3,6-Dimethyl-N1,N4-bis­(pyridin-2-yl)-1,2,4,5-tetra­zine-1,4-dicarboxamide

Rao, G.-W.; Guo, Y.-M.; Shen, Q.

doi:10.1107/S1600536812005405

organic compounds

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ISSN: 2056-9890

Volume 68| Part 3| March 2012| Pages o702-o703

doi:10.1107/S1600536812005405

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3,6-Dimethyl-N¹,N⁴-bis(pyridin-2-yl)-1,2,4,5-tetrazine-1,4-dicarboxamide

Guo-Wu Rao,^a ^* Yan-Mei Guo ^a and Qun Shen ^b

^aCollege of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou 310014, People's Republic of China, and ^bHangzhou Institute of Calibration and Testing for Quality and Technical Supervision, Hangzhou 310019, People's Republic of China
^*Correspondence e-mail: rgw@zjut.edu.cn

(Received 18 January 2012; accepted 7 February 2012; online 17 February 2012)

In the title molecule, C₁₆H₁₆N₈O₂, four atoms of the tetrazine ring are coplanar, with the largest deviation from the plane being 0.0236 (12) Å; the other two atoms of the tetrazine ring deviate on the same side from this plane by 0.320 (4) and 0.335 (4) Å. Therefore, the central tetrazine ring exhibits a boat conformation. The dihedral angles between the mean plane of the four coplanar atoms of the tetrazine ring and the two pyridine rings are 26.22 (10) and 6.97 (5)°. The two pyridine rings form a dihedral angle of 31.27 (8)°. In the molecule, there are a number of short C—H⋯O interactions. In the crystal, molecules are linked via a C—H⋯O interaction to form zigzag chains propagating along the [010] direction.

Related literature

For the activities of 1,2,4,5-tetrazine derivatives in chemical reactions, see: Domingo et al. (2009 ); Lorincz et al. (2010 ). For biological activities in 1,2,4,5-tetrazine derivatives, see: Eremeev et al. (1978 , 1980 ); Neunhoeffer (1984 ); Sauer (1996 ). For antitumor activities of 1,2,4,5-tetrazine derivatives, see: Hu et al. (2002 , 2004 ); Rao & Hu (2005 , 2006 ). For typical bond lengths for C=N double and C—N and N—N single bonds, see: Allen et al. (1987 ). For the synthesis of the title compound, see: Hu et al. (2004); Skorianetz & Kováts (1970 , 1971 ); Sun et al. (2003 ).

Experimental

Crystal data

C₁₆H₁₆N₈O₂
M_r = 352.37
Monoclinic, P 2₁ /c
a = 11.753 (2) Å
b = 20.081 (4) Å
c = 7.2012 (14) Å
β = 96.273 (3)°
V = 1689.4 (6) Å³
Z = 4
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 298 K
0.36 × 0.23 × 0.20 mm

Data collection

Bruker SMART CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 1997 ) T_min = 0.965, T_max = 0.981
7032 measured reflections
2985 independent reflections
2430 reflections with I > 2σ(I)
R_int = 0.024

Refinement

R[F² > 2σ(F²)] = 0.061
wR(F²) = 0.182
S = 1.07
2985 reflections
236 parameters
H-atom parameters constrained
Δρ_max = 0.44 e Å⁻³
Δρ_min = −0.33 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C1—H1A⋯O2	0.96	2.07	2.778 (4)	130
C2—H2A⋯O1	0.96	2.09	2.777 (4)	127
C8—H8⋯O1	0.93	2.31	2.886 (3)	120
C16—H16⋯O1ⁱ	0.93	2.39	3.229 (3)	150
Symmetry code: (i) $[-x+1, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ .

Data collection: SMART (Bruker, 1997); cell refinement: SAINT (Bruker, 1997); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ); software used to prepare material for publication: WinGX (Farrugia, 1999 ).

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536812005405/zj2056sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536812005405/zj2056Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536812005405/zj2056Isup3.cdx

Supporting information file. DOI: 10.1107/S1600536812005405/zj2056Isup4.cml

checkCIF report

Comment top

Tetrazine derivatives have high activities of chemical reaction (Domingo et al., 2009; Lorincz et al., 2010), and have been widely used in pesticides and medicines (Eremeev et al., 1978, 1980; Neunhoeffer, 1984; Sauer, 1996). In a continuation of our studies of antitumor activities in 1,2,4,5-tetrazine derivatives (Hu et al., 2002, 2004; Rao & Hu, 2005, 2006), we have obtained a colourless crystalline compound, (I). However, IR, NMR, and MS studies failed to prove whether the substituted groups of the nitrogen are located at the 1,4 or 1,2 position. The structure was confirmed by single-crystal X-ray diffraction.

The molecular structure of (I) is illustrated in Fig. 1. The N2═C3 [1.279 (3) Å] and N5═C6 [1.278 (3) Å] bonds correspond to typical double bonds of C═N, and the C3—N4 [1.395 (3) Å], N4—N5 [1.419 (3) Å], C6—N1 [1.388 (3) Å] and N1—N2 [1.420 (3) Å] bond lengths correspond to typical single bonds (Allen et al., 1987). Therefore, the tetrazine ring is the 1,4-dihydro structure with the N-substituted groups at the 1,4-positions and not the 1,2-positions, the compound being 3,6-dimethyl-N¹,N⁴-di(pyridin-2-yl)-1,2,4,5-tetrazine-1,4-dicarboxamide, rather than the 3,6-dimethyl-N¹,N²-di(pyridin-2-yl)-1,2,4,5-tetrazine-1,2-dicarboxamide.

In (I), atoms N2, C3, N5 and C6 are coplanar, with the largest deviation from this plane being ±0.0236 (12) Å. Atoms N1 and N4 deviate from this plane by -0.3202 (35) and -0.3345 (36) Å, respectively. The dihedral angle between the N2/C3/N5/C6 plane and the N1/N2/C6 plane is 26.25 (18)°, and between the N2/C3/N5/C6 plane and the N4/N5/C3 plane is 27.18 (19)°. Therefore, the central six-member ring of the compound, the tetrazine ring, has an obvious boat conformation. The dihedral angles between the N2/C3/N5/C6 plane and the two pyridyl rings are 26.22 (10) and 6.97 (5)°, respectively. And two pyridyl rings form a dihedral angle of 31.27 (8)°. In the molecule, there are a number of short C—H···O interactions. In the crystal, molecules are linked via a C—H···O interaction to form zigzag chains propagating along the [010] direction.

Related literature top

For the high activities of 1,2,4,5-tetrazine derivatives in chemical reactions, see: Domingo et al. (2009); Lorincz et al. (2010). For biological activities in 1,2,4,5-tetrazine derivatives, see: Eremeev et al. (1978, 1980); Neunhoeffer (1984); Sauer (1996). For antitumor activities in 1,2,4,5-tetrazine derivatives, see: Hu et al. (2002, 2004); Rao & Hu (2005, 2006). For typical bond lengths for C═N double and C—N and N—N single bonds, see: Allen et al. (1987). For the synthesis of the title compound, see: Hu et al. (2004); Skorianetz & Kováts (1970, 1971); Sun et al. (2003).

Experimental top

The title compound was prepared according to the procedure of Hu et al. (2004), Sun et al. (2003) and Skorianetz & Kováts (1970, 1971). A saturated solution of the compound in ethanol and dichloromethane (4:1, v/v) of 298 K was concentrated gradually at room temperature to afford colourless blocks.

Computing details top

Data collection: SMART (Bruker, 1997); cell refinement: SAINT (Bruker, 1997); data reduction: SAINT (Bruker, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top

	Fig. 1. The structure of (I), shown with 30% probability displacement ellipsoids.
	Fig. 2. A portion of the crystal packing of (I). Hydrogen bonds are shown as dashed lines. H atoms not involved in hydrogen bonding were omitted for clarity.

3,6-Dimethyl-N¹,N⁴-bis(pyridin-2-yl)-1,2,4,5-tetrazine-1,4- dicarboxamide top

Crystal data top

C₁₆H₁₆N₈O₂	Z = 4
M_r = 352.37	F(000) = 736
Monoclinic, P2₁/c	D_x = 1.385 Mg m⁻³
Hall symbol: -P 2ybc	Mo Kα radiation, λ = 0.71073 Å
a = 11.753 (2) Å	θ = 3.0–28.2°
b = 20.081 (4) Å	µ = 0.10 mm⁻¹
c = 7.2012 (14) Å	T = 298 K
β = 96.273 (3)°	Block, colourless
V = 1689.4 (6) Å³	0.36 × 0.23 × 0.20 mm

Data collection top

Bruker SMART CCD area-detector diffractometer	2985 independent reflections
Radiation source: fine-focus sealed tube	2430 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.024
ϕ and ω scans	θ_max = 25.0°, θ_min = 1.7°
Absorption correction: multi-scan (SADABS; Bruker, 1997)	h = −13→11
T_min = 0.965, T_max = 0.981	k = −23→22
7032 measured reflections	l = −8→8

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)] = 0.061	H-atom parameters constrained
wR(F²) = 0.182	w = 1/[σ²(F_o²) + (0.0986P)² + 0.7423P] where P = (F_o² + 2F_c²)/3
S = 1.07	(Δ/σ)_max < 0.001
2985 reflections	Δρ_max = 0.44 e Å⁻³
236 parameters	Δρ_min = −0.33 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: 0.012 (2)

Crystal data top

C₁₆H₁₆N₈O₂	V = 1689.4 (6) Å³
M_r = 352.37	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 11.753 (2) Å	µ = 0.10 mm⁻¹
b = 20.081 (4) Å	T = 298 K
c = 7.2012 (14) Å	0.36 × 0.23 × 0.20 mm
β = 96.273 (3)°

Data collection top

Bruker SMART CCD area-detector diffractometer	2985 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 1997)	2430 reflections with I > 2σ(I)
T_min = 0.965, T_max = 0.981	R_int = 0.024
7032 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.061	0 restraints
wR(F²) = 0.182	H-atom parameters constrained
S = 1.07	Δρ_max = 0.44 e Å⁻³
2985 reflections	Δρ_min = −0.33 e Å⁻³
236 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
N1	0.70522 (17)	0.06533 (10)	0.3165 (3)	0.0460 (5)
O2	0.94498 (16)	0.25045 (9)	0.2447 (3)	0.0587 (6)
O1	0.54879 (15)	0.00173 (9)	0.2281 (3)	0.0618 (6)
N4	0.80771 (16)	0.17897 (10)	0.3261 (3)	0.0464 (5)
N5	0.69810 (17)	0.17708 (10)	0.3912 (3)	0.0481 (6)
N2	0.82657 (17)	0.06420 (10)	0.3487 (3)	0.0480 (6)
N6	0.78462 (18)	0.29223 (10)	0.3540 (3)	0.0489 (6)
H6	0.7217	0.2801	0.3948	0.059*
N8	0.70889 (18)	0.39638 (11)	0.3514 (3)	0.0529 (6)
C12	0.8038 (2)	0.36064 (12)	0.3445 (3)	0.0434 (6)
C3	0.8743 (2)	0.12142 (12)	0.3484 (4)	0.0448 (6)
N7	0.7973 (2)	−0.14331 (12)	0.1576 (4)	0.0649 (7)
N3	0.72486 (18)	−0.04631 (10)	0.2546 (3)	0.0532 (6)
H3	0.7933	−0.0403	0.3073	0.064*
C6	0.6486 (2)	0.12036 (12)	0.3784 (3)	0.0432 (6)
C4	0.6513 (2)	0.00504 (12)	0.2642 (4)	0.0449 (6)
C5	0.8541 (2)	0.24270 (12)	0.3062 (4)	0.0453 (6)
C7	0.7024 (2)	−0.10818 (12)	0.1687 (4)	0.0470 (6)
C2	0.5324 (2)	0.11538 (14)	0.4433 (4)	0.0570 (7)
H2A	0.5046	0.0706	0.4263	0.086*
H2B	0.4811	0.1453	0.3721	0.086*
H2C	0.5369	0.1270	0.5733	0.086*
C13	0.9103 (2)	0.38885 (13)	0.3336 (4)	0.0503 (7)
H13	0.9753	0.3625	0.3325	0.060*
C8	0.5943 (2)	−0.13104 (13)	0.1018 (4)	0.0538 (7)
H8	0.5294	−0.1055	0.1130	0.065*
C16	0.7187 (2)	0.46207 (14)	0.3430 (4)	0.0585 (8)
H16	0.6530	0.4876	0.3476	0.070*
C9	0.5865 (3)	−0.19228 (15)	0.0190 (4)	0.0637 (8)
H9	0.5153	−0.2090	−0.0276	0.076*
C14	0.9165 (2)	0.45670 (14)	0.3243 (5)	0.0590 (8)
H14	0.9866	0.4773	0.3156	0.071*
C1	1.0012 (2)	0.12417 (14)	0.3833 (5)	0.0599 (8)
H1A	1.0262	0.1696	0.3778	0.090*
H1B	1.0340	0.0985	0.2900	0.090*
H1C	1.0255	0.1062	0.5047	0.090*
C15	0.8196 (2)	0.49461 (14)	0.3279 (4)	0.0617 (8)
H15	0.8225	0.5408	0.3204	0.074*
C11	0.7852 (3)	−0.20271 (15)	0.0760 (6)	0.0745 (10)
H11	0.8509	−0.2278	0.0673	0.089*
C10	0.6832 (3)	−0.22915 (15)	0.0042 (5)	0.0677 (9)
H10	0.6792	−0.2708	−0.0528	0.081*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.0367 (11)	0.0442 (12)	0.0563 (13)	−0.0043 (8)	0.0015 (9)	−0.0017 (9)
O2	0.0514 (11)	0.0516 (11)	0.0763 (14)	−0.0098 (8)	0.0211 (10)	−0.0047 (9)
O1	0.0400 (11)	0.0556 (12)	0.0884 (15)	−0.0066 (8)	0.0015 (10)	−0.0091 (10)
N4	0.0383 (11)	0.0449 (12)	0.0569 (13)	−0.0051 (9)	0.0096 (9)	−0.0016 (9)
N5	0.0416 (12)	0.0473 (12)	0.0564 (13)	−0.0014 (9)	0.0106 (10)	0.0033 (10)
N2	0.0385 (11)	0.0458 (12)	0.0589 (14)	−0.0031 (9)	0.0014 (9)	−0.0054 (10)
N6	0.0411 (11)	0.0452 (12)	0.0612 (14)	−0.0053 (9)	0.0091 (10)	0.0018 (10)
N8	0.0386 (12)	0.0528 (13)	0.0662 (15)	−0.0012 (9)	0.0005 (10)	−0.0054 (11)
C12	0.0392 (13)	0.0466 (14)	0.0435 (14)	−0.0031 (10)	−0.0001 (10)	−0.0015 (10)
C3	0.0423 (13)	0.0445 (14)	0.0476 (14)	−0.0025 (10)	0.0042 (11)	−0.0062 (11)
N7	0.0469 (14)	0.0496 (13)	0.097 (2)	−0.0010 (10)	0.0032 (13)	−0.0065 (13)
N3	0.0397 (12)	0.0461 (12)	0.0713 (16)	−0.0053 (9)	−0.0047 (10)	−0.0034 (11)
C6	0.0417 (13)	0.0430 (13)	0.0446 (14)	−0.0024 (10)	0.0037 (10)	0.0049 (10)
C4	0.0391 (14)	0.0456 (14)	0.0498 (15)	−0.0056 (10)	0.0033 (11)	0.0033 (11)
C5	0.0424 (14)	0.0458 (14)	0.0475 (14)	−0.0053 (11)	0.0048 (11)	−0.0032 (11)
C7	0.0438 (14)	0.0422 (14)	0.0546 (16)	−0.0047 (11)	0.0029 (11)	0.0049 (11)
C2	0.0475 (15)	0.0543 (16)	0.0718 (19)	−0.0021 (12)	0.0180 (13)	0.0038 (13)
C13	0.0383 (13)	0.0482 (15)	0.0634 (17)	−0.0017 (11)	0.0012 (12)	−0.0047 (12)
C8	0.0452 (15)	0.0504 (15)	0.0643 (18)	−0.0017 (11)	−0.0011 (13)	−0.0011 (13)
C16	0.0480 (15)	0.0530 (16)	0.074 (2)	0.0060 (12)	0.0023 (13)	−0.0084 (14)
C9	0.0574 (17)	0.0631 (18)	0.068 (2)	−0.0102 (14)	−0.0051 (14)	−0.0099 (15)
C14	0.0464 (15)	0.0530 (16)	0.079 (2)	−0.0108 (12)	0.0120 (14)	−0.0075 (14)
C1	0.0422 (15)	0.0531 (16)	0.083 (2)	−0.0020 (12)	0.0027 (14)	−0.0067 (14)
C15	0.0600 (18)	0.0449 (15)	0.081 (2)	−0.0065 (13)	0.0130 (15)	−0.0078 (14)
C11	0.0591 (19)	0.0521 (17)	0.113 (3)	0.0049 (14)	0.0123 (18)	−0.0106 (17)
C10	0.070 (2)	0.0518 (17)	0.081 (2)	−0.0028 (15)	0.0032 (16)	−0.0148 (15)

Geometric parameters (Å, º) top

N1—C6	1.388 (3)	C6—C2	1.494 (3)
N1—C4	1.399 (3)	C7—C8	1.387 (4)
N1—N2	1.420 (3)	C2—H2A	0.9600
O2—C5	1.210 (3)	C2—H2B	0.9600
O1—C4	1.206 (3)	C2—H2C	0.9600
N4—C3	1.395 (3)	C13—C14	1.367 (4)
N4—C5	1.405 (3)	C13—H13	0.9300
N4—N5	1.419 (3)	C8—C9	1.366 (4)
N5—C6	1.278 (3)	C8—H8	0.9300
N2—C3	1.279 (3)	C16—C15	1.369 (4)
N6—C5	1.356 (3)	C16—H16	0.9300
N6—C12	1.395 (3)	C9—C10	1.370 (4)
N6—H6	0.8600	C9—H9	0.9300
N8—C16	1.326 (4)	C14—C15	1.372 (4)
N8—C12	1.332 (3)	C14—H14	0.9300
C12—C13	1.384 (3)	C1—H1A	0.9600
C3—C1	1.487 (3)	C1—H1B	0.9600
N7—C7	1.329 (3)	C1—H1C	0.9600
N7—C11	1.331 (4)	C15—H15	0.9300
N3—C4	1.353 (3)	C11—C10	1.360 (4)
N3—C7	1.400 (3)	C11—H11	0.9300
N3—H3	0.8600	C10—H10	0.9300

C6—N1—C4	123.8 (2)	C6—C2—H2B	109.5
C6—N1—N2	117.91 (19)	H2A—C2—H2B	109.5
C4—N1—N2	116.61 (19)	C6—C2—H2C	109.5
C3—N4—C5	123.2 (2)	H2A—C2—H2C	109.5
C3—N4—N5	117.25 (19)	H2B—C2—H2C	109.5
C5—N4—N5	115.78 (19)	C14—C13—C12	117.7 (2)
C6—N5—N4	115.0 (2)	C14—C13—H13	121.2
C3—N2—N1	114.7 (2)	C12—C13—H13	121.2
C5—N6—C12	127.2 (2)	C9—C8—C7	117.7 (3)
C5—N6—H6	116.4	C9—C8—H8	121.1
C12—N6—H6	116.4	C7—C8—H8	121.1
C16—N8—C12	117.2 (2)	N8—C16—C15	124.0 (3)
N8—C12—C13	123.2 (2)	N8—C16—H16	118.0
N8—C12—N6	112.9 (2)	C15—C16—H16	118.0
C13—C12—N6	123.9 (2)	C8—C9—C10	120.2 (3)
N2—C3—N4	120.3 (2)	C8—C9—H9	119.9
N2—C3—C1	117.7 (2)	C10—C9—H9	119.9
N4—C3—C1	121.9 (2)	C13—C14—C15	120.2 (3)
C7—N7—C11	116.9 (2)	C13—C14—H14	119.9
C4—N3—C7	127.5 (2)	C15—C14—H14	119.9
C4—N3—H3	116.2	C3—C1—H1A	109.5
C7—N3—H3	116.2	C3—C1—H1B	109.5
N5—C6—N1	120.2 (2)	H1A—C1—H1B	109.5
N5—C6—C2	117.5 (2)	C3—C1—H1C	109.5
N1—C6—C2	122.3 (2)	H1A—C1—H1C	109.5
O1—C4—N3	125.2 (2)	H1B—C1—H1C	109.5
O1—C4—N1	121.2 (2)	C16—C15—C14	117.7 (3)
N3—C4—N1	113.6 (2)	C16—C15—H15	121.2
O2—C5—N6	125.4 (2)	C14—C15—H15	121.2
O2—C5—N4	121.5 (2)	N7—C11—C10	124.4 (3)
N6—C5—N4	113.0 (2)	N7—C11—H11	117.8
N7—C7—C8	123.1 (3)	C10—C11—H11	117.8
N7—C7—N3	112.3 (2)	C11—C10—C9	117.6 (3)
C8—C7—N3	124.6 (2)	C11—C10—H10	121.2
C6—C2—H2A	109.5	C9—C10—H10	121.2

C3—N4—N5—C6	−32.6 (3)	C6—N1—C4—N3	−164.0 (2)
C5—N4—N5—C6	168.6 (2)	N2—N1—C4—N3	0.8 (3)
C6—N1—N2—C3	−31.4 (3)	C12—N6—C5—O2	−0.8 (4)
C4—N1—N2—C3	162.8 (2)	C12—N6—C5—N4	−177.8 (2)
C16—N8—C12—C13	1.6 (4)	C3—N4—C5—O2	25.5 (4)
C16—N8—C12—N6	−179.9 (2)	N5—N4—C5—O2	−177.0 (2)
C5—N6—C12—N8	162.7 (2)	C3—N4—C5—N6	−157.3 (2)
C5—N6—C12—C13	−18.8 (4)	N5—N4—C5—N6	0.1 (3)
N1—N2—C3—N4	2.8 (3)	C11—N7—C7—C8	0.7 (5)
N1—N2—C3—C1	179.3 (2)	C11—N7—C7—N3	−179.2 (3)
C5—N4—C3—N2	−173.6 (2)	C4—N3—C7—N7	169.7 (3)
N5—N4—C3—N2	29.3 (3)	C4—N3—C7—C8	−10.2 (4)
C5—N4—C3—C1	10.0 (4)	N8—C12—C13—C14	−1.9 (4)
N5—N4—C3—C1	−147.1 (3)	N6—C12—C13—C14	179.8 (3)
N4—N5—C6—N1	4.2 (3)	N7—C7—C8—C9	−0.8 (4)
N4—N5—C6—C2	−179.5 (2)	N3—C7—C8—C9	179.1 (3)
C4—N1—C6—N5	−167.2 (2)	C12—N8—C16—C15	−0.1 (4)
N2—N1—C6—N5	28.1 (3)	C7—C8—C9—C10	0.1 (5)
C4—N1—C6—C2	16.6 (4)	C12—C13—C14—C15	0.7 (4)
N2—N1—C6—C2	−148.0 (2)	N8—C16—C15—C14	−1.0 (5)
C7—N3—C4—O1	13.6 (5)	C13—C14—C15—C16	0.7 (5)
C7—N3—C4—N1	−164.6 (2)	C7—N7—C11—C10	0.1 (5)
C6—N1—C4—O1	17.6 (4)	N7—C11—C10—C9	−0.7 (6)
N2—N1—C4—O1	−177.6 (2)	C8—C9—C10—C11	0.6 (5)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1A···O2	0.96	2.07	2.778 (4)	130
C2—H2A···O1	0.96	2.09	2.777 (4)	127
C8—H8···O1	0.93	2.31	2.886 (3)	120
C16—H16···O1ⁱ	0.93	2.39	3.229 (3)	150

Symmetry code: (i) −x+1, y+1/2, −z+1/2.

Experimental details

Crystal data
Chemical formula	C₁₆H₁₆N₈O₂
M_r	352.37
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	298
a, b, c (Å)	11.753 (2), 20.081 (4), 7.2012 (14)
β (°)	96.273 (3)
V (Å³)	1689.4 (6)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.10
Crystal size (mm)	0.36 × 0.23 × 0.20

Data collection
Diffractometer	Bruker SMART CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 1997)
T_min, T_max	0.965, 0.981
No. of measured, independent and observed [I > 2σ(I)] reflections	7032, 2985, 2430
R_int	0.024
(sin θ/λ)_max (Å⁻¹)	0.595

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.061, 0.182, 1.07
No. of reflections	2985
No. of parameters	236
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.44, −0.33

Computer programs: SMART (Bruker, 1997), SAINT (Bruker, 1997), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997), WinGX (Farrugia, 1999).

Selected bond lengths (Å) top

N1—C6	1.388 (3)	N4—N5	1.419 (3)
N1—N2	1.420 (3)	N5—C6	1.278 (3)
N4—C3	1.395 (3)	N2—C3	1.279 (3)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1A···O2	0.96	2.07	2.778 (4)	129.7
C2—H2A···O1	0.96	2.09	2.777 (4)	126.8
C8—H8···O1	0.93	2.31	2.886 (3)	119.7
C16—H16···O1ⁱ	0.93	2.39	3.229 (3)	149.7

Symmetry code: (i) −x+1, y+1/2, −z+1/2.

Acknowledgements

The authors are very grateful to the Natural Science Foundation of Zhejiang Province (grant No. Y2090985) and the National Natural Science Foundation of China (grant No. 20802069) for financial support.

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