Structures of 1-hydrophenanthroimidazoles: building blocks in the synthesis of expanded-ring bis(imidazoles).

The structures of 1H-phenanthro[9,10-d]imidazole, C15H10N2, (I), and 3,6-dibromo-1H-phenanthro[9,10-d]imidazole hemihydrate, C15H8Br2N(2).0.5H2O, (II), contain hydrogen-bonded polymeric chains linked by columns of pi-pi stacked essentially planar phenanthroimidazole monomers. In the structure of (I), the asymmetric unit consists of two independent molecules, denoted (Ia) and (Ib), of 1H-phenanthro[9,10-d]imidazole. Alternating molecules of (Ia) and (Ib), canted by 79.07 (3) degrees, form hydrogen-bonded zigzag polymer chains along the a-cell direction. The chains are linked by pi-pi stacking of molecules of (Ia) and (Ib) along the b-cell direction. In the structure of (II), the asymmetric unit consists of two independent molecules of 3,6-dibromo-1H-phenanthro[9,10-d]imidazole, denoted (IIa) and (IIb), along with a molecule of water. Alternating molecules of (IIa), (IIb) and water form hydrogen-bonded polymer chains along the [110] direction. The donor-acceptor distances in these N(imine)...H-O(water)...H-N(amine) hydrogen bonds are the shortest thus far reported for imidazole amine and imine hydrogen-bond interactions with water. Centrosymmetrically related molecules of (IIa) and (IIb) alternate in columns along the a-cell direction and are canted by 48.27 (3) degrees. The present study provides the first examples of structurally characterized 1H-phenanthroimidazoles.