Four new azo dyes: 2-[(3,5-diarnino-1H-pyrazol-4-Adiazenyl]-5-nitrobenzoic acid (A), 2-[(3-hydroxy-5methyl-IH-pyrazol-4-yl)diazenyl]-5-nitrobenzoic acid (B), 2-[(3,5-dimethyl-JH-pyrazol-4-yl)diazenyl]5-nitrobenzbic acid (C) and 2-[(5-amino-3-methyl-1H-pyrazol-4-yl)diazenyl]-5-nitrobenzoic acid (D) which have the same 4-nitrobenzene/azo/pyrazole skeleton and different substituted groups are synthesized in this work. The structures and spectroscopic properties of these new azo dyes are characterized by using spectroscopic methods such as FT-IR, H-1 NMR, C-13 NMR and UV-vis. Their solvatochromic properties in chloroform, acetic acid, methanol, dimethylformamide (DMF) and dimethylsulphoxide (DMSO) are studied. Moreover, molecular structures and some spectroscopic properties of azo dyes are investigated by utilizing the quantum computational chemistry method based on Density Functional Theory (DFT) employing B3LYP hybrid functional level with 6-31G(d) basis set. It is seen that experimental and theoretical results are compatible with each other. (C) 2017 Elsevier B.V. All rights reserved.