Structural and vibrational investigation of 2-amino-4-nitropyridine crystal

The X-ray structure of 2-amino-4-nitropyridine was determined at room temperature. The crystal belongs to the P2(1)/c space group of the monoclinic system (Z = 4, a = 6.7290(10), b = 10.946(2), c = 9.060(2) Angstrom, beta = 100.03(3) deg) and is built of layers parallel to the (102) crystallographic plane. The molecules in the layer are joined into centrosymmetric dimers by two N-H ... N hydrogen bonds (N ... N distance = 3.011(3) Angstrom), which form rings of Ci symmetry. The other N-H bonds of the amino groups are involved in N-H ... O hydrogen bonds with the oxygen atoms of the nitro groups (N ... O distance = 3.054(3) Angstrom). These hydrogen bonds join the dimers into an infinite plane. The powder IR and Raman spectra (4000-80 cm(-1)) were measured for normal and deuterated crystals and are discussed with respect to the crystal structure. The N-H stretching vibrations behave as the stretching vibrations of two almost independent hydrogen bonds. Strong A(g)-A(u)-type splitting is observed for the stretching vibrations of the N-H ... N type hydrogen bonds. (C) 1997 Elsevier Science B.V.