Crystal structure and spectroscopic properties of (E)-1,3-dimethyl-2-[3-(4-nitro­phen­yl)triaz-2-enyl­idene]-2,3-di­hydro-1H-imidazole

Heras Martinez, H.M.; Chavez Flores, D.; Hillesheim, P.C.; Patil, S.; Bugarin, A.

doi:10.1107/S2056989021000426

research communications

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ISSN: 2056-9890

Volume 77| Part 2| February 2021| Pages 130-133

https://doi.org/10.1107/S2056989021000426

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Crystal structure and spectroscopic properties of (E)-1,3-dimethyl-2-[3-(4-nitrophenyl)triaz-2-enylidene]-2,3-dihydro-1H-imidazole

Hector Mario Heras Martinez,^a David Chavez Flores,^b Patrick C. Hillesheim,^c Siddappa Patil ^d and Alejandro Bugarin ^a ^*

^aDepartment of Chemistry & Physics, Florida Gulf Coast University, 10501 FGCU, Boulevard South, Fort Myers, FL 33965, USA, ^bFacultad de Ciencias Químicas, Universidad Autónoma de Chihuahua, Nuevo Campus Universitario, Circuito Universitario, Chihuahua, Chih., CP 31125, Mexico, ^cDepartment of Chemistry and Physics, Ave Maria University, 5050 Ave Maria Blvd, Ave Maria, FL 34142, USA, and ^dCentre for Nano and Material Sciences, Jain University, Jain Global Campus, Kanakapura, Ramanagaram, Bangalore 562112, India
^*Correspondence e-mail: abugarin@fgcu.edu

Edited by J. Reibenspies, Texas A & M University, USA (Received 9 December 2020; accepted 12 January 2021; online 15 January 2021)

The title compound (E)-1,3-dimethyl-2-[3-(4-nitrophenyl)triaz-2-enylidene]-2,3-dihydro-1H-imidazole, C₁₁H₁₂N₆O₂, has monoclinic (C2/c) symmetry at 100 K. This triazene derivative was synthesized by the coupling reaction of 1,3-dimethylimidazolium iodide with 1-azido-4-nitro benzene in the presence of sodium hydride (60% in mineral oil) and characterized by ¹H NMR, ¹³C NMR, IR, mass spectrometry, and single-crystal X-ray diffraction. The molecule consists of six-membered and five-membered rings, which are connected by a triazene moiety (–N=N—N–). In the solid-state, the molecule is found to be planar due to conjugation throughout the molecule. The extended structure shows two layers of molecules, which present weak intermolecular interactions that facilitate the stacked arrangement of the molecules forming the extended structure. Furthermore, there are several weak pseudo-cyclical interactions between the nitro oxygen atoms and symmetry-adjacent H atoms, which help to arrange the molecules.

Keywords: crystal structure; azides; π-conjugated triazenes; N-heterocyclic carbene.

CCDC reference: 2055595

1. Chemical context

Triazenes are versatile compounds in preparative chemistry because of their stable and highly modular nature (Patil & Bugarin, 2016 ). Triazene derivatives have been studied for their potential anticancer properties (Rouzer et al., 1996 ; Connors et al., 1976 ), used as a protecting group in natural product synthesis (Nicolaou et al., 1999 ) and combinatorial chemistry (Brase et al., 2000 ), incorporated into polymers (Jones et al., 1997 ) and oligomer synthesis (Moore, 1997 ), and used to prepare heterocycles (Wirschun et al., 1998 ). Their modular nature allows triazenes to be converted into a different functional group after treatment with the appropriate reagents. For example, aryl triazenes can be transformed to useful cross-coupling reagents (iodoarenes) via iodomethane-induced decomposition (Zollinger, 1994 ). Further, aryl triazenes have been studied for their unique structural and chemical properties (Cornali et al., 2016 ; Knyazeva et al., 2017 ). They have been used in medicinal, combinatorial chemistry, in natural synthesis and as organometallic ligands (Kimball et al., 2002 ). In chemical biology, masked diazonium ions (triazabutadienes) have found use on protein surfaces for identifying host proteins that interact during early stages of viral entities (Jensen et al., 2016 ; Shadmehr et al., 2018 ). In addition, triazabutadienes have shown tunable reactivity under specific conditions. For example, unique transformations of triazabutadienes have been affected via water solubility, pH (Kimani & Jewett, 2015 ; Guzman et al., 2016 ; He et al., 2017 ), and photoinduced isomerization (He et al., 2015 ). In synthesis, these triazenes have been used as starting materials for aldehydes, ketones, ethers, and sulfides, under mild reaction conditions (Barragan & Bugarin, 2017 ; Cornali et al., 2016). Furthermore, natural sunlight has been utilized to activate those triazenes to produce bisaryls and anilides (Noonikara-Poyil et al., 2019 ; Barragan et al., 2020 ).

2. Structural commentary

The title compound 1 crystallizes in the monoclinic C2/c space group with a single moiety in the asymmetric unit (see Fig. 1). The molecule is nearly planar with a dihedral angle of 7.36 (9)° between the imidazole and benzene rings. Plane I (N1/N3/C2/C4–C7) makes dihedral angles of 9.70 (3) and 2.40 (6)°, respectively, with planes II (N7/C8–C13) and III (N4–N6) while plane II makes a dihedral angle of 7.36 (4)° with plane III.

Figure 1
ORTEP diagram of compound 1 showing the atom-labeling scheme with 50% probability displacement ellipsoids.

There are no lattice-held water molecules or organic solvent molecules in the unit cell of the determined structure, a potential issue since the starting material 1,3-dimethylimidazolium iodide is hydroscopic. The bond lengths and angles in 1 are similar to those reported for analogous structures (Khramov & Bielawski, 2005 ; Jishkariani et al., 2013 ). The C—C bond lengths in the phenyl rings are in the normal range of 1.33–1.40 Å, which is characteristic of delocalized phenyl rings. The C—C—C bond angles are around 120°, with the variation being less than 2°, which is characteristic of sp²-hybridized carbons.

3. Supramolecular features

Figs. 2 and 3 show a perspective view of the crystal packing of the title compound. The packing diagram shows two layers of molecules, which are independently arranged in the unit cell without intra- and inter molecular hydrogen bonds. In each layer, the molecules are alternately parallel.

Figure 2
Perspective view of the molecular packing of 1 (there are no hydrogen atoms involved in hydrogen-bonding interactions. Dotted lines represent weak non-covalent C—H⋯N and C—H⋯O interactions, which direct the packing.

Figure 3
Extended network of the structure of compound 1 viewed from (001). There are two layers of molecules, which are arranged independently in the unit cell without intra- and/or intermolecular hydrogen bonds. Dotted lines represent weak non-covalent C–H⋯N and C–H⋯O interactions, which direct the packing.

4. Database survey

The first X-ray structure of a π-conjugated triazene was reported by Khramov & Bielawski (2005). The current WebCSD structural database includes the structures of only 18 π-conjugated triazenes. However, there is only one structure, reported by our research group (Patil & Bugarin, 2014 ), that utilizes the small molecule (1,3-dimethylimidazolium iodide) as the carbene coupling partner, and one more that bears an electron-deficient aryl group in combination with the small carbene precursor (Patil et al., 2014 ). Those characteristics highlight the novelty and uniqueness of the compound reported herein.

5. Synthesis and crystallization

1-Azido-4-nitro benzene (Siddiki et al., 2013 ) and 1,3-dimethylimidazolium iodide (Oertel et al., 2011 ) were prepared according to literature procedures. For the synthesis of the title compound, 1-azido-4-nitro benzene (131.2 mg, 0.8 mmol) and 1,3-dimethylimidazolium iodide (89.5 mg, 0.4 mmol) were stirred at room temperature for 5 min. in dry THF (5 mL). NaH (16 mg, 0.4 mmol, 60% in mineral oil) was added in one portion and stirring was continued at room temperature overnight. A red precipitate formed, which was collected by filtration and dried under reduced pressure, giving the pure product (E)-1,3-dimethyl-2-[(4-nitrophenyl)triaz-2-enylidene])-2,3-dihydro-1H-imidazole as a red crystalline solid (88.2 mg, 85%). Crystals suitable for X-ray analysis were grown from the slow evaporation of a THF/hexane mixture yielding air-stable, red-colored crystals.

IR (neat) ν 3435, 1572, 1382, 1360, 1233 cm^{−1. 1}H NMR (400 MHz, DMSO-d6): δ 8.12 (d, J = 9.2 Hz, 2 H, Ph-H), 7.43 (d, J = 9.2 Hz, 2 H, Ph-H), 7.13 (s, 2 H, NCH), 3.62 (s, 6 H, N—CH₃). ¹³C NMR (100 MHz, DMSO-d6): δ 159.1, 150.7, 143.2, 125.5, 120.8, 118.9, 35.7. UV/Vis (0.1 µM, CH₂Cl₂): λ (ɛ) = 450 nm. HRMS (ESI, N₂): m/z calculated for C₁₁H₁₂N₆O₂Na [M + Na]⁺ 283.0914, found 283.0918.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. H atoms were included in calculated positions and treated as riding atoms: C—H = 0.95–0.98 Å with U_iso(H) = 1.2U_eq(C) or 1.5U_eq(C-methyl).

Table 1
Experimental details

Crystal data
Chemical formula	C₁₁H₁₂N₆O₂
M_r	260.27
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	100
a, b, c (Å)	27.7311 (18), 7.1747 (9), 11.7849 (14)
β (°)	94.101 (4)
V (Å³)	2338.7 (4)
Z	8
Radiation type	Mo Kα
μ (mm⁻¹)	0.11
Crystal size (mm)	0.11 × 0.05 × 0.02

Data collection
Diffractometer	Bruker AXS D8 Quest diffractometer with PhotonII charge-integrating pixel array detector (CPAD)
Absorption correction	Multi-scan (SADABS; Bruker, 2018 )
T_min, T_max	0.655, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	23709, 2807, 2206
R_int	0.077
(sin θ/λ)_max (Å⁻¹)	0.659

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.070, 0.158, 1.16
No. of reflections	2807
No. of parameters	174
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.36, −0.37
Computer programs: APEX3 and SAINT (Bruker, 2018), SHELXT2018/2 (Sheldrick, 2015a ), SHELXL (Sheldrick, 2015b ) and OLEX2 (Dolomanov et al., 2009 ).

Supporting information

CCDC reference: 2055595

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989021000426/jy2004sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989021000426/jy2004Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989021000426/jy2004Isup4.cdx

Supporting information file. DOI: https://doi.org/10.1107/S2056989021000426/jy2004Isup4.cml

checkCIF report

Computing details top

Data collection: APEX3 (Bruker, 2018); cell refinement: SAINT (Bruker, 2018); data reduction: SAINT (Bruker, 2018); program(s) used to solve structure: SHELXT2018/2 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL (Sheldrick, 2015b); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

(E)-1,3-Dimethyl-2-[3-(4-nitrophenyl)triaz-2-enylidene]-2,3-dihydro-1H-imidazole top

Crystal data top

C₁₁H₁₂N₆O₂	F(000) = 1088
M_r = 260.27	D_x = 1.478 Mg m⁻³
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 27.7311 (18) Å	Cell parameters from 4851 reflections
b = 7.1747 (9) Å	θ = 3.0–27.8°
c = 11.7849 (14) Å	µ = 0.11 mm⁻¹
β = 94.101 (4)°	T = 100 K
V = 2338.7 (4) Å³	Plates, red
Z = 8	0.11 × 0.05 × 0.02 mm

Data collection top

Bruker AXS D8 Quest diffractometer with PhotonII charge-integrating pixel array detector (CPAD)	2206 reflections with I > 2σ(I)
φ and ω scans	R_int = 0.077
Absorption correction: multi-scan (SADABS; Bruker, 2018)	θ_max = 27.9°, θ_min = 2.9°
T_min = 0.655, T_max = 0.746	h = −36→36
23709 measured reflections	k = −9→9
2807 independent reflections	l = −15→15

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.070	H-atom parameters constrained
wR(F²) = 0.158	w = 1/[σ²(F_o²) + (0.0623P)² + 4.2467P] where P = (F_o² + 2F_c²)/3
S = 1.16	(Δ/σ)_max < 0.001
2807 reflections	Δρ_max = 0.36 e Å⁻³
174 parameters	Δρ_min = −0.37 e Å⁻³

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
O2	0.90725 (6)	0.6192 (3)	0.42545 (14)	0.0208 (4)
O1	0.91792 (6)	0.7705 (3)	0.58417 (15)	0.0231 (4)
N5	0.67583 (7)	0.4345 (3)	0.54983 (15)	0.0122 (4)
N3	0.60385 (7)	0.2903 (3)	0.39246 (15)	0.0133 (4)
N6	0.70494 (7)	0.4980 (3)	0.63041 (15)	0.0144 (4)
N1	0.55532 (7)	0.2913 (3)	0.52968 (16)	0.0163 (4)
N7	0.89267 (7)	0.6760 (3)	0.51636 (16)	0.0156 (4)
N4	0.63305 (7)	0.3932 (3)	0.58753 (15)	0.0147 (4)
C2	0.60118 (8)	0.3293 (3)	0.50481 (18)	0.0132 (5)
C8	0.75071 (8)	0.5395 (3)	0.59381 (18)	0.0131 (5)
C13	0.76739 (8)	0.4927 (3)	0.48705 (19)	0.0138 (5)
H13	0.746476	0.430092	0.432205	0.017*
C10	0.82858 (8)	0.6785 (3)	0.64889 (18)	0.0140 (5)
H10	0.849717	0.740951	0.703362	0.017*
C12	0.81359 (8)	0.5371 (3)	0.46184 (19)	0.0150 (5)
H12	0.824761	0.505139	0.390018	0.018*
C9	0.78212 (8)	0.6344 (3)	0.67289 (18)	0.0140 (5)
H9	0.771038	0.668868	0.744390	0.017*
C11	0.84393 (8)	0.6295 (3)	0.54293 (19)	0.0148 (5)
C7	0.64554 (8)	0.3132 (3)	0.32329 (18)	0.0157 (5)
H7A	0.656635	0.442877	0.327693	0.023*
H7B	0.635989	0.281514	0.243959	0.023*
H7C	0.671761	0.230600	0.352109	0.023*
C4	0.55897 (8)	0.2268 (4)	0.34928 (19)	0.0184 (5)
H4	0.550771	0.189696	0.272952	0.022*
C5	0.52938 (8)	0.2270 (4)	0.4335 (2)	0.0200 (5)
H5	0.496428	0.189691	0.428140	0.024*
C6	0.53830 (9)	0.3056 (4)	0.6434 (2)	0.0249 (6)
H6A	0.553996	0.209729	0.692393	0.037*
H6B	0.503190	0.287618	0.639429	0.037*
H6C	0.546263	0.429166	0.674856	0.037*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O2	0.0169 (8)	0.0327 (10)	0.0134 (8)	−0.0025 (7)	0.0046 (6)	0.0010 (8)
O1	0.0202 (9)	0.0287 (10)	0.0195 (9)	−0.0084 (8)	−0.0042 (7)	−0.0001 (8)
N5	0.0143 (9)	0.0132 (9)	0.0092 (8)	0.0006 (7)	0.0006 (7)	0.0000 (7)
N3	0.0145 (9)	0.0185 (10)	0.0072 (8)	−0.0003 (8)	0.0022 (7)	0.0002 (7)
N6	0.0159 (10)	0.0204 (10)	0.0070 (8)	0.0011 (8)	0.0010 (7)	−0.0003 (8)
N1	0.0133 (9)	0.0269 (11)	0.0089 (9)	−0.0009 (8)	0.0009 (7)	0.0009 (8)
N7	0.0147 (9)	0.0192 (10)	0.0126 (9)	−0.0016 (8)	−0.0004 (7)	0.0040 (8)
N4	0.0136 (9)	0.0226 (10)	0.0080 (8)	0.0006 (8)	0.0013 (7)	−0.0019 (8)
C2	0.0158 (11)	0.0162 (11)	0.0076 (10)	0.0026 (9)	0.0002 (8)	0.0020 (8)
C8	0.0161 (11)	0.0134 (10)	0.0097 (10)	0.0022 (9)	0.0002 (8)	0.0015 (8)
C13	0.0149 (11)	0.0172 (11)	0.0090 (10)	−0.0015 (9)	−0.0004 (8)	−0.0032 (8)
C10	0.0174 (11)	0.0156 (11)	0.0084 (10)	0.0001 (9)	−0.0035 (8)	0.0003 (8)
C12	0.0180 (11)	0.0183 (11)	0.0088 (10)	0.0005 (9)	0.0014 (8)	0.0017 (9)
C9	0.0184 (11)	0.0177 (11)	0.0059 (9)	0.0032 (9)	0.0003 (8)	0.0008 (9)
C11	0.0146 (11)	0.0179 (11)	0.0118 (10)	−0.0005 (9)	−0.0007 (8)	0.0052 (9)
C7	0.0164 (11)	0.0238 (12)	0.0073 (10)	−0.0006 (9)	0.0047 (8)	−0.0004 (9)
C4	0.0171 (11)	0.0281 (13)	0.0096 (10)	−0.0009 (10)	−0.0024 (8)	−0.0011 (10)
C5	0.0146 (11)	0.0308 (14)	0.0141 (11)	−0.0040 (10)	−0.0032 (9)	0.0027 (10)
C6	0.0169 (11)	0.0473 (17)	0.0112 (11)	−0.0049 (12)	0.0063 (9)	−0.0017 (11)

Geometric parameters (Å, º) top

O2—N7	1.241 (3)	C13—C12	1.373 (3)
O1—N7	1.228 (3)	C10—H10	0.9500
N5—N6	1.285 (3)	C10—C9	1.375 (3)
N5—N4	1.330 (3)	C10—C11	1.393 (3)
N3—C2	1.360 (3)	C12—H12	0.9500
N3—C7	1.471 (3)	C12—C11	1.395 (3)
N3—C4	1.387 (3)	C9—H9	0.9500
N6—C8	1.402 (3)	C7—H7A	0.9800
N1—C2	1.353 (3)	C7—H7B	0.9800
N1—C5	1.378 (3)	C7—H7C	0.9800
N1—C6	1.456 (3)	C4—H4	0.9500
N7—C11	1.448 (3)	C4—C5	1.332 (3)
N4—C2	1.348 (3)	C5—H5	0.9500
C8—C13	1.412 (3)	C6—H6A	0.9800
C8—C9	1.405 (3)	C6—H6B	0.9800
C13—H13	0.9500	C6—H6C	0.9800

N6—N5—N4	111.13 (17)	C11—C12—H12	120.4
C2—N3—C7	128.02 (19)	C8—C9—H9	119.3
C2—N3—C4	108.35 (18)	C10—C9—C8	121.4 (2)
C4—N3—C7	123.61 (18)	C10—C9—H9	119.3
N5—N6—C8	112.51 (18)	C10—C11—N7	119.1 (2)
C2—N1—C5	109.43 (19)	C10—C11—C12	121.7 (2)
C2—N1—C6	123.82 (19)	C12—C11—N7	119.2 (2)
C5—N1—C6	126.6 (2)	N3—C7—H7A	109.5
O2—N7—C11	118.54 (19)	N3—C7—H7B	109.5
O1—N7—O2	122.5 (2)	N3—C7—H7C	109.5
O1—N7—C11	118.95 (19)	H7A—C7—H7B	109.5
N5—N4—C2	112.85 (18)	H7A—C7—H7C	109.5
N1—C2—N3	106.65 (19)	H7B—C7—H7C	109.5
N4—C2—N3	134.0 (2)	N3—C4—H4	125.9
N4—C2—N1	119.30 (19)	C5—C4—N3	108.1 (2)
N6—C8—C13	125.8 (2)	C5—C4—H4	125.9
N6—C8—C9	115.53 (19)	N1—C5—H5	126.3
C9—C8—C13	118.6 (2)	C4—C5—N1	107.5 (2)
C8—C13—H13	119.7	C4—C5—H5	126.3
C12—C13—C8	120.5 (2)	N1—C6—H6A	109.5
C12—C13—H13	119.7	N1—C6—H6B	109.5
C9—C10—H10	120.7	N1—C6—H6C	109.5
C9—C10—C11	118.5 (2)	H6A—C6—H6B	109.5
C11—C10—H10	120.7	H6A—C6—H6C	109.5
C13—C12—H12	120.4	H6B—C6—H6C	109.5
C13—C12—C11	119.2 (2)

O2—N7—C11—C10	174.5 (2)	C13—C12—C11—N7	179.9 (2)
O2—N7—C11—C12	−5.6 (3)	C13—C12—C11—C10	−0.1 (3)
O1—N7—C11—C10	−5.8 (3)	C9—C8—C13—C12	0.9 (3)
O1—N7—C11—C12	174.2 (2)	C9—C10—C11—N7	179.7 (2)
N5—N6—C8—C13	−9.6 (3)	C9—C10—C11—C12	−0.3 (3)
N5—N6—C8—C9	171.13 (19)	C11—C10—C9—C8	1.0 (3)
N5—N4—C2—N3	3.5 (4)	C7—N3—C2—N1	178.1 (2)
N5—N4—C2—N1	−176.5 (2)	C7—N3—C2—N4	−1.8 (4)
N3—C4—C5—N1	0.3 (3)	C7—N3—C4—C5	−178.5 (2)
N6—N5—N4—C2	178.84 (19)	C4—N3—C2—N1	−0.3 (3)
N6—C8—C13—C12	−178.4 (2)	C4—N3—C2—N4	179.8 (3)
N6—C8—C9—C10	178.0 (2)	C5—N1—C2—N3	0.5 (3)
N4—N5—N6—C8	178.84 (18)	C5—N1—C2—N4	−179.6 (2)
C2—N3—C4—C5	0.0 (3)	C6—N1—C2—N3	176.7 (2)
C2—N1—C5—C4	−0.5 (3)	C6—N1—C2—N4	−3.4 (4)
C8—C13—C12—C11	−0.2 (3)	C6—N1—C5—C4	−176.5 (2)
C13—C8—C9—C10	−1.3 (3)

Acknowledgements

We thank Florida Gulf Coast University and its facilities for the support provided to complete this work.

Funding information

Funding for this research was provided by: American Chemical Society Petroleum Research Fund (award No. 58269-ND1 to Alejandro Bugarin).

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