Dual colorimetric and fluorescent determination of iron (III) using a novel squaraine dye

A novel squaraine dye, 6-carboxy-2-[[3-[1,3-dihydro-3,3-dimethy-1-ethyl-2H-indol-2-ylidene)methyl]-2-hydroxy-4-oxo-2-cyclobuten-1-ylidene]methyl]-3,3-trimethy-3H-indolium, has been synthesized. The squaraine dye was found to be a dual colorimetric and fluorescent probe for the determination of iron (III) in CH₃CH₂OH/H₂O (4:1, v/v) exhibiting high selectivity and sensitivity. The binding of squaraine dye +Fe³⁺ was studied by a Job’s plot and Fourier transform infrared and ¹H nuclear magnetic resonance spectroscopies. The result indicates that the squaraine dye may be utilized as a naked-eye and real-time probe for the efficient determination of Fe^3+.