Evaluating the Merit of a Syringol Derived Fluorophore as a Charge Transfer Probe for Detection of Serum Albumins.

In this article a syringol-π-benz[e]indolium based donor-acceptor fluorophore has been reported. The fluorophore shows a solvent polarity dependent change in the absorption and emission spectra in solution. A combined spectroscopic and time dependent density functional theory (TDDFT) studies reveal higher dipole moment of the fluorophore in the excited state, resulting positive solvatochromism. In physiological pH, the phenol group in the fluorophore is easily deprotonated owing to the electron pulling effect of the substituents. Consequently, the phenolate (PhO-) becomes a strong active donor in the new donor-acceptor pair. In aqueous solution, the new phenolate fluorochrome shows negligible fluorescence due to energy loss via non-radiative pathways from the low-lying polar excited states. The fluorochrome can detect human and bovine serum albumins in physiological buffer solution with high selectivity. The underlying mechanism of human serum albumin (HSA) detection was estimated to be strong (1.46 × 10