Two aroylhydrazone, N'-(pyridine-4-ylmethylene)nicotic acid hydrazide (1) and N'-(pyridine-3-ylmethylene)nicotic acid hydrazide (2), were synthesized and their structures were determined by single-crystal X-ray diffraction analysis. The X-ray analysis indicated that the compound 1 was crystallized in triclinic crystal system with P -1 space group a = 8.7899 (2) angstrom, b = 10.8983 (3) angstrom, c = 11.7726 (3) angstrom, alpha = 89.952 (3)degrees, beta = 88.684 (3)degrees, gamma = 75.293 (2)degrees, V = 1090.50 (5) angstrom(3) and Z = 4 and compound 2 was crystallized in monoclinic crystal system with P2(1)/c space group, a = 11.9239 (3) angstrom, b = 8.6495 (2) angstrom, c = 11.1021 (3) angstrom, alpha = 90 (3)degrees, beta = 111.664 (3) (3)degrees, gamma = 90 degrees, V = 1064.14 (5) angstrom(3) and Z = 4. Intermolecular interactions of the compounds were determined by Hirhfeld Surface Analysis. The H center dot center dot center dot H interactions with 37.9% (for compound 1) and 37.5% (for compound 2) contributions are the most important interactions to the overall crystal packings. FT-IR, Raman, H-1 and C-13 NMR and UV-Vis spectroscopy methods were used for spectroscopic characterization of the compounds. The spectroscopic properties of the compounds were calculated theoretically by using Density Functional Theory (DFT) with B3LYP and ab initio Hartree-Fock (HF) methods at different basis sets. A correlation was found between the theoretical and experimental values for the spectroscopic results. Moreover, the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), electric dipole moment (mu), polarizability (alpha) and hyperpolarizability (beta) of the compounds were computed both DFT/B3LYP/6-311++G (d,p) and ab initio HF/6-311++G(d,p) methods. The calculated first hyperpolarizability value at the DFT/B3LYP/6-31 ++ G (d, p) level of compound 1 with dimer structure is 18.14 times larger than urea, the standard nonlinear optical material. So, this value implies that compound 1 considered have potential candidates for designing high quality nonlinear optical materials. The energy gap (Delta E-gap) and Molecular Electrostatic Potential (MEP) of the compounds were investigated. The structural and vibration frequency values calculated theoretically were compared with the experimental values. (C) 2020 Elsevier B.V. All rights reserved.