Crystal structure and Hirshfeld surface analysis of 3-cyano­phenyl­boronic acid

Cárdenas-Valenzuela, A.J.; González-García, G.; Zárraga- Nuñez, R.; Höpfl, H.; Campos-Gaxiola, J.J.; Cruz-Enríquez, A.

doi:10.1107/S2056989018003146

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ISSN: 2056-9890

Volume 74| Part 4| April 2018| Pages 441-444

https://doi.org/10.1107/S2056989018003146

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Crystal structure and Hirshfeld surface analysis of 3-cyanophenylboronic acid

A. Jaquelin Cárdenas-Valenzuela,^a Gerardo González-García,^b Ramón Zárraga- Nuñez,^b Herbert Höpfl,^c José J. Campos-Gaxiola ^a and Adriana Cruz-Enríquez ^a ^*

^aFacultad de Ingeniería Mochis, Universidad Autónoma de Sinaloa, Fuente de Poseidón y Prol. A. Flores S/N, CP 81223, C.U. Los Mochis, Sinaloa, México, ^bDepartamento de Química, División de Ciencias Naturales y Exactas, Campus Guanajuato, Universidad de Guanajuato, Sede Noria Alta, Noria Alta S/N, Col. Noria Alta, CP 36050, Guanajuato, Gto., México, and ^cCentro de Investigaciones Químicas, Instituto de Investigación en Ciencias Básicas y Aplicadas, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, CP 62209, Cuernavaca, Morelos, México
^*Correspondence e-mail: cruzadriana@uas.edu.mx

Edited by H. Stoeckli-Evans, University of Neuchâtel, Switzerland (Received 12 February 2018; accepted 23 February 2018; online 2 March 2018)

In the title compound, C₇H₆BNO₂, the mean plane of the –B(OH)₂ group is twisted by 21.28 (6)° relative to the cyanophenyl ring mean plane. In the crystal, molecules are linked by O—H⋯O and O—H⋯N hydrogen bonds, forming chains propagating along the [101] direction. Offset π–π and B⋯π stacking interactions link the chains, forming a three-dimensional network. Hirshfeld surface analysis shows that van der Waals interactions constitute a further major contribution to the intermolecular interactions, with H⋯H contacts accounting for 25.8% of the surface.

Keywords: crystal structure; boronic acid; hydrogen bonding; offset π–π interactions; Hirshfeld surface analysis.

CCDC reference: 1825335

1. Chemical context

Boron-containing compounds and particularly arylboronic acid are an important class of compounds in the fields of organic and medicinal chemistry, and have played a role in the development of modern organic synthesis, macromolecular chemistry, crystal engineering and molecular recognition (Fujita et al., 2008 ; Severin, 2009 ). As a result of their peculiar dynamic covalent reactivity with alcohols (Jin et al., 2013 ), arylboronic acids and their dehydrated derivatives enable the self-assembly of a large variety of architectures resulting from boronate esterification (Takahagi et al. 2009 ) as well as boroxine (Côté et al., 2005 ) and spiroborate formation (Du et al., 2016 ).

Boronic acids form neutral and charge-assisted homo- and heterodimeric hydrogen-bonding patterns resembling characteristics similar to those found for carboxylic acids (see Fig. 1a). However, the –B(OH)₂ moiety contains two O—H hydrogen-bond donors and can, thus, form two O—H⋯X hydrogen bonds and adopt different conformations (see Fig. 1b). This enables the generation of hydrogen-bonding networks with increased dimensionality (one to three dimensions) in the solid state (Fournier et al., 2003 ; Madura et al., 2015 ; Georgiou et al., 2017 ). In recent years, boronic acids have also been explored in the context of forming multicomponent molecular complexes with organic carboxylic acids (–COOH), amides (–CONH₂), alcohols (–OH) and pyridines, which are based on molecular recognition processes (Rodríguez-Cuamatzi et al., 2005 ; Madura et al., 2014 ; Hernández-Paredes et al., 2015 ; Campos-Gaxiola et al., 2017 ; Pedireddi & Lekshmi, 2004 ; Vega et al., 2010 ; TalwelkarShimpi et al., 2016 ). As part of our ongoing studies in this area, we report herein on the molecular and crystal structures of 3-cyanophenylboronic acid, I. In addition, a Hirshfeld surface analysis was performed to visualize and quantify the intermolecular interactions in the crystal structure of compound (I).

Figure 1
(a) Neutral and charge-assisted homo- and heterodimeric hydrogen-bonding motifs involving boronic acids. (b) Conformations of the boronic acid moiety.

2. Structural commentary

The molecular structure of the title compound (I) is illustrated in Fig. 2. It can be seen that the –B(OH)₂ group adopts the most preferred syn–anti conformation (Lekshmi & Pedireddi, 2007 ). As a result of the H⋯H repulsion between the endo-oriented B—OH hydrogen and the C—H hydrogen in position 2 of the aromatic ring, the –B(OH)₂ mean plane is twisted by 21.28 (6)° relative to the cyanophenyl ring mean plane. This torsion disables intramolecular C—H⋯O hydrogen bonding between the oxygen atom of the exo-oriented B—OH function and weakens the B—C π–π bonding interactions (Durka et al., 2012 ). The B1—O1, B1—O2 and B1—C1 bond lengths are 1.3455 (17), 1.3661 (18) and 1.5747 (18) Å, respectively. For comparison, in coplanar triphenyl boroxine the B—C bond lengths range from 1.544 (4) to 1.549 (4) Å (Brock et al., 1987 ). The C≡N bond length of 1.1416 (18) Å is typical for a bond with triple-bond character.

Figure 2
The molecular structure of the title compound (I)

, with the atom labeling. Displacement ellipsoids are drawn at the 50% probability level.

3. Supramolecular features

In the crystal of (I), the boronic acid molecules are in the first instance associated to form chains through two well-known double-bridged homodimeric motifs based on a –BOH⋯O(H)B– [motif A; graph set R₂²(8)] and C—H⋯N≡C hydrogen bonds [motif B; graph set R₂²(10)]. This hydrogen-bonding pattern is strengthened further by a –BOH⋯N≡C contact [motif C; graph set R₂¹(7)] (Fig. 3a, Table 1). In comparison to the crystal structure of 4-cyanophenylboronic acid, where the chains are almost linear (TalwelkarShimpi et al., 2017 ), in (I) they have a pronounced zigzag topology. The O1⋯O2ⁱ, C2⋯N1ⁱⁱ and O2⋯N1ⁱⁱ separations in motifs A, B and C are 2.796 (1), 3.452 (2) and 2.909 (2) Å, respectively (Table 1), and are similar to distances reported for related systems (Rodríguez-Cuamatzi et al., 2005; TalwelkarShimpi et al., 2017). Within the crystal structure, neighboring tapes are linked through additional C—H⋯O contacts to give an overall two-dimensional network running parallel to ( $[\overline{1}]$ 01) with macrocyclic motifs D [graph set R₆⁶(26)], see Fig. 3b. The C4⋯O1ⁱⁱⁱ distance is 3.469 (2) Å, see Table 1. The resulting 2D networks stack in a parallel fashion to form a layered 3D structure based on offset π–π interactions between adjacent 3-cyanophenylboronic acid molecules [Cg⋯Cg^iv = 3.8064 (8) Å; slippage 1.38 Å; symmetry code (iv) = −1 + x, y, z] and η²-type B⋯π contacts with B⋯C distances of 3.595 (2) and 3.673 (2) Å (Fig. 3c). Similar interactions are also depicted in molecular crystals formed between 1,4-benzenediboronic acid and aromatic amine N-oxides (Sarma & Baruah, 2009 ; Sarma et al., 2011 ).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯O2ⁱ	0.82	1.98	2.796 (1)	170
O2—H2⋯N1ⁱⁱ	0.82	2.12	2.909 (2)	160
C2—H2A⋯N1ⁱⁱ	0.93	2.71	3.452 (2)	138
C4—H4⋯O1ⁱⁱⁱ	0.93	2.67	3.469 (2)	144
Symmetry codes: (i) -x+2, -y+1, -z+1; (ii) -x+1, -y+1, -z; (iii) $[x-1, -y+{\script{3\over 2}}, z-{\script{1\over 2}}]$ .

Figure 3
Hydrogen-bonding motifs and π–π interactions found in the crystal structure of (I)

. [Symmetry codes: (i) 2 − x, 1 − y, 1 − z; (ii) 1 − x, 1 − y, −z; (iii) −1 + x, $[{3\over 2}]$ − y, − $[{1\over 2}]$ + z; (iv) −1 + x, y, z.]

4. Hirshfeld surface analysis

Hirshfeld surfaces and fingerprint plots were generated for (I) based on the crystallographic information file (CIF) using CrystalExplorer (Hirshfeld, 1977 ; McKinnon et al., 2004 ). Hirshfeld surfaces enable the visualization of intermolecular interactions by different colors and color intensity, representing short or long contacts and indicating the relative strength of the interactions. Fig. 4 shows the Hirshfeld surface of the title compound mapped over d_norm (−0.60 to 0.90 Å) and the shape-index (−1.0 to 1.0 Å). In the d_norm map, the vivid red spots in the Hirshfeld surface are due to short normalized O⋯H and N⋯H distances corresponding to O—H⋯O and O—H⋯N interactions. The white spots represent the contacts resulting from C—H⋯N hydrogen bonding (Fig. 4a). On the shape-index surface for compound (I), convex blue regions represent hydrogen-donor groups and concave red regions represent hydrogen-acceptor groups. The –B(OH)₂ group behaves simultaneously as a donor and an acceptor, meanwhile the –C≡N group is an acceptor only. The occurrence of offset π–π interactions is indicated by adjacent red and blue triangles (Fig. 4b).

Figure 4
Hirshfeld surfaces for compound (I)

, mapped with d_norm (top) and shape-index (bottom).

The two-dimensional fingerprint plots quantify the contributions of each type of non-covalent interaction to the Hirshfeld surface (McKinnon et al., 2007 ). The major contribution with 25.8% of the surface is due to H⋯H contacts, which represent van der Waals interactions, followed by N⋯H and O⋯H interactions, which contribute 23.6 and 20.4%, respectively (these contributions are observed as two sharp peaks in the plot of Fig. 5). This behavior is usual for strong hydrogen bonds (Spackman & McKinnon, 2002 ). Finally, the presence of C⋯C (11.4%) and B⋯C (2.3%) contacts corresponds to the π–π and B⋯π interactions, respectively, established in the crystal structure analysis section.

Figure 5
Two-dimensional fingerprints of compound (I)

, showing H⋯H, N⋯H, O⋯H, C⋯C and C⋯H close contacts.

5. Experimental

3-Cyanophenylboronic acid and the solvent used in this work are commercially available and were used without further purification. For single-crystal growth, a solution of 3-cyanophenylboronic acid (0.050 g) in 5 ml of ethanol was heated to reflux for 15 min. The solution was left to evaporate slowly at room temperature, giving after one week colorless crystals suitable for single-crystal X-ray diffraction analysis.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. Hydrogen atoms were positioned geometrically (O—H = 0.82 Å and C—H = 0.93 Å) and refined using a riding model, with U_iso(H) = 1.2U_eq(C) and 1.5U_eq(O).

Table 2
Experimental details

Crystal data
Chemical formula	C₇H₆BNO₂
M_r	146.94
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	293
a, b, c (Å)	3.8064 (2), 16.156 (1), 11.4585 (4)
β (°)	93.472 (4)
V (Å³)	703.36 (6)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	0.10
Crystal size (mm)	0.48 × 0.25 × 0.20

Data collection
Diffractometer	Rigaku OD SuperNova Single source at offset EosS2
Absorption correction	Gaussian (CrysAlis PRO; Rigaku OD, 2015 $[Rigaku OD (2015). CrysAlis PRO. Rigaku Oxford Diffraction. Yarnton, England.]$ )
T_min, T_max	0.992, 0.996
No. of measured, independent and observed [I > 2σ(I)] reflections	7332, 1434, 1347
R_int	0.023
(sin θ/λ)_max (Å⁻¹)	0.625

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.042, 0.110, 1.09
No. of reflections	1434
No. of parameters	102
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.20, −0.24
Computer programs: CrysAlis PRO (Rigaku OD, 2015 $[Rigaku OD (2015). CrysAlis PRO. Rigaku Oxford Diffraction. Yarnton, England.]$ ), SUPERFLIP (Palatinus & Chapuis, 2007 ; Palatinus & van der Lee, 2008 ; Palatinus et al., 2012 ), SHELXL2016 (Sheldrick, 2015 ) and OLEX2 (Dolomanov et al., 2009 ).

Supporting information

CCDC reference: 1825335

Crystal structure: contains datablocks Global, I. DOI: https://doi.org/10.1107/S2056989018003146/su5425sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989018003146/su5425Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989018003146/su5425Isup3.cml

checkCIF report

Computing details top

Data collection: CrysAlis PRO (Rigaku OD, 2015); cell refinement: CrysAlis PRO (Rigaku OD, 2015); data reduction: CrysAlis PRO (Rigaku OD, 2015); program(s) used to solve structure: SUPERFLIP (Palatinus & Chapuis, 2007; Palatinus & van der Lee, 2008; Palatinus et al., 2012); program(s) used to refine structure: SHELXL2016 (Sheldrick, 2015); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

3-Cyanophenylboronic acid top

Crystal data top

C₇H₆BNO₂	F(000) = 304
M_r = 146.94	D_x = 1.388 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 3.8064 (2) Å	Cell parameters from 4312 reflections
b = 16.156 (1) Å	θ = 4.4–29.1°
c = 11.4585 (4) Å	µ = 0.10 mm⁻¹
β = 93.472 (4)°	T = 293 K
V = 703.36 (6) Å³	Block, colourless
Z = 4	0.48 × 0.25 × 0.20 mm

Data collection top

Rigaku OD SuperNova Single source at offset EosS2 diffractometer	1434 independent reflections
Radiation source: micro-focus sealed X-ray tube, SuperNova (Mo) X-ray Source	1347 reflections with I > 2σ(I)
Mirror monochromator	R_int = 0.023
Detector resolution: 8.0945 pixels mm^-1	θ_max = 26.4°, θ_min = 3.6°
ω scans	h = −4→4
Absorption correction: gaussian (CrysAlis PRO; Rigaku OD, 2015)	k = −20→20
T_min = 0.992, T_max = 0.996	l = −14→14
7332 measured reflections

Refinement top

Refinement on F²	Primary atom site location: iterative
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.042	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.110	H-atom parameters constrained
S = 1.09	w = 1/[σ²(F_o²) + (0.0566P)² + 0.1839P] where P = (F_o² + 2F_c²)/3
1434 reflections	(Δ/σ)_max < 0.001
102 parameters	Δρ_max = 0.20 e Å⁻³
0 restraints	Δρ_min = −0.24 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
O2	0.8906 (3)	0.49351 (6)	0.34935 (8)	0.0436 (3)
H2	0.881271	0.482459	0.279381	0.065*
O1	0.8143 (3)	0.60701 (6)	0.47187 (8)	0.0507 (3)
H1	0.900315	0.572989	0.518407	0.076*
N1	0.0762 (4)	0.58588 (8)	−0.12243 (11)	0.0485 (4)
C3	0.3424 (3)	0.65006 (8)	0.06942 (10)	0.0307 (3)
C7	0.1909 (4)	0.61462 (8)	−0.03743 (11)	0.0355 (3)
C1	0.6246 (3)	0.62961 (8)	0.26214 (10)	0.0302 (3)
C2	0.4765 (3)	0.59744 (8)	0.15775 (11)	0.0309 (3)
H2A	0.467006	0.540428	0.146805	0.037*
C4	0.3561 (4)	0.73542 (8)	0.08286 (12)	0.0367 (3)
H4	0.267843	0.770116	0.023320	0.044*
C6	0.6325 (4)	0.71575 (8)	0.27423 (11)	0.0352 (3)
H6	0.727616	0.738593	0.343630	0.042*
C5	0.5031 (4)	0.76802 (8)	0.18615 (12)	0.0400 (3)
H5	0.515094	0.825073	0.196425	0.048*
B1	0.7827 (4)	0.57324 (9)	0.36442 (12)	0.0336 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O2	0.0679 (7)	0.0371 (5)	0.0242 (5)	0.0103 (5)	−0.0092 (5)	−0.0004 (4)
O1	0.0810 (8)	0.0414 (6)	0.0278 (5)	0.0165 (5)	−0.0120 (5)	−0.0029 (4)
N1	0.0625 (9)	0.0474 (7)	0.0339 (7)	0.0077 (6)	−0.0115 (6)	−0.0044 (5)
C3	0.0303 (6)	0.0361 (7)	0.0254 (6)	0.0025 (5)	−0.0001 (5)	0.0001 (5)
C7	0.0398 (7)	0.0365 (7)	0.0295 (7)	0.0077 (5)	−0.0031 (5)	0.0028 (5)
C1	0.0304 (6)	0.0332 (7)	0.0267 (6)	0.0014 (5)	−0.0002 (5)	0.0017 (5)
C2	0.0343 (7)	0.0291 (6)	0.0290 (6)	0.0019 (5)	−0.0011 (5)	0.0005 (5)
C4	0.0426 (8)	0.0353 (7)	0.0320 (7)	0.0063 (5)	0.0004 (5)	0.0067 (5)
C6	0.0397 (7)	0.0358 (7)	0.0296 (6)	−0.0019 (5)	−0.0016 (5)	−0.0031 (5)
C5	0.0520 (8)	0.0287 (7)	0.0390 (8)	0.0007 (6)	0.0009 (6)	0.0001 (5)
B1	0.0385 (8)	0.0347 (8)	0.0268 (7)	0.0006 (6)	−0.0038 (6)	0.0010 (5)

Geometric parameters (Å, º) top

O2—B1	1.3661 (18)	C1—C2	1.3917 (17)
O1—B1	1.3455 (17)	C1—C6	1.3987 (18)
N1—C7	1.1416 (18)	C1—B1	1.5747 (18)
C3—C7	1.4401 (18)	C4—C5	1.3825 (19)
C3—C2	1.3948 (17)	C6—C5	1.3834 (19)
C3—C4	1.3882 (19)

C2—C3—C7	119.00 (12)	C1—C2—C3	120.50 (12)
C4—C3—C7	119.98 (11)	C5—C4—C3	118.95 (12)
C4—C3—C2	121.02 (12)	C5—C6—C1	122.04 (12)
N1—C7—C3	178.81 (15)	C4—C5—C6	119.98 (12)
C2—C1—C6	117.51 (11)	O2—B1—C1	123.75 (11)
C2—C1—B1	122.70 (11)	O1—B1—O2	119.15 (12)
C6—C1—B1	119.79 (11)	O1—B1—C1	117.10 (12)

C3—C4—C5—C6	−0.2 (2)	C2—C1—B1—O1	−159.37 (13)
C7—C3—C2—C1	−179.96 (12)	C4—C3—C2—C1	0.64 (19)
C7—C3—C4—C5	−179.92 (12)	C6—C1—C2—C3	0.00 (18)
C1—C6—C5—C4	0.9 (2)	C6—C1—B1—O2	−158.17 (13)
C2—C3—C4—C5	−0.5 (2)	C6—C1—B1—O1	21.14 (19)
C2—C1—C6—C5	−0.8 (2)	B1—C1—C2—C3	−179.50 (12)
C2—C1—B1—O2	21.3 (2)	B1—C1—C6—C5	178.76 (13)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O2ⁱ	0.82	1.98	2.796 (1)	170
O2—H2···N1ⁱⁱ	0.82	2.12	2.909 (2)	160
C2—H2A···N1ⁱⁱ	0.93	2.71	3.452 (2)	138
C4—H4···O1ⁱⁱⁱ	0.93	2.67	3.469 (2)	144

Symmetry codes: (i) −x+2, −y+1, −z+1; (ii) −x+1, −y+1, −z; (iii) x−1, −y+3/2, z−1/2.

Funding information

This work was supported financially by the Consejo Nacional de Ciencia y Tecnología (CONACYT, Project Nos. 177616 and 229929) and Red Temática de Química Supramolecular (CONACYT, Project No. 281251). AJCV thanks the Consejo Nacional de Ciencia y Tecnología (CONACYT) for a graduate scholarship (273977).

References

Brock, C. P., Minton, R. P. & Niedenzu, K. (1987). Acta Cryst. C43, 1775–1779. CSD CrossRef CAS Web of Science IUCr Journals Google Scholar
Campos-Gaxiola, J. J., García-Grajeda, B. A., Hernández-Ahuactzi, I. F., Guerrero-Álvarez, J. A., Höpfl, H. & Cruz-Enríquez, A. (2017). CrystEngComm, 19, 3760–3775. CAS Google Scholar
Côté, A. P., Benin, A. I., Ockwig, N. W., O'Keeffe, M., Matzger, A. J. & Yaghi, O. M. (2005). Science, 310, 1166–1170. Web of Science PubMed Google Scholar
Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339–341. Web of Science CrossRef CAS IUCr Journals Google Scholar
Du, Y., Yang, H., Whiteley, J. M., Wan, S., Jin, Y., Lee, S. H. & Zhang, W. (2016). Angew. Chem. Int. Ed. 55, 1737–1741. Web of Science CrossRef CAS Google Scholar
Durka, K., Jarzembska, K. N., Kamiński, R., Luliński, S., Serwatowski, J. & Woźniak, K. (2012). Cryst. Growth Des. 12, 3720–3734. Web of Science CSD CrossRef CAS Google Scholar
Fournier, J. H., Maris, T., Wuest, J. D., Guo, W. & Galoppini, E. (2003). J. Am. Chem. Soc. 125, 1002–1006. Web of Science CSD CrossRef PubMed CAS Google Scholar
Fujita, N., Shinkai, S. & James, T. D. (2008). Chem. Asian J. 3, 1076–1091. Web of Science CrossRef PubMed CAS Google Scholar
Georgiou, I., Kervyn, S., Rossignon, A., De Leo, F., Wouters, J., Bruylants, G. & Bonifazi, D. (2017). J. Am. Chem. Soc. 139, 2710–2727. Web of Science CSD CrossRef CAS PubMed Google Scholar
Hernández-Paredes, J., Olvera-Tapia, A. L., Arenas-García, J. I., Höpfl, H., Morales-Rojas, H., Herrera-Ruiz, D., Gonzaga-Morales, A. I. & Rodríguez-Fragoso, L. (2015). CrystEngComm, 17, 5166–5186. Google Scholar
Hirshfeld, F. L. (1977). Theor. Chim. Acta, 44, 129–138. CrossRef CAS Web of Science Google Scholar
Jin, Y., Yu, C., Denman, R. J. & Zhang, W. (2013). Chem. Soc. Rev. 42, 6634–6654. Web of Science CrossRef CAS Google Scholar
Lekshmi, N. S. & Pedireddi, V. R. (2007). Cryst. Growth Des. 7, 944–949. Google Scholar
Madura, I. D., Adamczyk-Woźniak, A. & Sporzyński, A. (2015). J. Mol. Struct. 1083, 204–211. Web of Science CSD CrossRef CAS Google Scholar
Madura, I. D., Czerwińska, K. & Sołdańska, D. (2014). Cryst. Growth Des. 14, 5912–5921. Web of Science CSD CrossRef CAS Google Scholar
McKinnon, J. J., Jayatilaka, D. & Spackman, M. A. (2007). Chem. Commun. pp. 3814–3816. Web of Science CrossRef Google Scholar
McKinnon, J. J., Spackman, M. A. & Mitchell, A. S. (2004). Acta Cryst. B60, 627–668. Web of Science CrossRef CAS IUCr Journals Google Scholar
Palatinus, L. & Chapuis, G. (2007). J. Appl. Cryst. 40, 786–790. Web of Science CrossRef CAS IUCr Journals Google Scholar
Palatinus, L., Prathapa, S. J. & van Smaalen, S. (2012). J. Appl. Cryst. 45, 575–580. Web of Science CrossRef CAS IUCr Journals Google Scholar
Palatinus, L. & van der Lee, A. (2008). J. Appl. Cryst. 41, 975–984. Web of Science CrossRef CAS IUCr Journals Google Scholar
Pedireddi, V. R. & Lekshmi, N. S. (2004). Tetrahedron Lett. 45, 1903–1906. Web of Science CSD CrossRef CAS Google Scholar
Rigaku OD (2015). CrysAlis PRO. Rigaku Oxford Diffraction. Yarnton, England. Google Scholar
Rodríguez-Cuamatzi, P., Arillo-Flores, O. I., Bernal-Uruchurtu, M. I. & Höpfl, H. (2005). Cryst. Growth Des. 5, 167–175. Google Scholar
Sarma, R. & Baruah, J. B. (2009). J. Mol. Struct. 920, 350–354. Web of Science CSD CrossRef CAS Google Scholar
Sarma, R., Bhattacharyya, P. K. & Baruah, J. B. (2011). Comput. Theor. Chem. 963, 141–147. Web of Science CrossRef CAS Google Scholar
Severin, K. (2009). Dalton Trans. pp. 5254–5264. Web of Science CrossRef Google Scholar
Sheldrick, G. M. (2015). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Spackman, M. A. & McKinnon, J. J. (2002). CrystEngComm, 4, 378–392. Web of Science CrossRef CAS Google Scholar
Takahagi, H., Fujibe, S. & Iwasawa, N. (2009). Chem. Eur. J. 15, 13327–13330. Web of Science CSD CrossRef CAS Google Scholar
TalwelkarShimpi, M., Öberg, S., Giri, L. & Pedireddi, V. R. (2016). RSC Adv. 6, 43060–43068. Web of Science CSD CrossRef CAS Google Scholar
TalwelkarShimpi, M., Öberg, S., Giri, L. & Pedireddi, V. R. (2017). Cryst. Growth Des. 17, 6247–6254. Web of Science CSD CrossRef CAS Google Scholar
Vega, A., Zarate, M., Tlahuext, H. & Höpfl, H. (2010). Acta Cryst. C66, o219–o221. Web of Science CSD CrossRef IUCr Journals Google Scholar