Abstract

Synthesis of 5-methoxynaphtho[1, 2-d]thiazole-2-carboxylic acid was developed from new synthetic route starting from using potassium ferricyanide as catalyst. The absorption and fluorescence properties of structurally related 4-methoxynaphthalene-1-ylamine (4), N-(4-methoxynaphthalene-1-yl)-oxalamic acid ethyl ester (5), 2-(4-methoxynaphthalene-1-ylamino)-2-thioxoacetic acid (6) and 5-methoxynaphtho[1,2-d]thiazole-2-carboxylic acid (7) were investigated in 4 different solvents. The absorption maxima of these compounds (except 7) in the order C₆H₆ > cyclohexane >MeOH>EtOH+HCl. The spectral characteristics are solvent and compound specific. Fluorophores with electron withdrawing group have larger fluorescence quantum yields and greater solvatochromism than the compounds with electron donating groups. Protic solvents yielded higher fluorescence quantum efficiency. While no such relationship exists between the latter and electronic absorption maxima, fluorescence emission maxima, fluorescence quantum efficiency and Stokes shift.

Keywords

4-Methoxynaphthyl amine, Naphthothiazole, Solvatochromism, Stokes shift, Fluorophore