The two new azo dyes p-(p-acetylphenylazo)-o-allylphenol (compound 1) and p-(p-bromphenylazo)-o-allylphenol (compound 11) have been synthesized and studied by FT-IR, UV-VIS, H-1 NMR, C-13 NMR techniques, elemental analysis, X-ray structure analysis and TG, DTG, and DTA analyses. Compound I crystallizes in the monoclinic space group P21/c with a = 19.6130(15) Angstrom, b = 7.3586(6) Angstrom, c = 21.4752(15) Angstrom, alpha = 90.00degrees, beta = 101.413(6)degrees, gamma = 90.00degrees, Z = 8, V = 3038.1(4) Angstrom and the molecules are linked by two intermolecular (OO)-O-... hydrogen bonds. There are two independent molecules in the asymmetric unit of compound I. Compound II crystallizes in the nionoclinic space group Cc with a = 4.7194(7) Angstrom, b = 24.597(2) Angstrom, c = 12.2241(16) Angstrom, alpha = 90.00degrees, beta = 96.509(11)degrees, gamma = 90.00degrees, Z = 4, V = 1409.9(3) Angstrom(3) and the molecules are linked by (ON)-N-... and C-(HO)-O-... intermolecular hydrogen bonds. They are characterized by UV-VIS, FT-IR, H-1 NMR, C-13 NMR techniques, elemental analysis, TG, DTG, and DTA analyses. (C) 2004 Elsevier Ltd. All rights reserved.