine-based hemisquaraine dyes: Synthesis, molecular structure, and spectral properties

Environment-sensitive fluorescent dyes are widely used in biomedical research, clinical diagnostics, molecular and cellular biology, analytical and bioanalytical chemistry. Many sensing dyes in the series of cyanines, styryls, BODIPY, squaraines, fluoresceins, and rhodamines among others have been developed and employed for these applications. Meanwhile, push-pull hemisquaraine dyes have been only moderately explored as the environment sensors. Herein, we developed a series of hemisquaraine dyes containing methylamino (MeH), dimethylamino (MeMe), phenylamino (PhH), phenylmethylamino (PhMe), and diphenylamino (PhPh) groups. These substituents were found to strongly affect sensitivity of the dyes towards H-bond formation, polarity, pH, viscosity, and the presence of bovine serum albumin (BSA), which aids the development of sensors for particular applications.

Automated summary

Environment-sensitive fluorescent dyes are widely used in various fields including biomedical research and clinical diagnostics. While many sensing dyes have been developed and employed, the exploration of push-pull hemisquaraine dyes as environment sensors is still limited.