research papers
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, β = 93.357 (3)°; space group P21/c; Z = 4; Rp = 16.060, Rwp = 10.543, RB = 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; Rp = 13.270, Rwp = 12.083, RB = 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.
Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0021889805015827/aj5037sup1.cif |
CCDC references: 280204; 280205
Computing details top
For both compounds, data collection: MAR; cell refinement: CRYSFIRE, CHEKCELL; data reduction: FIT-2D; program(s) used to solve structure: DASH & FOX; program(s) used to refine structure: TOPAS; molecular graphics: DIAMOND.
(3BPBA) 3-borophenylboronic acid top
Crystal data top
Br(C6H4)B(OH)2 | Z = 4 |
Mr = 200.83 | Dx = 1.70 Mg m−3 |
Monoclinic, P21/c | synchrotron radiation, λ = 0.619383 Å |
Hall symbol: -P_2ybc | µ = 35.0 mm−1 |
a = 15.7797 (4) Å | T = 295 K |
b = 5.3085 (2) Å | Particle morphology: fine_powder |
c = 9.3757 (3) Å | white |
β = 93.357 (3)° | near_spehrical, 0.18 × 0.18 mm |
V = 784.02 (4) Å3 |
Data collection top
1-BM diffractometer | Specimen mounting: Small nylon loops (Hampton Research), 20 mm thick (500 to 700 mm in diameter), mounted on magnetic bases were used for sample mounting. For efficient sample preparation a very small amount (5 to 10 mg) of the sample was made into thick paste using mineral oil under the microscope, and was then scooped at the tip of the loop. The sample was rolled with care to ensure the sample remained near spherical. |
Radiation source: synchrotron, APS beamline 1-BM | Data collection mode: transmission |
PSL Si(111) monochromator | Scan method: Stationary detector |
Refinement top
Rp = 0.161 | 30 parameters |
Rwp = 0.105 | H-atom parameters not refined |
Rexp = 0.198 | (Δ/σ)max = 0.01 |
3450 data points | Background function: Chebychev 10th order polynomial |
Profile function: pseudo-Voigt | Preferred orientation correction: 4th order Spherical Harmonics |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
x | y | z | Uiso*/Ueq | ||
Br1 | 0.0792 | 0.3131 | 0.6898 | 1.000* | |
C1 | 0.3173 | 0.3635 | 0.5232 | 1.000* | |
C2 | 0.2487 | 0.3112 | 0.6049 | 1.000* | |
C3 | 0.1740 | 0.4509 | 0.5983 | 1.000* | |
C4 | 0.1693 | 0.6581 | 0.5073 | 1.000* | |
C5 | 0.2337 | 0.7265 | 0.4197 | 1.000* | |
C6 | 0.3049 | 0.5794 | 0.4307 | 1.000* | |
B1 | 0.3991 | 0.2070 | 0.5288 | 1.000* | |
O1 | 0.4279 | 0.1123 | 0.6588 | 1.000* | |
O2 | 0.4464 | 0.1663 | 0.4128 | 1.000* |
Geometric parameters (Å, º) top
Br1—C3 | 1.913 | C1—B1 | 1.533 |
C3—C2 | 1.391 | B1—O1 | 1.371 |
C3—C4 | 1.391 | B1—O2 | 1.372 |
C2—C1 | 1.390 | C4—C5 | 1.392 |
C1—C6 | 1.444 | C5—C6 | 1.367 |
C2—C3—C4 | 117.61 | O1—B1—O2 | 118.66 |
C2—C3—Br1 | 117.33 | O1—B1—C1 | 117.62 |
C4—C3—Br1 | 124.22 | O2—B1—C1 | 123.66 |
C3—C2—C1 | 123.65 | C3—C4—C5 | 123.61 |
C2—C1—C6 | 114.02 | C6—C5—C4 | 115.58 |
C2—C1—B1 | 123.64 | C5—C6—C1 | 125.5 |
C6—C1—B1 | 122.34 |
(T4BPB) Tris(4-bromophenyl)boroxine top
Crystal data top
Br(C6H4)3(BO)3 | Z = 4 |
Mr = 548.31 | Dx = 1.80 Mg m−3 |
Orthorhombic, Pnma | synchrotron radiation, λ = 0.619383 Å |
Hall symbol: -P_2ac_2n | µ = 41.8 mm−1 |
a = 18.9289 (6) Å | T = 295 K |
b = 21.8872 (6) Å | Particle morphology: fine_powder |
c = 4.8842 (2) Å | white |
V = 2023.5 (1) Å3 | near_spehrical, 0.16 × 0.16 mm |
Data collection top
1-BM diffractometer | Specimen mounting: Small nylon loops (Hampton Research), 20 mm thick (500 to 700 mm in diameter), mounted on magnetic bases were used for sample mounting. For efficient sample preparation a very small amount (5 to 10 mg) of the sample was made into thick paste using mineral oil under the microscope, and was then scooped at the tip of the loop. The sample was rolled with care to ensure the sample remained near spherical. |
Radiation source: synchrotron, APS beamline 1-BM | Data collection mode: transmission |
PSL Si(111) monochromator | Scan method: Stationary detector |
Refinement top
Rp = 0.133 | 29 parameters |
Rwp = 0.121 | H-atom parameters not refined |
Rexp = 0.133 | (Δ/σ)max = 0.01 |
2587 data points | Background function: Chebychev 10th order polynomial |
Profile function: pseudo-Voigt | Preferred orientation correction: 4th order Spherical Harmonics |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
x | y | z | Uiso*/Ueq | Occ. (<1) | |
B2 | 0.4237 | 0.3011 | 0.4344 | 1* | 0.500 |
C3 | 0.4026 | 0.3650 | 0.5399 | 1* | 0.500 |
C4 | 0.3535 | 0.3699 | 0.7503 | 1* | 0.500 |
C5 | 0.3349 | 0.4270 | 0.8492 | 1* | 0.500 |
C6 | 0.3655 | 0.4790 | 0.7397 | 1* | 0.500 |
Br7 | 0.3401 | 0.5572 | 0.8753 | 1* | 0.500 |
C8 | 0.4335 | 0.4171 | 0.4317 | 1* | 0.500 |
C9 | 0.4147 | 0.4739 | 0.5309 | 1* | 0.500 |
B10 | 0.4193 | 0.2014 | 0.4421 | 1* | 0.500 |
C11 | 0.3934 | 0.1405 | 0.5651 | 1* | 0.500 |
C12 | 0.3439 | 0.1406 | 0.7749 | 1* | 0.500 |
C13 | 0.3207 | 0.0858 | 0.8855 | 1* | 0.500 |
C14 | 0.3468 | 0.0310 | 0.7869 | 1* | 0.500 |
Br15 | 0.3150 | 0.9560 | 0.9383 | 1* | 0.500 |
C16 | 0.4197 | 0.0856 | 0.4665 | 1* | 0.500 |
C17 | 0.3965 | 0.0310 | 0.5769 | 1* | 0.500 |
O18 | 0.4725 | 0.2962 | 0.2240 | 1* | 0.500 |
O19 | 0.4686 | 0.2013 | 0.2338 | 1* | 0.500 |
B20 | 0.5056 | 0.2480 | 0.1048 | 1* | 0.500 |
C21 | 0.5654 | 0.2451 | 0.8908 | 1* | 0.500 |
C22 | 0.5940 | 0.1883 | 0.8194 | 1* | 0.500 |
C23 | 0.6476 | 0.1852 | 0.6273 | 1* | 0.500 |
C24 | 0.6728 | 0.2378 | 0.5066 | 1* | 0.500 |
Br25 | 0.7463 | 0.2341 | 0.2431 | 1* | 0.500 |
C26 | 0.5995 | 0.2986 | 0.8058 | 1* | 0.500 |
C27 | 0.6531 | 0.2964 | 0.6136 | 1* | 0.500 |
O28 | 0.3932 | 0.2538 | 0.5406 | 1* | 0.500 |
Geometric parameters (Å, º) top
B2—O28 | 1.295 | C11—C12 | 1.389 |
B2—O18 | 1.386 | C12—C13 | 1.386 |
B2—C3 | 1.543 | C13—C14 | 1.385 |
C3—C8 | 1.386 | C14—C17 | 1.391 |
C3—C4 | 1.389 | C16—C17 | 1.382 |
C4—C5 | 1.386 | O18—B20 | 1.358 |
C5—C6 | 1.385 | O19—B20 | 1.391 |
C6—C9 | 1.386 | C21—C22 | 1.400 |
C6—Br7 | 1.898 | C21—C26 | 1.400 |
C8—C9 | 1.382 | C22—C23 | 1.384 |
B10—O28 | 1.338 | C23—C24 | 1.377 |
B10—O19 | 1.380 | C24—C27 | 1.434 |
B10—C11 | 1.543 | C24—Br25 | 1.897 |
C11—C16 | 1.386 | C26—C27 | 1.384 |
O28—B2—O18 | 122.19 | C12—C11—B10 | 120.03 |
O28—B2—C3 | 118.4 | C13—C12—C11 | 120.03 |
O18—B2—C3 | 119.37 | C14—C13—C12 | 120.03 |
C8—C3—C4 | 120.03 | C13—C14—C17 | 120.03 |
C8—C3—B2 | 120.57 | C17—C16—C11 | 119.99 |
C4—C3—B2 | 119.38 | C16—C17—C14 | 120.19 |
C5—C4—C3 | 119.85 | B20—O18—B2 | 133.29 |
C6—C5—C4 | 120.02 | B10—O19—B20 | 132.34 |
C5—C6—C9 | 119.96 | O18—B20—O19 | 98.25 |
C5—C6—Br7 | 120.01 | C22—C21—C26 | 119.42 |
C9—C6—Br7 | 120.03 | C23—C22—C21 | 119.7 |
C9—C8—C3 | 119.93 | C24—C23—C22 | 120.22 |
C8—C9—C6 | 120.21 | C23—C24—C27 | 120.07 |
O28—B10—O19 | 121.11 | C23—C24—Br25 | 120.58 |
O28—B10—C11 | 118.86 | C27—C24—Br25 | 118.35 |
O19—B10—C11 | 120.02 | C27—C26—C21 | 120.51 |
C16—C11—C12 | 119.95 | C26—C27—C24 | 118.02 |
C16—C11—B10 | 120.02 | B2—O28—B10 | 112.09 |