Crystal structures of N-(pyridin-2-ylmeth­yl)pyrazine-2-carboxamide (monoclinic polymorph) and N-(pyridin-4-ylmeth­yl)pyrazine-2-carboxamide

The title compounds, C(11)H(10)N(4)O (HL1) and C(11)H(10)N(4)O (HL2), are pyridine 2-ylmethyl and 4-ylmethyl derivatives, respectively, of pyrazine-2-carboxamide. HL1 was measured at 153 K and crystallized in the monoclinic space group P2(1)/c with Z = 4. There has been a report of the same structure measured at room temperature but assumed to crystallize in the triclinic space group P-1 with Z = 4 [Sasan et al. (2008 ▸). Monatsh. Chem. 139, 773–780]. In HL1, the pyridine ring is inclined to the pyrazine ring by 61.34 (6)°, while in HL2 this dihedral angle is 84.33 (12)°. In both mol­ecules, there is a short N—H⋯N inter­action involving the pyrazine carboxamide unit. In the crystal of HL1, mol­ecules are linked by N—H⋯N hydrogen bonds, forming inversion dimers with an R (2) (2)(10) ring motif. The dimers are linked via bifurcated-acceptor C—H⋯O hydrogen bonds, forming sheets lying parallel to (102). The sheets are linked via C—H⋯N hydrogen bonds, forming a three-dimensional structure. In the crystal of HL2, mol­ecules are linked by N—H⋯N and C—H⋯N hydrogen bonds to form chains propagating along [010]. The chains are linked via C—H⋯O hydrogen bonds, forming sheets lying parallel to (100). Within the sheets there are π–π inter­actions involving neighbouring pyrazine rings [inter-centroid distance = 3.711 (15) Å]. Adjacent sheets are linked via parallel slipped π–π inter­actions involving inversion-related pyridine rings [inter-centroid distance = 3.6395 (17) Å], forming a three-dimensional structure.