N,N,N′-Trimethyl-N′′-(4-nitro­phen­yl)-N′-phenyl­guanidine

Tiritiris, I.; Frey, W.; Kantlehner, W.

doi:10.1107/S160053681400693X

organic compounds

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ISSN: 2056-9890

Volume 70| Part 5| May 2014| Pages o516-o517

doi:10.1107/S160053681400693X

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N,N,N′-Trimethyl-N′′-(4-nitrophenyl)-N′-phenylguanidine

Ioannis Tiritiris,^a Wolfgang Frey ^b and Willi Kantlehner ^a ^*

^aFakultät Chemie/Organische Chemie, Hochschule Aalen, Beethovenstrasse 1, D-73430 Aalen, Germany, and ^bInstitut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
^*Correspondence e-mail: willi.kantlehner@htw-aalen.de

(Received 12 March 2014; accepted 28 March 2014; online 5 April 2014)

The C—N bond lengths in the guanidine unit of the title compound, C₁₆H₁₈N₄O₂, are 1.298 (2), 1.353 (2) and 1.401 (3) Å, indicating double- and single-bond character. The N—C—N angles are 115.81 (16), 118.90 (18) and 125.16 (18)°, showing a deviation of the CN₃ plane from an ideal trigonal–planar geometry. In the crystal, C—H⋯O hydrogen bonds are observed between the methyl- and aromatic-H atoms and nitro-O atoms. One H atom of the phenyl ring and of the NMe₂ group associate with the O atoms of the nitro group, giving chains along the a- and b-axis directions. Cross-linking of these two chains results in a two-dimensional network along bc.

CCDC reference: 994178

Related literature

For the synthesis and characterization of compounds for blue OLEDs, see: Agarwal et al. (2011 ). For the crystal structures of N-methylated diphenylguanidines, see: Tanatani et al. (1998 ). For non-classical hydrogen bonds, see: Desiraju & Steiner (1999 ). For the crystal structure of N′′-(4-carbazol-9-yl-phenyl)-N,N′-diethyl-N,N′-diphenylguanidine, see: Tiritiris & Kantlehner (2013 ), and of N′′-(4-methoxyphenyl)-N,N,N′-trimethyl-N′-phenylguanidine, see: Tiritiris et al. (2014 ).

Experimental

Crystal data

C₁₆H₁₈N₄O₂
M_r = 298.34
Monoclinic, C 2/c
a = 18.409 (2) Å
b = 7.7140 (8) Å
c = 22.493 (3) Å
β = 109.503 (7)°
V = 3010.9 (6) Å³
Z = 8
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 293 K
0.35 × 0.25 × 0.20 mm

Data collection

Nicolet P3/F diffractometer
2974 measured reflections
2974 independent reflections
2237 reflections with I > 2σ(I)
3 standard reflections every 50 reflections intensity decay: 3%

Refinement

R[F² > 2σ(F²)] = 0.053
wR(F²) = 0.124
S = 1.06
2974 reflections
203 parameters
H-atom parameters constrained
Δρ_max = 0.18 e Å⁻³
Δρ_min = −0.22 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C12—H12⋯O2ⁱ	0.93	2.49	3.416 (3)	173
C2—H2A⋯O1ⁱⁱ	0.96	2.72	3.064 (3)	102
Symmetry codes: (i) x, y-1, z; (ii) $[x, -y+1, z-{\script{1\over 2}}]$ .

Data collection: XSCANS (Siemens, 1996 ); cell refinement: XSCANS; data reduction: SHELXTL (Sheldrick, 2008 ); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg & Putz, 2005 ); software used to prepare material for publication: SHELXL97.

Supporting information

CCDC reference: 994178

Crystal structure: contains datablocks I, global. DOI: 10.1107/S160053681400693X/nr2049sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S160053681400693X/nr2049Isup2.hkl

Supporting information file. DOI: 10.1107/S160053681400693X/nr2049Isup3.cml

checkCIF report

Comment top

We were interested in the synthesis and characterization of aromatic guanidines to examine their suitability in OLEDs (Agarwal et al., 2011). Because the crystal structure of the title compound was not known so far, it was decided to carry out an appropriate investigation. According to the structure analysis, the C1–N3 bond in the guanidine unit is 1.298 (2) Å, indicating double bond character. The bond lengths C1–N2 = 1.401 (3) Å and C1–N1 = 1.353 (2) Å are elongated and characteristic for C–N imine single bonds. The N–C1–N angles are 115.81 (16)° (N1–C1–N2), 125.16 (18)° (N2–C1–N3) and 118.90 (18)° (N1–C1–N3), showing a deviation of the CN₃ plane from an ideal trigonal planar geometry (Fig. 1). Similar bond lengths and angles of the guanidine CN₃ part have been found by structure analysis for N''-(4-Carbazol-9-yl-phenyl)- N,N'-diethyl-N,N'-diphenyl-guanidine (Tiritiris & Kantlehner, 2013), several N-methylated diphenylguanidines (Tanatani et al., 1998) and N''- (4-methoxyphenyl)-N,N,N'-trimethyl-N'- phenylguanidine (Tiritiris et al., 2014). Non-classical C–H···O hydrogen bonds (Desiraju & Steiner, 1999) between methyl hydrogen atoms, aromatic hydrogen atoms and oxygen atoms of the nitro groups are present [d(H···O) = 2.49 and 2.72 Å] (Tab. 1). One hydrogen atom of the phenyl ring (H12) is associated with the oxygen atom (O2) of the nitro group, resulting in chains along the b axis. A second hydrogen atom of the NMe₂ group (H2A) is connected with O1, giving chains along the a axis. By crosslinking of both chains, a two-dimensional network along bc results (Fig. 2).

Related literature top

For the synthesis and characterization of compounds for blue OLEDs, see: Agarwal et al. (2011). For the crystal structures of N-methylated diphenylguanidines, see: Tanatani et al. (1998). For non-classical hydrogen bonds, see: Desiraju & Steiner (1999). For the crystal structure of N''-(4-carbazol-9-yl-phenyl)-N,N'-diethyl-N,N'-diphenylguanidine, see: Tiritiris & Kantlehner (2013) and of N''-(4-methoxyphenyl)-N,N,N'-trimethyl-N'-phenylguanidine, see: Tiritiris et al. (2014).

Experimental top

One equivalent of N,N-dimethyl-N',N'-methylphenyl- chloroformamidinium-chloride (synthesized from N,N-dimethyl- N',N'-methylphenylthiourea and phosgene) was reacted with one equivalent of 4-nitroaniline (Sigma-Aldrich) in acetonitrile, in the presence of one equivalent triethylamine, at 273 K. The obtained mixture consisting of the guanidinium chloride and triethylammonium chloride was reacted in the next step with an excess of an aqueous sodium hydroxide solution at 273 K. After extraction of the guanidine with diethyl ether from the water phase, the solvent was evaporated and the title compound was isolated in form of a colourless solid. Single crystals have been obtained by recrystallization from a saturated acetonitrile solution at room temperature.

Computing details top

Data collection: XSCANS (Siemens, 1996); cell refinement: XSCANS (Siemens, 1996); data reduction: SHELXTL (Sheldrick, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg & Putz, 2005); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top

	Fig. 1. The structure of the title compound with atom labels and 50% probability displacement ellipsoids.
	Fig. 2. Packing diagram of the title compound. The C–H···O hydrogen bonds (indicated by dashed lines) are arranged in a two-dimensional network (bc-view). Only hydrogen atoms involved in the hydrogen bonding system are shown.

N,N,N'-Trimethyl-N''-(4-nitrophenyl)-N'-phenylguanidine top

Crystal data top

C₁₆H₁₈N₄O₂	F(000) = 1264
M_r = 298.34	D_x = 1.316 Mg m⁻³
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 35 reflections
a = 18.409 (2) Å	θ = 14–17°
b = 7.7140 (8) Å	µ = 0.09 mm⁻¹
c = 22.493 (3) Å	T = 293 K
β = 109.503 (7)°	Plate, colorless
V = 3010.9 (6) Å³	0.35 × 0.25 × 0.20 mm
Z = 8

Data collection top

Nicolet P3/F diffractometer	R_int = 0.000
Radiation source: sealed tube	θ_max = 26.0°, θ_min = 1.9°
Graphite monochromator	h = −22→21
Wyckoff scan	k = 0→9
2974 measured reflections	l = 0→27
2974 independent reflections	3 standard reflections every 50 reflections
2237 reflections with I > 2σ(I)	intensity decay: 3%

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)] = 0.053	H-atom parameters constrained
wR(F²) = 0.124	w = 1/[σ²(F_o²) + (0.0442P)² + 2.9581P] where P = (F_o² + 2F_c²)/3
S = 1.06	(Δ/σ)_max < 0.001
2974 reflections	Δρ_max = 0.18 e Å⁻³
203 parameters	Δρ_min = −0.22 e Å⁻³
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0044 (4)

Crystal data top

C₁₆H₁₈N₄O₂	V = 3010.9 (6) Å³
M_r = 298.34	Z = 8
Monoclinic, C2/c	Mo Kα radiation
a = 18.409 (2) Å	µ = 0.09 mm⁻¹
b = 7.7140 (8) Å	T = 293 K
c = 22.493 (3) Å	0.35 × 0.25 × 0.20 mm
β = 109.503 (7)°

Data collection top

Nicolet P3/F diffractometer	R_int = 0.000
2974 measured reflections	3 standard reflections every 50 reflections
2974 independent reflections	intensity decay: 3%
2237 reflections with I > 2σ(I)

Refinement top

R[F² > 2σ(F²)] = 0.053	0 restraints
wR(F²) = 0.124	H-atom parameters constrained
S = 1.06	Δρ_max = 0.18 e Å⁻³
2974 reflections	Δρ_min = −0.22 e Å⁻³
203 parameters

Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) 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
C1	0.11956 (11)	0.3349 (3)	0.21285 (9)	0.0330 (4)
N1	0.09025 (10)	0.2129 (2)	0.16803 (8)	0.0384 (4)
N2	0.16570 (9)	0.4615 (2)	0.19854 (7)	0.0356 (4)
N3	0.10725 (10)	0.3212 (2)	0.26620 (7)	0.0384 (4)
C2	0.12086 (14)	0.1763 (3)	0.11771 (10)	0.0493 (6)
H2A	0.0856	0.2179	0.0784	0.074*
H2B	0.1276	0.0534	0.1150	0.074*
H2C	0.1697	0.2333	0.1264	0.074*
C3	0.03122 (15)	0.0957 (3)	0.17362 (11)	0.0544 (6)
H3A	0.0551	−0.0061	0.1964	0.082*
H3B	−0.0021	0.0632	0.1323	0.082*
H3C	0.0016	0.1525	0.1958	0.082*
C4	0.24120 (12)	0.4984 (3)	0.24453 (11)	0.0467 (5)
H4A	0.2483	0.4306	0.2818	0.070*
H4B	0.2445	0.6194	0.2552	0.070*
H4C	0.2805	0.4697	0.2269	0.070*
C5	0.13871 (12)	0.5590 (3)	0.14236 (9)	0.0351 (4)
C6	0.05972 (12)	0.5794 (3)	0.11112 (10)	0.0426 (5)
H6	0.0246	0.5297	0.1277	0.051*
C7	0.03365 (14)	0.6734 (3)	0.05569 (10)	0.0506 (6)
H7	−0.0191	0.6847	0.0349	0.061*
C8	0.08444 (15)	0.7502 (3)	0.03083 (10)	0.0529 (6)
H8	0.0665	0.8125	−0.0067	0.063*
C9	0.16233 (15)	0.7334 (3)	0.06238 (11)	0.0529 (6)
H9	0.1971	0.7867	0.0462	0.064*
C10	0.18983 (13)	0.6391 (3)	0.11746 (10)	0.0451 (5)
H10	0.2426	0.6291	0.1380	0.054*
C11	0.11811 (11)	0.4595 (3)	0.30767 (9)	0.0343 (4)
C12	0.14071 (12)	0.4207 (3)	0.37217 (9)	0.0381 (5)
H12	0.1473	0.3054	0.3849	0.046*
C13	0.15342 (12)	0.5484 (3)	0.41700 (9)	0.0389 (5)
H13	0.1689	0.5200	0.4596	0.047*
C14	0.14288 (11)	0.7195 (3)	0.39797 (9)	0.0359 (5)
C15	0.11713 (12)	0.7640 (3)	0.33462 (9)	0.0400 (5)
H15	0.1088	0.8795	0.3224	0.048*
C16	0.10416 (12)	0.6349 (3)	0.29011 (9)	0.0403 (5)
H16	0.0858	0.6639	0.2476	0.048*
N4	0.15796 (10)	0.8552 (2)	0.44528 (8)	0.0420 (4)
O1	0.17013 (11)	0.8141 (2)	0.50039 (7)	0.0594 (5)
O2	0.15764 (12)	1.0061 (2)	0.42853 (9)	0.0682 (6)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0320 (10)	0.0350 (10)	0.0298 (9)	0.0008 (8)	0.0075 (8)	0.0000 (8)
N1	0.0432 (10)	0.0390 (9)	0.0322 (8)	−0.0066 (8)	0.0116 (7)	−0.0069 (7)
N2	0.0323 (8)	0.0417 (10)	0.0296 (8)	−0.0062 (7)	0.0062 (7)	−0.0008 (7)
N3	0.0466 (10)	0.0382 (10)	0.0318 (8)	−0.0040 (8)	0.0148 (7)	−0.0027 (7)
C2	0.0575 (14)	0.0557 (14)	0.0345 (11)	0.0041 (12)	0.0152 (10)	−0.0095 (10)
C3	0.0602 (15)	0.0503 (14)	0.0496 (13)	−0.0181 (12)	0.0141 (11)	−0.0088 (11)
C4	0.0341 (11)	0.0515 (14)	0.0465 (12)	−0.0057 (10)	0.0027 (9)	0.0047 (10)
C5	0.0376 (10)	0.0360 (11)	0.0314 (9)	−0.0010 (9)	0.0113 (8)	−0.0025 (8)
C6	0.0363 (11)	0.0529 (13)	0.0386 (11)	−0.0004 (10)	0.0124 (9)	0.0043 (10)
C7	0.0445 (13)	0.0609 (15)	0.0408 (12)	0.0045 (11)	0.0068 (10)	0.0038 (11)
C8	0.0671 (16)	0.0527 (14)	0.0349 (11)	−0.0012 (12)	0.0118 (11)	0.0083 (11)
C9	0.0603 (15)	0.0551 (15)	0.0477 (13)	−0.0103 (12)	0.0237 (12)	0.0064 (11)
C10	0.0412 (12)	0.0511 (13)	0.0430 (12)	−0.0064 (10)	0.0142 (9)	0.0027 (10)
C11	0.0327 (10)	0.0400 (11)	0.0318 (10)	−0.0023 (8)	0.0127 (8)	−0.0015 (9)
C12	0.0458 (12)	0.0339 (11)	0.0343 (10)	0.0012 (9)	0.0128 (9)	0.0033 (9)
C13	0.0430 (11)	0.0448 (12)	0.0290 (10)	0.0014 (10)	0.0118 (8)	0.0033 (9)
C14	0.0364 (11)	0.0397 (11)	0.0335 (10)	0.0008 (9)	0.0141 (8)	−0.0054 (9)
C15	0.0475 (12)	0.0356 (11)	0.0388 (11)	0.0094 (9)	0.0167 (9)	0.0031 (9)
C16	0.0471 (12)	0.0445 (12)	0.0279 (10)	0.0078 (10)	0.0108 (9)	0.0036 (9)
N4	0.0435 (10)	0.0426 (11)	0.0429 (10)	−0.0015 (8)	0.0184 (8)	−0.0078 (8)
O1	0.0782 (12)	0.0658 (12)	0.0362 (8)	−0.0074 (9)	0.0215 (8)	−0.0125 (8)
O2	0.1042 (16)	0.0391 (10)	0.0635 (11)	−0.0023 (10)	0.0309 (11)	−0.0080 (8)

Geometric parameters (Å, º) top

C1—N3	1.298 (2)	C7—C8	1.374 (3)
C1—N1	1.353 (2)	C7—H7	0.9300
C1—N2	1.401 (3)	C8—C9	1.377 (3)
N1—C2	1.451 (3)	C8—H8	0.9300
N1—C3	1.451 (3)	C9—C10	1.379 (3)
N2—C5	1.411 (2)	C9—H9	0.9300
N2—C4	1.457 (2)	C10—H10	0.9300
N3—C11	1.387 (2)	C11—C12	1.402 (3)
C2—H2A	0.9600	C11—C16	1.408 (3)
C2—H2B	0.9600	C12—C13	1.372 (3)
C2—H2C	0.9600	C12—H12	0.9300
C3—H3A	0.9600	C13—C14	1.381 (3)
C3—H3B	0.9600	C13—H13	0.9300
C3—H3C	0.9600	C14—C15	1.386 (3)
C4—H4A	0.9600	C14—N4	1.452 (3)
C4—H4B	0.9600	C15—C16	1.375 (3)
C4—H4C	0.9600	C15—H15	0.9300
C5—C10	1.390 (3)	C16—H16	0.9300
C5—C6	1.397 (3)	N4—O2	1.223 (2)
C6—C7	1.382 (3)	N4—O1	1.226 (2)
C6—H6	0.9300

N3—C1—N1	118.90 (18)	C8—C7—C6	121.0 (2)
N3—C1—N2	125.16 (18)	C8—C7—H7	119.5
N1—C1—N2	115.81 (16)	C6—C7—H7	119.5
C1—N1—C2	123.70 (18)	C7—C8—C9	118.8 (2)
C1—N1—C3	119.52 (17)	C7—C8—H8	120.6
C2—N1—C3	116.34 (18)	C9—C8—H8	120.6
C1—N2—C5	121.22 (16)	C8—C9—C10	121.3 (2)
C1—N2—C4	118.76 (16)	C8—C9—H9	119.4
C5—N2—C4	119.93 (17)	C10—C9—H9	119.4
C1—N3—C11	121.92 (18)	C9—C10—C5	120.1 (2)
N1—C2—H2A	109.5	C9—C10—H10	119.9
N1—C2—H2B	109.5	C5—C10—H10	119.9
H2A—C2—H2B	109.5	N3—C11—C12	117.26 (18)
N1—C2—H2C	109.5	N3—C11—C16	125.34 (17)
H2A—C2—H2C	109.5	C12—C11—C16	117.30 (18)
H2B—C2—H2C	109.5	C13—C12—C11	121.7 (2)
N1—C3—H3A	109.5	C13—C12—H12	119.1
N1—C3—H3B	109.5	C11—C12—H12	119.1
H3A—C3—H3B	109.5	C12—C13—C14	119.09 (18)
N1—C3—H3C	109.5	C12—C13—H13	120.5
H3A—C3—H3C	109.5	C14—C13—H13	120.5
H3B—C3—H3C	109.5	C13—C14—C15	121.30 (19)
N2—C4—H4A	109.5	C13—C14—N4	119.30 (18)
N2—C4—H4B	109.5	C15—C14—N4	119.39 (19)
H4A—C4—H4B	109.5	C16—C15—C14	119.0 (2)
N2—C4—H4C	109.5	C16—C15—H15	120.5
H4A—C4—H4C	109.5	C14—C15—H15	120.5
H4B—C4—H4C	109.5	C15—C16—C11	121.35 (18)
C10—C5—C6	118.56 (19)	C15—C16—H16	119.3
C10—C5—N2	120.95 (19)	C11—C16—H16	119.3
C6—C5—N2	120.48 (18)	O2—N4—O1	122.59 (19)
C7—C6—C5	120.2 (2)	O2—N4—C14	118.72 (18)
C7—C6—H6	119.9	O1—N4—C14	118.70 (19)
C5—C6—H6	119.9

N3—C1—N1—C2	−157.1 (2)	C8—C9—C10—C5	−0.2 (4)
N2—C1—N1—C2	18.9 (3)	C6—C5—C10—C9	−1.3 (3)
N3—C1—N1—C3	15.0 (3)	N2—C5—C10—C9	179.8 (2)
N2—C1—N1—C3	−169.05 (19)	C1—N3—C11—C12	−149.4 (2)
N3—C1—N2—C5	−130.6 (2)	C1—N3—C11—C16	34.4 (3)
N1—C1—N2—C5	53.7 (3)	N3—C11—C12—C13	179.57 (19)
N3—C1—N2—C4	46.0 (3)	C16—C11—C12—C13	−3.9 (3)
N1—C1—N2—C4	−129.7 (2)	C11—C12—C13—C14	0.7 (3)
N1—C1—N3—C11	−163.60 (18)	C12—C13—C14—C15	2.3 (3)
N2—C1—N3—C11	20.8 (3)	C12—C13—C14—N4	−178.60 (18)
C1—N2—C5—C10	−158.0 (2)	C13—C14—C15—C16	−2.0 (3)
C4—N2—C5—C10	25.4 (3)	N4—C14—C15—C16	178.97 (19)
C1—N2—C5—C6	23.1 (3)	C14—C15—C16—C11	−1.4 (3)
C4—N2—C5—C6	−153.4 (2)	N3—C11—C16—C15	−179.51 (19)
C10—C5—C6—C7	1.9 (3)	C12—C11—C16—C15	4.2 (3)
N2—C5—C6—C7	−179.2 (2)	C13—C14—N4—O2	171.2 (2)
C5—C6—C7—C8	−1.0 (4)	C15—C14—N4—O2	−9.8 (3)
C6—C7—C8—C9	−0.5 (4)	C13—C14—N4—O1	−9.2 (3)
C7—C8—C9—C10	1.1 (4)	C15—C14—N4—O1	169.88 (19)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C12—H12···O2ⁱ	0.93	2.49	3.416 (3)	173
C2—H2A···O1ⁱⁱ	0.96	2.72	3.064 (3)	102

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C12—H12···O2ⁱ	0.93	2.49	3.416 (3)	173
C2—H2A···O1ⁱⁱ	0.96	2.72	3.064 (3)	102

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

Acknowledgements

The authors thank Dr B. Iliev (IoLiTec GmbH) for the synthesis of the title compound.

References

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