Crystal structures of N-(pyridin-2-ylmeth-yl)pyrazine-2-carboxamide (monoclinic polymorph) and N-(pyridin-4-ylmeth-yl)pyrazine-2-carboxamide.

The title compounds, C11H10N4O (HL1) and C11H10N4O (HL2), are pyridine 2-ylmethyl and 4-ylmethyl derivatives, respectively, of pyrazine-2-carboxamide. HL1 was measured at 153 K and crystallized in the monoclinic space group P21/c with Z = 4. There has been a report of the same structure measured at room temperature but assumed to crystallize in the triclinic space group P-1 with Z = 4 [Sasan et al. (2008 ▶). Monatsh. Chem. 139, 773-780]. In HL1, the pyridine ring is inclined to the pyrazine ring by 61.34 (6)°, while in HL2 this dihedral angle is 84.33 (12)°. In both mol-ecules, there is a short N-H⋯N inter-action involving the pyrazine carboxamide unit. In the crystal of HL1, mol-ecules are linked by N-H⋯N hydrogen bonds, forming inversion dimers with an R 2 (2)(10) ring motif. The dimers are linked via bifurcated-acceptor C-H⋯O hydrogen bonds, forming sheets lying parallel to (102). The sheets are linked via C-H⋯N hydrogen bonds, forming a three-dimensional structure. In the crystal of HL2, mol-ecules are linked by N-H⋯N and C-H⋯N hydrogen bonds to form chains propagating along [010]. The chains are linked via C-H⋯O hydrogen bonds, forming sheets lying parallel to (100). Within the sheets there are π-π inter-actions involving neighbouring pyrazine rings [inter-centroid distance = 3.711 (15) Å]. Adjacent sheets are linked via parallel slipped π-π inter-actions involving inversion-related pyridine rings [inter-centroid distance = 3.6395 (17) Å], forming a three-dimensional structure.

Chemical context

The title compounds form part of a series of ligands synthesized in order to study their coordination chemistry with 3d transition metals (Cati, 2002 ▸).

They have been used to construct coordination polymers and multi-nuclear compounds, and to study their magnetic properties (Cati et al., 2004 ▸). Similar ligands have been synthesized by other groups who have studied, for example, the magnetic properties of some copper(II) complexes (Hausmann et al., 2003 ▸; Kingele et al., 2007 ▸).

Structural commentary

The mol­ecular structure of ligand HL1 is illustrated in Fig. 1 ▸. HL1 was measured at 153 K and crystallized in the monoclinic space group P21/c with Z = 4. The β angle is 91.461 (11)° and the systematic absences, the R nt value (0.0348) and the successful refinement {R1 [I > 2σ(I)] = 0.0319} clearly show that at 153 K the space group is monoclinic P21/c. The same structure measured at room temperature was reported to crystallize in the triclinic space group P with Z = 4 (Sasan et al., 2008 ▸). However, the three cell angles are close 90 (2)° [α = 91.802 (6), β = 89.834 (7), γ = 91.845 (6)°] and the crystal used was a very narrow needle. The final R1 [I > 2σ(I)] factor was rather high at 0.0699, hence it is possible that the choice of crystal system and space group are incorrect. However, this could not be confirmed when analysing the coordinates using the AddSymm routine in PLATON (Spek, 2009 ▸).

Figure 1

A view of the mol­ecular structure of HL1, with atom labelling. Displacement ellipsoids are drawn at the 50% probability level. The short intra­molecular N—H⋯N inter­action is shown as a dashed line (see Table 1 ▸ for details).

In the mol­ecule of HL1 there is a short N—H⋯N hydrogen bond present in the pyrazine carboxamide unit (Table 1 ▸), and the amide group, C5(=O1)N3, is approximately coplanar with the pyrazine (N1/N2/C1–C4) ring [dihedral angle = 2.56 (14)°]. The pyrazine and pyridine (N4/C7–C10) rings are inclined to one another by 61.34 (6)°. In the triclinic structure mentioned above, the same angle in the two independent mol­ecules is 63.31 (13) and 61.94 (13)°.

Table 1

Hydrogen-bond geometry (Å, °) for HL1

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N3—H3N⋯N1	0.901 (16)	2.332 (15)	2.7136 (15)	105.4 (11)
N3—H3N⋯N4i	0.901 (16)	2.206 (16)	2.9929 (14)	145.6 (13)
C3—H3⋯O1ii	0.95	2.51	3.1544 (15)	125
C4—H4⋯O1ii	0.95	2.56	3.1748 (15)	123
C10—H10⋯N2iii	0.95	2.62	3.5678 (17)	174

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

The mol­ecular structure of HL2 is illustrated in Fig. 2 ▸. Here too there is a short intra­molecular N—H⋯N contact involving the pyrazine carboxamide unit (Table 2 ▸), and the amide group, C5(=O1)N3, is almost coplanar with the pyrazine (N1/N2/C1–C4) ring with a dihedral angle of 3.9 (3)°. Here the pyrazine and pyridine (N4/C7–C10) rings are almost normal to one another with a dihedral angle of 84.33 (12)°.

Figure 2

A view of the mol­ecular structure of HL2, with atom labelling. Displacement ellipsoids are drawn at the 50% probability level. The short intra­molecular N—H⋯N inter­action is shown as a dashed line (see Table 2 ▸ for details).

Table 2

Hydrogen-bond geometry (Å, °) for HL2

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N3—H3N⋯N1	0.83 (3)	2.27 (3)	2.713 (3)	114 (2)
N3—H3N⋯N2i	0.83 (3)	2.52 (3)	3.214 (3)	142 (2)
C2—H2⋯N1ii	0.93	2.47	3.315 (3)	151
C8—H8⋯O1iii	0.93	2.55	3.373 (3)	148

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

Supra­molecular features

In the crystal of HL1, mol­ecules are linked by N—H⋯N hydrogen bonds, forming inversion dimers with an (10) ring motif. The dimers are linked via bifurcated-acceptor C—H⋯O hydrogen bonds, forming sheets lying parallel to (102) (see Table 1 ▸ and Fig. 3 ▸). The sheets are linked via C—H⋯N hydrogen bonds, forming a three-dimensional structure (Table 1 ▸ and Fig. 4 ▸).

Figure 3

A partial view along the a axis of the crystal packing of compound HL1. The N—H⋯N, C—H⋯O and C-H⋯N hydrogen bonds are shown as dashed lines (see Table 1 ▸ for details).

Figure 4

The crystal packing of compound HL1 viewed along the b axis. The N—H⋯N, C—H⋯O and C—H⋯N hydrogen bonds are shown as dashed lines (see Table 1 ▸ for details).

In the crystal of HL2, mol­ecules are linked by N—H⋯N and C—H⋯N hydrogen bonds to form chains propagating along [010], as shown in Table 2 ▸ and Fig. 5 ▸. The chains are linked via C—H⋯O hydrogen bonds, forming sheets lying parallel to (100). Within the sheets there are π–π inter­actions involving neighbouring pyrazine rings [Cg1⋯Cg1i = 3.7113 (15) Å; Cg1 is the centroid of the pyrazine ring N1/N2/C1–C4; symmetry code: (i) = x, −y + , z − ]. The sheets are linked via slipped parallel π–π inter­actions involving inversion-related pyridine rings [Cg2⋯Cg2ii = 3.6395 (11) Å, normal distance = 3.4164 (11), slippage = 1.255 Å; Cg2 is the centroid of pyridine ring N4/C7–C11; symmetry code: (ii) −x, −y, −z], forming a three-dimensional structure (Table 2 ▸ and Fig. 6 ▸).

Figure 5

A partial view along the c axis of the crystal packing of compound HL2. The N—H⋯N, and C—H⋯N hydrogen bonds are shown as dashed lines (see Table 2 ▸ for details).

Figure 6

The crystal packing of compound HL2 viewed along the c axis. The N—H⋯N, C—H⋯O and C—H⋯N hydrogen bonds are shown as dashed lines (see Table 2 ▸ for details).

Database survey

A search of the Cambridge Structural Database (Version 5.35, last update November 2013; Allen, 2002 ▸) indicated the presence of 282 structures containing the pyrazine-2-carboxamide unit. 81 of these concern pyrazine-2-carboxamide itself. There were 10 hits for complexes of ligand HL1. These include a cobalt(III) (Hellyer et al., 2009 ▸), a chromium(III) (Khavasi et al., 2010 ▸) and four copper(II) complexes (Mohamadou et al., 2012 ▸; Khavasi et al., 2011 ▸), all of which are mononuclear with the ligand coordinating in a tridentate manner. There are also two polymeric mercury chloride complexes (Khavasi & Sadegh, 2010 ▸), a binuclear manganese chloride complex (Khavasi et al., 2009 ▸), and a polymeric silver tetra­fluoro­borate complex (Hellyer et al., 2009 ▸), where the ligand coordinates in a bis-monodentate manner. Plus the report of the ligand itself as mentioned above (Sasan et al., 2008 ▸). For ligand HL2 there were no hits.

Synthesis and crystallization

The precursor pyrazine-2-carb­oxy­lic acid methyl ester (2-pze) was prepared following the procedure described by Alvarez-Ibarra et al. (1994 ▸). 6.21 g (50 mmol) of pyrazine-2-carb­oxy­lic acid were added to 50 ml of absolute methanol in a two-necked flask (100 ml). The mixture was heated to 303 K and then 0.4 ml of concentrated sulfuric acid was added slowly. The mixture was heated for 23 h, at least. It was then poured over ice and made alkaline using NaOH (2 N), then extracted with CH2Cl2. The organic extract was dried over Na2SO4. The resulting yellow product was purified by recrystallization from hexane, or by column chromatography on silica gel using CH2Cl2 as eluant, giving finally colourless crystals (yield 80%).

The ligand HL1 was prepared by refluxing 2-pze (1.80 g, 13 mmol) and an excess of 2-(amino­meth­yl)pyridine (1.84 g, 17 mmol) in 12 ml of methanol, for 6 h in a two-necked flask (50 ml). A yellowish oil remained when the methanol was evaporated off. The excess of 2-(amino­meth­yl)pyridine was eliminated by column chromatography on silica gel using CH2Cl2 as eluant (r = 2 cm, l = 8 cm). A yellow band of 2-(amino­meth­yl)pyridine remained on the column. After evaporation, the ligand could be recrystallized from diethyl ether, aceto­nitrile or ethyl acetate. HL1 is very soluble in MeOH and in CH2Cl2. Recrystallization from diethyl ether gave colourless blocks of HL1 (yield 91%; m.p. 388 K). Analysis for C11H10N4O (M = 214.46 g/mol) Calculated (%) C: 61.67 H: 4.71 N: 26.15; Found (%) C: 61.80 H: 4.76 N: 26.45. Spectroscopic data are available in the supporting information.

HL2 was prepared using the same procedure as for HL1. 2-pze (1.38 g, 10 mmol) with, this time, an excess of 4-(amino­meth­yl)pyridine (1.73 g, 16 mmol) were refluxed in 20 ml of methanol, for 20 h in a two-necked flask (50 ml). 4-(amino­meth­yl)pyridine (1g, 10 mmol) was then added to the red solution. After 4 h the solution was evaporated to about 8 ml. HL2 crystallized out at room temperature. About 20 ml of diethyl ether was added to filtrate the product. It was then recrystallized from a mixture of 3 ml of methanol and 40 ml of diethyl ether to give colourless blocks (yield 84%; m.p. 422 K). Anal. for C11H10N4O (M = 214.46 g/mol) Calculated (%) C: 61.67 H: 4.71 N: 26.15 Found (%) C: 61.57 H: 4.75 N: 26.20. Spectroscopic data are available in the supporting information.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3 ▸. The NH H atoms were located in difference Fourier maps and freely refined. The C-bound H atoms were included in calculated positions and treated as riding atoms: C—H = 0.95 Å for HL1 and = 0.93 Å for HL2, with U iso(H) = 1.2U eq(C).

Table 3

Experimental details

	HL1	HL2
Crystal data
Chemical formula	C11H10N4O	C11H10N4O
M r	214.23	214.23
Crystal system, space group	Monoclinic, P21/c	Monoclinic, P21/c
Temperature (K)	153	293
a, b, c (Å)	4.1527 (4), 20.4629 (18), 12.0106 (11)	13.8564 (14), 11.1841 (11), 6.9122 (10)
β (°)	91.461 (11)	104.356 (14)
V (Å3)	1020.28 (16)	1037.7 (2)
Z	4	4
Radiation type	Mo Kα	Mo Kα
μ (mm−1)	0.10	0.09
Crystal size (mm)	0.50 × 0.40 × 0.35	0.38 × 0.30 × 0.19
Data collection
Diffractometer	Stoe IPDS 1	Stoe AED2 four-circle
No. of measured, independent and observed [I > 2σ(I)] reflections	7822, 1958, 1548	4132, 1937, 1198
R int	0.035	0.032
(sin θ/λ)max (Å−1)	0.615	0.605
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.032, 0.088, 1.03	0.054, 0.127, 1.10
No. of reflections	1958	1937
No. of parameters	149	150
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement	H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3)	0.17, −0.17	0.17, −0.16

Computer programs: EXPOSE, CELL and INTEGRATE in IPDSI, STADI4 and X-RED (Stoe & Cie, 1997 ▸), SHELXS97 and SHELXL2013 (Sheldrick, 2008 ▸), Mercury (Macrae et al., 2008 ▸), PLATON (Spek, 2009 ▸) and publCIF (Westrip, 2010 ▸).

Crystal structure: contains datablock(s) HL1, HL2, global. DOI: 10.1107/S1600536814009519/hb0007sup1.cif

Structure factors: contains datablock(s) HL1. DOI: 10.1107/S1600536814009519/hb0007HL1sup2.hkl

Click here for additional data file.

Supporting information file. DOI: 10.1107/S1600536814009519/hb0007HL1sup4.cml

Structure factors: contains datablock(s) HL2. DOI: 10.1107/S1600536814009519/hb0007HL2sup3.hkl

Click here for additional data file.

Supporting information file. DOI: 10.1107/S1600536814009519/hb0007HL2sup5.cml

CCDC references: 1004272, 1004273

Additional supporting information: crystallographic information; 3D view; checkCIF report

C11H10N4O	F(000) = 448
Mr = 214.23	Dx = 1.395 Mg m−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 4.1527 (4) Å	Cell parameters from 6532 reflections
b = 20.4629 (18) Å	θ = 2.0–25.9°
c = 12.0106 (11) Å	µ = 0.10 mm−1
β = 91.461 (11)°	T = 153 K
V = 1020.28 (16) Å3	Block, colourless
Z = 4	0.50 × 0.40 × 0.35 mm

Stoe IPDS 1 diffractometer	1548 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.035
Plane graphite monochromator	θmax = 25.9°, θmin = 2.0°
φ rotation scans	h = −5→5
7822 measured reflections	k = −25→25
1958 independent reflections	l = −14→14

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.032	Hydrogen site location: mixed
wR(F2) = 0.088	H atoms treated by a mixture of independent and constrained refinement
S = 1.03	w = 1/[σ2(Fo2) + (0.0539P)2 + 0.0704P] where P = (Fo2 + 2Fc2)/3
1958 reflections	(Δ/σ)max < 0.001
149 parameters	Δρmax = 0.17 e Å−3
0 restraints	Δρmin = −0.17 e Å−3

Experimental. Spectrosopic data for HL1: 1H NMR (400 MHz, DMSO-d6; code Hh/NH, Hl/C3, Hn/C1, Hm/C2, Hb/C11, Hd/C9, He/C8, Hc/C10, Hg/C6): 9.50 (t, 1H, Jhg = 6.0, Hh); 9.23 (d, 1H, Jlm = 1.5, Hl); 8.91 (d, 1H, Jnm = 2.5, Hn); 8.78 (dd, 1H, Jmn = 2.5, Jml = 1.5, Hm); 8.53 (ddd, 1H, Jbc = 4.8, Jbd = 1.8, Jbe = 0.8, Hb); 7.76 (td, 1H, Jdc = 7.7, Jdb = 1.8, Hd); 7.35 (d, 1H, Jed = 7.9, He); 7.28 (dd, 1H, Jcd = 7.7, Jcb = 4.8, Hc); 4.64 (d, 2H, Jgh = 6.0, He). 13C NMR (400 MHz, DMSO-d6): 163.9, 158.6, 149.7, 148.6, 145.5, 144.4, 144.3, 137.6, 123.1, 121.9, 45.0. IR (KBr pellet, cm-1): 3248 (m), 3066 (w), 3018 (w), 2949 (w), 1669 (versus), 1593 (m), 1570 (m), 1517 (versus), 1478 (m), 1462 (s), 1440 (s), 1423 (s), 1389 (s), 1350 (m), 1320 (m), 1287 (s), 1250 (m), 1221 (m), 1168 (s), 1148 (m), 1103 (m), 1055 (m), 1021 (s), 1000 (m), 975 (m), 870 (m), 840 (w), 776 (m), 753 (s), 707 (m), 634 (m), 611 (m), 528 (m), 444 (m).

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.

	x	y	z	Uiso*/Ueq
N1	0.7345 (3)	0.30055 (5)	0.42625 (8)	0.0260 (2)
N2	0.7780 (3)	0.16917 (5)	0.49125 (9)	0.0343 (3)
N3	0.4290 (2)	0.38859 (5)	0.55546 (8)	0.0224 (2)
H3N	0.514 (4)	0.3982 (7)	0.4892 (13)	0.037 (4)*
N4	0.5222 (3)	0.53951 (5)	0.66045 (8)	0.0293 (3)
O1	0.3074 (2)	0.30857 (4)	0.67870 (7)	0.0344 (2)
C1	0.6100 (3)	0.27903 (5)	0.52119 (9)	0.0215 (3)
C2	0.6318 (3)	0.21416 (6)	0.55317 (10)	0.0287 (3)
H2	0.5401	0.2011	0.6213	0.034*
C3	0.9010 (3)	0.19099 (6)	0.39702 (10)	0.0305 (3)
H3	1.0071	0.1609	0.3501	0.037*
C4	0.8800 (3)	0.25567 (6)	0.36486 (10)	0.0290 (3)
H4	0.9724	0.2686	0.2967	0.035*
C5	0.4355 (3)	0.32697 (6)	0.59277 (9)	0.0229 (3)
C6	0.2435 (3)	0.43932 (6)	0.60984 (10)	0.0263 (3)
H6A	0.0627	0.4186	0.6488	0.032*
H6B	0.1503	0.4688	0.5522	0.032*
C7	0.4391 (3)	0.47934 (5)	0.69249 (9)	0.0219 (3)
C8	0.5266 (3)	0.45428 (6)	0.79615 (10)	0.0271 (3)
H8	0.4640	0.4113	0.8163	0.033*
C9	0.7051 (3)	0.49220 (6)	0.86977 (10)	0.0312 (3)
H9	0.7682	0.4757	0.9410	0.037*
C10	0.7906 (4)	0.55455 (6)	0.83801 (11)	0.0350 (3)
H10	0.9115	0.5822	0.8870	0.042*
C11	0.6957 (4)	0.57556 (6)	0.73353 (11)	0.0376 (3)
H11	0.7569	0.6183	0.7117	0.045*

	U11	U22	U33	U12	U13	U23
N1	0.0305 (6)	0.0246 (5)	0.0231 (5)	−0.0011 (4)	0.0045 (4)	−0.0005 (4)
N2	0.0434 (7)	0.0239 (5)	0.0356 (6)	0.0046 (5)	0.0043 (5)	−0.0006 (4)
N3	0.0263 (5)	0.0207 (5)	0.0201 (5)	0.0007 (4)	0.0020 (4)	−0.0008 (4)
N4	0.0412 (7)	0.0219 (5)	0.0249 (5)	0.0016 (4)	0.0022 (4)	0.0007 (4)
O1	0.0454 (6)	0.0295 (5)	0.0288 (5)	0.0000 (4)	0.0154 (4)	0.0036 (4)
C1	0.0219 (6)	0.0217 (6)	0.0208 (5)	−0.0024 (5)	−0.0014 (4)	−0.0008 (4)
C2	0.0369 (8)	0.0247 (6)	0.0246 (6)	0.0006 (5)	0.0032 (5)	0.0016 (5)
C3	0.0327 (7)	0.0275 (6)	0.0313 (7)	0.0029 (5)	0.0039 (5)	−0.0067 (5)
C4	0.0321 (7)	0.0305 (6)	0.0246 (6)	−0.0012 (5)	0.0056 (5)	−0.0028 (5)
C5	0.0233 (6)	0.0242 (6)	0.0211 (6)	−0.0021 (5)	−0.0003 (5)	−0.0001 (4)
C6	0.0244 (7)	0.0248 (6)	0.0296 (6)	0.0062 (5)	−0.0010 (5)	−0.0021 (5)
C7	0.0210 (6)	0.0213 (6)	0.0235 (6)	0.0055 (5)	0.0057 (4)	−0.0011 (4)
C8	0.0275 (7)	0.0258 (6)	0.0281 (6)	0.0005 (5)	0.0024 (5)	0.0046 (5)
C9	0.0333 (7)	0.0374 (7)	0.0228 (6)	0.0044 (6)	−0.0001 (5)	0.0010 (5)
C10	0.0420 (8)	0.0310 (7)	0.0317 (7)	−0.0002 (6)	−0.0034 (6)	−0.0093 (5)
C11	0.0554 (9)	0.0207 (6)	0.0366 (7)	−0.0046 (6)	−0.0022 (6)	−0.0006 (5)

N1—C4	1.3323 (16)	C3—H3	0.9500
N1—C1	1.3386 (15)	C4—H4	0.9500
N2—C3	1.3307 (17)	C6—C7	1.5082 (16)
N2—C2	1.3387 (16)	C6—H6A	0.9900
N3—C5	1.3382 (15)	C6—H6B	0.9900
N3—C6	1.4570 (15)	C7—C8	1.3865 (17)
N3—H3N	0.901 (16)	C8—C9	1.3784 (18)
N4—C7	1.3379 (15)	C8—H8	0.9500
N4—C11	1.3422 (17)	C9—C10	1.3806 (18)
O1—C5	1.2319 (14)	C9—H9	0.9500
C1—C2	1.3842 (16)	C10—C11	1.3745 (19)
C1—C5	1.5028 (16)	C10—H10	0.9500
C2—H2	0.9500	C11—H11	0.9500
C3—C4	1.3808 (18)
C4—N1—C1	115.80 (10)	N3—C6—C7	113.57 (9)
C3—N2—C2	115.53 (11)	N3—C6—H6A	108.9
C5—N3—C6	121.84 (10)	C7—C6—H6A	108.9
C5—N3—H3N	119.7 (9)	N3—C6—H6B	108.9
C6—N3—H3N	117.7 (9)	C7—C6—H6B	108.9
C7—N4—C11	117.12 (10)	H6A—C6—H6B	107.7
N1—C1—C2	121.86 (11)	N4—C7—C8	122.34 (11)
N1—C1—C5	118.36 (10)	N4—C7—C6	116.69 (10)
C2—C1—C5	119.76 (10)	C8—C7—C6	120.97 (11)
N2—C2—C1	122.19 (11)	C9—C8—C7	119.49 (11)
N2—C2—H2	118.9	C9—C8—H8	120.3
C1—C2—H2	118.9	C7—C8—H8	120.3
N2—C3—C4	122.47 (11)	C8—C9—C10	118.73 (11)
N2—C3—H3	118.8	C8—C9—H9	120.6
C4—C3—H3	118.8	C10—C9—H9	120.6
N1—C4—C3	122.14 (11)	C11—C10—C9	118.14 (12)
N1—C4—H4	118.9	C11—C10—H10	120.9
C3—C4—H4	118.9	C9—C10—H10	120.9
O1—C5—N3	124.27 (11)	N4—C11—C10	124.17 (12)
O1—C5—C1	120.30 (10)	N4—C11—H11	117.9
N3—C5—C1	115.43 (10)	C10—C11—H11	117.9
C4—N1—C1—C2	0.03 (17)	C2—C1—C5—N3	179.54 (11)
C4—N1—C1—C5	−178.51 (11)	C5—N3—C6—C7	95.48 (13)
C3—N2—C2—C1	0.06 (19)	C11—N4—C7—C8	−0.18 (18)
N1—C1—C2—N2	−0.1 (2)	C11—N4—C7—C6	179.86 (11)
C5—C1—C2—N2	178.43 (11)	N3—C6—C7—N4	104.41 (12)
C2—N2—C3—C4	0.03 (19)	N3—C6—C7—C8	−75.55 (14)
C1—N1—C4—C3	0.05 (18)	N4—C7—C8—C9	0.12 (18)
N2—C3—C4—N1	−0.1 (2)	C6—C7—C8—C9	−179.92 (11)
C6—N3—C5—O1	−5.16 (19)	C7—C8—C9—C10	0.33 (19)
C6—N3—C5—C1	174.05 (10)	C8—C9—C10—C11	−0.7 (2)
N1—C1—C5—O1	177.36 (11)	C7—N4—C11—C10	−0.2 (2)
C2—C1—C5—O1	−1.21 (18)	C9—C10—C11—N4	0.6 (2)
N1—C1—C5—N3	−1.88 (16)

D—H···A	D—H	H···A	D···A	D—H···A
N3—H3N···N1	0.901 (16)	2.332 (15)	2.7136 (15)	105.4 (11)
N3—H3N···N4i	0.901 (16)	2.206 (16)	2.9929 (14)	145.6 (13)
C3—H3···O1ii	0.95	2.51	3.1544 (15)	125
C4—H4···O1ii	0.95	2.56	3.1748 (15)	123
C10—H10···N2iii	0.95	2.62	3.5678 (17)	174

C11H10N4O	F(000) = 448
Mr = 214.23	Dx = 1.371 Mg m−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 13.8564 (14) Å	Cell parameters from 20 reflections
b = 11.1841 (11) Å	θ = 10.4–17.6°
c = 6.9122 (10) Å	µ = 0.09 mm−1
β = 104.356 (14)°	T = 293 K
V = 1037.7 (2) Å3	Block, colourless
Z = 4	0.38 × 0.30 × 0.19 mm

Stoe AED2 four-circle diffractometer	Rint = 0.032
Radiation source: fine-focus sealed tube	θmax = 25.5°, θmin = 2.4°
Plane graphite monochromator	h = −16→16
2θ/ω scans	k = −13→0
4132 measured reflections	l = −8→8
1937 independent reflections	2 standard reflections every 60 min
1198 reflections with I > 2σ(I)	intensity decay: 2%

Refinement on F2	Hydrogen site location: mixed
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F2 > 2σ(F2)] = 0.054	w = 1/[σ2(Fo2) + (0.0426P)2 + 0.1904P] where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.127	(Δ/σ)max < 0.001
S = 1.10	Δρmax = 0.17 e Å−3
1937 reflections	Δρmin = −0.16 e Å−3
150 parameters	Extinction correction: SHELXL2013 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraints	Extinction coefficient: 0.014 (2)

Experimental. Spectroscopic data for HL2: 1H NMR (400 MHz, DMSO-d6; code Hh/NH, Hl/C3, Hn/C1, Hm/C2, Hb/C11, Hd/C9, Ha/C11/, He/C8, Hg/C6): 9.63 (t, 1H, Jhg = 6.3, Hh); 9.21 (d, 1H, Jlm = 1.5, Hl); 8.90 (d, 1H, Jnm = 2.5, Hn); 8.77 (dd, 1H, Jmn = 2.5, Jml = 1.5, Hm); 8.49 (dd, 2H, Jba = 4.4, Jbe = 1.6, Hb = Hd); 7.31 (dd, 2H, Jab = 4.4, Jad = 1.6, Ha = He); 4.54 (d, 2H, Jgh = 6.3, Hg). 13C NMR (400 MHz, DMSO-d6): 164.2, 150.4, 149.0, 148.5, 145.4, 144.5, 144.3, 123.0, 42.4. IR (KBr pellet, cm-1): 3366 (versus), 3089 (s), 3050 (m), 3031 (s), 2967 (m), 2935 (s), 1966 (w), 1924 (w), 1834 (w), 1674 (versus), 1634 (s), 1602 (versus), 1585 (s), 1564 (s) 1526 (versus), 1467 (versus), 1429 (versus), 1415 (versus), 1399 (versus), 1359 (s), 1329 (s), 1288 (versus), 1240 (m), 1216 (versus), 1167 (s), 1155 (s), 1059 (versus), 1025 (versus), 1020 (versus), 993 (s), 981 (s), 968 (s), 887 (m), 870 (s), 842 (s), 832 (s), 804 (versus), 775 (s), 731 (m), 652 (versus), 608 (s), 517 (s), 479 (m), 445 (versus), 411 (m).

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.

	x	y	z	Uiso*/Ueq
O1	0.32038 (14)	0.28041 (15)	0.2248 (3)	0.0618 (6)
N1	0.52051 (15)	0.08089 (17)	0.2297 (3)	0.0456 (6)
N2	0.61838 (17)	0.29856 (19)	0.2153 (3)	0.0530 (6)
N3	0.32823 (16)	0.0787 (2)	0.2548 (3)	0.0495 (6)
H3N	0.367 (2)	0.022 (2)	0.251 (4)	0.057 (9)*
N4	0.04496 (18)	−0.1046 (2)	−0.2659 (4)	0.0677 (7)
C1	0.47371 (18)	0.1855 (2)	0.2255 (3)	0.0389 (6)
C2	0.5226 (2)	0.2927 (2)	0.2174 (4)	0.0477 (7)
H2	0.4870	0.3635	0.2132	0.057*
C3	0.6641 (2)	0.1935 (2)	0.2189 (4)	0.0531 (7)
H3	0.7309	0.1925	0.2166	0.064*
C4	0.61612 (19)	0.0861 (2)	0.2258 (4)	0.0510 (7)
H4	0.6515	0.0153	0.2279	0.061*
C5	0.36661 (19)	0.1863 (2)	0.2342 (4)	0.0442 (6)
C6	0.22661 (19)	0.0590 (2)	0.2660 (4)	0.0548 (7)
H6A	0.1972	0.1350	0.2877	0.066*
H6B	0.2267	0.0080	0.3795	0.066*
C7	0.16399 (17)	0.0020 (2)	0.0798 (4)	0.0431 (6)
C8	0.1571 (2)	0.0498 (2)	−0.1071 (4)	0.0534 (7)
H8	0.1922	0.1187	−0.1216	0.064*
C9	0.0979 (2)	−0.0052 (3)	−0.2711 (5)	0.0652 (8)
H9	0.0943	0.0291	−0.3953	0.078*
C10	0.0528 (2)	−0.1497 (2)	−0.0853 (5)	0.0627 (8)
H10	0.0171	−0.2188	−0.0752	0.075*
C11	0.11055 (19)	−0.1010 (2)	0.0887 (4)	0.0517 (7)
H11	0.1134	−0.1374	0.2110	0.062*

	U11	U22	U33	U12	U13	U23
O1	0.0615 (13)	0.0417 (11)	0.0868 (15)	0.0116 (10)	0.0272 (11)	−0.0013 (10)
N1	0.0459 (13)	0.0334 (12)	0.0586 (14)	0.0012 (10)	0.0149 (10)	−0.0024 (10)
N2	0.0553 (15)	0.0427 (14)	0.0610 (15)	−0.0100 (11)	0.0144 (11)	−0.0006 (11)
N3	0.0421 (14)	0.0421 (14)	0.0663 (16)	−0.0008 (11)	0.0170 (11)	−0.0043 (11)
N4	0.0590 (16)	0.0684 (18)	0.0749 (19)	0.0011 (13)	0.0148 (14)	−0.0111 (15)
C1	0.0441 (14)	0.0323 (13)	0.0399 (14)	−0.0006 (11)	0.0101 (11)	−0.0028 (11)
C2	0.0560 (18)	0.0325 (15)	0.0531 (17)	0.0008 (12)	0.0109 (13)	−0.0023 (12)
C3	0.0488 (17)	0.0505 (16)	0.0607 (17)	−0.0050 (14)	0.0149 (13)	0.0007 (14)
C4	0.0496 (16)	0.0406 (15)	0.0646 (18)	0.0044 (13)	0.0174 (13)	−0.0019 (13)
C5	0.0501 (16)	0.0376 (14)	0.0447 (15)	0.0009 (13)	0.0117 (12)	−0.0045 (12)
C6	0.0471 (16)	0.0585 (18)	0.0625 (19)	−0.0012 (13)	0.0206 (14)	−0.0040 (14)
C7	0.0321 (13)	0.0416 (14)	0.0582 (18)	0.0048 (11)	0.0162 (12)	0.0016 (12)
C8	0.0442 (15)	0.0551 (17)	0.0646 (19)	−0.0022 (13)	0.0204 (14)	0.0059 (15)
C9	0.0589 (19)	0.084 (2)	0.056 (2)	0.0091 (17)	0.0214 (16)	0.0066 (17)
C10	0.0530 (18)	0.0444 (16)	0.092 (3)	−0.0008 (14)	0.0204 (17)	−0.0063 (17)
C11	0.0457 (15)	0.0439 (15)	0.0674 (19)	0.0043 (13)	0.0179 (13)	0.0087 (14)

O1—C5	1.225 (3)	C3—H3	0.9300
N1—C4	1.333 (3)	C4—H4	0.9300
N1—C1	1.334 (3)	C6—C7	1.504 (3)
N2—C3	1.332 (3)	C6—H6A	0.9700
N2—C2	1.333 (3)	C6—H6B	0.9700
N3—C5	1.338 (3)	C7—C11	1.379 (3)
N3—C6	1.446 (3)	C7—C8	1.379 (4)
N3—H3N	0.83 (3)	C8—C9	1.369 (4)
N4—C10	1.325 (4)	C8—H8	0.9300
N4—C9	1.337 (4)	C9—H9	0.9300
C1—C2	1.385 (3)	C10—C11	1.381 (4)
C1—C5	1.500 (3)	C10—H10	0.9300
C2—H2	0.9300	C11—H11	0.9300
C3—C4	1.379 (3)
C4—N1—C1	116.2 (2)	N3—C6—C7	112.4 (2)
C3—N2—C2	115.2 (2)	N3—C6—H6A	109.1
C5—N3—C6	124.1 (2)	C7—C6—H6A	109.1
C5—N3—H3N	113.8 (19)	N3—C6—H6B	109.1
C6—N3—H3N	121.9 (19)	C7—C6—H6B	109.1
C10—N4—C9	115.1 (3)	H6A—C6—H6B	107.9
N1—C1—C2	121.3 (2)	C11—C7—C8	116.9 (3)
N1—C1—C5	119.0 (2)	C11—C7—C6	121.2 (2)
C2—C1—C5	119.6 (2)	C8—C7—C6	121.9 (2)
N2—C2—C1	122.8 (2)	C9—C8—C7	119.3 (3)
N2—C2—H2	118.6	C9—C8—H8	120.3
C1—C2—H2	118.6	C7—C8—H8	120.3
N2—C3—C4	122.5 (3)	N4—C9—C8	124.8 (3)
N2—C3—H3	118.7	N4—C9—H9	117.6
C4—C3—H3	118.7	C8—C9—H9	117.6
N1—C4—C3	121.9 (2)	N4—C10—C11	124.4 (3)
N1—C4—H4	119.0	N4—C10—H10	117.8
C3—C4—H4	119.0	C11—C10—H10	117.8
O1—C5—N3	124.2 (2)	C7—C11—C10	119.5 (3)
O1—C5—C1	120.9 (2)	C7—C11—H11	120.3
N3—C5—C1	114.9 (2)	C10—C11—H11	120.3
C4—N1—C1—C2	0.1 (3)	C2—C1—C5—N3	−175.8 (2)
C4—N1—C1—C5	−178.6 (2)	C5—N3—C6—C7	108.0 (3)
C3—N2—C2—C1	0.9 (4)	N3—C6—C7—C11	126.7 (3)
N1—C1—C2—N2	−0.7 (4)	N3—C6—C7—C8	−53.3 (3)
C5—C1—C2—N2	178.0 (2)	C11—C7—C8—C9	0.8 (4)
C2—N2—C3—C4	−0.5 (4)	C6—C7—C8—C9	−179.2 (2)
C1—N1—C4—C3	0.3 (4)	C10—N4—C9—C8	0.0 (4)
N2—C3—C4—N1	−0.1 (4)	C7—C8—C9—N4	−0.3 (4)
C6—N3—C5—O1	0.9 (4)	C9—N4—C10—C11	−0.1 (4)
C6—N3—C5—C1	−179.9 (2)	C8—C7—C11—C10	−0.9 (4)
N1—C1—C5—O1	−177.8 (2)	C6—C7—C11—C10	179.1 (2)
C2—C1—C5—O1	3.4 (4)	N4—C10—C11—C7	0.6 (4)
N1—C1—C5—N3	2.9 (3)

D—H···A	D—H	H···A	D···A	D—H···A
N3—H3N···N1	0.83 (3)	2.27 (3)	2.713 (3)	114 (2)
N3—H3N···N2i	0.83 (3)	2.52 (3)	3.214 (3)	142 (2)
C2—H2···N1ii	0.93	2.47	3.315 (3)	151
C8—H8···O1iii	0.93	2.55	3.373 (3)	148