2,4-Di­methyl­pyrido[1,2-a]pyrimidin-5-ium perchlorate

Posel, M.; Stoeckli-Evans, H.

doi:10.1107/S2414314616015431

organic compounds

IUCrDATA

ISSN: 2414-3146

Volume 1| Part 10| October 2016| x161543

https://doi.org/10.1107/S2414314616015431

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2,4-Dimethylpyrido[1,2-a]pyrimidin-5-ium perchlorate

Maciej Posel ^a and Helen Stoeckli-Evans ^b ^*

^aInstitute of Chemistry, University of Neuchâtel, Av. de Bellevaux 51, CH-2000 Neuchâtel, Switzerland, and ^bInstitute of Physics, University of Neuchâtel, rue Emile-Argand 11, CH-2000 Neuchâtel, Switzerland
^*Correspondence e-mail: helen.stoeckli-evans@unine.ch

Edited by D.-J. Xu, Zhejiang University (Yuquan Campus), China (Received 25 September 2016; accepted 2 October 2016; online 14 October 2016)

In the title molecular salt, C₁₀H₁₁N₂⁺·ClO₄⁻, the pyrido[1,2-a]pyrimidin-5-ium cation is planar, with an r.m.s. deviation of 0.027 Å for all 12 non-H atoms. The perchlorate anions are distributed over two twofold rotation axes; for one, three of the O atoms are disordered over two sites (occupancies of 1/2). In the crystal, the cations are linked via C—H⋯N hydrogen bonds, forming chains propagating along [001]. The chains are linked by a C—H⋯O hydrogen bond involving the non-disordered perchlorate anion, forming double layers parallel to the bc plane. These layers are linked by a number of weak C—H⋯O hydrogen bonds involving the disordered perchlorate anion, forming a three-dimensional framework.

Keywords: crystal structure; pyrido[1,2-a]pyrimidin-5-ium; pyrimidinium; perchlorate; hydrogen bonding; framework.

CCDC reference: 1507737

Structure description

Reports on the crystal structures of pyrido[1,2-a]pyrimidin-5-ium cations are rare (Koval'chukova et al., 2000 , 2003 ). The title compound was obtained when studying the reaction of the ligand 5,7-bis(2-aminopyridine)-5H,-6,7-dihydropyrrolo[3.4-b]pyrazine (L1) with Mn(ClO₄)₂·6H₂O in methanol in the presence of triethylamine (Posel, 1998 ). The solid obtained from this reaction was recrystallized from a mixture of solvents (methanol/acetonitrile/water) also containing acetylacetone, and dark-brown crystals of the title molecular salt were obtained.

The molecular structure of the title molecular salt is illustrated in Fig. 1. The perchlorate anions are distributed over two twofold rotation axes and for one, involving atom Cl1, three O atoms are disordered over two sites (occupancies of 1/2). The pyrido[1,2-a]pyrimidin-5-ium cation is planar (r.m.s. deviation of 0.027 Å for all twelve non-H atoms). The bond distances and angles in the cation are very similar to those observed for 2,4-dimethyl-9-hydroxypyrido[1,2-a]pyrimidinium perchlorate (Koval'chukova et al., 2000).

Figure 1
A view of the molecular structure of the title molecular salt, showing the atom labelling. Displacement ellipsoids are drawn at the 50% probability level. For clarity, the perchlorate anions have been omitted.

In the crystal, the cations are linked via C—H⋯N hydrogen bonds, forming chains propagating along the c-axis direction (Table 1 and Fig. 2). The chains are linked by a C—H⋯O interaction involving the Cl2 perchlorate anion, forming double layers parallel to the bc plane. The layers are linked by weak C—H⋯O hydrogen bonds (H⋯A > 2.6 Å), involving the Cl1 disordered perchlorate anion, forming a three-dimensional framework (Table 1 and Fig. 2).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C4—H4⋯N1ⁱ	0.93	2.49	3.349 (6)	154
C2—H2⋯O21	0.93	2.47	3.345 (7)	158
C5—H5⋯O12ⁱⁱ	0.93	2.62	3.541 (14)	170
C5—H5⋯O14ⁱⁱⁱ	0.93	2.61	3.449 (12)	150
C9—H9B⋯O14^iv	0.96	2.64	3.493 (13)	149
Symmetry codes: (i) $[x, -y, z-{\script{1\over 2}}]$ ; (ii) $[-x+1, y-1, -z+{\script{1\over 2}}]$ ; (iii) x, y-1, z; (iv) $[x, -y+1, z+{\script{1\over 2}}]$ .

Figure 2
A view along the b axis of the crystal packing of the title molecular salt. The hydrogen bonds are shown as dashed lines (see Table 1

) and only the H atoms involved in these interactions have been included.

Synthesis and crystallization

To a mixture of 5,7-bis(2-aminopyridine)-5H,-6,7-dihydropyrrolo[3.4 − b]pyrazine [L1] (0.0646 g, 0.0001 mol) in 7 ml of dry methanol and 0.1 ml of triethylamine was added Mn(ClO₄)₂·6H₂O (0.0362 g, 0.0001 mol) in 3 ml of dry methanol, and the mixture stirred at room temperature under nitrogen for four days. The mixture was then filtered and the filtrate left to evaporate, but no crystals were obtained. The solid left after evaporation of the solvent was recrystallized several times from different solvents (containing acetylacetone). Finally a mixture of solvents, methanol/acetonitrile/water (1/4/3) was used and it gave a small amount of brown block-like crystals that were examined by X-ray diffraction analysis, and shown to be the title molecular salt (yield 0.0036 g, m.p. > 623 K). The IR spectrum (KBr pellet, cm⁻¹) is shown in Fig. 3. Compound L1 was synthesized by reacting 2,3-dicyanopyrazine with 2-aminopyridine (Posel, 1998). It is possible that during the reaction of L1 with Mn(ClO₄)₂, it decomposed reforming 2-aminopyridine which then reacted with the acetylacetone to form the title compound.

Figure 3
The IR spectrum of the title molecular salt.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. The perchlorate anions are distributed over two twofold rotation axes and for one, involving atom Cl1, the O atoms (O12–O14) are disordered with occupancies of 0.5. Only one equivalent of data were measured, hence R_int = 0.

Table 2
Experimental details

Crystal data
Chemical formula	C₁₀H₁₁N₂⁺·ClO₄⁻
M_r	258.66
Crystal system, space group	Monoclinic, P2/c
Temperature (K)	293
a, b, c (Å)	12.5178 (11), 7.8321 (9), 12.6354 (15)
β (°)	107.763 (8)
V (Å³)	1179.7 (2)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	0.33
Crystal size (mm)	0.30 × 0.27 × 0.27

Data collection
Diffractometer	Stoe AED2 four-circle
No. of measured, independent and observed [I > 2σ(I)] reflections	2198, 2198, 1447
(sin θ/λ)_max (Å⁻¹)	0.606

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.072, 0.168, 1.13
No. of reflections	2198
No. of parameters	172
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.43, −0.24
Computer programs: STADI4 and X-RED (Stoe & Cie, 1997 ), SHELXS97 (Sheldrick, 2008 ), Mercury (Macrae et al., 2008 ), SHELXL2014 (Sheldrick, 2015 ), PLATON (Spek, 2009 ) and publCIF (Westrip, 2010 ).

Structural data

CCDC reference: 1507737

Crystal structure: contains datablocks I, Global. DOI: https://doi.org/10.1107/S2414314616015431/xu4014sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314616015431/xu4014Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2414314616015431/xu4014Isup3.cml

checkCIF report

Computing details top

Data collection: STADI4 (Stoe & Cie, 1997); cell refinement: STADI4 (Stoe & Cie, 1997); data reduction: X-RED (Stoe & Cie, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL2014 (Sheldrick, 2015), PLATON (Spek, 2009) and publCIF (Westrip, 2010).

2,4-Dimethylpyrido[1,2-a]pyrimidin-5-ium perchlorate top

Crystal data top

C₁₀H₁₁N₂⁺·ClO₄⁻	F(000) = 536
M_r = 258.66	D_x = 1.456 Mg m⁻³
Monoclinic, P2/c	Mo Kα radiation, λ = 0.71073 Å
a = 12.5178 (11) Å	Cell parameters from 25 reflections
b = 7.8321 (9) Å	θ = 14.1–17.4°
c = 12.6354 (15) Å	µ = 0.33 mm⁻¹
β = 107.763 (8)°	T = 293 K
V = 1179.7 (2) Å³	Block, brown
Z = 4	0.30 × 0.27 × 0.27 mm

Data collection top

Stoe AED2 four-circle diffractometer	R_int = 0.0
Radiation source: fine-focus sealed tube	θ_max = 25.5°, θ_min = 2.6°
Graphite monochromator	h = −15→14
ω/2θ scans	k = 0→9
2198 measured reflections	l = 0→15
2198 independent reflections	2 standard reflections every 120 min
1447 reflections with I > 2σ(I)	intensity decay: 2%

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)] = 0.072	H-atom parameters constrained
wR(F²) = 0.168	w = 1/[σ²(F_o²) + (0.0364P)² + 1.9648P] where P = (F_o² + 2F_c²)/3
S = 1.13	(Δ/σ)_max = 0.001
2198 reflections	Δρ_max = 0.43 e Å⁻³
172 parameters	Δρ_min = −0.24 e Å⁻³
0 restraints	Extinction correction: SHELXL2014 (Sheldrick, 2015), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0139 (17)

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	Occ. (<1)
N1	0.2789 (3)	0.1607 (5)	0.4607 (3)	0.0569 (10)
N2	0.2637 (3)	0.0349 (4)	0.2851 (3)	0.0448 (9)
C1	0.2140 (4)	0.2878 (6)	0.4095 (4)	0.0611 (13)
C2	0.1683 (4)	0.2900 (6)	0.2934 (4)	0.0579 (12)
H2	0.1214	0.3791	0.2591	0.069*
C3	0.1918 (4)	0.1641 (6)	0.2309 (4)	0.0540 (11)
C4	0.2936 (4)	−0.0962 (6)	0.2268 (4)	0.0571 (12)
H4	0.2671	−0.0963	0.1496	0.069*
C5	0.3607 (4)	−0.2242 (6)	0.2802 (5)	0.0681 (14)
H5	0.3798	−0.3117	0.2396	0.082*
C6	0.4009 (4)	−0.2262 (7)	0.3946 (5)	0.0697 (14)
H6	0.4465	−0.3153	0.4311	0.084*
C7	0.3741 (4)	−0.0984 (6)	0.4536 (4)	0.0607 (13)
H7	0.4024	−0.0992	0.5307	0.073*
C8	0.3036 (3)	0.0364 (5)	0.3996 (3)	0.0481 (10)
C9	0.1890 (5)	0.4263 (8)	0.4800 (5)	0.0931 (19)
H9C	0.1338	0.5022	0.4343	0.140*
H9B	0.2564	0.4888	0.5154	0.140*
H9A	0.1607	0.3766	0.5356	0.140*
C10	0.1435 (5)	0.1578 (7)	0.1067 (4)	0.0770 (16)
H10C	0.0931	0.2521	0.0817	0.115*
H10B	0.1033	0.0526	0.0852	0.115*
H10A	0.2030	0.1646	0.0737	0.115*
Cl1	0.5000	0.3239 (2)	0.2500	0.0559 (5)
O11	0.5000	0.1448 (6)	0.2500	0.101 (2)
O12	0.5458 (15)	0.4207 (12)	0.3408 (8)	0.113 (4)	0.5
O13	0.5533 (12)	0.3630 (13)	0.1648 (11)	0.116 (4)	0.5
O14	0.3885 (7)	0.3640 (14)	0.1956 (14)	0.125 (5)	0.5
Cl2	0.0000	0.7762 (2)	0.2500	0.0607 (5)
O21	0.0652 (5)	0.6759 (7)	0.2040 (5)	0.151 (2)
O22	−0.0649 (5)	0.8791 (8)	0.1674 (4)	0.163 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.068 (2)	0.057 (2)	0.044 (2)	0.005 (2)	0.0147 (19)	−0.0025 (19)
N2	0.049 (2)	0.047 (2)	0.0399 (19)	−0.0041 (17)	0.0152 (16)	0.0012 (17)
C1	0.072 (3)	0.053 (3)	0.061 (3)	0.001 (3)	0.023 (2)	−0.003 (2)
C2	0.062 (3)	0.051 (3)	0.056 (3)	0.004 (2)	0.011 (2)	0.011 (2)
C3	0.057 (3)	0.057 (3)	0.047 (2)	−0.009 (2)	0.015 (2)	0.006 (2)
C4	0.065 (3)	0.056 (3)	0.053 (3)	−0.008 (2)	0.023 (2)	−0.008 (2)
C5	0.073 (3)	0.054 (3)	0.080 (4)	0.007 (3)	0.028 (3)	−0.006 (3)
C6	0.063 (3)	0.063 (3)	0.078 (4)	0.013 (3)	0.014 (3)	0.007 (3)
C7	0.060 (3)	0.066 (3)	0.051 (3)	0.006 (3)	0.011 (2)	0.007 (2)
C8	0.051 (3)	0.047 (2)	0.047 (3)	−0.001 (2)	0.015 (2)	0.002 (2)
C9	0.120 (5)	0.076 (4)	0.079 (4)	0.025 (4)	0.023 (4)	−0.016 (3)
C10	0.091 (4)	0.085 (4)	0.050 (3)	0.007 (3)	0.013 (3)	0.014 (3)
Cl1	0.0524 (10)	0.0447 (9)	0.0658 (11)	0.000	0.0110 (8)	0.000
O11	0.124 (5)	0.044 (3)	0.141 (6)	0.000	0.048 (4)	0.000
O12	0.172 (12)	0.080 (7)	0.066 (6)	−0.005 (8)	0.005 (7)	−0.020 (5)
O13	0.143 (9)	0.099 (7)	0.141 (11)	−0.010 (7)	0.098 (9)	0.011 (7)
O14	0.051 (5)	0.095 (8)	0.204 (15)	0.026 (5)	0.003 (7)	0.019 (8)
Cl2	0.0508 (9)	0.0570 (10)	0.0725 (12)	0.000	0.0161 (8)	0.000
O21	0.148 (5)	0.124 (4)	0.214 (6)	0.063 (4)	0.103 (5)	0.008 (4)
O22	0.174 (5)	0.210 (6)	0.104 (4)	0.122 (5)	0.041 (3)	0.056 (4)

Geometric parameters (Å, º) top

N1—C1	1.322 (6)	C10—H10C	0.9600
N1—C8	1.337 (5)	C10—H10B	0.9600
N2—C8	1.378 (5)	C10—H10A	0.9600
N2—C4	1.381 (5)	Cl1—O12ⁱ	1.349 (9)
N2—C3	1.388 (5)	Cl1—O12	1.349 (9)
C1—C2	1.402 (6)	Cl1—O14	1.390 (8)
C1—C9	1.497 (7)	Cl1—O14ⁱ	1.391 (8)
C2—C3	1.351 (6)	Cl1—O11	1.402 (5)
C2—H2	0.9300	Cl1—O13	1.461 (8)
C3—C10	1.501 (6)	Cl1—O13ⁱ	1.461 (8)
C4—C5	1.349 (7)	O12—O14ⁱ	1.147 (13)
C4—H4	0.9300	O12—O13ⁱ	1.301 (14)
C5—C6	1.378 (7)	O13—O12ⁱ	1.301 (14)
C5—H5	0.9300	O13—O14ⁱ	1.690 (15)
C6—C7	1.350 (7)	O14—O12ⁱ	1.147 (13)
C6—H6	0.9300	O14—O13ⁱ	1.690 (15)
C7—C8	1.411 (6)	Cl2—O22ⁱⁱ	1.371 (5)
C7—H7	0.9300	Cl2—O22	1.371 (5)
C9—H9C	0.9600	Cl2—O21ⁱⁱ	1.382 (5)
C9—H9B	0.9600	Cl2—O21	1.382 (5)
C9—H9A	0.9600

C1—N1—C8	118.8 (4)	H10C—C10—H10A	109.5
C8—N2—C4	119.7 (4)	H10B—C10—H10A	109.5
C8—N2—C3	119.0 (4)	O12ⁱ—Cl1—O12	111.5 (9)
C4—N2—C3	121.2 (4)	O12ⁱ—Cl1—O14	49.5 (6)
N1—C1—C2	121.0 (4)	O12—Cl1—O14	113.3 (7)
N1—C1—C9	117.6 (4)	O12ⁱ—Cl1—O14ⁱ	113.3 (7)
C2—C1—C9	121.4 (5)	O12—Cl1—O14ⁱ	49.5 (6)
C3—C2—C1	120.7 (4)	O14—Cl1—O14ⁱ	153.9 (9)
C3—C2—H2	119.6	O12ⁱ—Cl1—O11	124.2 (4)
C1—C2—H2	119.6	O12—Cl1—O11	124.2 (4)
C2—C3—N2	117.8 (4)	O14—Cl1—O11	103.1 (5)
C2—C3—C10	123.1 (5)	O14ⁱ—Cl1—O11	103.1 (5)
N2—C3—C10	119.1 (4)	O12ⁱ—Cl1—O13	55.0 (6)
C5—C4—N2	121.0 (4)	O12—Cl1—O13	109.7 (7)
C5—C4—H4	119.5	O14—Cl1—O13	101.7 (7)
N2—C4—H4	119.5	O14ⁱ—Cl1—O13	72.7 (7)
C4—C5—C6	120.4 (5)	O11—Cl1—O13	102.1 (4)
C4—C5—H5	119.8	O12ⁱ—Cl1—O13ⁱ	109.7 (7)
C6—C5—H5	119.8	O12—Cl1—O13ⁱ	55.0 (6)
C7—C6—C5	119.9 (5)	O14—Cl1—O13ⁱ	72.7 (6)
C7—C6—H6	120.1	O14ⁱ—Cl1—O13ⁱ	101.7 (7)
C5—C6—H6	120.1	O11—Cl1—O13ⁱ	102.1 (4)
C6—C7—C8	120.8 (5)	O13—Cl1—O13ⁱ	155.8 (9)
C6—C7—H7	119.6	O14ⁱ—O12—O13ⁱ	129.2 (11)
C8—C7—H7	119.6	O14ⁱ—O12—Cl1	67.2 (7)
N1—C8—N2	122.6 (4)	O13ⁱ—O12—Cl1	66.9 (7)
N1—C8—C7	119.1 (4)	O12ⁱ—O13—Cl1	58.1 (5)
N2—C8—C7	118.3 (4)	O12ⁱ—O13—O14ⁱ	98.9 (8)
C1—C9—H9C	109.5	Cl1—O13—O14ⁱ	51.7 (4)
C1—C9—H9B	109.5	O12ⁱ—O14—Cl1	63.3 (6)
H9C—C9—H9B	109.5	O12ⁱ—O14—O13ⁱ	106.6 (10)
C1—C9—H9A	109.5	Cl1—O14—O13ⁱ	55.6 (5)
H9C—C9—H9A	109.5	O22ⁱⁱ—Cl2—O22	108.0 (6)
H9B—C9—H9A	109.5	O22ⁱⁱ—Cl2—O21ⁱⁱ	107.6 (3)
C3—C10—H10C	109.5	O22—Cl2—O21ⁱⁱ	111.4 (4)
C3—C10—H10B	109.5	O22ⁱⁱ—Cl2—O21	111.4 (4)
H10C—C10—H10B	109.5	O22—Cl2—O21	107.6 (3)
C3—C10—H10A	109.5	O21ⁱⁱ—Cl2—O21	110.7 (5)

C8—N1—C1—C2	2.2 (7)	O13ⁱ—Cl1—O12—O14ⁱ	157.6 (11)
C8—N1—C1—C9	−179.3 (5)	O12ⁱ—Cl1—O12—O13ⁱ	99.6 (8)
N1—C1—C2—C3	−1.6 (7)	O14ⁱ—Cl1—O12—O13ⁱ	−157.6 (11)
C9—C1—C2—C3	179.9 (5)	O14—Cl1—O12—O13ⁱ	45.8 (9)
C1—C2—C3—N2	−1.0 (7)	O11—Cl1—O12—O13ⁱ	−80.4 (8)
C1—C2—C3—C10	178.6 (5)	O13—Cl1—O12—O13ⁱ	158.7 (8)
C8—N2—C3—C2	2.8 (6)	O12—Cl1—O13—O12ⁱ	−103.0 (11)
C4—N2—C3—C2	−178.6 (4)	O14ⁱ—Cl1—O13—O12ⁱ	−136.4 (9)
C8—N2—C3—C10	−176.8 (4)	O14—Cl1—O13—O12ⁱ	17.2 (9)
C4—N2—C3—C10	1.8 (6)	O11—Cl1—O13—O12ⁱ	123.5 (6)
C8—N2—C4—C5	0.6 (6)	O13ⁱ—Cl1—O13—O12ⁱ	−56.5 (6)
C3—N2—C4—C5	−177.9 (4)	O12ⁱ—Cl1—O13—O14ⁱ	136.4 (9)
N2—C4—C5—C6	−0.1 (7)	O12—Cl1—O13—O14ⁱ	33.4 (7)
C4—C5—C6—C7	−0.7 (8)	O14—Cl1—O13—O14ⁱ	153.6 (9)
C5—C6—C7—C8	1.0 (8)	O11—Cl1—O13—O14ⁱ	−100.1 (5)
C1—N1—C8—N2	−0.3 (7)	O13ⁱ—Cl1—O13—O14ⁱ	79.9 (5)
C1—N1—C8—C7	179.1 (4)	O12—Cl1—O14—O12ⁱ	99.1 (12)
C4—N2—C8—N1	179.1 (4)	O14ⁱ—Cl1—O14—O12ⁱ	55.9 (7)
C3—N2—C8—N1	−2.3 (6)	O11—Cl1—O14—O12ⁱ	−124.1 (7)
C4—N2—C8—C7	−0.3 (6)	O13—Cl1—O14—O12ⁱ	−18.6 (9)
C3—N2—C8—C7	178.3 (4)	O13ⁱ—Cl1—O14—O12ⁱ	137.1 (10)
C6—C7—C8—N1	−179.9 (4)	O12ⁱ—Cl1—O14—O13ⁱ	−137.1 (10)
C6—C7—C8—N2	−0.5 (7)	O12—Cl1—O14—O13ⁱ	−37.9 (7)
O12ⁱ—Cl1—O12—O14ⁱ	−102.8 (10)	O14ⁱ—Cl1—O14—O13ⁱ	−81.2 (5)
O14—Cl1—O12—O14ⁱ	−156.6 (9)	O11—Cl1—O14—O13ⁱ	98.8 (5)
O11—Cl1—O12—O14ⁱ	77.2 (10)	O13—Cl1—O14—O13ⁱ	−155.6 (9)
O13—Cl1—O12—O14ⁱ	−43.7 (10)

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C4—H4···N1ⁱⁱⁱ	0.93	2.49	3.349 (6)	154
C2—H2···O21	0.93	2.47	3.345 (7)	158
C5—H5···O12^iv	0.93	2.62	3.541 (14)	170
C5—H5···O14^v	0.93	2.61	3.449 (12)	150
C9—H9B···O14^vi	0.96	2.64	3.493 (13)	149

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

Acknowledgements

We are grateful to the Swiss National Science Foundation and the University of Neuchâtel for financial support.

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