Crystal Structures and Hydrogen Bonding in One-Dimensional Chains of 4,5-Dicyanoimidazole and 4,5-Dichloroimidazole

Abstract The crystal structure of 4,5-dicyanoimidazole ((CN)2Imd) was determined by an X-ray diffraction at room temperature; monoclinic, P21/a, a = 7.259(2), b = 7.529(1), c = 10.0972(9) Å, β = 102.74(1)°, V = 538.2(2) Å3, Z = 4, R = 0.043, and Rw=0.066 for 1090 observed reflections. Crystal structure of 4,5-dichloroimidazole (Cl2Imd) was redetermined; tetragonal, P41212, a = 6.843(4), c = 24.236(7) Å, V = 1134(1) Å3, Z = 8, R = 0.043, and Rw = 0.058 for 427 observed reflections. Molecules in Cl2Imd and in (CN)2Imd are linked by intermolecular N–H···N hydrogen bonds to form one-dimensional chains. The hydrogen bonds in Cl2Imd are formed between the ring nitrogen atoms, while those in (CN)2Imd are between the ring and the cyano nitrogens. The hydrogen bond distance (3.051(2) Å) of N···N in (CN)2Imd is long, compared with that (2.800(6) Å) in Cl2Imd. The weak hydrogen bond in (CN)2Imd was also indicated by IR and 15N CP/MAS NMR spectra.