A series of novel di-[3(thiophen-2-yl-methyl)-4,5-dihydro-1H-[1,2,4] triazole-5-one-4yl]n-alkanes (2a-h) were obtained by the reaction of N'-1-ethoxy-2-thiophen-2-yl-ethylydene hydrazino carboxylic acid ethyl ester (1) and diamines. Compound 3 was reacted with aldehydes and 4-(arylidene-amino)3-thiophen-2-yl-methyl-4,5-dihydro-1H-[1,2,4] triazole-5-ones (4, 5, and 8) with Schiff base character were synthesized. (4-(arylidene-amino)-5-oxo-3-thiophen-2-yl-methyl-4,5-dihydro-1H-[1,2,4] triazole-1-yl)-acetic acid ethyl esters (6, 7, and 9) were obtained by the reaction of 4-(arylidene-amino)-3thiophen-2-yl-methyl-4,5-dihydro-1H-[1,2,4]triazole-5-ones (4, 5, and 8) and ethyl bromoacetate. The structures of the new compounds were inferred through IR, H-1/C-13 NMR, elemental analyses, and mass spectral data. Compound 8i was characterized by IR, H-1/C-13 NMR, elemental analyses, mass, and X-ray spectral techniques. Geometry optimization of compounds 2a, 2c, 2f, 4, and 5 was achieved by computer using the AM1 method.