(Z)-3-(Dicyanomethylene)-4-((5-fluoro-3,3-dimethyl-1-(3-phenylpropyl)-3H-indol-1-ium-2-yl) methylene)-2-(((E)-5-fluoro-3,3-dimethyl-1-(3-phenylpropyl)indolin-2-ylidene)methyl) cyclobut-1-en-1-olate

Abstract

Recent literature on this topic highlights the significance of adding malononitrile moiety and halogen substituents to the squaraine scaffold to create redshifted fluorophores into the near-infrared optical region. Herein, a redshifted hydrophobic squaraine dye is synthesized via a three-step pathway. The reported dye is characterized by spectroscopic techniques, such as 1H NMR, 19F NMR, 13C NMR, and high-resolution mass spectroscopy. Optical properties are also reported using absorbance and fluorescence studies. The hydrophobicity of the dye was studied with absorbance and fluorescence spectroscopy in water–methanol mixtures and showed J-aggregates as the water concentration increased. Density functional theory calculations were conducted to assess its electron delocalization as well as observe the three-dimensional geometry of the dye as a result of the dicyanomethylene modification and the two bulky phenyl groups.