Novel compounds of 4-amino-1,2,4-triazole with dicarboxylic acids – crystal structures, vibrational spectra and non-linear optical properties

Three novel 4-amino-1,2,4-triazole compounds with oxalic, succinic and adipic acids have been prepared and X-ray structural analysis has been carried out. The organic salt 4-amino-1,2,4-triazol-1-ium hydrogen oxalate crystallizes in the monoclinic space group P21, a = 3.7280(2), b = 18.349(1), c = 4.9680(4) Å, β = 101.134(5)°, V = 333.44(4) Å3, Z = 2, R = 0.0284 for 1328 observed reflections. The crystal structure consists of periodically alternating layers (parallel to a axis) formed by chains of hydrogen oxalate anions connected by strong O–H⋯O hydrogen bonds. The layers are interconnected by 4-amino-1,2,4-triazol-1-ium cations via N–H⋯O hydrogen bonds.The addition compound 4-amino-1,2,4-triazole–succinic acid (1:1) crystallizes in the monoclinic space group P21/c, a = 11.8130(5), b = 5.0690(3), c = 16.5280(5) Å, β = 117.285(3)°, V = 879.58(7) Å3, Z = 4, R = 0.0352 for 1701 observed reflections. The crystal structure is formed by zig-zag chains (parallel to b axis) of 4-amino-1,2,4-triazole molecules, connected by N–H⋯N hydrogen bonds, and isolated molecules of succinic acid which interconnect these chains by O–H⋯N and N–H⋯O hydrogen bonds.The addition compound 4-amino-1,2,4-triazole–adipic acid (2:1) crystallizes in the monoclinic space group P21/c, a = 6.3610(3), b = 8.0580(2), c = 14.8750(5) Å, β = 104.072(2)°, V = 739.57(5) Å3, Z = 2, R = 0.0487 for 1793 observed reflections. The crystal structure consists of pairs of parallel linear chains (mediated by N–H⋯N hydrogen bonds) of 4-amino-1,2,4-triazole molecules that are interconnected by isolated adipic acid molecules via O–H⋯N and N–H⋯O hydrogen bonds. Neighbouring chains, which are parallel to a axis, do not exhibit any H-bond contact between each other.The FTIR and FT Raman spectra of all three compounds were recorded, calculated and discussed.Quantitative measurements of second harmonic generation of powdered 4-amino-1,2,4-triazol-1-ium hydrogen oxalate at 800 nm were performed and a relative efficiency of 38% (compared to KDP) was observed.