The role of multiple observations in small-molecule single-crystal service X-ray structure determination

In order to gain a better understanding of how to improve the quality of small-molecule single-crystal X-ray diffraction data achievable in a finite time, a study was carried out to investigate the effect of varying the multiplicity, acquisition time, detector binning, maximum resolution and completeness. The results suggest that, unless there are strong arguments for a different strategy, a good routine procedure might be to optimize the conditions necessary to get the best data from single scans, and then choose a multiplicity of observations (MoO) to utilize the available time fully. Different strategies may be required if the crystal is highly absorbing, is larger than the incident beam, is enclosed in a capillary tube or is unusual in some other way. The signal-to-noise ratio should be used with care, as collecting data for longer or at higher multiplicity appears to give a systematic underestimate of the intensity uncertainties. Further, the results demonstrate that including poor-quality data in a refinement may degrade the result and, in the general case, the accidental omission of reflections has a very small impact on the refinement as long as they are omitted at random. Systematic omission of reflections needs a convincing procedural justification.

Computing details

Data collection: SuperNova, (Oxford Diffraction, 2010); cell refinement: CrysAlis PRO (Rigaku Oxford Diffraction, 2017); data reduction: CrysAlis PRO (Rigaku Oxford Diffraction, 2017); program(s) used to solve structure: Superflip (Palatinus & Chapuis, 2007); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: CRYSTALS (Betteridge et al., 2003).

(I)

Crystal data

C24H16	F(000) = 640
Mr = 304.39	Dx = 1.216 Mg m^−3
Monoclinic, P21/n	Melting point: not measured K
Hall symbol: -P 2yn	Cu Kα radiation, λ = 1.54184 Å
a = 9.8367 (5) Å	Cell parameters from 1470 reflections
b = 17.1456 (8) Å	θ = 5–76°
c = 9.8764 (4) Å	µ = 0.52 mm^−1
β = 93.730 (4)°	T = 290 K
V = 1662.19 (13) Å^3	Lath, clear_pale_colourless
Z = 4	0.25 × 0.12 × 0.03 mm

Data collection

Oxford Diffraction SuperNova diffractometer	2035 reflections with I > 2.0σ(I)
Focussing mirrors monochromator	Rint = 0.057
ω scans	θmax = 77.0°, θmin = 5.2°
Absorption correction: multi-scan CrysAlisPro (Rigaku Oxford Diffraction, 2017)	h = −12→12
Tmin = 0.88, Tmax = 1.00	k = −21→21
13736 measured reflections	l = −12→7
3489 independent reflections

Refinement

Refinement on F^2	Primary atom site location: other
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.059	H-atom parameters constrained
wR(F^2) = 0.173	Method = Modified Sheldrick w = 1/[σ^2(F^2) + ( 0.06P)^2 + 0.29P] , where P = (max(Fo^2,0) + 2Fc^2)/3
S = 1.02	(Δ/σ)max = 0.0002
3488 reflections	Δρmax = 0.30 e Å^−3
217 parameters	Δρmin = −0.33 e Å^−3
0 restraints

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

	x	y	z	Uiso*/Ueq
C241	0.4227 (3)	0.70696 (15)	0.4119 (2)	0.0531
C242	0.3843 (3)	0.64034 (14)	0.3202 (2)	0.0510
C243	0.3012 (3)	0.58001 (14)	0.3598 (2)	0.0510
C244	0.2516 (3)	0.57509 (14)	0.4996 (2)	0.0521
C245	0.1561 (3)	0.62754 (15)	0.5452 (2)	0.0518
C246	0.0983 (3)	0.69156 (15)	0.4567 (2)	0.0508
C247	0.1781 (3)	0.75212 (14)	0.4123 (2)	0.0501
C248	0.3258 (3)	0.75993 (14)	0.4525 (2)	0.0526
C249	0.3709 (4)	0.82531 (16)	0.5274 (3)	0.0690
C250	0.5083 (4)	0.8367 (2)	0.5622 (3)	0.0869
C251	0.6022 (4)	0.7840 (2)	0.5239 (3)	0.0880
C252	0.5605 (3)	0.7196 (2)	0.4485 (3)	0.0710
C253	0.1153 (3)	0.81115 (15)	0.3319 (3)	0.0623
C254	−0.0220 (3)	0.8102 (2)	0.2965 (3)	0.0734
C255	−0.1001 (3)	0.7509 (2)	0.3410 (3)	0.0784
C256	−0.0413 (3)	0.69247 (19)	0.4207 (3)	0.0662
C257	0.1087 (3)	0.61708 (18)	0.6740 (3)	0.0650
C258	0.1562 (4)	0.55616 (19)	0.7567 (3)	0.0756
C259	0.2512 (4)	0.50555 (19)	0.7121 (3)	0.0786
C260	0.2979 (3)	0.51439 (17)	0.5847 (3)	0.0663
C261	0.2680 (3)	0.51992 (16)	0.2681 (3)	0.0680
C262	0.3163 (4)	0.51976 (18)	0.1400 (3)	0.0775
C263	0.4004 (4)	0.57836 (18)	0.1020 (3)	0.0744
C264	0.4347 (3)	0.63796 (17)	0.1910 (3)	0.0636
H2491	0.3048	0.8610	0.5566	0.0830*
H2501	0.5345	0.8812	0.6128	0.1037*
H2511	0.6961	0.7923	0.5490	0.1061*
H2521	0.6258	0.6836	0.4189	0.0854*
H2531	0.1709	0.8509	0.2992	0.0750*
H2541	−0.0617	0.8512	0.2430	0.0880*
H2551	−0.1945	0.7500	0.3179	0.0942*
H2561	−0.0957	0.6509	0.4523	0.0799*
H2571	0.0421	0.6521	0.7043	0.0779*
H2581	0.1233	0.5502	0.8439	0.0907*
H2591	0.2845	0.4645	0.7695	0.0945*
H2601	0.3622	0.4789	0.5536	0.0797*
H2611	0.2090	0.4794	0.2956	0.0817*
H2621	0.2906	0.4793	0.0775	0.0929*
H2631	0.4352	0.5779	0.0152	0.0891*
H2641	0.4938	0.6793	0.1677	0.0761*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C241	0.0522 (14)	0.0560 (14)	0.0515 (13)	−0.0093 (11)	0.0055 (11)	0.0089 (11)
C242	0.0514 (14)	0.0481 (13)	0.0540 (13)	0.0074 (11)	0.0061 (11)	0.0044 (10)
C243	0.0596 (15)	0.0416 (12)	0.0524 (13)	0.0073 (11)	0.0077 (11)	−0.0003 (10)
C244	0.0605 (15)	0.0446 (13)	0.0516 (13)	−0.0062 (11)	0.0065 (11)	0.0018 (10)
C245	0.0570 (15)	0.0496 (13)	0.0489 (12)	−0.0077 (11)	0.0049 (11)	−0.0007 (10)
C246	0.0504 (13)	0.0543 (14)	0.0481 (12)	0.0032 (11)	0.0064 (10)	−0.0045 (11)
C247	0.0614 (15)	0.0449 (12)	0.0442 (11)	0.0072 (11)	0.0038 (10)	−0.0062 (9)
C248	0.0635 (15)	0.0468 (13)	0.0472 (12)	−0.0072 (11)	0.0005 (11)	0.0033 (10)
C249	0.097 (2)	0.0529 (15)	0.0556 (15)	−0.0176 (15)	−0.0026 (15)	−0.0009 (12)
C250	0.113 (3)	0.085 (2)	0.0604 (17)	−0.051 (2)	−0.0080 (18)	0.0031 (16)
C251	0.076 (2)	0.114 (3)	0.072 (2)	−0.045 (2)	−0.0051 (17)	0.013 (2)
C252	0.0549 (16)	0.088 (2)	0.0699 (17)	−0.0148 (15)	0.0035 (13)	0.0138 (16)
C253	0.085 (2)	0.0467 (13)	0.0546 (14)	0.0124 (13)	0.0030 (13)	−0.0010 (11)
C254	0.080 (2)	0.082 (2)	0.0569 (16)	0.0349 (18)	−0.0017 (15)	−0.0043 (14)
C255	0.0590 (18)	0.114 (3)	0.0624 (16)	0.0226 (18)	0.0045 (14)	−0.0009 (17)
C256	0.0521 (15)	0.089 (2)	0.0585 (15)	0.0030 (14)	0.0104 (12)	−0.0024 (14)
C257	0.0715 (19)	0.0691 (18)	0.0557 (15)	−0.0070 (14)	0.0144 (13)	−0.0021 (13)
C258	0.096 (2)	0.077 (2)	0.0555 (16)	−0.0119 (18)	0.0155 (16)	0.0117 (14)
C259	0.103 (3)	0.0665 (19)	0.0667 (18)	−0.0044 (18)	0.0075 (17)	0.0199 (15)
C260	0.081 (2)	0.0516 (15)	0.0671 (16)	0.0031 (14)	0.0084 (14)	0.0106 (13)
C261	0.096 (2)	0.0431 (14)	0.0659 (17)	0.0008 (14)	0.0093 (15)	−0.0037 (12)
C262	0.122 (3)	0.0512 (16)	0.0594 (16)	0.0177 (17)	0.0078 (17)	−0.0068 (13)
C263	0.105 (3)	0.0636 (18)	0.0567 (15)	0.0267 (18)	0.0220 (16)	0.0026 (13)
C264	0.0706 (18)	0.0617 (17)	0.0602 (15)	0.0122 (14)	0.0171 (13)	0.0094 (13)

Geometric parameters (Å, º)

C241—C242	1.491 (3)	C252—H2521	0.951
C241—C248	1.395 (4)	C253—C254	1.373 (4)
C241—C252	1.397 (4)	C253—H2531	0.945
C242—C243	1.391 (3)	C254—C255	1.365 (5)
C242—C264	1.399 (3)	C254—H2541	0.948
C243—C244	1.497 (3)	C255—C256	1.377 (4)
C243—C261	1.396 (3)	C255—H2551	0.942
C244—C245	1.396 (3)	C256—H2561	0.955
C244—C260	1.395 (3)	C257—C258	1.388 (4)
C245—C246	1.492 (3)	C257—H2571	0.951
C245—C257	1.395 (3)	C258—C259	1.369 (4)
C246—C247	1.390 (3)	C258—H2581	0.946
C246—C256	1.396 (3)	C259—C260	1.376 (4)
C247—C248	1.488 (4)	C259—H2591	0.949
C247—C253	1.405 (3)	C260—H2601	0.943
C248—C249	1.399 (3)	C261—C262	1.380 (4)
C249—C250	1.387 (4)	C261—H2611	0.956
C249—H2491	0.952	C262—C263	1.369 (5)
C250—C251	1.363 (5)	C262—H2621	0.952
C250—H2501	0.939	C263—C264	1.376 (4)
C251—C252	1.380 (5)	C263—H2631	0.944
C251—H2511	0.951	C264—H2641	0.954
C242—C241—C248	121.5 (2)	C247—C253—C254	121.6 (3)
C242—C241—C252	118.6 (3)	C247—C253—H2531	118.1
C248—C241—C252	119.6 (3)	C254—C253—H2531	120.3
C241—C242—C243	121.9 (2)	C253—C254—C255	119.4 (3)
C241—C242—C264	119.0 (2)	C253—C254—H2541	119.7
C243—C242—C264	119.0 (2)	C255—C254—H2541	120.8
C242—C243—C244	122.3 (2)	C254—C255—C256	120.1 (3)
C242—C243—C261	118.9 (2)	C254—C255—H2551	120.0
C244—C243—C261	118.7 (2)	C256—C255—H2551	119.9
C243—C244—C245	121.9 (2)	C246—C256—C255	121.5 (3)
C243—C244—C260	119.0 (2)	C246—C256—H2561	118.1
C245—C244—C260	119.1 (2)	C255—C256—H2561	120.3
C244—C245—C246	121.6 (2)	C245—C257—C258	120.9 (3)
C244—C245—C257	118.9 (2)	C245—C257—H2571	119.0
C246—C245—C257	119.4 (2)	C258—C257—H2571	120.1
C245—C246—C247	122.2 (2)	C257—C258—C259	119.9 (3)
C245—C246—C256	119.2 (2)	C257—C258—H2581	119.7
C247—C246—C256	118.5 (3)	C259—C258—H2581	120.4
C246—C247—C248	123.0 (2)	C258—C259—C260	120.0 (3)
C246—C247—C253	118.7 (3)	C258—C259—H2591	119.6
C248—C247—C253	118.2 (2)	C260—C259—H2591	120.4
C247—C248—C241	122.6 (2)	C244—C260—C259	121.2 (3)
C247—C248—C249	118.9 (3)	C244—C260—H2601	119.0
C241—C248—C249	118.4 (3)	C259—C260—H2601	119.8
C248—C249—C250	120.9 (3)	C243—C261—C262	121.1 (3)
C248—C249—H2491	118.5	C243—C261—H2611	118.2
C250—C249—H2491	120.6	C262—C261—H2611	120.7
C249—C250—C251	120.4 (3)	C261—C262—C263	120.0 (3)
C249—C250—H2501	118.4	C261—C262—H2621	120.3
C251—C250—H2501	121.2	C263—C262—H2621	119.7
C250—C251—C252	119.8 (3)	C262—C263—C264	119.8 (3)
C250—C251—H2511	119.5	C262—C263—H2631	120.2
C252—C251—H2511	120.7	C264—C263—H2631	119.9
C241—C252—C251	120.9 (3)	C242—C264—C263	121.2 (3)
C241—C252—H2521	118.9	C242—C264—H2641	117.2
C251—C252—H2521	120.2	C263—C264—H2641	121.7