Cyclotriphosphazene cored naphthalimide-BODIPY dendrimeric systems: Synthesis, photophysical and antimicrobial properties

In this work, we report the synthesis and characterization of novel fluorescent naphthalimide (NI)-boron dipyrromethene (BODIPY) dyads and dendrimeric triad systems, based on NI functionalized mono- and distyrylBODIPY derivatives with cyclotriphosphazene core. The structures of new dyads and triad systems were characterized by H-1, C-13 and P-31 NMR. Spectroscopic properties including absorption, emission profiles, fluorescence quantum yield and fluorescence lifetime of NI-BODIPY dyads and NI-BODIPY-cyclotriphosphazene triads were investigated via UV-Vis absorption and fluorescence emission (2D and 3D) techniques. The NI groups on BODIPYs 3- and 5-positions procure the red-shift in absorption and emission spectra compared to BODIPY core. The energy transfer process inhibited the emission of NI moiety and induced the fluorescence from BODIPY unit. The dendrimeric mono- and di-styryl NI-BODIPY-cyclotriphosphazene systems (7 and 8) presented intense absorption bands about 570 and 639 nm respectively both excited from NI and BODIPY subunits. Also, the triad systems (7 and 8) were screened against Gram-positive and Gram-negative bacterial strains. The results demonstrated that naphthalimide-BODIPY-cyclotriphosphazene triads had an antimicrobial activity against Gram-positive Staphylococcus aureus.