Synthesis, Crystal Structure and ab Initio Studies of 5-Phenylamino-3-phenylimino-3H[1, 2]dithiole-4-carboxylic acid ethyl ester

5-Phenylamino-3-phenylimino-3H[1, 2]dithiole-4-carboxylic acid ethyl ester, C 18 H 16 N 2 O 2 S 2 , (I), has been synthesized and the structure has been solved by X–ray diffraction. The crystals are triclinic, space group , with a = 5.7127(2) Å, b = 12.1757(5) Å, c = 14.0734(5) Å, α = 112.1217(16)°, β = 97.786(2)°, γ = 100.694(2)°, Mr = 356.45, V = 868.11(6) Å 3 , Z = 2 and R = 0.0373. In the title compound there is an intramolecular N–H···O hydrogen bond. The crystal structure is stabilized only by weak C–H···π and π···π interactions as well as by van der Waals forces. The geometry of the isolated molecule was optimized by ab initio quantum mechanical calculations, employing both molecular orbital Hartree-Fock (HF) and density functional theory (DFT) methods. In the DFT calculation the minimum energy was achieved for a conformation very similar to that of the solid-state molecule. Graphical Abstract The crystal packing of 3-phenylamino-5-phenylimino-[1, 2]dithiolane-4-carboxylic acid ethyl ester is stabilized only by weak interactions. Ab nitio calculations for the free molecule show that the crystal packing has little influence on the molecular conformation.