Survey, fluorescence spectra, and solubility of liquid cyanine dyes
We synthesized four liquid cyanine dyes, namely N,N′-didodecyl 44,N,N′-dioctadecyl indolenium 45,N,N′-bis(2,5,8-trioxa-10-octadecanyl)benzoxazolium 50 and benzothiazolium 51, which have a bis(perfluorobutylsulfonyl)imide anion. In the neat form, these liquid dyes exhibit more intense fluorescence at −196 °C than at 25 °C. The liquid N,N′-dialkylated indolenium derivatives 44 and 45 exhibited larger solubility in hexane than the corresponding solid derivatives. In addition, the liquid N,N′-bis(2,5,8-trioxa-10-octadecanyl)benzoxazolium and benzothiazolium derivatives 50 and 51 were more soluble in propanol than the corresponding solid derivatives.