A pH-Sensitive Fluorescent Chemosensor Turn-On Based in a Salen Iron (III) Complex: Synthesis, Photophysical Properties, and Live-Cell Imaging Application.

pH regulation is essential to allow normal cell function, and their imbalance is associated with different pathologic situations, including cancer. In this study, we present the synthesis of 2-(((2-aminoethyl)imino)methyl)phenol (HL1) and the iron (III) complex (Fe(L1)Br, ()), confirmed by X-ray diffraction analysis. The absorption and emission properties of complex were assessed in the presence and absence of different physiologically relevant analytes, finding a fluorescent turn-on when OH was added. So, we determined the limit of detection (LOD = 3.97 × 10 M), stoichiometry (1:1), and association constant (K = 5.86 × 10 M). Using DFT calculations, we proposed a spontaneous decomposition mechanism for . After characterization, complex was evaluated as an intracellular pH chemosensor on the human primary gastric adenocarcinoma (AGS) and non-tumoral gastric epithelia (GES-1) cell lines, finding fluorescent signal activation in the latter when compared to AGS cells due to the lower intracellular pH of AGS cells caused by the increased metabolic rate. However, when complex was used on metastatic cancer cell lines (MKN-45 and MKN-74), a fluorescent turn-on was observed in both cell lines because the intracellular lactate amount increased. Our results could provide insights about the application of complex as a metabolic probe to be used in cancer cell imaging.