Spectral properties of binaphthalene–coumarins interconnected through hydrazone linkage

Photophysical properties of new coumarin-3-carbaldehyde (dihydrodinaphtho[2,1-c:1′,2′-e]azepin-N-yl)imines bearing dimethylamino and methoxy groups at position 7 of coumarin were investigated. Dimethylamino derivative exhibits different solvent polarity dependence of fluorescent characteristics for nonpolar, medium polar and highly polar solvents. This effect can be rationalized by diverse charge distribution in the singlet excited state due to its different stabilization by solvation in the solvents of particular group. While 2-fold higher values of Stokes shift were observed for methoxy derivative, its quantum yield of fluorescence is much lower due to high nonradiative decay rate constant of the excited state.

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► The photophysical properties of prepared title compounds have been studied.
► Different fluorescence characteristics dependence on solvent polarity were observed.
► Methoxy derivative has larger values of Stokes shift than dimethylamino derivative.
► However, the quantum yield of fluorescence of the former is much lower.
► The observed properties are promising for monitoring of interphase interactions.