Crystal structures of 3-(4-pyridinyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrimidine and its 6-hydroxy derivative

Abstract

(1): C₁₀H₁₁N₅,M _r=201.23, from water, P$\bar 1$,a=6.913(1),b=8.198(2),c=9.212(2) Å, α=72.36(2), β=109.03(2) and γ=88.13(1)^o,D _x=1.436 g/cm³,Z=2. FinalR=0.043 for 1477 observed reflections. (2): C₁₀H₁₁N₅O,M _r=217.23, from methanol/water solution. P2₁/c,a=9.291(2),b=11.263(3),c=10.454(3) Å, and β=114.05(1)^o,D _x=1.444, g/cm³,Z=4. FinalR 0.056 for 1587 observed reflections. The data were collected on a diffractometer at room temperature. Structures were solved by direct methods and refined by anisotropic full-matrix least-squares method. In the solid state both molecules have the same conformation and are packed in similar manner. The planarity of the condensed triazole ring and its π electrons conjugation with a lone pair at N8 impose C6 sofa conformation of the saturated diazine rings. Hydroxy group in2 is in an energetically unfavorable axial position. Both in1 and2, N8−H ... N34 hydrogen bonds join molecules into infinite chains, and O6−H ... N1 hydrogen bonds in2 span the chains into two-dimensional net. The molecules in hydrogen bonded chains and sheets have the same chirality.