A new cationic indolium based styryl dye as a fluorescent probe, (E)-2-(4-(dibutylamino)styryl)-1,3,3trimethyl-3H-indol-1-ium iodide (Ci), was synthesized and its anions selectivity/sensitivity properties /molecular interactions with protease enzymes (pepsin/trypsin) and ctDNA has been studied by spectroscopic and computational methods. The fluorescence measurements at different temperatures indicated that quenching mechanism of enzymes by Ci was static. H and S data pointed out electrostatic/hydrophobic interactions with pepsin, and also hydrogen bonds/van der Waals forces with trypsin of Ci. According to Förster's non-radiative energy transfer, binding distances (r) were calculated as 3.53/3.27 nm for pepsin/trypsin. It was also investigated that groove binding is effective in interaction with ctDNA. The results were supported with molecular docking analyzes which have same tendency. Ci has been demonstrated hypsochromic effect with a decrease in solvent polarity and it showed highly selective colorimetric and fluorometric sensing behavior for cyanide ions in organic solvent and aqueous solution. 1 H NMR titration was performed to examine the interaction mechanism between Ci and cyanide ions. The LOD values of cyanide ion were reported as 4.87x10 -9 M and 9.70x10 -7 M in DMSO and DMSO/H2O binary mixture, respectively. In addition, sensitivity of Ci as a chemosensor to cyanide ions was investigated in bitter almond samples.

A new cationic indolium based styryl dye as a fluorescent probe, (E)-2-(4-(dibutylamino)styryl)-1,3,3-trimethyl-3H-indol-1-ium iodide (Ci), was synthesized and its anions selectivity/sensitivity properties /molecular interactions with protease enzymes (pepsin/trypsin) and ctDNA has been studied by spectroscopic and computational methods. The fluorescence measurements at different temperatures indicated that quenching mechanism of enzymes by Ci was static. ΔH and ΔS data pointed out electrostatic/hydrophobic interactions with pepsin, and also hydrogen bonds/van der Waals forces with trypsin of Ci. According to Förster’s non-radiative energy transfer, binding distances (r) were calculated as 3.53/3.27 nm for pepsin/trypsin. It was also investigated that groove binding is effective in interaction with ctDNA. The results were supported with molecular docking analyzes which have same tendency. Ci has been demonstrated hypsochromic effect with a decrease in solvent polarity and it showed highly selective colorimetric and fluorometric sensing behavior for cyanide ions in organic solvent and aqueous solution. 1H NMR titration was performed to examine the interaction mechanism between Ci and cyanide ions. The LOD values of cyanide ion were reported as 4.87x10− 9 M and 9.70x10− 7 M in DMSO and DMSO/H2O binary mixture, respectively. In addition, sensitivity of Ci as a chemosensor to cyanide ions was investigated in bitter almond samples.