Synthesis of Two 1,3,4-thiadiazole Compounds: Crystal Structure, Theoretical and Antifungal Activity Study

Two novel 1,3,4-thiadiazole compounds, C15H10N4S2 (5a) and C18H19N3S2 (5b) were designed and synthesized by reactions of key intermediate 5-(pyridin-4-yl)-1,3,4-thiadiazole-2-thiol and two substituted benzyl chloride (4-t-Bu and 3-CN). The two 1,3,4-thiadiazole structures were confirmed by H-1-NMR, MS, elemental analyses and X-Ray diffraction. Compound 5a is triclinic with space group P-1 and cell constants: a = 6.1426 (7), b = 8.5323 (14), c = 13.840 (2) angstrom, alpha = 90.199 (12), beta = 90.002 (11), gamma = 106.762 (13)degrees, Dc = 1.484 g/cm(3), Z = 2, V = 694.52 (17) angstrom(3), the final R = 0.0400 and wR = 0.111 for 1786 observed reflections with I > 2 sigma(I). Compound 5b is triclinic with space group P2(1)/c and cell constants: a = 10.490 (5), b = 19.818 (10), c = 8.825(5) angstrom, alpha = 90, beta = 98.989(10), gamma = 90 degrees, Dc = 1.252 g/cm(3), Z = 4, V = 1812.2(16) angstrom(3), the final R = 0.0630 and wR = 0.192 for 2023 observed reflections with I > 2s(I). Theoretical calculation was carried out by DFT method using 6-31G basis set. The compounds also possessed moderate fungicidal activity.