Journal of Applied Crystallography

Volume 38, Part 4 (August 2005)

research papers

J. Appl. Cryst. (2005). 38, 632-638 [ doi:10.1107/S0021889805015827 ]

A novel strategy for ab initio structure determination using micro-powder X-ray diffraction: structure solution and refinement of 3-bromophenylboronic acid and tris(4-bromophenyl)boroxine

N. S. P. Bhuvanesh, J. H. Reibenspies, Y. Zhang and P. L. Lee

Abstract: Micro-powder X-ray diffraction patterns of two compounds, namely 3-bromophenylboronic acid and tris(4-bromophenyl)boroxine, were recorded with microgram quantities of sample using a recently developed method employing nylon loops with synchrotron radiation and an image-plate detector. This method, besides using small amount of samples, offers the advantage of recording the powder pattern in the shortest possible time (less than a minute). The structures of the two compounds have been solved by ab initio methods using real-space techniques (simulated annealing and/or parallel tempering) followed by Rietveld refinements with soft restraints on the bond lengths of the rigid bodies. The former compound crystallizes in the monoclinic system [a = 15.7797 (4), b = 5.3085 (2), c = 9.3757 (3) Å, [beta] = 93.357 (3)°; space group P2₁/c; Z = 4; R_p = 16.060, R_wp = 10.543, R_B = 4.25] with sheets of individual molecules linked through an extended hydrogen-bonding network. Tris(4-bromophenyl)boroxine, displaying molecular disorder, crystallizes in the orthorhombic system [a = 18.9289 (6), b = 21.8872 (6), c = 4.8842 (2) Å; space group Pnma; Z = 4; R_p = 13.270, R_wp = 12.083, R_B = 6.06], with discrete molecules held by weak van der Waals forces in a zigzag fashion. It is believed that this is the first time that powder X-ray diffraction patterns using microgram samples have been successfully employed for the structure solution and refinement of molecules with reasonable complexity.

Keywords: micro-powder X-ray diffraction; ab initio structure determination; bromophenyl boronic acid.