2,3-Dimeth­oxy-5,12-tetra­cenequinone

Chitoshi Kitamura; Naoki Akamatsu; Akio Yoneda; Takeshi Kawase

doi:10.1107/S1600536809001147

. 2009 Jan 17;65(Pt 2):o324. doi: 10.1107/S1600536809001147

2,3-Dimethoxy-5,12-tetracenequinone

Chitoshi Kitamura ^a,^*, Naoki Akamatsu ^a, Akio Yoneda ^a, Takeshi Kawase ^a

PMCID: PMC2968390 PMID: 21581929

Abstract

The molecule of the title compound, C₂₀H₁₄O₄, is approximately planar [maximum deviation 0.168 (2) Å]. The two methoxy groups are slightly twisted relative to the plane of the 5,12-tetracenequinone system, with twist angles of 3.3 (3) and 5.6 (2)°. All O atoms are involved in intermolecular C—H⋯O interactions and the molecules are arranged into slipped face-to-face stacks along the b axis via π–π interactions with an interplanar distance of 3.407 (2) Å.

Related literature

For general background, see: Kitamura et al. (2008 ▶). For the synthetic procedures, see: McOmie & Perry (1973 ▶); Vets et al. (2004 ▶). For another synthetic method leading to the title compound, see: Reichwagen et al. (2005 ▶).

Experimental

Crystal data

C₂₀H₁₄O₄
M _r = 318.31
Monoclinic,
a = 8.290 (3) Å
b = 6.9781 (19) Å
c = 25.779 (8) Å
β = 97.883 (1)°
V = 1477.2 (8) Å³
Z = 4
Mo Kα radiation
μ = 0.1 mm⁻¹
T = 223 K
0.5 × 0.1 × 0.05 mm

Data collection

Rigaku Mercury CCD area-detector diffractometer
Absorption correction: numerical (NUMABS; Higashi, 1999 ▶) T _min = 0.988, T _max = 0.997
11405 measured reflections
3370 independent reflections
2773 reflections with I > 2σ(I)
R _int = 0.033

Refinement

R[F ² > 2σ(F ²)] = 0.050
wR(F ²) = 0.147
S = 1.12
3370 reflections
219 parameters
H-atom parameters constrained
Δρ_max = 0.28 e Å⁻³
Δρ_min = −0.18 e Å⁻³

Data collection: CrystalClear (Rigaku, 2001 ▶); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SIR2004 (Burla et al., 2005 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ▶) and Mercury (Macrae et al., 2006 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809001147/gk2182sup1.cif

e-65-0o324-sup1.cif^{(19.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809001147/gk2182Isup2.hkl

e-65-0o324-Isup2.hkl^{(161.9KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C8—H8⋯O3ⁱ	0.94	2.30	3.210 (2)	162
C15—H15⋯O4ⁱⁱ	0.94	2.60	3.383 (2)	141
C20—H20B⋯O1ⁱⁱⁱ	0.97	2.55	3.486 (2)	162
C20—H20B⋯O2ⁱⁱⁱ	0.97	2.48	3.206 (2)	131

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) .

Acknowledgments

We thank the Instrument Center of the Institute for Molecular Science for the X-ray structural analysis. This work was supported by a Grant-in-Aid (No. 20550128) for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, Japan.

supplementary crystallographic information

Comment

Although the title compound (I) was already synthesized (Reichwagen et al., 2005), the X-ray structre was not reported. We prepared 2,3-dimethoxytetracene from 8,9-dimethoxy-5,12-tetracenequinone (McOmie & Perry, 1973), and attemped to perform the X-ray analysis of crystals made by recrystallization from a hot DMF solution under air and light. The analysis revealed that the molecule was not as expected 2,3-dimethoxytetracene but the title compound. Quinones have a weak dipole moment along the molecular long axis and are expected to take a antiparallel arrangement with respect to one another. The latter propensity may lead to the formation of face-to-face π-overlap along the stacking direction (Kitamura et al., 2008).

The molecular structure is shown in Fig. 1. The molecule is approximately planar. The displacements of atoms O1, O2, O3, O4, C19, and C20 relative to the plane of the tetracene framework are -0.025 (1), -0.022 (1), -0.092 (1), 0.029 (1), -0.168 (2), and -0.113 (2) Å, respectively. The torsion angles of the two methoxy groups are -5.6 (2)° for C1—C2—O1—C19 and 3.3 (3)° for C4—C3—O2—C20, displaying that the C_methyl—O bonds are directed along the molecular short axis.

In the crystal structure, the molecules are linked through intermolecular C—H···O hydrogen bonds between the methoxy groups as well as between the tetracene groups (Table 1, Fig. 2). Interestingly, along the stacking direction, not antiparallel but just slipped π-π stacking can be found. The interplanar distance is 3.407 (2) Å. The dipole moment of (I) was calculated by MO calculations (B3LYP/6–31G*), which afforded an estimation of 0.01 debye. Thus, (I) is a non-polar molecule. Therefore, it seems reasonably to conclude that the electrostatic property can determine either an antiparallel or a non-antiparallel arrangement.

Experimental

8,9-Dimethoxy-5,12-tetracenequinone was prepared according to the method described by McOmie & Perry (1973). Transformation of tetracenequinone into tetracene was performed using two successive LiAlH₄ reductions by Vets et al. (2004). To a suspension of LiAlH₄ (224 mg, 5.9 mmol) in dry THF (15 ml), 8,9-dimethoxy-5,12-tetracenequinone (479 mg, 1.5 mmol) was added under nitrogen. The mixture was refluxed for 30 min, cooled to room temperature, and 6M HCl (7 ml) was added under cooling with ice. The residue was filtered, and washed with water, MeOH, and Et₂O. After drying, a yellow solid was isolated. The solid was added into a suspension of LiAlH₄ (235 mg, 6.2 mmol) in dry THF (15 ml). The mixture was again refluxed for 30 min, cooled to room temperature, and 6M HCl (7 ml) was added under cooling with ice. The product was filtered, and washed with water, MeOH, and Et₂O. After drying, 2,3-dimethoxytetracene was obtained (287 mg, 66%) as a yellow solid. Heating the tetracene in DMF under air and light, and then cooling the solution to room temperature resulted in deposition of brown crystals suitable for X-ray analysis.