Structural analysis of some benzoxazoles containing strong electron donor-acceptor groups

The crystal structure analysis of two benzoxazole containing molecules is reported: 2-[4-N,N-bis(2-hydroxyethyl)] phenyl-6-nitrobenzoxazole monohydrate (1) and 2-[4-N-(6-hydroxyhexyl)-N-methyl] phenyl-6-nitrobenzoxazole (2). These compounds are monomer precursors of polymers with nonlinear optical properties of the second order, The crystal structures have been determined at room temperature by direct methods and refined by full-matrix least-squares method. Some differences have been found in the molecular geometry of 1 and 2 as compared to published data on similar benzoxazole containing compounds. These differences are due to the strong electron donor effect of the amino group and indicate enhanced conjugation in the molecules. The pattern of hydrogen bonding in the two compounds is also discussed.