Solvatochromic properties of a new isocyanonaphthalene based fluorophore

The photophysical properties of a new naphthalene based fluorophore, namely the 1-amino-5-isocyanonaphthalene (ICAN) investigated by steady-state and time-resolved fluorescence methods are reported. The molecule showed positive solvatochromic properties, that is a more than Δ v ¯ = 4800  cm − 1 red-shift of the emission maximum was observed (from 409 nm in hexane to 513 nm in water). The fluorescence quantum efficiency was found to decrease with increasing solvent polarity, from an excellent ΦF = 0.95 in 1,4-dioxane to ΦF = 0.04 in water. The Kamlet–Taft theory turned out to give the most appropriate description of the solvatochromic properties of the ICAN in various solvents including both protic and non-protic solvents. By carrying out experiments in cyclohexane/tetrahydrofuran binary mixtures of different compositions, evidence was found for the preferential solvation of ICAN. Based on laser light flash photometry measurements the radiative decay rate of ICAN was determined for six different solvents of largely different polarity. The decay rates show only minor solvent dependence and the life-times of the excited states are in the order of 10 ns which are in good agreement with the calculated values. The practical applicability of ICAN was demonstrated by determining the critical micelle concentration of sodium laurylsulfate in water.