2-Amino-4-(4-meth­oxy­phen­yl)-6-(4-methyl­phen­yl)pyrimidin-1-ium chloride

Lee, J.H.; Koh, D.

doi:10.1107/S2414314618011525

organic compounds

IUCrDATA

ISSN: 2414-3146

Volume 3| Part 8| August 2018| x181152

https://doi.org/10.1107/S2414314618011525

Open

access

2-Amino-4-(4-methoxyphenyl)-6-(4-methylphenyl)pyrimidin-1-ium chloride

Ji Hye Lee ^a and Dongsoo Koh ^a ^*

^aDepartment of Applied Chemistry, Dongduk Women's University, Seoul 136-714, Republic of Korea
^*Correspondence e-mail: dskoh@dongduk.ac.kr

Edited by A. J. Lough, University of Toronto, Canada (Received 6 August 2018; accepted 15 August 2018; online 16 August 2018)

In the title salt, C₁₈H₁₈N₃O⁺·Cl⁻, the aminopyrimidine molecule is protonated at one of the pyrimidine N atoms. The chloride anion interacts with the protonated pyrimidine N—H group and one of the amino N—H groups through two N—H⋯Cl hydrogen bonds, forming a six-membered ring. The chloride anion interacts further with the other amino N—H group to form an additional N—H⋯Cl hydrogen bond, which links the molecules along [001] in a helical manner.

Keywords: crystal structure; pyrimidinium; molecular salt; N—H⋯Cl hydrogen bonds.

CCDC reference: 1862115

Structure description

As a result of their being a natural component of nucleic acid, aminopyrimidine derivatives are biologically important and have shown a broad spectrum of biological activities including anti-platelet (Giridhar et al., 2012 ), antitumor (Lee et al., 2011 ), anti-bacterial (Nagarajan et al., 2014 ) and anti-diabetic properties (Singh et al., 2011 ). As a continuation of our research program to expand the use of novel synthetic chalcones (Lee et al. 2016 ), the title aminopyrimidine compound was synthesized from chalcone and its crystal structure was determined. Other examples of aminopyrimidinium salt structures have been published recently (Swinton Darious et al., 2018 ; Jeevaraj et al., 2016 ).

The molecular structure of the title compound is shown in Fig. 1. The aminopyrimidine molecule is protonated at one of the pyrimidine nitrogen atoms. As a result, the two C—N—C bond angles in the pyrimidine ring are different: the C1—N2—C4 angle at protonated atom N2 is 121.1 (2)°, while for the unprotonated atom N1, the C1—N1—C2 angle is 117.8 (2)°.

Figure 1
The molecular structure of the title compound, showing the atom-labelling scheme and displacement ellipsoids drawn at the 30% probability level.

In the crystal, a six-membered ring is formed through N—H⋯Cl hydrogen bonds (aqua coloured dashed lines in Fig. 2, Table 1) involving one of the hydrogen atoms in the amino group (N3—H3B) and a hydrogen atom in the pyrimidium ring (N2—H2A) and the chlorine anion. An additional hydrogen bond is formed by the other hydrogen atom in the amino group (N3—H3A) and the chloride anion (orange dashed line in Fig. 2, Table 1), which links the molecules into a chain along [001]. The three N—H⋯Cl hydrogen bonds connect the molecules in helical manner along [001]. Six molecules are involved in one turn of the helix (Fig. 3).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N2—H2A⋯Cl1ⁱ	0.87	2.27	3.106 (3)	160
N3—H3A⋯Cl1ⁱⁱ	0.87	2.44	3.305 (3)	172
N3—H3B⋯Cl1ⁱ	0.87	2.56	3.332 (3)	148
C14—H14⋯O1ⁱⁱⁱ	0.94	2.46	3.300 (4)	148
Symmetry codes: (i) $[y+1, -x+y+1, z+{\script{1\over 6}}]$ ; (ii) x+1, y+1, z; (iii) $[-x+y, -x+1, z+{\script{1\over 3}}]$ .

Figure 2
Part of the crystal structure with intermolecular hydrogen bonds are shown as red and blue dashed lines. For clarity, only those H atoms involved in hydrogen bonding are shown.

Figure 3
Part of the crystal structure shown along the c axis. The three N—H⋯Cl hydrogen bonds connect molecules in a helical manner along the c axis.

Synthesis and crystallization

The same synthetic procedures were used as described in our previous report (Koh & Lee, 2018 ), but starting from 4-methoxy acetophenone and 4-methyl benzaldehyde for the synthesis of the chalcone intermediate, as shown in Fig. 4.

Figure 4
Synthetic scheme for the preparation of the title compound.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2.

Table 2
Experimental details

Crystal data
Chemical formula	C₁₈H₁₈N₃O⁺·Cl⁻
M_r	327.80
Crystal system, space group	Hexagonal, P6₅
Temperature (K)	223
a, c (Å)	9.9013 (9), 28.981 (2)
V (Å³)	2460.6 (5)
Z	6
Radiation type	Mo Kα
μ (mm⁻¹)	0.24
Crystal size (mm)	0.18 × 0.10 × 0.07

Data collection
Diffractometer	Bruker PHOTON 100 CMOS
Absorption correction	Multi-scan (SADABS; Bruker, 2012 )
T_min, T_max	0.721, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	135729, 4073, 3401
R_int	0.081
(sin θ/λ)_max (Å⁻¹)	0.668

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.040, 0.083, 1.10
No. of reflections	4073
No. of parameters	228
No. of restraints	1
H-atom treatment	Only H-atom displacement parameters refined
Δρ_max, Δρ_min (e Å⁻³)	0.19, −0.15
Absolute structure	Flack x determined using 1416 quotients [(I⁺)−(I⁻)]/[(I⁺)+(I⁻)] (Parsons et al., 2013 )
Absolute structure parameter	0.016 (15)
Computer programs: APEX2 and SAINT (Bruker, 2012), SHELXS and SHELXTL (Sheldrick, 2008 ), SHELXL2014 (Sheldrick, 2015 )and publCIF (Westrip, 2010 ).

Structural data

CCDC reference: 1862115

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314618011525/lh4038sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314618011525/lh4038Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2414314618011525/lh4038Isup3.cml

checkCIF report

Computing details top

Data collection: APEX2 (Bruker, 2012); cell refinement: SAINT (Bruker, 2012); data reduction: SAINT (Bruker, 2012); program(s) used to solve structure: SHELXS (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: publCIF (Westrip, 2010).

2-Amino-4-(4-methoxyphenyl)-6-(4-methylphenyl)pyrimidin-1-ium chloride top

Crystal data top

C₁₈H₁₈N₃O⁺·Cl⁻	D_x = 1.327 Mg m⁻³
M_r = 327.80	Mo Kα radiation, λ = 0.71073 Å
Hexagonal, P6₅	Cell parameters from 9935 reflections
a = 9.9013 (9) Å	θ = 2.4–26.1°
c = 28.981 (2) Å	µ = 0.24 mm⁻¹
V = 2460.6 (5) Å³	T = 223 K
Z = 6	Block, colourless
F(000) = 1032	0.18 × 0.10 × 0.07 mm

Data collection top

Bruker PHOTON 100 CMOS diffractometer	3401 reflections with I > 2σ(I)
φ and ω scans	R_int = 0.081
Absorption correction: multi-scan (SADABS; Bruker, 2012)	θ_max = 28.3°, θ_min = 2.4°
T_min = 0.721, T_max = 0.746	h = −13→13
135729 measured reflections	k = −13→13
4073 independent reflections	l = −38→38

Refinement top

Refinement on F²	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	Only H-atom displacement parameters refined
R[F² > 2σ(F²)] = 0.040	w = 1/[σ²(F_o²) + (0.0281P)² + 0.7437P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.083	(Δ/σ)_max = 0.005
S = 1.10	Δρ_max = 0.19 e Å⁻³
4073 reflections	Δρ_min = −0.15 e Å⁻³
228 parameters	Absolute structure: Flack x determined using 1416 quotients [(I⁺)-(I^-)]/[(I⁺)+(I^-)] (Parsons et al., 2013)
1 restraint	Absolute structure parameter: 0.016 (15)

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
C1	1.1580 (3)	0.9339 (3)	0.12113 (9)	0.0327 (6)
N1	1.0866 (3)	0.9519 (3)	0.08454 (8)	0.0324 (5)
C2	0.9390 (3)	0.8427 (3)	0.07668 (9)	0.0317 (6)
C3	0.8602 (3)	0.7103 (3)	0.10505 (10)	0.0363 (6)
H3	0.7569	0.6335	0.0984	0.041 (9)*
C4	0.9356 (3)	0.6949 (3)	0.14220 (9)	0.0327 (6)
N2	1.0862 (3)	0.8080 (3)	0.14949 (8)	0.0335 (5)
H2A	1.1373	0.7995	0.1727	0.056 (11)*
N3	1.3025 (3)	1.0421 (3)	0.13150 (9)	0.0402 (6)
H3A	1.3512	1.1252	0.1145	0.050 (10)*
H3B	1.3488	1.0301	0.1554	0.052 (11)*
C5	0.8595 (3)	0.8685 (3)	0.03772 (9)	0.0314 (6)
C6	0.9184 (3)	1.0184 (3)	0.01960 (10)	0.0353 (6)
H6	1.0093	1.1017	0.0323	0.038 (8)*
C7	0.8450 (4)	1.0454 (3)	−0.01649 (10)	0.0385 (7)
H7	0.8863	1.1466	−0.0286	0.041 (9)*
C8	0.7090 (3)	0.9226 (4)	−0.03525 (10)	0.0355 (6)
C9	0.6482 (4)	0.7740 (3)	−0.01741 (10)	0.0373 (6)
H9	0.5561	0.6912	−0.0298	0.047 (9)*
C10	0.7234 (4)	0.7477 (3)	0.01875 (10)	0.0358 (6)
H10	0.6819	0.6464	0.0307	0.039 (8)*
O1	0.6439 (3)	0.9614 (3)	−0.07036 (8)	0.0485 (6)
C11	0.5094 (4)	0.8394 (4)	−0.09247 (12)	0.0523 (9)
H11A	0.5351	0.7651	−0.1058	0.076 (13)*
H11B	0.4752	0.8831	−0.1167	0.073 (12)*
H11C	0.4266	0.7869	−0.0700	0.066 (12)*
C12	0.8636 (3)	0.5676 (3)	0.17621 (9)	0.0337 (6)
C13	0.7053 (4)	0.4976 (5)	0.18546 (15)	0.0597 (10)
H13	0.6432	0.5276	0.1687	0.084 (14)*
C14	0.6380 (4)	0.3837 (5)	0.21918 (15)	0.0617 (11)
H14	0.5307	0.3381	0.2252	0.079 (13)*
C15	0.7247 (4)	0.3361 (4)	0.24390 (10)	0.0417 (7)
C16	0.8803 (4)	0.3997 (4)	0.23269 (11)	0.0474 (8)
H16	0.9402	0.3638	0.2479	0.059 (11)*
C17	0.9500 (4)	0.5155 (3)	0.19954 (11)	0.0406 (7)
H17	1.0567	0.5586	0.1930	0.062 (11)*
C18	0.6526 (5)	0.2185 (4)	0.28224 (12)	0.0597 (10)
H18A	0.7155	0.1703	0.2880	0.088 (16)*
H18B	0.5481	0.1391	0.2734	0.082 (14)*
H18C	0.6477	0.2704	0.3101	0.12 (2)*
Cl1	0.47413 (9)	0.33310 (8)	0.05723 (3)	0.0449 (2)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0317 (15)	0.0354 (15)	0.0304 (13)	0.0165 (13)	0.0060 (11)	0.0016 (11)
N1	0.0319 (12)	0.0331 (13)	0.0304 (12)	0.0149 (10)	0.0030 (10)	0.0038 (10)
C2	0.0343 (15)	0.0355 (15)	0.0288 (13)	0.0201 (12)	0.0038 (11)	0.0026 (11)
C3	0.0316 (16)	0.0355 (15)	0.0392 (15)	0.0148 (13)	0.0015 (12)	0.0062 (12)
C4	0.0334 (15)	0.0339 (15)	0.0319 (15)	0.0177 (12)	0.0053 (11)	0.0033 (11)
N2	0.0328 (13)	0.0387 (13)	0.0294 (12)	0.0182 (11)	0.0019 (10)	0.0042 (10)
N3	0.0298 (13)	0.0434 (15)	0.0385 (14)	0.0117 (11)	0.0008 (11)	0.0092 (11)
C5	0.0338 (15)	0.0329 (14)	0.0293 (13)	0.0181 (12)	0.0038 (11)	0.0019 (11)
C6	0.0349 (15)	0.0331 (15)	0.0346 (15)	0.0145 (13)	−0.0005 (12)	0.0010 (12)
C7	0.0411 (17)	0.0331 (15)	0.0398 (16)	0.0174 (14)	0.0005 (13)	0.0050 (13)
C8	0.0410 (16)	0.0439 (17)	0.0281 (14)	0.0261 (14)	−0.0010 (12)	0.0004 (12)
C9	0.0387 (16)	0.0364 (16)	0.0334 (15)	0.0162 (13)	−0.0032 (12)	−0.0035 (12)
C10	0.0427 (16)	0.0297 (14)	0.0327 (14)	0.0163 (13)	0.0032 (12)	0.0022 (12)
O1	0.0548 (14)	0.0477 (13)	0.0455 (13)	0.0277 (12)	−0.0140 (10)	0.0018 (10)
C11	0.061 (2)	0.058 (2)	0.047 (2)	0.0364 (19)	−0.0178 (17)	−0.0105 (16)
C12	0.0370 (15)	0.0343 (15)	0.0317 (15)	0.0194 (13)	0.0047 (11)	0.0044 (11)
C13	0.0438 (19)	0.075 (3)	0.072 (2)	0.038 (2)	0.0222 (17)	0.041 (2)
C14	0.047 (2)	0.068 (3)	0.076 (3)	0.0336 (19)	0.0296 (19)	0.038 (2)
C15	0.0532 (19)	0.0341 (16)	0.0328 (15)	0.0181 (14)	0.0045 (13)	0.0022 (13)
C16	0.0474 (18)	0.0349 (16)	0.0466 (19)	0.0106 (14)	−0.0143 (15)	0.0093 (14)
C17	0.0335 (16)	0.0342 (15)	0.0455 (17)	0.0105 (13)	−0.0069 (13)	0.0048 (13)
C18	0.080 (3)	0.043 (2)	0.0413 (19)	0.019 (2)	0.0055 (18)	0.0100 (16)
Cl1	0.0498 (5)	0.0295 (3)	0.0452 (4)	0.0122 (3)	−0.0071 (3)	−0.0003 (3)

Geometric parameters (Å, º) top

C1—N3	1.324 (4)	C9—C10	1.384 (4)
C1—N1	1.335 (4)	C9—H9	0.9400
C1—N2	1.360 (4)	C10—H10	0.9400
N1—C2	1.333 (4)	O1—C11	1.426 (4)
C2—C3	1.407 (4)	C11—H11A	0.9700
C2—C5	1.470 (4)	C11—H11B	0.9700
C3—C4	1.361 (4)	C11—H11C	0.9700
C3—H3	0.9400	C12—C17	1.377 (4)
C4—N2	1.361 (4)	C12—C13	1.387 (4)
C4—C12	1.473 (4)	C13—C14	1.385 (5)
N2—H2A	0.8700	C13—H13	0.9400
N3—H3A	0.8700	C14—C15	1.369 (5)
N3—H3B	0.8700	C14—H14	0.9400
C5—C10	1.391 (4)	C15—C16	1.380 (5)
C5—C6	1.397 (4)	C15—C18	1.506 (4)
C6—C7	1.374 (4)	C16—C17	1.386 (4)
C6—H6	0.9400	C16—H16	0.9400
C7—C8	1.396 (4)	C17—H17	0.9400
C7—H7	0.9400	C18—H18A	0.9700
C8—O1	1.359 (4)	C18—H18B	0.9700
C8—C9	1.381 (4)	C18—H18C	0.9700

N3—C1—N1	120.2 (3)	C9—C10—C5	121.2 (3)
N3—C1—N2	117.6 (3)	C9—C10—H10	119.4
N1—C1—N2	122.2 (3)	C5—C10—H10	119.4
C2—N1—C1	117.8 (2)	C8—O1—C11	118.1 (3)
N1—C2—C3	121.9 (3)	O1—C11—H11A	109.5
N1—C2—C5	117.1 (2)	O1—C11—H11B	109.5
C3—C2—C5	121.0 (3)	H11A—C11—H11B	109.5
C4—C3—C2	119.1 (3)	O1—C11—H11C	109.5
C4—C3—H3	120.4	H11A—C11—H11C	109.5
C2—C3—H3	120.4	H11B—C11—H11C	109.5
N2—C4—C3	117.9 (3)	C17—C12—C13	118.5 (3)
N2—C4—C12	117.5 (2)	C17—C12—C4	121.6 (3)
C3—C4—C12	124.6 (3)	C13—C12—C4	119.9 (3)
C1—N2—C4	121.1 (2)	C14—C13—C12	120.4 (3)
C1—N2—H2A	119.5	C14—C13—H13	119.8
C4—N2—H2A	119.5	C12—C13—H13	119.8
C1—N3—H3A	120.0	C15—C14—C13	121.4 (3)
C1—N3—H3B	120.0	C15—C14—H14	119.3
H3A—N3—H3B	120.0	C13—C14—H14	119.3
C10—C5—C6	118.3 (3)	C14—C15—C16	117.9 (3)
C10—C5—C2	121.8 (3)	C14—C15—C18	121.0 (3)
C6—C5—C2	119.9 (3)	C16—C15—C18	121.0 (3)
C7—C6—C5	120.8 (3)	C15—C16—C17	121.4 (3)
C7—C6—H6	119.6	C15—C16—H16	119.3
C5—C6—H6	119.6	C17—C16—H16	119.3
C6—C7—C8	120.0 (3)	C12—C17—C16	120.2 (3)
C6—C7—H7	120.0	C12—C17—H17	119.9
C8—C7—H7	120.0	C16—C17—H17	119.9
O1—C8—C9	124.4 (3)	C15—C18—H18A	109.5
O1—C8—C7	115.6 (3)	C15—C18—H18B	109.5
C9—C8—C7	120.0 (3)	H18A—C18—H18B	109.5
C8—C9—C10	119.6 (3)	C15—C18—H18C	109.5
C8—C9—H9	120.2	H18A—C18—H18C	109.5
C10—C9—H9	120.2	H18B—C18—H18C	109.5

N3—C1—N1—C2	−177.3 (3)	O1—C8—C9—C10	−179.4 (3)
N2—C1—N1—C2	1.2 (4)	C7—C8—C9—C10	−0.6 (4)
C1—N1—C2—C3	−1.4 (4)	C8—C9—C10—C5	0.2 (4)
C1—N1—C2—C5	176.8 (2)	C6—C5—C10—C9	0.5 (4)
N1—C2—C3—C4	1.6 (4)	C2—C5—C10—C9	178.9 (3)
C5—C2—C3—C4	−176.6 (3)	C9—C8—O1—C11	−4.4 (4)
C2—C3—C4—N2	−1.5 (4)	C7—C8—O1—C11	176.8 (3)
C2—C3—C4—C12	175.9 (3)	N2—C4—C12—C17	−32.0 (4)
N3—C1—N2—C4	177.3 (3)	C3—C4—C12—C17	150.6 (3)
N1—C1—N2—C4	−1.2 (4)	N2—C4—C12—C13	147.8 (3)
C3—C4—N2—C1	1.3 (4)	C3—C4—C12—C13	−29.6 (5)
C12—C4—N2—C1	−176.3 (2)	C17—C12—C13—C14	3.4 (6)
N1—C2—C5—C10	162.7 (3)	C4—C12—C13—C14	−176.4 (4)
C3—C2—C5—C10	−19.1 (4)	C12—C13—C14—C15	−0.6 (7)
N1—C2—C5—C6	−19.0 (4)	C13—C14—C15—C16	−3.1 (6)
C3—C2—C5—C6	159.2 (3)	C13—C14—C15—C18	176.7 (4)
C10—C5—C6—C7	−0.9 (4)	C14—C15—C16—C17	4.1 (5)
C2—C5—C6—C7	−179.3 (3)	C18—C15—C16—C17	−175.7 (3)
C5—C6—C7—C8	0.6 (5)	C13—C12—C17—C16	−2.4 (5)
C6—C7—C8—O1	179.1 (3)	C4—C12—C17—C16	177.4 (3)
C6—C7—C8—C9	0.2 (4)	C15—C16—C17—C12	−1.4 (5)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2A···Cl1ⁱ	0.87	2.27	3.106 (3)	160
N3—H3A···Cl1ⁱⁱ	0.87	2.44	3.305 (3)	172
N3—H3B···Cl1ⁱ	0.87	2.56	3.332 (3)	148
C14—H14···O1ⁱⁱⁱ	0.94	2.46	3.300 (4)	148

Symmetry codes: (i) y+1, −x+y+1, z+1/6; (ii) x+1, y+1, z; (iii) −x+y, −x+1, z+1/3.

Funding information

The authors acknowledge financial support from the Basic Science Research Program (award No. NRF– 2016R1D1A1B03931623).

References

Bruker (2012). APEX2, SAINT and SADABS, Bruker AXS Inc. Madison, Wisconsin, USA. Google Scholar
Giridhar, R., Tamboli, R. S., Ramajayam, R., Prajapati, D. G. & Yadav, M. R. (2012). Eur. J. Med. Chem. 50, 428–432. Web of Science CrossRef Google Scholar
Jeevaraj, M., Edison, B., Kavitha, S. J., Thanikasalam, K., Britto, S. & Balasubramani, K. (2016). IUCrData, 1, x161010. Google Scholar
Koh, D. & Lee, J. (2018). IUCrData, 3, x180796. Google Scholar
Lee, Y., Kim, B. S., Ahn, S., Koh, D., Lee, Y. H., Shin, S. Y. & Lim, Y. (2016). Bioorg. Chem. 68, 166–176. Web of Science CrossRef Google Scholar
Lee, J., Kim, K.-H. & Jeong, S. (2011). Bioorg. Med. Chem. Lett. 21, 4203–4205. Web of Science CrossRef Google Scholar
Nagarajan, S., Shanmugavelan, P., Sathishkumar, M., Selvi, R., Ponnuswamy, A., Harikrishnan, H., Shanmugaiah, V. & Murugavel, S. (2014). Bioorg. Med. Chem. Lett. 24, 4999–5007. Web of Science CrossRef Google Scholar
Parsons, S., Flack, H. D. & Wagner, T. (2013). Acta Cryst. B69, 249–259. Web of Science CrossRef CAS IUCr Journals Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Sheldrick, G. M. (2015). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Singh, N., Pandey, S. K., Anand, N., Dwivedi, R., Singh, S., Sinha, S. K., Chaturvedi, V., Jaiswal, N., Srivastava, A. K., Shah, P., Siddiqui, M. I. & Tripathi, R. P. (2011). Bioorg. Med. Chem. Lett. 21, 4404–4408. Web of Science CrossRef Google Scholar
Swinton Darious, R., Thomas Muthiah, P. & Perdih, F. (2018). Acta Cryst. E74, 237–241. Web of Science CrossRef IUCr Journals Google Scholar
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Web of Science CrossRef CAS IUCr Journals Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.