Series of monoazo dyes from some ethyl 2-amino-4-(4'-substitutedphenyl) thiophenes were prepared and characterized. The structure of the substances was confirmed by FT-IR, H-1 NMR and mass spectroscopic techniques. The relationship among the structure of the dyes, their absorption characteristics and the solvatochromic and halochromic behaviors of the dyes were investigated. Introduction of electron-accepting substituent into the diazo moiety results in large bathochromic shifts in all solvents used. The dyes exhibited positive solvatochromism and their solvatochromic properties were discussed in relation to tautomerism. (C) 2014 Elsevier B.V. All rights reserved.