Molecular, crystallographic and algorithmic factors in structure determination from powder diffraction data by simulated annealing

The crystal structure of famotidine form B has been solved directly from powder diffraction data by the application of simulated annealing. The molecule crystallizes in the monoclinic space group P2₁/c with refined unit-cell dimensions a = 17.6547 (4), b = 5.2932 (1), c = 18.2590 (3) Å and β = 123.558 (1)° at T = 130 K. The core of this work is a systematic investigation of the influence of algorithmic, crystallographic and molecular factors on the structure solution process. With an appropriate choice of annealing schedule, molecular description and diffraction data range, the overall number of successes in solving the crystal structure is close to 100%. Other factors, including crystallographic search space restrictions and parameter sampling method, have little effect on the structure solution process. The basic principles elucidated here have been factored into the design of the DASH structure solution program.

Computing details

Data collection: BM16 instrument software; cell refinement: DASH; data reduction: BM16 instrument software; program(s) used to solve structure: DASH; program(s) used to refine structure: SR15LS.

Figures

3-(2-(Diaminomethyleneamino)-1,3-thiazol-4-yl)methylthio)-N'- sulfamoylpropionamidine

Crystal data

C8H15N7O2S3	V = 1421.9 Å^3
Mr = ?	Z = 4
Monoclinic, P21/c	? radiation, λ = 0.8507473 Å
a = 17.6547 (4) Å	T = 130 K
b = 5.2932 (1) Å	white
c = 18.2590 (3) Å	cylinder, 10 × 1 mm
β = 123.558 (1)°	Specimen preparation: Prepared at 130 K

Data collection

2 circle diffractometer	Data collection mode: transmission
Radiation source: synchrotron, ESRF BM16	Scan method: step
Si 111 monochromator	2θmin = 3.000°, 2θmax = 53.000°, 2θstep = 0.005°
Specimen mounting: 1.0mm borosilicate capillary

Refinement

Least-squares matrix: full with fixed elements per cycle	124 parameters
Rp = 0.122	0 restraints
Rwp = 0.125	0 constraints
Rexp = 0.097	H-atom parameters not refined
χ^2 = 1.664	Weighting scheme based on measured s.u.'s
10001 data points
Profile function: Voigt with axial divergence correction	Background function: Chebyshev polynomial

Special details

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All e.s.d.'s are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Biso*/Beq
C1	0.3445 (4)	0.5849 (7)	−0.1027 (5)	1.25 (6)*
H2	0.3199 (7)	0.6130 (16)	−0.1602 (6)	3.00*
H3	0.3889 (5)	0.6983 (7)	−0.0707 (9)	3.00*
C4	0.2706 (3)	0.612 (1)	−0.0830 (3)	1.25 (6)*
C5	0.1866 (4)	0.4661 (13)	−0.1504 (2)	1.25 (6)*
H6	0.2916 (4)	0.5499 (18)	−0.0290 (3)	3.00*
H7	0.2563 (5)	0.7757 (11)	−0.0850 (6)	3.00*
N8	0.1531 (6)	0.3188 (15)	−0.1174 (3)	1.25 (6)*
N9	0.1611 (3)	0.4861 (12)	−0.2326 (2)	1.25 (6)*
H10	0.0915 (6)	0.28 (2)	−0.162 (3)	3.00*
H11	0.173 (3)	0.344 (15)	−0.0577 (5)	3.00*
S12	0.0665 (2)	0.3658 (5)	−0.31076 (16)	1.10 (5)*
O13	−0.0128 (4)	0.4249 (13)	−0.3100 (4)	1.25 (6)*
O14	0.0527 (5)	0.443 (1)	−0.3929 (3)	1.25 (6)*
N15	0.0725 (5)	0.0587 (5)	−0.3043 (4)	1.25 (6)*
H16	0.088 (7)	−0.0012 (16)	−0.340 (5)	3.00*
H17	0.115 (5)	0.0124 (10)	−0.2487 (13)	3.00*
S18	0.3918 (3)	0.2693 (5)	−0.07467 (19)	1.10 (5)*
C19	0.4647 (3)	0.2692 (10)	−0.1171 (2)	1.25 (6)*
C20	0.4096 (4)	0.3210 (9)	−0.21366 (19)	1.27 (6)*
H21	0.5076 (3)	0.3894 (16)	−0.0895 (3)	3.00*
H22	0.4918 (5)	0.1174 (14)	−0.1071 (4)	3.00*
C23	0.4299 (5)	0.4943 (13)	−0.2553 (2)	1.27 (6)*
S24	0.3560 (3)	0.4657 (5)	−0.36786 (18)	1.27 (6)*
C25	0.3049 (5)	0.2044 (13)	−0.3524 (2)	1.27 (6)*
N26	0.3422 (5)	0.1479 (11)	−0.2689 (2)	1.27 (6)*
H27	0.4767 (12)	0.604 (4)	−0.2280 (3)	3.00*
N28	0.2337 (4)	0.0950 (12)	−0.4255 (2)	1.25 (6)*
C29	0.1899 (5)	−0.0972 (15)	−0.4173 (3)	1.25 (6)*
N30	0.2076 (5)	−0.1873 (12)	−0.3413 (3)	1.25 (6)*
N31	0.1211 (4)	−0.2026 (13)	−0.4902 (3)	1.25 (6)*
H32	0.270 (4)	−0.176 (12)	−0.2904 (3)	3.00*
H33	0.158 (4)	−0.271 (11)	−0.3418 (6)	3.00*
H34	0.097 (4)	−0.124 (8)	−0.5423 (10)	3.00*
H35	0.101 (4)	−0.357 (7)	−0.4881 (12)	3.00*

Geometric parameters (Å, º)

S12—O13	1.440 (9)	N15—H17	0.90 (3)
S12—O14	1.440 (6)	N15—H16	0.89 (11)
S12—N9	1.612 (5)	N30—H32	0.97 (5)
S12—N15	1.629 (4)	N30—H33	0.98 (7)
S18—C1	1.810 (6)	N31—H34	0.90 (3)
S18—C19	1.833 (8)	N31—H35	0.90 (4)
S24—C23	1.728 (4)	C1—C4	1.540 (11)
S24—C25	1.757 (9)	C4—C5	1.514 (8)
N8—C5	1.309 (11)	C19—C20	1.495 (4)
N9—C5	1.311 (5)	C20—C23	1.360 (9)
N26—C20	1.395 (8)	C1—H2	0.899 (12)
N26—C25	1.318 (5)	C1—H3	0.900 (12)
N28—C25	1.356 (7)	C4—H6	0.902 (7)
N28—C29	1.335 (11)	C4—H7	0.898 (8)
N30—C29	1.331 (8)	C19—H21	0.900 (9)
N31—C29	1.331 (8)	C19—H22	0.901 (9)
N8—H10	0.95 (4)	C23—H27	0.90 (2)
N8—H11	0.95 (2)
O13—S12—O14	110.1 (5)	S18—C19—C20	110.3 (4)
O13—S12—N9	116.3 (4)	N26—C20—C19	118.1 (4)
O13—S12—N15	104.0 (5)	N26—C20—C23	115.0 (4)
O14—S12—N9	107.7 (4)	C19—C20—C23	125.6 (5)
O14—S12—N15	109.0 (4)	S24—C23—C20	110.3 (5)
N9—S12—N15	109.6 (4)	S24—C25—N26	113.1 (5)
C1—S18—C19	101.7 (4)	N26—C25—N28	129.7 (7)
C23—S24—C25	89.7 (3)	S24—C25—N28	117.2 (4)
S12—N9—C5	120.9 (5)	N28—C29—N31	118.2 (5)
C20—N26—C25	111.6 (6)	N30—C29—N31	116.8 (8)
C25—N28—C29	119.7 (5)	N28—C29—N30	124.9 (6)
H10—N8—H11	122 (4)	S18—C1—H2	109.4 (8)
C5—N8—H10	109 (4)	S18—C1—H3	109.4 (8)
C5—N8—H11	118 (4)	C4—C1—H2	109.4 (11)
H16—N15—H17	109 (7)	C4—C1—H3	109.4 (10)
S12—N15—H16	110 (2)	H2—C1—H3	109.4 (12)
S12—N15—H17	109.5 (7)	C1—C4—H6	109.4 (7)
C29—N30—H32	118 (3)	C1—C4—H7	109.6 (8)
C29—N30—H33	117.4 (11)	C5—C4—H6	109.2 (7)
H32—N30—H33	125 (3)	C5—C4—H7	109.4 (8)
C29—N31—H34	120 (3)	H6—C4—H7	109.4 (10)
C29—N31—H35	120.1 (16)	S18—C19—H21	109.5 (5)
H34—N31—H35	120 (3)	S18—C19—H22	109.5 (7)
S18—C1—C4	109.7 (4)	C20—C19—H21	109.2 (6)
C1—C4—C5	109.8 (5)	C20—C19—H22	109.2 (6)
N8—C5—N9	128.2 (6)	H21—C19—H22	109.2 (9)
N8—C5—C4	114.7 (4)	S24—C23—H27	124.9 (9)
N9—C5—C4	116.8 (6)	C20—C23—H27	124.7 (7)
O13—S12—N9—C5	49.5 (7)	C25—N26—C20—C19	−174.1 (7)
O14—S12—N9—C5	173.6 (6)	C25—N28—C29—N30	3.4 (13)
N15—S12—N9—C5	−68.0 (7)	C29—N28—C25—S24	−177.1 (7)
C19—S18—C1—C4	172.6 (4)	C29—N28—C25—N26	1.4 (14)
C1—S18—C19—C20	−59.1 (4)	C25—N28—C29—N31	−179.1 (8)
C23—S24—C25—N28	178.5 (7)	S18—C1—C4—C5	−72.7 (6)
C23—S24—C25—N26	−0.3 (7)	C1—C4—C5—N9	−43.1 (7)
C25—S24—C23—C20	−3.3 (6)	C1—C4—C5—N8	131.6 (7)
S12—N9—C5—N8	13.5 (12)	S18—C19—C20—C23	130.7 (7)
S12—N9—C5—C4	−172.8 (5)	S18—C19—C20—N26	−63.0 (7)
C20—N26—C25—S24	3.7 (9)	N26—C20—C23—S24	6.1 (9)
C20—N26—C25—N28	−174.9 (8)	C19—C20—C23—S24	172.7 (5)
C25—N26—C20—C23	−6.4 (10)