the 5-(3-hydroxybenzylidene)thiazolidine-2,4-dione (1) according
to the literature methods [15] (Scheme 1, step 1). The new bis-azo
dyes 3a–e, were synthesized by coupling 5-(3-hydroxybenzylidene)
thiazolidine-2,4-dione as coupler and corresponding aromatic diazo-
nium salts in alkaline medium in good yields (Scheme 1, step 2). The
structures of prepared dyes were confirmed by analyzing their spec-
tral characteristics.