2,2′-Biimidazolium 5-amino-2,4,6-tri­bromo­isophthalate

Zhang, K.-L.; Huang, H.; Ng, S.W.

doi:10.1107/S1600536810041899

organic compounds

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ISSN: 2056-9890

Volume 66| Part 11| November 2010| Page o2919

https://doi.org/10.1107/S1600536810041899

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2,2′-Biimidazolium 5-amino-2,4,6-tribromoisophthalate

Kou-Lin Zhang,^a Han Huang ^a and Seik Weng Ng ^b ^*

^aCollege of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, People's Republic of China, and ^bDepartment of Chemistry, University of Malaya, 50603 Kuala Lumpur, Malaysia
^*Correspondence e-mail: seikweng@um.edu.my

(Received 12 October 2010; accepted 16 October 2010; online 23 October 2010)

In the cation of the title salt, C₆H₈N₄²⁺·C₈H₂Br₃NO₄²⁻, the dihedral angle between the two five-membered rings is 2.1 (3)°. In the anion, the mean planes of the carboxyl units are twisted from the benzene ring by 84.3 (4) and 86.2 (3)°. In the crystal, the components are linked by imidazolium–carboxylate N—H⋯O hydrogen bonds, generating a chain running along [1 $[\overline{1}]$ 0].

Related literature

For the structure of 5-amino-2,4,6-tribromidoisophthalic acid, see: Beck et al. (2009 ). For the structures of other 2,2′-bis(imidazolium) carboxylates, see: Gao et al. (2009 ); Li & Yang (2007 ); Zhou et al. (2009 ).

Experimental

Crystal data

C₆H₈N₄²⁺·C₈H₂Br₃NO₄²⁻
M_r = 552.00
Triclinic, $[P \overline 1]$
a = 9.0525 (10) Å
b = 9.2043 (10) Å
c = 11.5252 (12) Å
α = 90.262 (1)°
β = 108.332 (1)°
γ = 93.136 (1)°
V = 909.96 (17) Å³
Z = 2
Mo Kα radiation
μ = 6.68 mm⁻¹
T = 293 K
0.35 × 0.25 × 0.15 mm

Data collection

Bruker SMART APEX diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ) T_min = 0.203, T_max = 0.434
8042 measured reflections
4104 independent reflections
3129 reflections with I > 2σ(I)
R_int = 0.025

Refinement

R[F² > 2σ(F²)] = 0.035
wR(F²) = 0.120
S = 1.12
4104 reflections
259 parameters
6 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.81 e Å⁻³
Δρ_min = −0.56 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N2—H2⋯O1	0.88 (1)	1.74 (2)	2.608 (4)	168 (6)
N3—H3⋯O3ⁱ	0.88 (1)	1.78 (2)	2.624 (5)	160 (5)
N4—H4⋯O4ⁱ	0.88 (1)	1.74 (1)	2.614 (5)	175 (7)
N5—H5⋯O2	0.88 (1)	1.79 (2)	2.636 (4)	160 (4)
Symmetry code: (i) x+1, y-1, z.

Data collection: APEX2 (Bruker, 2005 ); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001 ); software used to prepare material for publication: publCIF (Westrip, 2010 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S1600536810041899/lh5152sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810041899/lh5152Isup2.hkl

checkCIF report

Comment top

The crystal structure of 5-Amino-2,4,6-tribromoiodoisophthalic acid exists as a chains in which adjacent molecules are linked by O–H···O hydrogen bonds. In addition, pairs of chains are connected by further O–H···O hydrogen bonds (Beck et al., 2009). This acid furnishes a small number of coordination compounds. An attempt to synthesize a lead(II) derivative that can be linked by 2,2'-biimidazole gave instead the title salt, [C₆H₈N₄]²⁺ [C₈H₂NO₄I₃]^2–(1). Other examples of crystal structure of 2,2'-bis(imidazolium) carboxylates already appear in the literature (Gao et al., 2009; Li & Yang, 2007; Zhou et al., 2009).

The asymmetric unit of (1) is shown in Fig. 1. The cation is nearly planar as its two five-membered rings are twisted along the C_imidazolyl–C_imidazolyl bond by 2.1 (3) ° only. In the anion, both –CO₂ units are almost orthogonal to the bezene ring mean plane [dihedral angles between –CO₂ plane and benzene ring (r.m.s. deviation 0.018 Å) are 84.3 (4)° and 86.2 (3) °]. In the crystal structure, cations and anions are linked by N_imidazolyl–H···O hydrogen bonds to generate a chain formation running along [110](Fig. 2).

Related literature top

For the structure of 5-amino-2,4,6-tribromidoisophthalic acid, see: Beck et al. (2009). For the structures of other 2,2'-bis(imidazolium) carboxylates, see: Gao et al. (2009); Li & Yang (2007); Zhou et al. (2009).

Experimental top

An aqueous solution of lead nitrate (0.006 g, 0.2 mmol) in water (5 ml) was added to a mixture of 5-amino-2,4,6-tribromidoisophthalic acid (0.056 g, 0.1 mmol) in water (5 ml) and sodium hydroxide (0.2 ml, 0.5 M). To this solution was added 2,2'-biimidazole (0.014 g, 0.1 mmol) in DMF (5 ml). The solution was filtered; slow evaporation yielded pale yellow crystals which were collected (30% yield). CH&N elemental analysis. Calc. for C₁₄H₁₀Br₃N₅O₄: C 30.46, H 1.83, N 12.69%.; Found: C, 30.38; H, 1.91; N, 12.77%.

Structure description top

Computing details top

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top

	Fig. 1. Thermal ellipsoid plot (Barbour, 2001) of C₆H₈N₄²⁺ C₈H₂NO₄Br₃^2– at the 50% probability level; hydrogen atoms are drawn as spheres of arbitrary radius.
	Fig. 2. Part of the crystal structure showing hydrogen bonds as dashed lines.

2,2'-Biimidazolium 5-amino-2,4,6-tribromoisophthalate top

Crystal data top

C₆H₈N₄²⁺·C₈H₂Br₃NO₄²⁻	Z = 2
M_r = 552.00	F(000) = 532
Triclinic, P1	D_x = 2.015 Mg m⁻³
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 9.0525 (10) Å	Cell parameters from 2718 reflections
b = 9.2043 (10) Å	θ = 2.4–27.4°
c = 11.5252 (12) Å	µ = 6.68 mm⁻¹
α = 90.262 (1)°	T = 293 K
β = 108.332 (1)°	Prism, pale yellow
γ = 93.136 (1)°	0.35 × 0.25 × 0.15 mm
V = 909.96 (17) Å³

Data collection top

Bruker SMART APEX diffractometer	4104 independent reflections
Radiation source: fine-focus sealed tube	3129 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.025
ω scans	θ_max = 27.5°, θ_min = 1.9°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −11→11
T_min = 0.203, T_max = 0.434	k = −11→11
8042 measured reflections	l = −14→14

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.035	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.120	H atoms treated by a mixture of independent and constrained refinement
S = 1.12	w = 1/[σ²(F_o²) + (0.0618P)² + 0.430P] where P = (F_o² + 2F_c²)/3
4104 reflections	(Δ/σ)_max = 0.001
259 parameters	Δρ_max = 0.81 e Å⁻³
6 restraints	Δρ_min = −0.56 e Å⁻³

Crystal data top

C₆H₈N₄²⁺·C₈H₂Br₃NO₄²⁻	γ = 93.136 (1)°
M_r = 552.00	V = 909.96 (17) Å³
Triclinic, P1	Z = 2
a = 9.0525 (10) Å	Mo Kα radiation
b = 9.2043 (10) Å	µ = 6.68 mm⁻¹
c = 11.5252 (12) Å	T = 293 K
α = 90.262 (1)°	0.35 × 0.25 × 0.15 mm
β = 108.332 (1)°

Data collection top

Bruker SMART APEX diffractometer	4104 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	3129 reflections with I > 2σ(I)
T_min = 0.203, T_max = 0.434	R_int = 0.025
8042 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.035	6 restraints
wR(F²) = 0.120	H atoms treated by a mixture of independent and constrained refinement
S = 1.12	Δρ_max = 0.81 e Å⁻³
4104 reflections	Δρ_min = −0.56 e Å⁻³
259 parameters

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

	x	y	z	U_iso*/U_eq
Br1	0.44985 (5)	0.68067 (5)	0.04955 (4)	0.03399 (14)
Br2	0.30262 (7)	0.89508 (6)	0.45860 (5)	0.05335 (18)
Br3	0.80240 (6)	0.52283 (6)	0.52786 (5)	0.05028 (17)
O1	0.6388 (4)	0.3751 (3)	0.2311 (3)	0.0364 (7)
O2	0.8128 (4)	0.5529 (3)	0.2201 (3)	0.0424 (8)
O3	0.1481 (4)	0.8223 (4)	0.1385 (3)	0.0419 (8)
O4	0.3322 (4)	1.0034 (3)	0.1754 (4)	0.0465 (9)
N1	0.5757 (6)	0.7119 (6)	0.5998 (4)	0.0536 (12)
N2	0.7881 (4)	0.1504 (4)	0.2018 (4)	0.0326 (8)
N3	0.9353 (4)	−0.0118 (4)	0.1680 (4)	0.0356 (9)
N4	1.1546 (4)	0.2242 (4)	0.1272 (3)	0.0305 (8)
N5	1.0016 (4)	0.3864 (4)	0.1539 (3)	0.0258 (7)
C1	0.6952 (5)	0.5045 (5)	0.2451 (4)	0.0300 (9)
C2	0.6062 (5)	0.6121 (4)	0.2971 (4)	0.0265 (8)
C3	0.4913 (5)	0.6934 (4)	0.2216 (4)	0.0246 (8)
C4	0.4030 (5)	0.7833 (4)	0.2686 (4)	0.0276 (9)
C5	0.4310 (5)	0.7852 (5)	0.3941 (4)	0.0329 (10)
C6	0.5465 (5)	0.7061 (5)	0.4750 (4)	0.0343 (10)
C7	0.6352 (5)	0.6244 (4)	0.4223 (4)	0.0293 (9)
C8	0.2831 (5)	0.8777 (4)	0.1859 (4)	0.0310 (9)
C9	0.7208 (6)	0.0171 (5)	0.2144 (5)	0.0491 (13)
H9	0.6293	−0.0004	0.2337	0.059*
C10	0.8132 (6)	−0.0853 (5)	0.1932 (5)	0.0485 (13)
H10	0.7967	−0.1857	0.1954	0.058*
C11	0.9166 (5)	0.1302 (4)	0.1731 (4)	0.0260 (8)
C12	1.0206 (5)	0.2449 (4)	0.1518 (4)	0.0253 (8)
C13	1.2192 (5)	0.3590 (5)	0.1138 (4)	0.0343 (10)
H13	1.3118	0.3773	0.0960	0.041*
C14	1.1255 (5)	0.4600 (4)	0.1306 (4)	0.0307 (9)
H14	1.1414	0.5604	0.1273	0.037*
H2	0.751 (7)	0.232 (4)	0.217 (5)	0.068 (19)*
H3	1.005 (5)	−0.054 (5)	0.143 (5)	0.054 (16)*
H4	1.215 (6)	0.151 (5)	0.139 (6)	0.09 (2)*
H5	0.923 (4)	0.424 (5)	0.171 (4)	0.035 (13)*
H11	0.519 (6)	0.764 (6)	0.631 (5)	0.07 (2)*
H12	0.624 (6)	0.640 (4)	0.643 (4)	0.056 (18)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br1	0.0363 (3)	0.0361 (3)	0.0319 (2)	0.01227 (19)	0.01250 (19)	−0.00142 (18)
Br2	0.0560 (4)	0.0543 (4)	0.0623 (4)	0.0200 (3)	0.0340 (3)	−0.0138 (3)
Br3	0.0441 (3)	0.0611 (4)	0.0420 (3)	0.0224 (3)	0.0049 (2)	0.0071 (2)
O1	0.0342 (17)	0.0232 (15)	0.060 (2)	0.0058 (13)	0.0254 (15)	−0.0047 (14)
O2	0.0372 (19)	0.0282 (17)	0.075 (2)	0.0075 (14)	0.0350 (18)	0.0010 (16)
O3	0.0223 (16)	0.0374 (19)	0.063 (2)	0.0091 (14)	0.0084 (15)	−0.0072 (16)
O4	0.0372 (19)	0.0170 (16)	0.088 (3)	0.0121 (14)	0.0217 (18)	0.0094 (16)
N1	0.067 (3)	0.062 (3)	0.036 (2)	0.020 (3)	0.019 (2)	−0.005 (2)
N2	0.0230 (18)	0.0250 (19)	0.055 (2)	0.0067 (15)	0.0198 (17)	−0.0002 (17)
N3	0.028 (2)	0.0250 (19)	0.059 (2)	0.0073 (16)	0.0192 (18)	−0.0025 (17)
N4	0.0188 (17)	0.034 (2)	0.042 (2)	0.0098 (15)	0.0134 (15)	0.0030 (16)
N5	0.0170 (16)	0.0258 (18)	0.0388 (19)	0.0093 (14)	0.0134 (14)	0.0022 (15)
C1	0.034 (2)	0.030 (2)	0.030 (2)	0.0114 (19)	0.0135 (18)	0.0013 (17)
C2	0.027 (2)	0.0187 (19)	0.036 (2)	0.0059 (16)	0.0125 (17)	−0.0015 (16)
C3	0.028 (2)	0.020 (2)	0.0280 (19)	0.0052 (16)	0.0116 (17)	−0.0030 (15)
C4	0.024 (2)	0.021 (2)	0.041 (2)	0.0066 (16)	0.0145 (18)	−0.0016 (17)
C5	0.031 (2)	0.030 (2)	0.044 (2)	0.0102 (19)	0.019 (2)	−0.0103 (19)
C6	0.034 (2)	0.036 (2)	0.036 (2)	0.005 (2)	0.015 (2)	−0.0061 (19)
C7	0.025 (2)	0.024 (2)	0.039 (2)	0.0078 (17)	0.0091 (18)	0.0007 (17)
C8	0.031 (2)	0.020 (2)	0.048 (3)	0.0161 (18)	0.018 (2)	−0.0008 (18)
C9	0.041 (3)	0.034 (3)	0.084 (4)	−0.002 (2)	0.035 (3)	−0.002 (3)
C10	0.042 (3)	0.023 (2)	0.088 (4)	0.002 (2)	0.031 (3)	0.003 (2)
C11	0.029 (2)	0.0151 (19)	0.034 (2)	0.0067 (16)	0.0089 (17)	−0.0003 (16)
C12	0.030 (2)	0.0144 (18)	0.033 (2)	0.0075 (16)	0.0107 (17)	0.0003 (15)
C13	0.036 (2)	0.027 (2)	0.045 (3)	0.0033 (19)	0.019 (2)	0.0031 (19)
C14	0.035 (2)	0.0154 (19)	0.042 (2)	0.0045 (17)	0.0125 (19)	0.0054 (17)

Geometric parameters (Å, º) top

Br1—C3	1.901 (4)	N5—C12	1.325 (5)
Br2—C5	1.895 (4)	N5—C14	1.377 (5)
Br3—C7	1.911 (4)	N5—H5	0.882 (10)
O1—C1	1.259 (5)	C1—C2	1.541 (5)
O2—C1	1.248 (5)	C2—C7	1.386 (6)
O3—C8	1.250 (5)	C2—C3	1.386 (5)
O4—C8	1.237 (5)	C3—C4	1.399 (5)
N1—C6	1.378 (6)	C4—C5	1.388 (6)
N1—H11	0.877 (10)	C4—C8	1.517 (6)
N1—H12	0.879 (10)	C5—C6	1.403 (6)
N2—C11	1.327 (5)	C6—C7	1.396 (6)
N2—C9	1.369 (6)	C9—C10	1.364 (7)
N2—H2	0.880 (10)	C9—H9	0.9300
N3—C11	1.330 (5)	C10—H10	0.9300
N3—C10	1.373 (6)	C11—C12	1.449 (6)
N3—H3	0.879 (10)	C13—C14	1.346 (6)
N4—C12	1.352 (5)	C13—H13	0.9300
N4—C13	1.373 (6)	C14—H14	0.9300
N4—H4	0.880 (10)

C6—N1—H11	120 (4)	C6—C5—Br2	118.5 (3)
C6—N1—H12	118 (4)	N1—C6—C7	121.3 (4)
H11—N1—H12	119 (6)	N1—C6—C5	122.5 (4)
C11—N2—C9	108.4 (4)	C7—C6—C5	116.1 (4)
C11—N2—H2	129 (4)	C2—C7—C6	123.0 (4)
C9—N2—H2	122 (4)	C2—C7—Br3	118.6 (3)
C11—N3—C10	108.3 (4)	C6—C7—Br3	118.4 (3)
C11—N3—H3	127 (4)	O4—C8—O3	127.7 (4)
C10—N3—H3	124 (4)	O4—C8—C4	114.7 (4)
C12—N4—C13	107.4 (4)	O3—C8—C4	117.7 (4)
C12—N4—H4	132 (4)	C10—C9—N2	107.2 (4)
C13—N4—H4	117 (4)	C10—C9—H9	126.4
C12—N5—C14	108.8 (3)	N2—C9—H9	126.4
C12—N5—H5	124 (3)	C9—C10—N3	106.9 (4)
C14—N5—H5	127 (3)	C9—C10—H10	126.6
O2—C1—O1	126.7 (4)	N3—C10—H10	126.6
O2—C1—C2	117.9 (4)	N2—C11—N3	109.2 (4)
O1—C1—C2	115.4 (4)	N2—C11—C12	125.3 (4)
C7—C2—C3	118.2 (4)	N3—C11—C12	125.5 (4)
C7—C2—C1	119.9 (4)	N5—C12—N4	108.7 (3)
C3—C2—C1	121.8 (4)	N5—C12—C11	126.1 (4)
C2—C3—C4	121.7 (4)	N4—C12—C11	125.2 (4)
C2—C3—Br1	119.4 (3)	C14—C13—N4	108.2 (4)
C4—C3—Br1	118.9 (3)	C14—C13—H13	125.9
C5—C4—C3	117.6 (4)	N4—C13—H13	125.9
C5—C4—C8	121.0 (3)	C13—C14—N5	106.9 (4)
C3—C4—C8	121.3 (4)	C13—C14—H14	126.5
C4—C5—C6	123.2 (4)	N5—C14—H14	126.5
C4—C5—Br2	118.3 (3)

O2—C1—C2—C7	−96.8 (5)	C5—C6—C7—C2	−4.4 (6)
O1—C1—C2—C7	83.9 (5)	N1—C6—C7—Br3	−1.2 (6)
O2—C1—C2—C3	86.3 (5)	C5—C6—C7—Br3	176.5 (3)
O1—C1—C2—C3	−93.0 (5)	C5—C4—C8—O4	85.3 (5)
C7—C2—C3—C4	−1.5 (6)	C3—C4—C8—O4	−93.6 (5)
C1—C2—C3—C4	175.4 (4)	C5—C4—C8—O3	−93.5 (5)
C7—C2—C3—Br1	179.4 (3)	C3—C4—C8—O3	87.6 (5)
C1—C2—C3—Br1	−3.7 (5)	C11—N2—C9—C10	0.4 (6)
C2—C3—C4—C5	−2.0 (6)	N2—C9—C10—N3	0.0 (7)
Br1—C3—C4—C5	177.1 (3)	C11—N3—C10—C9	−0.4 (6)
C2—C3—C4—C8	176.9 (4)	C9—N2—C11—N3	−0.7 (5)
Br1—C3—C4—C8	−4.1 (5)	C9—N2—C11—C12	179.9 (4)
C3—C4—C5—C6	2.5 (6)	C10—N3—C11—N2	0.7 (5)
C8—C4—C5—C6	−176.4 (4)	C10—N3—C11—C12	−179.9 (4)
C3—C4—C5—Br2	−175.5 (3)	C14—N5—C12—N4	−0.2 (5)
C8—C4—C5—Br2	5.6 (6)	C14—N5—C12—C11	179.4 (4)
C4—C5—C6—N1	178.2 (5)	C13—N4—C12—N5	0.0 (5)
Br2—C5—C6—N1	−3.8 (6)	C13—N4—C12—C11	−179.7 (4)
C4—C5—C6—C7	0.6 (7)	N2—C11—C12—N5	−2.3 (7)
Br2—C5—C6—C7	178.6 (3)	N3—C11—C12—N5	178.4 (4)
C3—C2—C7—C6	4.9 (6)	N2—C11—C12—N4	177.3 (4)
C1—C2—C7—C6	−172.0 (4)	N3—C11—C12—N4	−2.0 (7)
C3—C2—C7—Br3	−176.0 (3)	C12—N4—C13—C14	0.2 (5)
C1—C2—C7—Br3	7.0 (5)	N4—C13—C14—N5	−0.4 (5)
N1—C6—C7—C2	177.9 (4)	C12—N5—C14—C13	0.4 (5)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2···O1	0.88 (1)	1.74 (2)	2.608 (4)	168 (6)
N3—H3···O3ⁱ	0.88 (1)	1.78 (2)	2.624 (5)	160 (5)
N4—H4···O4ⁱ	0.88 (1)	1.74 (1)	2.614 (5)	175 (7)
N5—H5···O2	0.88 (1)	1.79 (2)	2.636 (4)	160 (4)

Symmetry code: (i) x+1, y−1, z.

Experimental details

Crystal data
Chemical formula	C₆H₈N₄²⁺·C₈H₂Br₃NO₄²⁻
M_r	552.00
Crystal system, space group	Triclinic, P1
Temperature (K)	293
a, b, c (Å)	9.0525 (10), 9.2043 (10), 11.5252 (12)
α, β, γ (°)	90.262 (1), 108.332 (1), 93.136 (1)
V (Å³)	909.96 (17)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	6.68
Crystal size (mm)	0.35 × 0.25 × 0.15

Data collection
Diffractometer	Bruker SMART APEX
Absorption correction	Multi-scan (SADABS; Sheldrick, 1996)
T_min, T_max	0.203, 0.434
No. of measured, independent and observed [I > 2σ(I)] reflections	8042, 4104, 3129
R_int	0.025
(sin θ/λ)_max (Å⁻¹)	0.649

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.035, 0.120, 1.12
No. of reflections	4104
No. of parameters	259
No. of restraints	6
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.81, −0.56

Computer programs: APEX2 (Bruker, 2005), SAINT (Bruker, 2005), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), X-SEED (Barbour, 2001), publCIF (Westrip, 2010).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2···O1	0.88 (1)	1.74 (2)	2.608 (4)	168 (6)
N3—H3···O3ⁱ	0.88 (1)	1.78 (2)	2.624 (5)	160 (5)
N4—H4···O4ⁱ	0.88 (1)	1.74 (1)	2.614 (5)	175 (7)
N5—H5···O2	0.88 (1)	1.79 (2)	2.636 (4)	160 (4)

Symmetry code: (i) x+1, y−1, z.

Acknowledgements

We thank the Key Laboratory of Environmental Material and Environmental Engineering of Jiangsu Province, Yangzhou University and the University of Malaya for supporting this study.

References

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