Synthesis, Characterization, and Photo-Physical Properties of Dendrimers Modified With 1,8-Naphthalimide Derivatives as Novel Fluorescent pH Sensors

This paper reports the synthesis, characterization, application, and photo-physical properties of a novel polyamidoamine zero generation dendrimer (G0) modified with two derivatives of 1,8-naphthalimide. The chemical structures of synthesized dendrimers were confirmed using FTIR, ¹HNMR, ¹³CNMR, UV-Vis, and DSC techniques. The photo-physical properties of the synthesized dendrimers were investigated in various organic solvents having different polarity: N, N-dimethylformamide (DMF), methanol, ethanol, acetone, 1,4-dioxane, and water/DMF (4:1, v/v) solutions. The results showed that the property of the synthesized dendrimers is dependent on the nature of the substituent at C-4 position of the 1,8-naphthalimide molecule and polarity of the solvent. The quantum yield of fluorescence of the novel compounds revealed that a photo-induced electron transfer is proceeding from the core of the dendrimer molecule to the naphthalimide-fluorophore located in its periphery. A positive solvatochromism was obtained for all synthesized compounds and dependence of the fluorescence quantum yield to nature of solvents and substitutions at C-4 position has also been observed. Two modified denderimers with various naphthalimide derivatives were examined as pH sensor and their functioning were analyzed. The results indicated that, the modified dendrimer (G0) with 4-amino and (acetylamino)-1,8-naphthalimide have the potential of being fluorescence pH sensor.