A study on fluorescence quenching of LD-425 by aromatic amines in 1,4-dioxane–acetonitrile mixtures

The fluorescence quenching of 4-methyl-7-(4-morpholiny)-2H-pyrano[2,3-b]pyridin-2-one (LD-425) by aromatic amines aniline (AN), dimethyl aniline (DMAN) and diethyl aniline (DEAN) in solvent mixtures of 1,4-dioxane and acetonitrile has been studied at room temperature by steady-state and time-resolved methods. The positive deviation from linearity has been observed in the Stern–Volmer (S–V) plots. Various quenching rate parameters have been determined using the extended S–V equation and are found to be dependent on solvent polarity. The quenching ability of amines increases with increase in their ionization energies. Further, with the use of the sphere of action static quenching model and finite sink approximation model, it is concluded that the bimolecular quenching reactions are due to the presence of both dynamic and static quenching processes. 4-methyl-7-(4-morpholiny)-2H-pyrano[2,3-b]pyridin-2-one (LD-425) [Display omitted] ► S–V plots of LD-425 show positive deviation in DIO–ACN solvent mixtures with all aromatic amines. ► r>R and kq>4πN′R′D indicate that quenching reactions are due to static quenching with diffusion limited. ► The time resolved measurements indicate the presence of the dynamic quenching process. ► The increase in kq with dielectric constant of solvents indicates the charge transfer character. ► Quenching efficiency increasing with amines ionization energies shows electron transfer nature.