Acta Crystallographica Section C

Crystal Structure Communications

Volume 58, Part 2 (February 2002)

Acta Cryst. (2002). C58, o125-o128 [doi:10.1107/S0108270101021564]

2-(4-Bromophenyl)-1,2-dihydropyrimido[1,2-a]benzimidazol-4(3H)-one and 4-(4-methylphenyl)-3,4-dihydropyrimido[1,2-a]benzimidazol-2(1H)-one form hydrogen-bonded base-paired dimers

J. N. Low, J. Cobo, B. Insuasty, M. Nogueras, A. Salcedo and A. Sánchez

Abstract: The title compounds, 2-(4-bromophenyl)-1,2-dihydropyrimido[1,2-a]benzimidazol-4-(3H)-one, C₁₆H₁₂BrN₃O, (IVa), and 4-(4-methylphenyl)-3,4-dihydropyrimido[1,2-a]benzimidazol-2-(1H)-one, C₁₇H₁₅N₃O, (Vb), both form R ${_2^2}$ (8) centrosymmetric dimers via N-HN hydrogen bonds. The NN distance is 2.943 (3) Å for (IVa) and 2.8481 (16) Å for (Vb), with the corresponding N-HN angles being 129 and 167°, respectively. However, in other respects, the supramolecular structures of the two compounds differ. Both compounds contain different C-H [bold pi] interactions, in which the C-H(centroid) distances are 2.59 and 2.47 Å for (IVa) and (Vb), respectively (the latter being a short distance), with C-H(centroid) angles of 158 and 159°, respectively. The supramolecular structures also differ, with a short BrO distance of 3.117 (2) Å in bromo derivative (IVa), and a C-HO interaction with a CO distance of 3.2561 (19) Å and a C-HO angle of 127° in tolyl system (Vb). The dihydropyrimido part of (Vb) is disordered, with a ratio of the major and minor components of 0.9:0.1. The disorder consists of two non-interchangeable envelope conformers, each with an equatorial tolyl group and an axial methine H atom.

Formula: C₁₆H₁₂BrN₃O and C₁₇H₁₅N₃O

Online 31 January 2002


	Structure factor file (CIF format) (149.6 kbytes) Contains datablock IVa

	Structure factor file (CIF format) (155.6 kbytes) Contains datablock Vb

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