Synthesis of BODIPY-cyclotetraphosphazene triad systems and their sensing behaviors toward Co(II) and Cu(II)

In the present work, novel distyryl-BODIPY derivatives (2 and 3) containing thiophene and thianaphthene scaffolds were successfully employed to generate triazole-linked BODIPY-cyclotetraphosphazene triad systems (5 and 6). The identity of the newly synthesized compounds was confirmed utilizing H-1 NMR, P-31 NMR and C-13 NMR spectroscopy. Fluorescence spectroscopic techniques were used to investigate the photophysical properties of the targeted compounds. Additionally, the metal sensing behaviour of the triad systems (5 and 6) was determined in THE/water (20:1) via fluorescence spectroscopy. The targeted cyclotetraphosphazenes were found to be selective and sensitive toward cobalt(II) and copper(II) ions over other examined cations. The fluorescence and absorbance titrations (Job's plot) suggested a 1:4 and 1:2 binding stoichiometry (triad:metal) for Cu(II) and Co(II), respectively. The cyclotetraphosphazene cored triad systems revealed potential to detect Co(II) and Cu(II) ions as reversible dual fluorescent sensors (turn-off) in aqueous solution.