Supra­molecular inter­actions in the 1:2 co-crystal of 4,4′-bipyridine and 3-chloro­thio­phene-2-carb­oxy­lic acid

Prajina, O.; Thomas Muthiah, P.; Geiger, D.K.

doi:10.1107/S2056989016013724

research communications

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Volume 72| Part 10| October 2016| Pages 1362-1365

https://doi.org/10.1107/S2056989016013724

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Supramolecular interactions in the 1:2 co-crystal of 4,4′-bipyridine and 3-chlorothiophene-2-carboxylic acid

Olakkandiyil Prajina,^a Packianathan Thomas Muthiah ^a ^* and David K. Geiger ^b

^aSchool of Chemistry, Bharathidasan University, Tiruchirappalli 620 024, Tamilnadu, India, and ^bDepartment of Chemistry, SUNY-College at Geneseo, Geneseo, New York 14454, USA
^*Correspondence e-mail: tommtrichy@yahoo.co.in

Edited by P. C. Healy, Griffith University, Australia (Received 17 August 2016; accepted 26 August 2016; online 5 September 2016)

The asymmetric unit of the title compound, 2C₅H₃ClO₂S·C₁₀H₈N₂, is comprised of a molecule of 3-chlorothiophene-2-carboxylic acid (3TPC) and half of a molecule of 4,4′-bipyridine (BPY). A distinctive O—H⋯N-based synthon is present. Cl⋯Cl and π–π stacking interactions further stabilize the crystal structure, forming a two-dimensional network parallel to the bc plane.

Keywords: crystal structure; 3-chlorothiophene-2-carboxylic acid; 4,4′-bipyridine; O—H⋯N-based synthon; co-crystal.

CCDC reference: 1501060

1. Chemical context

Structurally homogeneous crystalline solids in well defined stochiometry are called co-crystals. In recent years, the physicochemical properties of active pharmaceutical ingredients have been improved widely with the use of co-crystals (Lemmerer & Bernstein, 2010 ). Supramolecular synthons – modular representation of primary recognition between functional groups – are of great importance in providing an effective strategy for designing solids in crystal engineering. All geometrical and chemical information of molecular recognition is contained in the structural units called synthons. In the context of co-crystal formation, heterosynthons provide a predictive justification in terms of unique intermolecular interactions (Mukherjee et al., 2011 , 2013 ). There are many literature cases of O—H⋯N-bonded interactions between acid and pyridine-based systems (Shattock et al., 2008 ; Lemmerer et al., 2015 ). 4,4′-Bipyridine (BPY) is a weak bidentate base commonly used in crystal engineering on account of its bridging abilities. It also acts as the co-crystal former in the present study because it readily participates in hydrogen bonds with carboxyl-attached organic molecules (Pan et al., 2008 ).

Intermolecular interactions involving halogen substituents, particularly chlorides, play an important role in molecular self-assembly in supra- and biomolecular systems to prepare highly stereoregular organic polymers. It has been observed that these interactions act as a tool in crystal engineering to enhance crystal formation and for the design of supramolecular aggregates (Cavallo et al., 2016 ). In this context, the study of the effect of various halogens on the molecular packing and crystalline architecture of solids has attracted great attention (Csöregh et al., 2001 ). The structure-forming ability of Cl⋯Cl interactions in assembling chains, ladders, two-dimensional sheets, etc. has been studied extensively (Navon et al., 1997 ; Metrangolo & Resnati, 2014 ). It is based on the values of the two C—Hal⋯Hal angles, θ1 and θ2 (Vener et al., 2013 ).

2. Structural commentary

The asymmetric unit of the title compound (I) consists of a molecule of 3-chlorothiophene-2-carboxylic acid, 3TPC, and a half of a molecule of 4,4′-bipyridine, BPY, which is located on a crystallographic inversion center. The internal angle at N1 in BPY is 117.1 (3)° and bond lengths [N1-C6= 1.336 (5) Å and N1-C10 = 1.329 (5) Å] agree with those reported for neutral BPY structures (see for example Jennifer & Muthiah, 2014 ; Atria et al., 2014 ; Moon & Park, 2012 ; Qin, 2011 ; Najafpour et al., 2008 ). The two external bond angles at the carbon of the carboxyl group are 123.7 (3)° and 112.4 (3)°. The high discrepancy between these two angles is typical of an unionized carboxyl group, as are the C=O distance of 1.219 (4) Å and C—OH distance of 1.3254 (5) Å (see for example Prajina et al., 2016 ; Atria et al., 2014; Jennifer & Muthiah, 2014; Qin, 2011). The bond distances and angles of the thiophene ring agree with those in structures reported earlier (Zhang et al., 2014 ).

3. Supramolecular features

3TPC and BPY are interconnected via O—H⋯N hydrogen-bonding interactions between (O1—H1) of the carboxyl group and the nitrogen (N1) of BPY (Table 1 and Fig. 1). This O—H⋯N hydrogen bond is a frequently observed supramolecular synthon in crystal engineering involving a carboxylic acid and a pyridine system (Dubey & Desiraju, 2015 ; Lemmerer & Bernstein, 2010; Mukherjee et al., 2011, 2013; Prajina et al., 2016; Seaton, 2014 ; Thomas et al., 2010 ). This supramolecular synthon is also present in the co-crystal of 5-chlorothiophene-2-carboxylic acid with BPY (5TPC44BIPY) and in the co-crystal of thiophene-2-carboxylic acid with BPY reported from our laboratory (Jennifer & Muthiah, 2014). The co-crystal 5TPC44BIPY and the title co-crystal differ only in the position of chlorine in the thiophene ring with the same base. A chloro derivative was chosen as co-molecule with the expectation that the presence of a Cl atom would result in halogen–halogen interactions. As expected, a Cl⋯Cl interaction plays the key role in connecting the O—H⋯N hydrogen-bonded units to form an infinite zigzag chain, i.e., the three-molecule aggregates are further linked to similar neighbouring aggregates through Cl⋯Cl interactions [3.3925 (12) Å, C3—Cl1⋯Cl1ⁱⁱⁱ = 151.71 (1)°; symmetry code: (iii) 1 − x, y, $[{1\over 2}]$ − z] (Vener et al., 2013; Sarma & Desiraju, 1986 ; Capdevila-Cortada et al., 2014 ). The hydrogen-bonded units are stabilized via π–π stacking interactions between the aromatic systems of BPY molecules [Cg1⋯Cg1ⁱⁱ = 3.794 (2) Å; Cg1 is the centroid of the N1/C6/C7/C8/C9/C10 ring; symmetry code: (ii) 1 − x, 2 − y, 1 − z]. The perpendicular distance between two parallel molecules is 3.4812 (15) Å. This weak interaction holds the hydrogen-bonded chains together, supporting a two-dimensional supramolecular network parallel to the bc plane, as seen in Fig. 2.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯N1ⁱ	0.89 (5)	1.77 (5)	2.659 (4)	178 (5)
Symmetry code: (i) x, y-1, z.

Figure 1
The asymmetric unit of the title compound, showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. The dashed line represents the O—H⋯N hydrogen bond. [Symmetry code: (i) −x + 1, −y + 1, −z + 1.]

Figure 2
A view of the O—H⋯N hydrogen bonds (black dashed lines), π–π stacking (brown dashed lines) and Cl⋯Cl interactions (blue dashed lines). Symmetry codes: (i) x, y − 1, z; (ii) 1 − x, 2 − y, 1 – z; (iii) 1 − x, y, $[{1\over 2}]$ − z.

4. Database survey

In the title compound, the most dominant interaction is the O—H⋯N hydrogen bond formed between a carboxyl group and a pyridine N atom (Fig. 1). The length of this hydrogen bond [O⋯N = 2.659 (4) Å] is very close to those of O—H⋯N bonds found in similar reported co-crystals, such as in the adduct of 2,5-dihydroxy-1,4-benzoquinone and BPY (Cowan et al., 2001 ) and in the co-crystal of BPY with N,N′-dioxide-3-hydroxy-2-naphthoic acid (1/2) (Lou & Huang, 2007 ) and in a series of nine co-crystals involving acridine and benzoic acids (Kowalska et al., 2015 ). The angle of the hydrogen bond formed between the 3CTPC and BPY molecules is 178 (5)°. A similar value is found in the co-crystal of BPY with 3,5-dinitro benzoic acid for which the O⋯N distance is 2.547 (2) Å (Thomas et al., 2010). In the crystal structure of the co-crystal of adamantane-1,3-dicarboxylic acid and 4,4′-bipyridine, π–π interactions connect the O—H⋯N hydrogen-bonded zigzag chains, supporting a two-dimensional network (Pan et al., 2008).

5. Synthesis and crystallization

To 10 ml of a hot methanol solution of 3TPC (40.6 mg, 25 mmol), 10 ml of a hot methanolic solution of BPY (39.0 mg, 25 mmol) was added. The resulting solution was warmed over a water bath for half an hour and then kept at room temperature for crystallization. After a week, clear yellow plates were obtained. The crystal used for X-ray diffraction data collection was cut from a larger crystal.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. All hydrogen atoms were located in difference Fourier maps. The hydrogen atoms bonded to carbon were refined using a riding model with C—H = 0.95 Å and U_iso(H) = 1.2U_eq(C). The carboxylic acid hydrogen atom was freely refined, including its isotropic displacement parameter.

Table 2
Experimental details

Crystal data
Chemical formula	2C₅H₃ClO₂S·C₁₀H₈N₂
M_r	481.35
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	200
a, b, c (Å)	13.538 (4), 5.1230 (18), 30.167 (10)
β (°)	95.968 (9)
V (Å³)	2080.8 (12)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	0.54
Crystal size (mm)	0.50 × 0.50 × 0.10

Data collection
Diffractometer	Bruker SMART X2S benchtop
Absorption correction	Multi-scan (SADABS; Bruker, 2013 )
T_min, T_max	0.69, 0.95
No. of measured, independent and observed [I > 2σ(I)] reflections	10427, 1907, 1563
R_int	0.078
(sin θ/λ)_max (Å⁻¹)	0.607

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.055, 0.136, 1.19
No. of reflections	1907
No. of parameters	140
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.37, −0.32
Computer programs: APEX2 (Bruker, 2013), SAINT (Bruker, 2013), SHELXS97 (Sheldrick, 2008 ), SHELXL2014 (Sheldrick, 2015 ), PLATON (Spek, 2009 ), Mercury (Macrae et al., 2008 ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 1501060

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989016013724/hg5476sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989016013724/hg5476Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989016013724/hg5476Isup3.cml

checkCIF report

Computing details top

Data collection: APEX2 (Bruker, 2013); cell refinement: SAINT (Bruker, 2013); data reduction: SAINT (Bruker, 2013); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: PLATON (Spek, 2009) and Mercury (Macrae et al., 2008); software used to prepare material for publication: publCIF (Westrip, 2010).

bis(3-Chlorothiophene-2-carboxylic acid); 4,4'-bipyridine top

Crystal data top

2C₅H₃ClO₂S·C₁₀H₈N₂	F(000) = 984
M_r = 481.35	D_x = 1.537 Mg m⁻³
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 13.538 (4) Å	Cell parameters from 3438 reflections
b = 5.1230 (18) Å	θ = 2.7–24.8°
c = 30.167 (10) Å	µ = 0.54 mm⁻¹
β = 95.968 (9)°	T = 200 K
V = 2080.8 (12) Å³	Plate, clear colourless
Z = 4	0.50 × 0.50 × 0.10 mm

Data collection top

Bruker SMART X2S benchtop diffractometer	1563 reflections with I > 2σ(I)
Radiation source: sealed microfocus tube	R_int = 0.078
ω scans	θ_max = 25.6°, θ_min = 1.4°
Absorption correction: multi-scan (SADABS; Bruker, 2013)	h = −16→16
T_min = 0.69, T_max = 0.95	k = −6→6
10427 measured reflections	l = −36→36
1907 independent reflections

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Hydrogen site location: mixed
R[F² > 2σ(F²)] = 0.055	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.136	w = 1/[σ²(F_o²) + (0.0431P)² + 4.3057P] where P = (F_o² + 2F_c²)/3
S = 1.19	(Δ/σ)_max < 0.001
1907 reflections	Δρ_max = 0.37 e Å⁻³
140 parameters	Δρ_min = −0.32 e Å⁻³

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
N1	0.3544 (2)	0.9782 (6)	0.54889 (10)	0.0363 (7)
C8	0.4696 (2)	0.6000 (7)	0.51024 (11)	0.0312 (8)
C7	0.4776 (3)	0.6415 (8)	0.55606 (12)	0.0406 (9)
H7	0.5227	0.5401	0.5752	0.049*
C6	0.4200 (3)	0.8304 (8)	0.57370 (11)	0.0385 (9)
H6	0.4275	0.8563	0.6051	0.046*
C10	0.3468 (3)	0.9421 (8)	0.50506 (12)	0.0423 (9)
H10	0.3016	1.0481	0.4868	0.051*
C9	0.4017 (3)	0.7571 (7)	0.48451 (12)	0.0386 (9)
H9	0.3931	0.7377	0.4530	0.046*
S1	0.12214 (6)	0.6112 (2)	0.64475 (3)	0.0420 (3)
Cl1	0.40721 (6)	0.8001 (2)	0.70764 (3)	0.0447 (3)
O1	0.24836 (19)	0.2918 (6)	0.59585 (9)	0.0462 (7)
O2	0.39160 (18)	0.3397 (5)	0.63983 (8)	0.0411 (6)
C2	0.2498 (2)	0.5841 (7)	0.65494 (11)	0.0304 (7)
C5	0.1177 (3)	0.8526 (8)	0.68316 (12)	0.0454 (10)
H5	0.0579	0.9341	0.6899	0.054*
C4	0.2091 (3)	0.9160 (8)	0.70321 (12)	0.0414 (9)
H4	0.2210	1.0482	0.7252	0.050*
C3	0.2846 (2)	0.7602 (7)	0.68722 (10)	0.0312 (8)
C1	0.3043 (3)	0.3936 (7)	0.63023 (11)	0.0325 (8)
H1	0.283 (4)	0.184 (10)	0.5800 (16)	0.072 (15)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.0315 (16)	0.0350 (17)	0.0435 (17)	−0.0014 (13)	0.0097 (13)	−0.0083 (13)
C8	0.0258 (18)	0.0349 (19)	0.0340 (17)	−0.0042 (15)	0.0083 (14)	−0.0031 (14)
C7	0.041 (2)	0.049 (2)	0.0321 (18)	0.0065 (18)	0.0083 (16)	−0.0011 (16)
C6	0.042 (2)	0.042 (2)	0.0330 (18)	−0.0001 (17)	0.0108 (15)	−0.0080 (15)
C10	0.040 (2)	0.046 (2)	0.041 (2)	0.0100 (18)	0.0024 (16)	−0.0040 (17)
C9	0.041 (2)	0.042 (2)	0.0331 (18)	0.0043 (17)	0.0029 (15)	−0.0075 (15)
S1	0.0207 (5)	0.0602 (7)	0.0448 (5)	0.0069 (4)	0.0021 (4)	−0.0076 (4)
Cl1	0.0261 (5)	0.0630 (7)	0.0440 (5)	0.0012 (4)	−0.0013 (4)	−0.0081 (4)
O1	0.0313 (14)	0.0611 (19)	0.0459 (15)	0.0083 (13)	0.0023 (12)	−0.0207 (14)
O2	0.0254 (13)	0.0515 (17)	0.0466 (14)	0.0130 (12)	0.0047 (11)	−0.0053 (12)
C2	0.0196 (16)	0.040 (2)	0.0316 (17)	0.0064 (14)	0.0048 (13)	0.0036 (14)
C5	0.031 (2)	0.061 (3)	0.045 (2)	0.0188 (19)	0.0092 (16)	−0.0057 (18)
C4	0.038 (2)	0.051 (2)	0.0357 (19)	0.0114 (18)	0.0063 (16)	−0.0071 (16)
C3	0.0233 (17)	0.042 (2)	0.0282 (16)	0.0065 (15)	0.0034 (13)	0.0029 (14)
C1	0.0294 (19)	0.0352 (19)	0.0335 (17)	0.0025 (15)	0.0056 (14)	0.0019 (14)

Geometric parameters (Å, º) top

N1—C10	1.329 (5)	S1—C2	1.729 (3)
N1—C6	1.336 (5)	Cl1—C3	1.721 (3)
C8—C7	1.391 (5)	O1—C1	1.325 (4)
C8—C9	1.395 (5)	O1—H1	0.89 (5)
C8—C8ⁱ	1.489 (7)	O2—C1	1.219 (4)
C7—C6	1.384 (5)	C2—C3	1.374 (5)
C7—H7	0.9500	C2—C1	1.472 (5)
C6—H6	0.9500	C5—C4	1.359 (6)
C10—C9	1.389 (5)	C5—H5	0.9500
C10—H10	0.9500	C4—C3	1.421 (5)
C9—H9	0.9500	C4—H4	0.9500
S1—C5	1.700 (4)

C10—N1—C6	117.1 (3)	C1—O1—H1	112 (3)
C7—C8—C9	116.3 (3)	C3—C2—C1	129.8 (3)
C7—C8—C8ⁱ	121.8 (4)	C3—C2—S1	109.7 (3)
C9—C8—C8ⁱ	121.8 (4)	C1—C2—S1	120.5 (3)
C6—C7—C8	120.0 (3)	C4—C5—S1	112.4 (3)
C6—C7—H7	120.0	C4—C5—H5	123.8
C8—C7—H7	120.0	S1—C5—H5	123.8
N1—C6—C7	123.4 (3)	C5—C4—C3	111.7 (3)
N1—C6—H6	118.3	C5—C4—H4	124.2
C7—C6—H6	118.3	C3—C4—H4	124.2
N1—C10—C9	123.4 (3)	C2—C3—C4	113.8 (3)
N1—C10—H10	118.3	C2—C3—Cl1	125.4 (3)
C9—C10—H10	118.3	C4—C3—Cl1	120.9 (3)
C10—C9—C8	119.8 (3)	O2—C1—O1	123.9 (3)
C10—C9—H9	120.1	O2—C1—C2	123.7 (3)
C8—C9—H9	120.1	O1—C1—C2	112.4 (3)
C5—S1—C2	92.46 (18)

C9—C8—C7—C6	0.0 (5)	S1—C5—C4—C3	−0.9 (5)
C8ⁱ—C8—C7—C6	179.7 (4)	C1—C2—C3—C4	179.3 (3)
C10—N1—C6—C7	−1.4 (6)	S1—C2—C3—C4	−0.4 (4)
C8—C7—C6—N1	0.8 (6)	C1—C2—C3—Cl1	−0.3 (6)
C6—N1—C10—C9	1.4 (6)	S1—C2—C3—Cl1	180.0 (2)
N1—C10—C9—C8	−0.7 (6)	C5—C4—C3—C2	0.9 (5)
C7—C8—C9—C10	−0.1 (5)	C5—C4—C3—Cl1	−179.5 (3)
C8ⁱ—C8—C9—C10	−179.7 (4)	C3—C2—C1—O2	10.6 (6)
C5—S1—C2—C3	−0.1 (3)	S1—C2—C1—O2	−169.7 (3)
C5—S1—C2—C1	−179.8 (3)	C3—C2—C1—O1	−168.0 (4)
C2—S1—C5—C4	0.6 (3)	S1—C2—C1—O1	11.7 (4)

Symmetry code: (i) −x+1, −y+1, −z+1.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···N1ⁱⁱ	0.89 (5)	1.77 (5)	2.659 (4)	178 (5)

Symmetry code: (ii) x, y−1, z.

Acknowledgements

OKP thanks the UGC–SAP and UGC–BSR India for the award of an RFSMS. PTM is thankful to the UGC, New Delhi, for a UGC–BSR one-time grant to Faculty. DKG thanks the US Department of Education for the X-ray diffractometer (grant No. P116Z100020).

References

Atria, A. M., Garland, M. T. & Baggio, R. (2014). Acta Cryst. E70, 157–160. CSD CrossRef IUCr Journals Google Scholar
Bruker (2013). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Capdevila-Cortada, M., Castelló, J. & Novoa, J. J. (2014). CrystEngComm, 16, 8232–8242. CAS Google Scholar
Cavallo, G., Metrangolo, P., Milani, R., Pilati, T., Priimagi, A., Resnati, G. & Terraneo, G. (2016). Chem. Rev. 116, 2478–2601. Web of Science CrossRef CAS PubMed Google Scholar
Cowan, J. A., Howard, J. A. K. & Leech, M. A. (2001). Acta Cryst. C57, 302–303. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Csöregh, I., Brehmer, T., Bombicz, P. & Weber, E. (2001). Cryst. Eng. 4, 343–357. Web of Science CSD CrossRef CAS Google Scholar
Dubey, R. & Desiraju, G. R. (2015). IUCrJ, 2, 402–408. Web of Science CSD CrossRef CAS PubMed IUCr Journals Google Scholar
Jennifer, S. J. & Muthiah, P. T. (2014). Chem. Cent. J. 8, 20. Web of Science CSD CrossRef PubMed Google Scholar
Kowalska, K., Trzybiński, D. & Sikorski, A. (2015). CrystEngComm, 17, 7199–7212. Web of Science CSD CrossRef CAS Google Scholar
Lemmerer, A. & Bernstein, J. (2010). CrystEngComm, 12, 2029–2033. Web of Science CSD CrossRef CAS Google Scholar
Lemmerer, A., Govindraju, S., Johnston, M., Motloung, X. & Savig, K. L. (2015). CrystEngComm, 17, 3591–3595. Web of Science CSD CrossRef CAS Google Scholar
Lou, B.-Y. & Huang, Y.-B. (2007). Acta Cryst. C63, o246–o248. Web of Science CSD CrossRef IUCr Journals Google Scholar
Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466–470. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Metrangolo, P. & Resnati, G. (2014). IUCrJ, 1, 5–7. Web of Science CrossRef CAS PubMed IUCr Journals Google Scholar
Moon, S.-H. & Park, K.-M. (2012). Acta Cryst. E68, o1201. CSD CrossRef IUCr Journals Google Scholar
Mukherjee, A., Tothadi, S., Chakraborty, S., Ganguly, S. & Desiraju, G. R. (2011). Cryst. Growth Des. 11, 2637–2653. Web of Science CSD CrossRef CAS Google Scholar
Mukherjee, A., Tothadi, S., Chakraborty, S., Ganguly, S. & Desiraju, G. R. (2013). CrystEngComm, 15, 4640–4654. Web of Science CSD CrossRef CAS Google Scholar
Najafpour, M. M., Hołyńska, M. & Lis, T. (2008). Acta Cryst. E64, o985. Web of Science CSD CrossRef IUCr Journals Google Scholar
Navon, O., Bernstein, J. & Khodorkovsky, V. (1997). Angew. Chem. Int. Ed. Engl. 36, 601–603. CrossRef CAS Web of Science Google Scholar
Pan, Y., Li, K., Bi, W. & Li, J. (2008). Acta Cryst. C64, o41–o43. Web of Science CSD CrossRef IUCr Journals Google Scholar
Prajina, O., Thomas Muthiah, P. & Perdih, F. (2016). Acta Cryst. E72, 659–662. Web of Science CSD CrossRef IUCr Journals Google Scholar
Qin, J.-L. (2011). Acta Cryst. E67, o589. Web of Science CSD CrossRef IUCr Journals Google Scholar
Sarma, J. A. R. P. & Desiraju, G. R. (1986). Acc. Chem. Res. 19, 222–228. CrossRef CAS Web of Science Google Scholar
Seaton, C. C. (2014). CrystEngComm, 16, 5878–5886. Web of Science CSD CrossRef CAS Google Scholar
Shattock, T. R., Arora, K. K., Vishweshwar, P. & Zaworotko, M. J. (2008). Cryst. Growth Des. 8, 4533–4545. Web of Science CSD CrossRef CAS 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
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar
Thomas, L. H., Blagden, N., Gutmann, M. J., Kallay, A. A., Parkin, A., Seaton, C. C. & Wilson, C. C. (2010). Cryst. Growth Des. 10, 2770–2774. Web of Science CSD CrossRef CAS Google Scholar
Vener, M. V., Shishkina, A. V., Rykounov, A. A. & Tsirelson, V. G. (2013). J. Phys. Chem. A, 117, 8459–8467. Web of Science CrossRef CAS PubMed Google Scholar
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Web of Science CrossRef CAS IUCr Journals Google Scholar
Zhang, Q., Luo, J., Ye, L., Wang, H., Huang, B., Zhang, J., Wu, J., Zhang, S. & Tian, Y. (2014). J. Mol. Struct. 1074, 33–42. Web of Science CSD CrossRef CAS Google Scholar

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