New thiadiazole compounds, 3-imino-4-(anthracene-9-yl)-1,2,5-thiadiazolidine 1,1-dioxide (I) and 3-imino-4-(10-chloroanthracene-9-yl)-1,2,5-thiadiazolidine 1,1-dioxide (II) were synthesized and characterized by Fourier Transform Infrared Spectroscopy (FTIR), C-13 and H-1 NMR and UV-vis spectroscopic methods. Calculations of molecular geometries and spectroscopic parameters were performed using DFT/6-311++G(d,p) method. Frontier Molecular Orbitals (FMOs), Non-Linear Optical (NLO) properties and Molecular Electrostatic Potential (MEP) maps of newly synthesised compounds were obtained. The some considerable differences between experimental and calculated vibrational frequencies and NMR chemical shift values can be attributed to the presence of N-H center dot center dot center dot O type intermolecular hydrogen bonds in the molecular structures of both compounds. NLO properties of compounds were determined by using the mean polarizability (alpha) and the first-order hyperpolarizability (beta) values calculated as 36.8326 x 10(-24)/18.7571 x 10(-31) esu for I, 36.9489 x 10(-24)/31.6544 x 10(-31) esu for II, respectively at the mentioned computational level. These values are greater than the ones of urea (alpha = 4.9067 x 10(-24) and beta = 7.8782 x 10(-31) esu) and therefore, NLO properties study demonstrates that the both compounds, especially compound II, can be suggested as a good nonlinear optical material. (C) 2018 Elsevier B.V. All rights reserved.