3,3′-(Ethane-1,2-di­yl)bis­(3,4-dihydro-2H-1,3-benzoxazine)

Rivera, A.; Camacho, J.; Ríos-Motta, J.; Fejfarová, K.; Dušek, M.

doi:10.1107/S1600536811053530

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 68| Part 1| January 2012| Page o148

doi:10.1107/S1600536811053530

Open

access

3,3′-(Ethane-1,2-diyl)bis(3,4-dihydro-2H-1,3-benzoxazine)

Augusto Rivera,^a ^* Jairo Camacho,^a Jaime Ríos-Motta,^a Karla Fejfarová ^b and Michal Dušek ^b

^aDepartamento de Química, Universidad Nacional de Colombia, Ciudad Universitaria, Bogotá, Colombia, and ^bInstitute of Physics ASCR, v.v.i., Na Slovance 2, 182 21 Praha 8, Czech Republic
^*Correspondence e-mail: ariverau@unal.edu.co

(Received 9 December 2011; accepted 12 December 2011; online 17 December 2011)

The title compound, C₁₈H₂₀N₂O₂, was prepared by Mannich-type reaction of phenol, ethane-1,2-diamine and formaldehyde. The heterocyclic rings adopt half-chair conformations. The acyclic methylene groups attached to the N atoms are in an axial position. In the crystal, weak C—H⋯O hydrogen bonds link the molecules into dimers. These dimers are further connected via C—H⋯π contacts.

Related literature

For related structures see: Rivera et al. (2011 , 2010 ). For the preparation of the title compound, see: Rivera et al. (1989 ). For ring conformations, see Cremer & Pople (1975 ). For weak hydrogen bonds, see: Desiraju & Steiner (1999 ).

Experimental

Crystal data

C₁₈H₂₀N₂O₂
M_r = 296.4
Monoclinic, P 2₁
a = 10.868 (2) Å
b = 5.1693 (13) Å
c = 13.327 (3) Å
β = 102.623 (18)°
V = 730.6 (3) Å³
Z = 2
Cu Kα radiation
μ = 0.71 mm⁻¹
T = 120 K
0.97 × 0.10 × 0.04 mm

Data collection

Agilent Xcalibur diffractometer with an Atlas (Gemini ultra Cu) detector
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2010 ) T_min = 0.77, T_max = 1
2799 measured reflections
1341 independent reflections
785 reflections with I > 3σ(I)
R_int = 0.079

Refinement

R[F² > 2σ(F²)] = 0.067
wR(F²) = 0.171
S = 1.38
1341 reflections
199 parameters
H-atom parameters constrained
Δρ_max = 0.28 e Å⁻³
Δρ_min = −0.25 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

Cg4 is the centroid of the C12–C17 ring.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C11—H11a⋯O2ⁱ	0.96	2.47	3.415 (10)	168
C11—H11b⋯Cg4ⁱⁱ	0.96	2.58	3.523 (10)	169
Symmetry codes: (i) $[-x+2, y+{\script{1\over 2}}, -z+2]$ ; (ii) x, y+1, z.

Data collection: CrysAlis PRO (Agilent, 2010); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SIR2002 (Burla et al., 2003 ); program(s) used to refine structure: JANA2006 (Petříček et al., 2006 ); molecular graphics: DIAMOND (Brandenburg & Putz, 2005 ); software used to prepare material for publication: JANA2006.

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536811053530/bt5748sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811053530/bt5748Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536811053530/bt5748Isup3.cml

checkCIF report

Comment top

We have recently reported the molecular structure of two 3,3'-(ethane-1,2-diyl)bis(6-substituted-3,4-dihydro-2H-1,3-benzoxazine). The substituents in position 6 were methyl and chlorine respectively (Rivera et al., 2011, 2010). Their crystal structures established the existence of an anomeric effect in N—C—O sequence in oxazine ring. In connection with our interest in anomeric effect in benzo-fused oxazine ring, we decided it was important to establish the effect of substituent at the aromatic ring in the N—C—O moiety. Thus, we obtained the title compound (I) which has no substituent in position 6.

The molecular structure of the title compound is illustrated in Fig. 1. Unlike the related structures, which crystallized in monoclinic space groups P2₁/n (Rivera et al., 2011) and C2/c (Rivera et al., 2010) utilizing the crystallography inversion center in the molecular symmetry, the title compound (I) crystallizes in the polar space group P2₁ with one molecule in the asymmetric unit. The molecules of (I) thus have no internal symmetry. The fused six-membered heterocyclic rings exists in the approximate half-chair conformations with puckering parameters Q = 0.479 (9) Å, θ = 49.2 (11)° and ϕ = 94.4 (13)° for O1/C2/N1/C9/C8/C3 and Q = 0.482 (8) Å, θ = 50.0 (10)° and ϕ = 101.1 (13)° for O2/C11/N2/C18/C17/C12 (Cremer & Pople, 1975). The C—O bond lengths [C2—O1, 1.451 (13) Å; C11—O2, 1.475 (11) Å] are longer than the values observed in related structure where the p-substituents in the aromatic rings is methyl [1.3755 (14) Å and 1.4525 (13) Å] (Rivera et al., 2011). However, in p-chlorine derivative, the C—O bond distance is significantlly longer from those in (I), [1.421 (2) Å and 1.529 (2) Å] (Rivera et al., 2010). The N1—C2 and N2—C11 bond lengths of 1.416 (9) Å and 1.431 (10) Å respectively, which are shorter than the expected bond length of 1.468 Å, provides structural evidence for the existence of an anomeric effect in both N—C—O groups.

In the crystal weak intermolecular C—H···O contacts (Table 1) that could be considered as weak hydrogen bonds (Desiraju & Steiner, 1999) link molecules into dimers (Fig. 2). Neighboring pair of these dimers are linked together via weaker C—H···π contacts into chains extended along the b axis (Figure 2).

Related literature top

For related structures see: Rivera et al. (2011, 2010). For the preparation of the title compound, see: Rivera et al. (1989). For ring conformations, see Cremer & Pople (1975). For weak hydrogen bonds, see: Desiraju & Steiner (1999).

Experimental top

To a stirred mixture of ethane-1,2-diamine (0.34 ml, 5 mmol) and phenol (0.94 g, 10 mmol) dissolved in dioxane (10 ml) was added dropwise an aqueous solution of formaldehyde (1.5 ml, 20 mmol). The reaction mixture was stirred for4 h. at room temperature. The resultant precipitate was collected, washed with water, dried in vacuum and recrystallized from ethanol to give title compound.

Computing details top

Data collection: CrysAlis PRO (Agilent, 2010); cell refinement: CrysAlis PRO (Agilent, 2010); data reduction: CrysAlis PRO (Agilent, 2010); program(s) used to solve structure: SIR2002 (Burla et al., 2003); program(s) used to refine structure: JANA2006 (Petříček et al., 2006); molecular graphics: DIAMOND (Brandenburg & Putz, 2005); software used to prepare material for publication: JANA2006 (Petříček et al., 2006).

Figures top

	Fig. 1. A view of (I) with the numbering scheme.displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. Packing of the molecules of the title compound view along b axis.

3,3'-(Ethane-1,2-diyl)bis(3,4-dihydro-2H-1,3-benzoxazine) top

Crystal data top

C₁₈H₂₀N₂O₂	F(000) = 316
M_r = 296.4	D_x = 1.347 Mg m⁻³
Monoclinic, P2₁	Cu Kα radiation, λ = 1.5418 Å
Hall symbol: P 2yb	Cell parameters from 1061 reflections
a = 10.868 (2) Å	θ = 3.4–65.5°
b = 5.1693 (13) Å	µ = 0.71 mm⁻¹
c = 13.327 (3) Å	T = 120 K
β = 102.623 (18)°	Needle, colourless
V = 730.6 (3) Å³	0.97 × 0.10 × 0.04 mm
Z = 2

Data collection top

Agilent Xcalibur diffractometer with an Atlas (Gemini ultra Cu) detector	1341 independent reflections
Radiation source: Enhance Ultra (Cu) X-ray Source	785 reflections with I > 3σ(I)
Mirror monochromator	R_int = 0.079
Detector resolution: 10.3784 pixels mm^-1	θ_max = 65.7°, θ_min = 3.4°
Rotation method data acquisition using ω scans	h = −12→9
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2010)	k = −4→5
T_min = 0.77, T_max = 1	l = −15→15
2799 measured reflections

Refinement top

Refinement on F²	81 constraints
R[F² > 2σ(F²)] = 0.067	H-atom parameters constrained
wR(F²) = 0.171	Weighting scheme based on measured s.u.'s w = 1/[σ²(I) + 0.0016I²]
S = 1.38	(Δ/σ)_max = 0.004
1341 reflections	Δρ_max = 0.28 e Å⁻³
199 parameters	Δρ_min = −0.25 e Å⁻³
0 restraints

Crystal data top

C₁₈H₂₀N₂O₂	V = 730.6 (3) Å³
M_r = 296.4	Z = 2
Monoclinic, P2₁	Cu Kα radiation
a = 10.868 (2) Å	µ = 0.71 mm⁻¹
b = 5.1693 (13) Å	T = 120 K
c = 13.327 (3) Å	0.97 × 0.10 × 0.04 mm
β = 102.623 (18)°

Data collection top

Agilent Xcalibur diffractometer with an Atlas (Gemini ultra Cu) detector	1341 independent reflections
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2010)	785 reflections with I > 3σ(I)
T_min = 0.77, T_max = 1	R_int = 0.079
2799 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.067	0 restraints
wR(F²) = 0.171	H-atom parameters constrained
S = 1.38	Δρ_max = 0.28 e Å⁻³
1341 reflections	Δρ_min = −0.25 e Å⁻³
199 parameters

Special details top

Experimental. CrysAlisPro (Agilent, 2010) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.

Refinement. The refinement was carried out against all reflections. The conventional R-factor is always based on F. The goodness of fit as well as the weighted R-factor are based on F and F² for refinement carried out on F and F², respectively. The threshold expression is used only for calculating R-factors etc. and it is not relevant to the choice of reflections for refinement.

The program used for refinement, Jana2006, uses the weighting scheme based on the experimental expectations, see _refine_ls_weighting_details, that does not force S to be one. Therefore the values of S are usually larger than the ones from the SHELX program.

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

	x	y	z	U_iso*/U_eq
C1	0.9998 (6)	0.619 (2)	0.7044 (5)	0.038 (2)
N1	1.0853 (5)	0.4006 (19)	0.7006 (4)	0.040 (2)
C2	1.2051 (7)	0.420 (2)	0.7681 (6)	0.049 (3)
O1	1.2790 (5)	0.6444 (18)	0.7528 (4)	0.0482 (19)
C3	1.2853 (7)	0.677 (2)	0.6506 (5)	0.039 (3)
C4	1.3740 (7)	0.854 (2)	0.6314 (6)	0.050 (3)
C5	1.3841 (7)	0.898 (2)	0.5301 (6)	0.051 (3)
C6	1.3057 (7)	0.766 (2)	0.4522 (6)	0.049 (3)
C7	1.2171 (7)	0.595 (2)	0.4717 (6)	0.046 (3)
C8	1.2051 (7)	0.549 (2)	0.5724 (5)	0.036 (2)
C9	1.1083 (7)	0.361 (2)	0.5963 (5)	0.040 (3)
C10	0.9615 (6)	0.630 (2)	0.8071 (5)	0.039 (2)
N2	0.8679 (5)	0.8366 (19)	0.8073 (4)	0.036 (2)
C11	0.8763 (7)	0.948 (2)	0.9069 (5)	0.039 (3)
O2	0.8508 (4)	0.7615 (18)	0.9838 (3)	0.0389 (16)
C12	0.7491 (7)	0.605 (2)	0.9472 (5)	0.036 (2)
C13	0.7116 (6)	0.445 (2)	1.0211 (5)	0.037 (2)
C14	0.6127 (7)	0.273 (2)	0.9901 (6)	0.043 (3)
C15	0.5531 (7)	0.262 (2)	0.8873 (5)	0.039 (2)
C16	0.5905 (6)	0.416 (2)	0.8150 (5)	0.040 (3)
C17	0.6897 (6)	0.589 (2)	0.8434 (5)	0.033 (2)
C18	0.7386 (6)	0.756 (2)	0.7673 (5)	0.035 (2)
H1a	0.925907	0.601938	0.65019	0.0451*
H1b	1.040864	0.777887	0.693451	0.0451*
H2a	1.252659	0.265585	0.763506	0.0584*
H2b	1.195273	0.416764	0.837985	0.0584*
H4	1.427396	0.94568	0.687131	0.0595*
H5	1.444994	1.018264	0.5152	0.0611*
H6	1.313009	0.793375	0.382469	0.0593*
H7	1.163036	0.505915	0.415763	0.0546*
H9a	1.030594	0.380027	0.546277	0.0478*
H9b	1.136814	0.186835	0.590176	0.0478*
H10a	0.926386	0.466841	0.820454	0.0473*
H10b	1.034626	0.662279	0.860732	0.0473*
H11a	0.958427	1.021981	0.930714	0.0474*
H11b	0.818703	1.090401	0.901728	0.0474*
H13	0.754437	0.454456	1.092073	0.0449*
H14	0.585732	0.163708	1.039393	0.0519*
H15	0.484253	0.143471	0.865763	0.0472*
H16	0.547427	0.403116	0.744117	0.0481*
H18a	0.733488	0.661676	0.70447	0.0422*
H18b	0.685945	0.905848	0.750886	0.0422*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.041 (4)	0.046 (4)	0.027 (3)	0.005 (4)	0.010 (3)	0.005 (3)
N1	0.042 (3)	0.041 (3)	0.038 (4)	0.008 (3)	0.012 (3)	0.002 (3)
C2	0.058 (5)	0.053 (5)	0.037 (4)	0.011 (5)	0.013 (4)	0.010 (4)
O1	0.049 (3)	0.064 (3)	0.029 (3)	0.002 (3)	0.003 (2)	−0.004 (3)
C3	0.044 (5)	0.044 (4)	0.029 (4)	−0.002 (4)	0.008 (3)	−0.001 (3)
C4	0.039 (4)	0.050 (5)	0.059 (6)	−0.001 (4)	0.009 (4)	−0.017 (4)
C5	0.053 (5)	0.035 (4)	0.068 (6)	−0.005 (4)	0.022 (4)	−0.006 (4)
C6	0.060 (5)	0.040 (4)	0.053 (5)	0.003 (5)	0.023 (4)	0.004 (4)
C7	0.054 (5)	0.040 (4)	0.043 (4)	0.002 (4)	0.010 (4)	−0.001 (4)
C8	0.045 (4)	0.034 (4)	0.028 (4)	0.004 (4)	0.009 (3)	−0.002 (3)
C9	0.047 (5)	0.035 (4)	0.040 (4)	−0.002 (3)	0.014 (3)	−0.004 (3)
C10	0.048 (4)	0.044 (4)	0.025 (4)	0.006 (4)	0.006 (3)	0.003 (3)
N2	0.036 (3)	0.041 (3)	0.033 (4)	0.003 (3)	0.010 (3)	0.002 (3)
C11	0.042 (4)	0.034 (4)	0.042 (4)	−0.003 (4)	0.008 (3)	0.004 (3)
O2	0.046 (3)	0.036 (2)	0.032 (3)	−0.008 (3)	0.004 (2)	−0.001 (2)
C12	0.039 (4)	0.033 (4)	0.035 (4)	0.000 (4)	0.009 (3)	−0.001 (3)
C13	0.043 (4)	0.046 (4)	0.024 (4)	0.003 (4)	0.011 (3)	−0.003 (3)
C14	0.050 (5)	0.041 (4)	0.041 (4)	−0.001 (4)	0.016 (3)	−0.004 (4)
C15	0.044 (4)	0.035 (4)	0.039 (4)	−0.004 (4)	0.008 (3)	−0.001 (3)
C16	0.043 (4)	0.042 (4)	0.035 (4)	0.004 (4)	0.008 (3)	−0.004 (3)
C17	0.038 (4)	0.039 (4)	0.022 (3)	0.003 (4)	0.005 (3)	−0.007 (3)
C18	0.046 (4)	0.030 (3)	0.028 (4)	0.008 (4)	0.006 (3)	0.006 (3)

Geometric parameters (Å, º) top

C1—N1	1.471 (13)	C10—N2	1.474 (12)
C1—C10	1.516 (10)	C10—H10a	0.96
C1—H1a	0.96	C10—H10b	0.96
C1—H1b	0.96	N2—C11	1.431 (10)
N1—C2	1.416 (9)	N2—C18	1.450 (9)
N1—C9	1.480 (10)	C11—O2	1.475 (11)
C2—O1	1.451 (13)	C11—H11a	0.96
C2—H2a	0.96	C11—H11b	0.96
C2—H2b	0.96	O2—C12	1.370 (10)
O1—C3	1.388 (9)	C12—C13	1.415 (12)
C3—C4	1.394 (13)	C12—C17	1.395 (9)
C3—C8	1.373 (11)	C13—C14	1.386 (12)
C4—C5	1.397 (12)	C13—H13	0.96
C4—H4	0.96	C14—C15	1.383 (9)
C5—C6	1.373 (12)	C14—H14	0.96
C5—H5	0.96	C15—C16	1.378 (12)
C6—C7	1.373 (13)	C15—H15	0.96
C6—H6	0.96	C16—C17	1.390 (12)
C7—C8	1.397 (11)	C16—H16	0.96
C7—H7	0.96	C17—C18	1.514 (12)
C8—C9	1.518 (13)	C18—H18a	0.96
C9—H9a	0.96	C18—H18b	0.96
C9—H9b	0.96

N1—C1—C10	111.1 (7)	C1—C10—N2	110.8 (7)
N1—C1—H1a	109.4711	C1—C10—H10a	109.4713
N1—C1—H1b	109.4709	C1—C10—H10b	109.4708
C10—C1—H1a	109.4717	N2—C10—H10a	109.4714
C10—C1—H1b	109.4713	N2—C10—H10b	109.4714
H1a—C1—H1b	107.7691	H10a—C10—H10b	108.1247
C1—N1—C2	115.1 (8)	C10—N2—C11	112.8 (6)
C1—N1—C9	112.2 (6)	C10—N2—C18	113.9 (8)
C2—N1—C9	106.6 (6)	C11—N2—C18	108.4 (6)
N1—C2—O1	115.3 (7)	N2—C11—O2	113.5 (8)
N1—C2—H2a	109.4712	N2—C11—H11a	109.4711
N1—C2—H2b	109.4708	N2—C11—H11b	109.4713
O1—C2—H2a	109.4715	O2—C11—H11a	109.4716
O1—C2—H2b	109.4712	O2—C11—H11b	109.4711
H2a—C2—H2b	102.9256	H11a—C11—H11b	105.115
C2—O1—C3	112.5 (7)	C11—O2—C12	113.3 (5)
O1—C3—C4	116.4 (7)	O2—C12—C13	115.5 (6)
O1—C3—C8	121.8 (8)	O2—C12—C17	123.5 (8)
C4—C3—C8	121.8 (7)	C13—C12—C17	120.9 (8)
C3—C4—C5	119.1 (8)	C12—C13—C14	119.4 (6)
C3—C4—H4	120.4314	C12—C13—H13	120.2967
C5—C4—H4	120.4309	C14—C13—H13	120.2963
C4—C5—C6	119.0 (9)	C13—C14—C15	119.2 (8)
C4—C5—H5	120.5111	C13—C14—H14	120.4096
C6—C5—H5	120.5112	C15—C14—H14	120.4094
C5—C6—C7	121.4 (8)	C14—C15—C16	121.5 (8)
C5—C6—H6	119.2825	C14—C15—H15	119.2499
C7—C6—H6	119.2824	C16—C15—H15	119.2504
C6—C7—C8	120.5 (7)	C15—C16—C17	120.8 (6)
C6—C7—H7	119.7553	C15—C16—H16	119.6195
C8—C7—H7	119.7559	C17—C16—H16	119.6206
C3—C8—C7	118.1 (8)	C12—C17—C16	118.3 (8)
C3—C8—C9	120.3 (7)	C12—C17—C18	118.4 (7)
C7—C8—C9	121.6 (7)	C16—C17—C18	123.4 (6)
N1—C9—C8	112.0 (7)	N2—C18—C17	111.8 (5)
N1—C9—H9a	109.4708	N2—C18—H18a	109.4715
N1—C9—H9b	109.4706	N2—C18—H18b	109.4717
C8—C9—H9a	109.4711	C17—C18—H18a	109.471
C8—C9—H9b	109.4722	C17—C18—H18b	109.4706
H9a—C9—H9b	106.8364	H18a—C18—H18b	107.0112

Hydrogen-bond geometry (Å, º) top

Cg4 is the centroid of the C12–C17 ring.

D—H···A	D—H	H···A	D···A	D—H···A
C11—H11a···O2ⁱ	0.96	2.47	3.415 (10)	168
C11—H11b···Cg4ⁱⁱ	0.96	2.58	3.523 (10)	169

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

Experimental details

Crystal data
Chemical formula	C₁₈H₂₀N₂O₂
M_r	296.4
Crystal system, space group	Monoclinic, P2₁
Temperature (K)	120
a, b, c (Å)	10.868 (2), 5.1693 (13), 13.327 (3)
β (°)	102.623 (18)
V (Å³)	730.6 (3)
Z	2
Radiation type	Cu Kα
µ (mm⁻¹)	0.71
Crystal size (mm)	0.97 × 0.10 × 0.04

Data collection
Diffractometer	Agilent Xcalibur diffractometer with an Atlas (Gemini ultra Cu) detector
Absorption correction	Multi-scan (CrysAlis PRO; Agilent, 2010)
T_min, T_max	0.77, 1
No. of measured, independent and observed [I > 3σ(I)] reflections	2799, 1341, 785
R_int	0.079
(sin θ/λ)_max (Å⁻¹)	0.591

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.067, 0.171, 1.38
No. of reflections	1341
No. of parameters	199
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.28, −0.25

Computer programs: CrysAlis PRO (Agilent, 2010), SIR2002 (Burla et al., 2003), JANA2006 (Petříček et al., 2006), DIAMOND (Brandenburg & Putz, 2005).

Hydrogen-bond geometry (Å, º) top

Cg4 is the centroid of the C12–C17 ring.

D—H···A	D—H	H···A	D···A	D—H···A
C11—H11a···O2ⁱ	0.96	2.47	3.415 (10)	168.40
C11—H11b···Cg4ⁱⁱ	0.96	2.58	3.523 (10)	169

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

Acknowledgements

We acknowledge the Dirección de Investigaciones, Sede Bogotá (DIB) de la Universidad Nacional de Colombia, for financial support of this work, as well as the Institutional research plan No. AVOZ10100521 of the Institute of Physics and the Praemium Academiae project of the Academy of Sciences of the Czech Republic.

References

Agilent (2010). CrysAlis PRO. Agilent Technologies, Yarnton, England. Google Scholar
Brandenburg, K. & Putz, H. (2005). DIAMOND. Crystal Impact, Bonn, Germany. Google Scholar
Burla, M. C., Camalli, M., Carrozzini, B., Cascarano, G. L., Giacovazzo, C., Polidori, G. & Spagna, R. (2003). J. Appl. Cryst. 36, 1103. CrossRef IUCr Journals Google Scholar
Cremer, D. & Pople, J. A. (1975). J. Am. Chem. Soc. 97, 1354–1358. CrossRef CAS Web of Science Google Scholar
Desiraju, G. R. & Steiner, T. (1999). The Weak Hydrogen Bond. Oxford University Press. Google Scholar
Petříček, V., Dušek, M. & Palatinus, L. (2006). JANA2006. Institute of Physics, Praha, Czech Republic. Google Scholar
Rivera, A., Aguilar, Z., Clavijo, D. & Joseph-Nathan, P. (1989). Anal. Quim. 85, 9–10. CAS Google Scholar
Rivera, A., Camacho, J., Ríos-Motta, J., Pojarová, M. & Dušek, M. (2011). Acta Cryst. E67, o2028. Web of Science CSD CrossRef IUCr Journals Google Scholar
Rivera, A., Rojas, J. J., Ríos-Motta, J., Dušek, M. & Fejfarová, K. (2010). Acta Cryst. E66, o1134. Web of Science CSD CrossRef 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.

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 68| Part 1| January 2012| Page o148

doi:10.1107/S1600536811053530

Open

access