2,4,6-Trimethyl­pyridinium 4-nitro­benzoate–4-nitro­benzoic acid (1/1)

Abbasi, M.A.; Nazir, K.; Akkurt, M.; Aziz-ur-Rehman; Khan, I.U.; Mustafa, G.

doi:10.1107/S1600536811032922

organic compounds

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ISSN: 2056-9890

Volume 67| Part 9| September 2011| Page o2375

doi:10.1107/S1600536811032922

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2,4,6-Trimethylpyridinium 4-nitrobenzoate–4-nitrobenzoic acid (1/1)

Muhammad Athar Abbasi,^a ‡ Kenneth Nazir,^a Mehmet Akkurt,^b ^* Aziz-ur-Rehman,^a Islam Ullah Khan ^a and Ghulam Mustafa ^a

^aDepartment of Chemistry, Government College University, Lahore 54000, Pakistan, and ^bDepartment of Physics, Faculty of Sciences, Erciyes University, 38039 Kayseri, Turkey
^*Correspondence e-mail: akkurt@erciyes.edu.tr

(Received 27 July 2011; accepted 13 August 2011; online 27 August 2011)

The asymmetric unit of the title co-crystal, C₈H₁₂N⁺·C₇H₄NO₄⁻·C₇H₅NO₄, contains two cations, two anions and two neutral 4-nitrobenzoic acid molecules. In the crystal, O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds connect the ions and molecules, forming a three-dimensional network.

Related literature

For related structures, see: Ishida et al. (2004 ); Quah et al. (2008 ); Dong et al. (2010 ). For bond-length data, see: Allen et al. (1987).

Experimental

Crystal data

C₈H₁₂N⁺·C₇H₄NO₄⁻·C₇H₅NO₄
M_r = 455.42
Orthorhombic, P c a 2₁
a = 14.4061 (15) Å
b = 8.4461 (10) Å
c = 36.787 (4) Å
V = 4476.1 (9) Å³
Z = 8
Mo Kα radiation
μ = 0.11 mm⁻¹
T = 296 K
0.54 × 0.44 × 0.37 mm

Data collection

Bruker APEXII CCD diffractometer
23612 measured reflections
5658 independent reflections
2131 reflections with I > 2σ(I)
R_int = 0.090

Refinement

R[F² > 2σ(F²)] = 0.044
wR(F²) = 0.102
S = 0.79
5658 reflections
602 parameters
1 restraint
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.18 e Å⁻³
Δρ_min = −0.17 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1E—H1E⋯O3Dⁱ	0.86	1.78	2.636 (4)	171
N1F—H1F⋯O4Cⁱ	0.86	1.76	2.613 (4)	173
O4A—H1O⋯O4Dⁱⁱ	0.90	1.67	2.549 (5)	164
O4B—H2O⋯O3Cⁱⁱⁱ	0.90	1.65	2.536 (5)	165
C4E—H4E⋯O1B^iv	0.93	2.58	3.398 (7)	147
C7E—H7K⋯O4D^v	0.96	2.57	3.475 (6)	156
C7E—H7L⋯O1B^iv	0.96	2.55	3.455 (9)	158
Symmetry codes: (i) $[x-{\script{1\over 2}}, -y+1, z]$ ; (ii) $[x-{\script{1\over 2}}, -y+1, z+1]$ ; (iii) $[-x+{\script{1\over 2}}, y, z+{\script{1\over 2}}]$ ; (iv) $[x+{\script{1\over 2}}, -y+1, z-1]$ ; (v) x, y+1, z.

Data collection: APEX2 (Bruker, 2007 ); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ); software used to prepare material for publication: WinGX (Farrugia, 1999 ) and PLATON (Spek, 2009 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536811032922/hb6339sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811032922/hb6339Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536811032922/hb6339Isup3.cml

checkCIF report

Comment top

The asymmetric unit of the title co-crystal, (I), contains two molecules of 2,4,6-trimethylpyridinium 4-nitrobenzoate and 4-nitrobenzoic acid (Fig. 1). All bond lengths and bond angles are as expected for this kind of compounds (Allen et al., 1987).

In the structure, the molecular packing is stabilized by intermolecular O—H···O, N—H···O and C—H···O hydrogen bonds, forming a three dimensional network (Table 1, Figs. 2 & 3).

Related literature top

For related structures, see: Ishida et al. (2004); Quah et al. (2008); Dong et al. (2010). For bond-length data, see: Allen et al. (1987).

Experimental top

10 ml of ethanol were taken in 25 ml round bottom flask and 1.25 g of p-nitrobenzoic acid were added and suspension was heated to homogenize the mixture. Then 1 ml of sym-collidine (2,4,6-trimethylpyridine) was added and this mixture was refluxed for 1.5 h. Then this solution was concentrated on water bath to half amount and poured into sample vial and left for crystallization. On crystallization, colourless prisms of (I) were obtained.

Computing details top

Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999) and PLATON (Spek, 2009).

Figures top

	Fig. 1. The molecules in the asymmetric unit of the title compound shown with 30% probability displacement ellipsoids. For clarity, only N atoms are labelled.
	Fig. 2. View of the packing and hydrogen bonding of the title compound down the a axis. H atoms not involved in hydrogen bonding have been omitted for clarity.
	Fig. 3. View of the packing and hydrogen bonding of the title compound down the b axis. H atoms not involved in hydrogen bonding have been omitted for clarity.

2,4,6-Trimethylpyridinium 4-nitrobenzoate–4-nitrobenzoic acid (1/1) top

Crystal data top

C₈H₁₂N⁺·C₇H₄NO₄⁻·C₇H₅NO₄	F(000) = 1904
M_r = 455.42	D_x = 1.352 Mg m⁻³
Orthorhombic, Pca2₁	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2c -2ac	Cell parameters from 2857 reflections
a = 14.4061 (15) Å	θ = 2.7–20.2°
b = 8.4461 (10) Å	µ = 0.11 mm⁻¹
c = 36.787 (4) Å	T = 296 K
V = 4476.1 (9) Å³	Prism, colourless
Z = 8	0.54 × 0.44 × 0.37 mm

Data collection top

Bruker APEXII CCD diffractometer	2131 reflections with I > 2σ(I)
Radiation source: sealed tube	R_int = 0.090
Graphite monochromator	θ_max = 28.3°, θ_min = 2.4°
ϕ and ω scans	h = −19→10
23612 measured reflections	k = −11→9
5658 independent reflections	l = −41→49

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.044	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.102	w = 1/[σ²(F_o²) + (0.0372P)²] where P = (F_o² + 2F_c²)/3
S = 0.79	(Δ/σ)_max < 0.001
5658 reflections	Δρ_max = 0.18 e Å⁻³
602 parameters	Δρ_min = −0.17 e Å⁻³
1 restraint	Extinction correction: SHELXL97 (Sheldrick, 2008), FC^*=KFC[1+0.001XFC²Λ³/SIN(2Θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0019 (3)

Crystal data top

C₈H₁₂N⁺·C₇H₄NO₄⁻·C₇H₅NO₄	V = 4476.1 (9) Å³
M_r = 455.42	Z = 8
Orthorhombic, Pca2₁	Mo Kα radiation
a = 14.4061 (15) Å	µ = 0.11 mm⁻¹
b = 8.4461 (10) Å	T = 296 K
c = 36.787 (4) Å	0.54 × 0.44 × 0.37 mm

Data collection top

Bruker APEXII CCD diffractometer	2131 reflections with I > 2σ(I)
23612 measured reflections	R_int = 0.090
5658 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.044	1 restraint
wR(F²) = 0.102	H atoms treated by a mixture of independent and constrained refinement
S = 0.79	Δρ_max = 0.18 e Å⁻³
5658 reflections	Δρ_min = −0.17 e Å⁻³
602 parameters

Special details top

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su'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

Refinement. Refinement on F² for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The observed criterion of F² > σ(F²) is used only for calculating -R-factor-obs etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

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

	x	y	z	U_iso*/U_eq
N1E	0.0951 (2)	0.6583 (4)	0.01485 (10)	0.0507 (13)
C1E	0.1321 (3)	0.7651 (5)	0.03852 (14)	0.0500 (19)
C2E	0.2221 (3)	0.8086 (6)	0.03352 (15)	0.0610 (19)
C3E	0.2737 (3)	0.7498 (6)	0.00536 (15)	0.0580 (18)
C4E	0.2331 (3)	0.6421 (5)	−0.01785 (14)	0.0553 (16)
C5E	0.1438 (3)	0.5961 (5)	−0.01280 (13)	0.0497 (16)
C6E	0.0701 (3)	0.8265 (6)	0.06769 (13)	0.0703 (19)
C7E	0.3732 (3)	0.7980 (6)	0.00030 (18)	0.089 (3)
C8E	0.0923 (3)	0.4817 (6)	−0.03699 (16)	0.071 (2)
N1F	−0.1353 (2)	0.8367 (4)	0.22390 (10)	0.0447 (13)
C1F	−0.0849 (3)	0.8986 (5)	0.25124 (13)	0.0483 (16)
C2F	0.0058 (3)	0.8497 (5)	0.25489 (13)	0.0560 (17)
C3F	0.0433 (3)	0.7401 (6)	0.23086 (16)	0.0597 (19)
C4F	−0.0131 (3)	0.6816 (5)	0.20373 (14)	0.0567 (19)
C5F	−0.1040 (3)	0.7304 (5)	0.20001 (15)	0.0487 (19)
C6F	−0.1295 (3)	1.0153 (6)	0.27559 (17)	0.072 (2)
C7F	0.1435 (3)	0.6847 (7)	0.23554 (19)	0.096 (3)
C8F	−0.1693 (3)	0.6715 (6)	0.17190 (15)	0.073 (2)
O1A	0.3337 (3)	0.8459 (7)	0.82422 (15)	0.140 (3)
O2A	0.4000 (3)	1.0348 (7)	0.85151 (18)	0.154 (3)
O3A	0.0552 (2)	1.0121 (4)	0.98158 (12)	0.0765 (15)
O4A	−0.01771 (19)	0.8303 (4)	0.94775 (9)	0.0700 (11)
N1A	0.3371 (4)	0.9421 (8)	0.84779 (16)	0.098 (3)
C1A	0.1158 (3)	0.8436 (6)	0.89404 (15)	0.064 (2)
C2A	0.1873 (3)	0.8444 (6)	0.86886 (14)	0.0713 (19)
C3A	0.2605 (3)	0.9417 (7)	0.87478 (14)	0.065 (2)
C4A	0.2678 (3)	1.0374 (6)	0.90457 (16)	0.070 (2)
C5A	0.1970 (3)	1.0351 (6)	0.92933 (16)	0.064 (2)
C6A	0.1205 (3)	0.9379 (5)	0.92473 (13)	0.0490 (18)
C7A	0.0485 (3)	0.9338 (6)	0.95380 (16)	0.0563 (19)
O1B	−0.1107 (3)	0.3497 (8)	0.91296 (15)	0.150 (3)
O2B	−0.1729 (4)	0.5467 (7)	0.88524 (17)	0.160 (3)
O3B	0.1768 (2)	0.5131 (4)	0.75805 (11)	0.0763 (16)
O4B	0.2464 (2)	0.3288 (4)	0.79171 (9)	0.0753 (11)
N1B	−0.1128 (4)	0.4515 (8)	0.88884 (17)	0.097 (2)
C1B	0.1109 (3)	0.3415 (6)	0.84378 (15)	0.066 (2)
C2B	0.0394 (3)	0.3459 (6)	0.86889 (15)	0.075 (2)
C3B	−0.0337 (3)	0.4471 (7)	0.86285 (16)	0.067 (2)
C4B	−0.0389 (3)	0.5436 (6)	0.83350 (18)	0.077 (2)
C5B	0.0330 (3)	0.5380 (6)	0.80844 (14)	0.0640 (19)
C6B	0.1076 (3)	0.4385 (6)	0.81337 (15)	0.0530 (19)
C7B	0.1806 (3)	0.4309 (7)	0.78477 (16)	0.060 (2)
O1C	−0.2126 (3)	0.0101 (5)	0.11550 (15)	0.111 (2)
O2C	−0.2654 (2)	0.2206 (6)	0.14139 (12)	0.109 (2)
O3C	0.1291 (2)	0.2807 (5)	0.24426 (12)	0.0857 (16)
O4C	0.19185 (19)	0.0829 (4)	0.21284 (11)	0.0787 (13)
N1C	−0.2061 (3)	0.1190 (7)	0.13629 (14)	0.079 (2)
C1C	0.0359 (3)	0.0609 (6)	0.16908 (14)	0.0567 (18)
C2C	−0.0454 (3)	0.0446 (6)	0.14892 (13)	0.0603 (17)
C3C	−0.1192 (3)	0.1379 (6)	0.15836 (14)	0.0550 (18)
C4C	−0.1162 (3)	0.2450 (6)	0.18644 (15)	0.0570 (19)
C5C	−0.0356 (3)	0.2575 (6)	0.20585 (14)	0.0513 (17)
C6C	0.0404 (3)	0.1651 (5)	0.19758 (12)	0.0453 (16)
C7C	0.1274 (3)	0.1787 (6)	0.22040 (16)	0.0597 (19)
O1D	−0.0520 (2)	0.2967 (5)	0.08810 (10)	0.0843 (15)
O2D	0.0105 (3)	0.4724 (6)	0.12218 (15)	0.116 (2)
O3D	0.41943 (19)	0.4058 (4)	0.02846 (10)	0.0757 (13)
O4D	0.3581 (2)	0.2083 (4)	−0.00369 (11)	0.0883 (18)
N1D	0.0139 (3)	0.3771 (6)	0.09787 (13)	0.0653 (17)
C1D	0.1914 (3)	0.2332 (5)	0.03318 (14)	0.0507 (19)
C2D	0.1092 (3)	0.2513 (5)	0.05167 (14)	0.0550 (19)
C3D	0.1047 (3)	0.3539 (5)	0.08009 (13)	0.0497 (17)
C4D	0.1804 (3)	0.4396 (6)	0.09091 (13)	0.0587 (17)
C5D	0.2617 (3)	0.4257 (5)	0.07166 (14)	0.0570 (19)
C6D	0.2680 (2)	0.3227 (5)	0.04234 (13)	0.0473 (16)
C7D	0.3560 (3)	0.3117 (6)	0.02039 (15)	0.0583 (19)
H1E	0.03830	0.62960	0.01770	0.0610*
H2E	0.24920	0.87990	0.04960	0.0730*
H4E	0.26710	0.60070	−0.03710	0.0660*
H6K	0.04390	0.73930	0.08090	0.1050*
H6L	0.02120	0.88800	0.05700	0.1050*
H6M	0.10540	0.89200	0.08400	0.1050*
H7K	0.37990	0.90860	0.00570	0.1330*
H7L	0.39150	0.77880	−0.02440	0.1330*
H7M	0.41190	0.73730	0.01640	0.1330*
H8K	0.02780	0.50980	−0.03770	0.1070*
H8L	0.09880	0.37630	−0.02760	0.1070*
H8M	0.11760	0.48630	−0.06110	0.1070*
H1F	−0.19180	0.86790	0.22170	0.0530*
H2F	0.04230	0.89040	0.27360	0.0670*
H4F	0.01070	0.60740	0.18750	0.0680*
H6P	−0.08390	1.05820	0.29190	0.1080*
H6R	−0.17750	0.96420	0.28930	0.1080*
H6S	−0.15590	1.09910	0.26130	0.1080*
H7P	0.15710	0.60450	0.21780	0.1440*
H7R	0.15160	0.64200	0.25950	0.1440*
H7S	0.18480	0.77270	0.23220	0.1440*
H8P	−0.19170	0.75890	0.15770	0.1100*
H8R	−0.22070	0.61960	0.18350	0.1100*
H8S	−0.13790	0.59780	0.15630	0.1100*
H1A	0.06430	0.77930	0.89030	0.0770*
H1O	−0.05570	0.82900	0.96720	0.0840*
H2A	0.18510	0.77980	0.84840	0.0850*
H4A	0.31930	1.10210	0.90790	0.0840*
H5A	0.20040	1.10020	0.94970	0.0760*
H1B	0.16100	0.27380	0.84730	0.0790*
H2B	0.04070	0.28170	0.88940	0.0890*
H2O	0.28270	0.31080	0.77220	0.0900*
H4B	−0.08910	0.61140	0.83020	0.0920*
H5B	0.03080	0.60260	0.78800	0.0770*
H1C	0.08770	0.00040	0.16310	0.0680*
H2C	−0.04940	−0.02690	0.12980	0.0730*
H4C	−0.16740	0.30730	0.19210	0.0680*
H5C	−0.03200	0.32940	0.22490	0.0610*
H1D	0.19540	0.16000	0.01440	0.0610*
H2D	0.05710	0.19380	0.04480	0.0660*
H4D	0.17690	0.50620	0.11100	0.0700*
H5D	0.31300	0.48590	0.07830	0.0680*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1E	0.0350 (17)	0.054 (2)	0.063 (3)	−0.0029 (18)	0.000 (2)	0.007 (2)
C1E	0.046 (3)	0.051 (3)	0.053 (4)	0.004 (2)	0.000 (3)	0.002 (3)
C2E	0.045 (3)	0.061 (3)	0.077 (4)	−0.006 (2)	−0.009 (3)	0.006 (3)
C3E	0.041 (2)	0.065 (3)	0.068 (4)	0.001 (2)	−0.001 (3)	0.015 (3)
C4E	0.041 (2)	0.066 (3)	0.059 (3)	0.007 (2)	0.010 (2)	0.011 (3)
C5E	0.047 (2)	0.055 (3)	0.047 (3)	0.006 (2)	0.006 (2)	0.002 (2)
C6E	0.074 (3)	0.075 (3)	0.062 (4)	0.012 (3)	0.006 (3)	−0.006 (3)
C7E	0.043 (3)	0.089 (4)	0.135 (6)	−0.015 (3)	0.002 (3)	0.027 (4)
C8E	0.067 (3)	0.067 (4)	0.079 (5)	−0.009 (3)	−0.003 (3)	−0.013 (3)
N1F	0.0351 (17)	0.050 (2)	0.049 (3)	−0.0017 (17)	−0.0008 (18)	0.004 (2)
C1F	0.047 (2)	0.048 (3)	0.050 (3)	−0.004 (2)	0.004 (2)	0.005 (2)
C2F	0.049 (3)	0.062 (3)	0.057 (3)	−0.008 (3)	−0.009 (2)	0.008 (3)
C3F	0.046 (3)	0.047 (3)	0.086 (4)	0.005 (2)	0.004 (3)	0.023 (3)
C4F	0.060 (3)	0.045 (3)	0.065 (4)	0.004 (2)	0.011 (3)	0.000 (3)
C5F	0.049 (3)	0.045 (3)	0.052 (4)	0.003 (2)	0.010 (2)	0.006 (3)
C6F	0.075 (3)	0.075 (4)	0.066 (4)	−0.005 (3)	0.010 (3)	−0.017 (3)
C7F	0.041 (3)	0.101 (4)	0.146 (6)	0.012 (3)	−0.009 (3)	0.020 (4)
C8F	0.075 (3)	0.068 (4)	0.076 (4)	−0.004 (3)	−0.024 (3)	−0.014 (3)
O1A	0.107 (3)	0.218 (6)	0.095 (4)	0.017 (4)	0.043 (3)	−0.028 (4)
O2A	0.093 (3)	0.212 (6)	0.157 (6)	−0.040 (4)	0.056 (3)	−0.017 (5)
O3A	0.0626 (19)	0.092 (3)	0.075 (3)	0.0027 (19)	0.017 (2)	−0.018 (2)
O4A	0.0501 (16)	0.091 (2)	0.069 (2)	−0.0086 (18)	0.0127 (17)	0.008 (2)
N1A	0.070 (3)	0.147 (6)	0.076 (4)	0.011 (3)	0.023 (3)	0.006 (4)
C1A	0.059 (3)	0.073 (4)	0.059 (4)	−0.015 (3)	−0.003 (3)	0.003 (3)
C2A	0.070 (3)	0.093 (4)	0.051 (3)	−0.004 (3)	0.011 (3)	−0.009 (3)
C3A	0.053 (3)	0.088 (4)	0.054 (4)	0.011 (3)	0.014 (3)	0.011 (3)
C4A	0.056 (3)	0.090 (4)	0.064 (4)	−0.013 (3)	0.007 (3)	0.001 (4)
C5A	0.058 (3)	0.068 (4)	0.065 (4)	−0.008 (3)	0.012 (3)	−0.005 (3)
C6A	0.041 (2)	0.053 (3)	0.053 (4)	0.006 (2)	0.005 (2)	0.006 (3)
C7A	0.041 (3)	0.058 (3)	0.070 (4)	0.005 (2)	−0.001 (3)	0.010 (3)
O1B	0.120 (4)	0.241 (7)	0.090 (4)	0.000 (4)	0.045 (3)	0.029 (4)
O2B	0.116 (4)	0.209 (6)	0.155 (5)	0.065 (4)	0.064 (4)	0.015 (5)
O3B	0.067 (2)	0.096 (3)	0.066 (3)	−0.007 (2)	0.021 (2)	0.018 (2)
O4B	0.0538 (18)	0.103 (2)	0.069 (2)	0.0109 (19)	0.0072 (17)	−0.021 (2)
N1B	0.081 (3)	0.140 (5)	0.070 (4)	−0.011 (3)	0.022 (3)	0.002 (4)
C1B	0.059 (3)	0.081 (4)	0.058 (4)	0.006 (3)	0.000 (3)	−0.007 (3)
C2B	0.076 (3)	0.094 (4)	0.054 (4)	−0.005 (3)	0.003 (3)	0.007 (3)
C3B	0.055 (3)	0.094 (4)	0.053 (4)	−0.007 (3)	0.005 (3)	−0.013 (3)
C4B	0.066 (3)	0.087 (4)	0.078 (5)	0.009 (3)	0.005 (3)	−0.002 (4)
C5B	0.063 (3)	0.070 (3)	0.059 (4)	0.005 (3)	0.013 (3)	0.007 (3)
C6B	0.049 (3)	0.059 (3)	0.051 (4)	−0.008 (2)	−0.001 (2)	−0.006 (3)
C7B	0.046 (3)	0.070 (4)	0.065 (4)	−0.010 (3)	0.004 (3)	−0.017 (3)
O1C	0.121 (3)	0.101 (4)	0.111 (4)	−0.011 (3)	−0.064 (3)	−0.004 (3)
O2C	0.067 (2)	0.128 (4)	0.131 (4)	0.016 (2)	−0.037 (2)	0.025 (3)
O3C	0.068 (2)	0.095 (3)	0.094 (3)	−0.011 (2)	−0.029 (2)	−0.025 (3)
O4C	0.0420 (17)	0.074 (2)	0.120 (3)	−0.0020 (18)	−0.0133 (19)	0.005 (2)
N1C	0.063 (3)	0.089 (4)	0.084 (4)	0.000 (3)	−0.013 (3)	0.028 (3)
C1C	0.040 (2)	0.061 (3)	0.069 (4)	0.002 (2)	0.003 (2)	0.003 (3)
C2C	0.070 (3)	0.060 (3)	0.051 (3)	−0.007 (3)	−0.007 (3)	0.003 (3)
C3C	0.041 (2)	0.059 (3)	0.065 (4)	−0.001 (2)	−0.015 (2)	0.015 (3)
C4C	0.048 (3)	0.054 (3)	0.069 (4)	0.009 (2)	0.006 (3)	0.010 (3)
C5C	0.048 (3)	0.054 (3)	0.052 (3)	−0.006 (2)	0.005 (3)	0.001 (3)
C6C	0.039 (2)	0.043 (3)	0.054 (3)	−0.005 (2)	−0.001 (2)	0.003 (2)
C7C	0.041 (3)	0.059 (3)	0.079 (4)	−0.013 (3)	−0.007 (3)	0.014 (3)
O1D	0.0528 (18)	0.106 (3)	0.094 (3)	0.001 (2)	0.019 (2)	0.023 (2)
O2D	0.115 (3)	0.130 (4)	0.102 (4)	0.011 (3)	0.053 (3)	−0.024 (3)
O3D	0.0381 (15)	0.082 (2)	0.107 (3)	0.0000 (17)	0.0182 (18)	−0.013 (2)
O4D	0.067 (2)	0.090 (3)	0.108 (4)	−0.003 (2)	0.035 (2)	−0.036 (3)
N1D	0.066 (3)	0.072 (3)	0.058 (3)	0.014 (2)	0.025 (2)	0.016 (3)
C1D	0.046 (3)	0.047 (3)	0.059 (4)	−0.003 (2)	0.012 (3)	−0.003 (3)
C2D	0.038 (3)	0.058 (3)	0.069 (4)	−0.005 (2)	0.012 (2)	0.006 (3)
C3D	0.048 (3)	0.052 (3)	0.049 (3)	0.013 (2)	0.013 (2)	0.015 (3)
C4D	0.061 (3)	0.060 (3)	0.055 (3)	0.003 (3)	0.008 (2)	−0.010 (3)
C5D	0.048 (3)	0.063 (3)	0.060 (4)	−0.001 (2)	−0.008 (3)	−0.005 (3)
C6D	0.038 (2)	0.048 (3)	0.056 (3)	0.008 (2)	0.007 (2)	0.007 (3)
C7D	0.042 (3)	0.057 (3)	0.076 (4)	0.006 (3)	0.006 (3)	0.000 (3)

Geometric parameters (Å, º) top

O1A—N1A	1.189 (9)	C4F—H4F	0.9300
O2A—N1A	1.205 (8)	C6F—H6P	0.9600
O3A—C7A	1.221 (7)	C6F—H6R	0.9600
O4A—C7A	1.313 (6)	C6F—H6S	0.9600
O4A—H1O	0.9000	C7F—H7S	0.9600
O1B—N1B	1.236 (9)	C7F—H7P	0.9600
O2B—N1B	1.189 (9)	C7F—H7R	0.9600
O3B—C7B	1.205 (7)	C8F—H8P	0.9600
O4B—C7B	1.307 (6)	C8F—H8S	0.9600
O4B—H2O	0.9000	C8F—H8R	0.9600
O1C—N1C	1.200 (7)	C1A—C6A	1.383 (7)
O2C—N1C	1.225 (7)	C1A—C2A	1.385 (7)
O3C—C7C	1.230 (7)	C2A—C3A	1.355 (7)
O4C—C7C	1.263 (6)	C3A—C4A	1.366 (8)
O1D—N1D	1.221 (6)	C4A—C5A	1.368 (7)
N1E—C1E	1.362 (6)	C5A—C6A	1.385 (6)
N1E—C5E	1.343 (6)	C6A—C7A	1.490 (7)
O2D—N1D	1.204 (7)	C1A—H1A	0.9300
O3D—C7D	1.247 (6)	C2A—H2A	0.9300
O4D—C7D	1.244 (6)	C4A—H4A	0.9300
N1E—H1E	0.8600	C5A—H5A	0.9300
N1F—C5F	1.335 (6)	C1B—C6B	1.387 (8)
N1F—C1F	1.346 (6)	C1B—C2B	1.384 (7)
N1F—H1F	0.8600	C2B—C3B	1.374 (7)
N1A—C3A	1.484 (7)	C3B—C4B	1.355 (8)
N1B—C3B	1.488 (8)	C4B—C5B	1.387 (7)
N1C—C3C	1.501 (6)	C5B—C6B	1.376 (7)
N1D—C3D	1.476 (6)	C6B—C7B	1.489 (7)
C1E—C2E	1.360 (6)	C1B—H1B	0.9300
C1E—C6E	1.489 (7)	C2B—H2B	0.9300
C2E—C3E	1.368 (7)	C4B—H4B	0.9300
C3E—C7E	1.502 (6)	C5B—H5B	0.9300
C3E—C4E	1.378 (7)	C1C—C2C	1.393 (6)
C4E—C5E	1.357 (6)	C1C—C6C	1.370 (7)
C5E—C8E	1.509 (7)	C2C—C3C	1.368 (7)
C2E—H2E	0.9300	C3C—C4C	1.374 (7)
C4E—H4E	0.9300	C4C—C5C	1.367 (7)
C6E—H6L	0.9600	C5C—C6C	1.379 (6)
C6E—H6K	0.9600	C6C—C7C	1.513 (7)
C6E—H6M	0.9600	C1C—H1C	0.9300
C7E—H7M	0.9600	C2C—H2C	0.9300
C7E—H7K	0.9600	C4C—H4C	0.9300
C7E—H7L	0.9600	C5C—H5C	0.9300
C8E—H8M	0.9600	C1D—C2D	1.374 (6)
C8E—H8L	0.9600	C1D—C6D	1.379 (6)
C8E—H8K	0.9600	C2D—C3D	1.360 (7)
C1F—C6F	1.479 (7)	C3D—C4D	1.368 (6)
C1F—C2F	1.377 (6)	C4D—C5D	1.374 (6)
C2F—C3F	1.389 (7)	C5D—C6D	1.389 (7)
C3F—C4F	1.379 (7)	C6D—C7D	1.506 (6)
C3F—C7F	1.527 (6)	C1D—H1D	0.9300
C4F—C5F	1.380 (6)	C2D—H2D	0.9300
C5F—C8F	1.484 (7)	C4D—H4D	0.9300
C2F—H2F	0.9300	C5D—H5D	0.9300

C7A—O4A—H1O	108.00	C5F—C8F—H8P	110.00
C7B—O4B—H2O	112.00	C2A—C1A—C6A	120.4 (4)
C1E—N1E—C5E	122.6 (3)	C1A—C2A—C3A	118.3 (5)
C1E—N1E—H1E	119.00	C2A—C3A—C4A	123.2 (5)
C5E—N1E—H1E	119.00	N1A—C3A—C4A	118.6 (5)
C1F—N1F—C5F	124.8 (3)	N1A—C3A—C2A	118.2 (5)
C5F—N1F—H1F	118.00	C3A—C4A—C5A	117.9 (4)
C1F—N1F—H1F	118.00	C4A—C5A—C6A	121.4 (5)
O2A—N1A—C3A	119.0 (6)	C5A—C6A—C7A	118.7 (4)
O1A—N1A—O2A	123.9 (6)	C1A—C6A—C7A	122.6 (4)
O1A—N1A—C3A	117.1 (6)	C1A—C6A—C5A	118.7 (4)
O2B—N1B—C3B	120.2 (6)	O3A—C7A—O4A	124.1 (5)
O1B—N1B—C3B	115.2 (5)	O4A—C7A—C6A	113.6 (4)
O1B—N1B—O2B	124.6 (6)	O3A—C7A—C6A	122.2 (4)
O1C—N1C—O2C	125.5 (5)	C2A—C1A—H1A	120.00
O2C—N1C—C3C	115.1 (5)	C6A—C1A—H1A	120.00
O1C—N1C—C3C	119.4 (5)	C3A—C2A—H2A	121.00
O1D—N1D—C3D	119.0 (4)	C1A—C2A—H2A	121.00
O2D—N1D—C3D	117.0 (4)	C3A—C4A—H4A	121.00
O1D—N1D—O2D	124.0 (5)	C5A—C4A—H4A	121.00
N1E—C1E—C2E	117.7 (4)	C6A—C5A—H5A	119.00
N1E—C1E—C6E	117.2 (4)	C4A—C5A—H5A	119.00
C2E—C1E—C6E	125.1 (4)	C2B—C1B—C6B	119.8 (4)
C1E—C2E—C3E	121.5 (5)	C1B—C2B—C3B	118.6 (5)
C2E—C3E—C4E	118.6 (4)	C2B—C3B—C4B	123.1 (5)
C2E—C3E—C7E	120.9 (5)	N1B—C3B—C4B	117.0 (5)
C4E—C3E—C7E	120.5 (5)	N1B—C3B—C2B	119.9 (5)
C3E—C4E—C5E	120.5 (4)	C3B—C4B—C5B	117.9 (4)
N1E—C5E—C8E	116.1 (4)	C4B—C5B—C6B	121.1 (5)
N1E—C5E—C4E	119.2 (4)	C5B—C6B—C7B	119.0 (5)
C4E—C5E—C8E	124.7 (4)	C1B—C6B—C7B	121.3 (4)
C1E—C2E—H2E	119.00	C1B—C6B—C5B	119.6 (4)
C3E—C2E—H2E	119.00	O4B—C7B—C6B	113.8 (5)
C5E—C4E—H4E	120.00	O3B—C7B—C6B	121.3 (4)
C3E—C4E—H4E	120.00	O3B—C7B—O4B	124.9 (5)
H6K—C6E—H6L	110.00	C2B—C1B—H1B	120.00
H6L—C6E—H6M	109.00	C6B—C1B—H1B	120.00
C1E—C6E—H6M	109.00	C3B—C2B—H2B	121.00
C1E—C6E—H6L	109.00	C1B—C2B—H2B	121.00
C1E—C6E—H6K	109.00	C3B—C4B—H4B	121.00
H6K—C6E—H6M	109.00	C5B—C4B—H4B	121.00
C3E—C7E—H7K	110.00	C6B—C5B—H5B	119.00
H7L—C7E—H7M	109.00	C4B—C5B—H5B	119.00
H7K—C7E—H7L	109.00	C2C—C1C—C6C	120.7 (4)
C3E—C7E—H7M	109.00	C1C—C2C—C3C	117.5 (5)
C3E—C7E—H7L	109.00	N1C—C3C—C2C	116.7 (5)
H7K—C7E—H7M	109.00	N1C—C3C—C4C	120.2 (4)
C5E—C8E—H8K	110.00	C2C—C3C—C4C	123.1 (4)
C5E—C8E—H8M	109.00	C3C—C4C—C5C	118.1 (4)
C5E—C8E—H8L	110.00	C4C—C5C—C6C	121.0 (5)
H8L—C8E—H8M	109.00	C5C—C6C—C7C	119.5 (4)
H8K—C8E—H8L	110.00	C1C—C6C—C7C	120.8 (4)
H8K—C8E—H8M	109.00	C1C—C6C—C5C	119.7 (4)
C2F—C1F—C6F	123.6 (4)	O3C—C7C—O4C	126.3 (5)
N1F—C1F—C2F	117.9 (4)	O3C—C7C—C6C	117.8 (4)
N1F—C1F—C6F	118.5 (4)	O4C—C7C—C6C	116.0 (5)
C1F—C2F—C3F	120.5 (4)	C2C—C1C—H1C	120.00
C2F—C3F—C7F	120.0 (5)	C6C—C1C—H1C	120.00
C4F—C3F—C7F	121.9 (5)	C3C—C2C—H2C	121.00
C2F—C3F—C4F	118.1 (4)	C1C—C2C—H2C	121.00
C3F—C4F—C5F	121.6 (4)	C3C—C4C—H4C	121.00
C4F—C5F—C8F	124.8 (4)	C5C—C4C—H4C	121.00
N1F—C5F—C8F	118.1 (4)	C4C—C5C—H5C	119.00
N1F—C5F—C4F	117.2 (4)	C6C—C5C—H5C	119.00
C3F—C2F—H2F	120.00	C2D—C1D—C6D	120.5 (4)
C1F—C2F—H2F	120.00	C1D—C2D—C3D	119.5 (4)
C5F—C4F—H4F	119.00	N1D—C3D—C2D	117.9 (4)
C3F—C4F—H4F	119.00	N1D—C3D—C4D	120.5 (4)
H6P—C6F—H6S	110.00	C2D—C3D—C4D	121.5 (4)
C1F—C6F—H6P	109.00	C3D—C4D—C5D	119.0 (4)
H6R—C6F—H6S	110.00	C4D—C5D—C6D	120.6 (4)
C1F—C6F—H6S	109.00	C1D—C6D—C5D	118.7 (4)
C1F—C6F—H6R	109.00	C1D—C6D—C7D	120.6 (4)
H6P—C6F—H6R	110.00	C5D—C6D—C7D	120.7 (4)
H7P—C7F—H7S	109.00	O3D—C7D—O4D	126.8 (4)
C3F—C7F—H7R	109.00	O3D—C7D—C6D	116.7 (4)
H7P—C7F—H7R	110.00	O4D—C7D—C6D	116.5 (4)
C3F—C7F—H7P	109.00	C2D—C1D—H1D	120.00
H7R—C7F—H7S	109.00	C6D—C1D—H1D	120.00
C3F—C7F—H7S	110.00	C1D—C2D—H2D	120.00
H8P—C8F—H8S	109.00	C3D—C2D—H2D	120.00
H8R—C8F—H8S	109.00	C3D—C4D—H4D	121.00
C5F—C8F—H8R	109.00	C5D—C4D—H4D	120.00
C5F—C8F—H8S	110.00	C4D—C5D—H5D	120.00
H8P—C8F—H8R	109.00	C6D—C5D—H5D	120.00

C5E—N1E—C1E—C2E	−0.2 (6)	C4A—C5A—C6A—C7A	176.4 (5)
C5E—N1E—C1E—C6E	179.2 (4)	C4A—C5A—C6A—C1A	−1.0 (7)
C1E—N1E—C5E—C4E	−0.8 (6)	C5A—C6A—C7A—O3A	−0.6 (7)
C1E—N1E—C5E—C8E	−178.9 (4)	C5A—C6A—C7A—O4A	−175.8 (4)
C5F—N1F—C1F—C2F	0.3 (7)	C1A—C6A—C7A—O3A	176.6 (5)
C1F—N1F—C5F—C8F	178.7 (4)	C1A—C6A—C7A—O4A	1.5 (7)
C5F—N1F—C1F—C6F	−179.9 (4)	C2B—C1B—C6B—C5B	−0.2 (8)
C1F—N1F—C5F—C4F	−0.3 (7)	C6B—C1B—C2B—C3B	0.2 (8)
O2A—N1A—C3A—C4A	−5.4 (9)	C2B—C1B—C6B—C7B	−176.7 (5)
O1A—N1A—C3A—C4A	172.2 (6)	C1B—C2B—C3B—C4B	−0.3 (8)
O1A—N1A—C3A—C2A	−6.8 (8)	C1B—C2B—C3B—N1B	178.4 (5)
O2A—N1A—C3A—C2A	175.6 (6)	N1B—C3B—C4B—C5B	−178.3 (5)
O1B—N1B—C3B—C4B	172.2 (6)	C2B—C3B—C4B—C5B	0.5 (8)
O2B—N1B—C3B—C4B	−6.7 (9)	C3B—C4B—C5B—C6B	−0.5 (8)
O1B—N1B—C3B—C2B	−6.6 (9)	C4B—C5B—C6B—C7B	176.9 (5)
O2B—N1B—C3B—C2B	174.5 (6)	C4B—C5B—C6B—C1B	0.3 (8)
O1C—N1C—C3C—C4C	−169.2 (5)	C1B—C6B—C7B—O3B	178.6 (5)
O1C—N1C—C3C—C2C	11.0 (8)	C5B—C6B—C7B—O3B	2.1 (8)
O2C—N1C—C3C—C4C	11.1 (7)	C1B—C6B—C7B—O4B	−1.3 (7)
O2C—N1C—C3C—C2C	−168.7 (5)	C5B—C6B—C7B—O4B	−177.8 (5)
O2D—N1D—C3D—C2D	−177.5 (5)	C6C—C1C—C2C—C3C	1.0 (7)
O1D—N1D—C3D—C2D	4.7 (7)	C2C—C1C—C6C—C5C	−1.6 (7)
O2D—N1D—C3D—C4D	−0.8 (7)	C2C—C1C—C6C—C7C	177.7 (5)
O1D—N1D—C3D—C4D	−178.6 (5)	C1C—C2C—C3C—C4C	0.0 (8)
C6E—C1E—C2E—C3E	−178.1 (5)	C1C—C2C—C3C—N1C	179.9 (5)
N1E—C1E—C2E—C3E	1.1 (7)	C2C—C3C—C4C—C5C	−0.4 (8)
C1E—C2E—C3E—C4E	−1.1 (8)	N1C—C3C—C4C—C5C	179.8 (5)
C1E—C2E—C3E—C7E	−179.6 (5)	C3C—C4C—C5C—C6C	−0.2 (8)
C2E—C3E—C4E—C5E	0.2 (7)	C4C—C5C—C6C—C7C	−178.1 (5)
C7E—C3E—C4E—C5E	178.6 (5)	C4C—C5C—C6C—C1C	1.1 (7)
C3E—C4E—C5E—C8E	178.7 (5)	C1C—C6C—C7C—O3C	175.9 (5)
C3E—C4E—C5E—N1E	0.8 (7)	C1C—C6C—C7C—O4C	−4.0 (7)
N1F—C1F—C2F—C3F	0.2 (7)	C5C—C6C—C7C—O3C	−4.8 (7)
C6F—C1F—C2F—C3F	−179.7 (5)	C5C—C6C—C7C—O4C	175.3 (5)
C1F—C2F—C3F—C7F	−179.0 (5)	C6D—C1D—C2D—C3D	−2.6 (7)
C1F—C2F—C3F—C4F	−0.6 (7)	C2D—C1D—C6D—C7D	−175.5 (4)
C2F—C3F—C4F—C5F	0.6 (7)	C2D—C1D—C6D—C5D	3.0 (7)
C7F—C3F—C4F—C5F	179.0 (5)	C1D—C2D—C3D—N1D	176.5 (4)
C3F—C4F—C5F—C8F	−179.1 (5)	C1D—C2D—C3D—C4D	−0.3 (7)
C3F—C4F—C5F—N1F	−0.2 (7)	N1D—C3D—C4D—C5D	−174.1 (4)
C2A—C1A—C6A—C7A	−176.0 (5)	C2D—C3D—C4D—C5D	2.5 (7)
C6A—C1A—C2A—C3A	−1.2 (7)	C3D—C4D—C5D—C6D	−2.0 (7)
C2A—C1A—C6A—C5A	1.3 (7)	C4D—C5D—C6D—C1D	−0.8 (7)
C1A—C2A—C3A—N1A	179.9 (5)	C4D—C5D—C6D—C7D	177.8 (4)
C1A—C2A—C3A—C4A	0.9 (8)	C1D—C6D—C7D—O3D	174.1 (4)
N1A—C3A—C4A—C5A	−179.6 (5)	C1D—C6D—C7D—O4D	−6.6 (7)
C2A—C3A—C4A—C5A	−0.6 (8)	C5D—C6D—C7D—O3D	−4.4 (7)
C3A—C4A—C5A—C6A	0.7 (8)	C5D—C6D—C7D—O4D	174.9 (4)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1E—H1E···O3Dⁱ	0.86	1.78	2.636 (4)	171
N1F—H1F···O4Cⁱ	0.86	1.76	2.613 (4)	173
O4A—H1O···O4Dⁱⁱ	0.90	1.67	2.549 (5)	164
O4B—H2O···O3Cⁱⁱⁱ	0.90	1.65	2.536 (5)	165
C4E—H4E···O1B^iv	0.93	2.58	3.398 (7)	147
C7E—H7K···O4D^v	0.96	2.57	3.475 (6)	156
C7E—H7L···O1B^iv	0.96	2.55	3.455 (9)	158

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

Experimental details

Crystal data
Chemical formula	C₈H₁₂N⁺·C₇H₄NO₄⁻·C₇H₅NO₄
M_r	455.42
Crystal system, space group	Orthorhombic, Pca2₁
Temperature (K)	296
a, b, c (Å)	14.4061 (15), 8.4461 (10), 36.787 (4)
V (Å³)	4476.1 (9)
Z	8
Radiation type	Mo Kα
µ (mm⁻¹)	0.11
Crystal size (mm)	0.54 × 0.44 × 0.37

Data collection
Diffractometer	Bruker APEXII CCD diffractometer
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	23612, 5658, 2131
R_int	0.090
(sin θ/λ)_max (Å⁻¹)	0.667

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.044, 0.102, 0.79
No. of reflections	5658
No. of parameters	602
No. of restraints	1
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.18, −0.17

Computer programs: APEX2 (Bruker, 2007), SAINT (Bruker, 2007), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997), WinGX (Farrugia, 1999) and PLATON (Spek, 2009).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1E—H1E···O3Dⁱ	0.86	1.78	2.636 (4)	171
N1F—H1F···O4Cⁱ	0.86	1.76	2.613 (4)	173
O4A—H1O···O4Dⁱⁱ	0.90	1.67	2.549 (5)	164
O4B—H2O···O3Cⁱⁱⁱ	0.90	1.65	2.536 (5)	165
C4E—H4E···O1B^iv	0.93	2.58	3.398 (7)	147
C7E—H7K···O4D^v	0.96	2.57	3.475 (6)	156
C7E—H7L···O1B^iv	0.96	2.55	3.455 (9)	158

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

Footnotes

‡Additional correspondence author, e-mail: atrabbasi@yahoo.com.

Acknowledgements

The authors are grateful to the Higher Education Commission of Pakistan for providing financial support.

References

Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–19. CrossRef Web of Science Google Scholar
Bruker (2007). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Dong, G.-Y., Liu, X.-H., Liu, T.-F. & Khan, I. U. (2010). Acta Cryst. E66, o1485. CrossRef IUCr Journals Google Scholar
Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565. CrossRef IUCr Journals Google Scholar
Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837–838. CrossRef CAS IUCr Journals Google Scholar
Ishida, H., Rahman, B. & Kashino, S. (2004). Acta Cryst. E60, o1661–o1663. Web of Science CSD CrossRef IUCr Journals Google Scholar
Quah, C. K., Jebas, S. R. & Fun, H.-K. (2008). Acta Cryst. E64, o1878–o1879. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar