Hydrogen-bonding landscape of the carbamoyl­cyano­nitro­somethanide anion in the crystal structure of its ammonium salt

The structure of the title salt, ammonium carbamoyl­cyano­nitro­somethanide, NH₄⁺·C₃H₂N₃O₂⁻, features the co-existence of different hydrogen-bonding patterns, which are specific to each of the three functional groups (nitroso, carbamoyl and cyano) of the methanide anion. The nitroso O-atoms accept as many as three N—H⋯O bonds from the ammonium cations [N⋯O = 2.688 (3)–3.000 (3) Å] to form chains of fused rhombs [(NH₄)(O)₂]. The most prominent bonds of the carbamoyl groups are mutual and they yield 2₁ helices [N⋯O = 2.903 (2) Å], whereas the cyano N-atoms accept hydrogen bonds from sterically less accessible carbamoyl H-atoms [N⋯N = 3.004 (3) Å]. Two weaker NH₄⁺⋯O=C bonds [N⋯O = 3.021 (2), 3.017 (2) Å] complete the hydrogen-bonded environment of the carbamoyl groups. A Hirshfeld surface analysis indicates that the most important inter­actions are overwhelmingly O⋯H/H⋯O and N⋯H/H⋯N, in total accounting for 64.1% of the contacts for the individual anions. The relatively simple scheme of these inter­actions allows the delineation of the supra­molecular synthons, which may be applicable to crystal engineering of hydrogen-bonded solids containing polyfunctional methanide anions.

1. Chemical context

Resonance-stabilized methanide-type anions are excellent ligands in metal–organic chemistry, which reveal a variety of coordination modes toward metal ions (Gerasimchuk, 2019; Turner et al., 2011). The rich mol­ecular functionality of such species, as is exemplified by different nitrile-, nitroso- and carbamoyl-substituted derivatives, also predetermines their special properties as potent acceptors of conventional hydrogen bonds. These kinds of inter­actions are important for the solvation and solvatochromism of cyano­anions (Gerasimchuk et al., 2010) and inter­molecular bonding in the crystal structures of metal complexes (Gerasimchuk et al., 2015), but it could also influence the specific targeting of cyano­anions in biomedical systems (Gerasimchuk et al., 2007) and their behavior as anionic components for ionic liquids (Janikowski et al., 2013). It is worth noting that extensive conjugation and charge delocalization within the mol­ecular frameworks support higher electron densities at all three functional sites (Chesman et al., 2014), which is beneficial for stronger and more directional inter­actions. Therefore, methanide-type anions are well suited for the crystal engineering of hydrogen-bonded solids with cationic H-atom donors (Turner et al., 2009).

The specific hydrogen-bonding preferences associated with each of the different functional groups at the methanide core could result in a variety of predictable patterns, as well as providing a degree of selectivity for the inter­actions with hydrogen-bond donors. In this view, structurally similar methanides possess a distinct potential for crystal design. For example, either nitroso or carbamoyl groups equally well complement the cyano groups in methanide systems, but the chemical outputs of such functionalization, represented by closely related [ONC(CN)₂]⁻ and [C(CN)₂(CONH₂)]⁻ anions, are rather different with regard to their hydrogen-bonding behavior. The nitroso groups favor direct inter­actions with hydrogen-bond-donor cations and the assembly of cation/anion pairs (Arulsamy et al., 1999), while the crystal chemistry of carbamoyldi­cyano­methanide is dominated by mutual amide/amide and amide/cyano inter­actions with the generation of less-common anion–anion networks (Turner & Batten, 2010). The particular combination of nitrile, nitroso and carbamoyl groups in carbamoyl­cyano­nitro­somethanide [ONC(CN)(CONH₂)]⁻, which is a well known product of the nucleophylic addition of water to [ONC(CN)₂]⁻ (Arulsamy & Bohle, 2000), presumably allows one to unite the individual structural trends for the two kinds of anions. One can anti­cipate the assembly of such hybrid hydrogen-bonded structures in a predictable fashion, while taking into account the hierarchy of homo- and heterosynthons formed by each of the functional groups and appropriate hydrogen-bond donors.

In the present contribution, we report the construction of a three-dimensional hydrogen-bonded framework in ammonium carbamoyl­cyano­nitro­somethanide NH₄(nccm), which features the co-existence and inter­play of the above-mentioned anion–cation and mutual anion–anion inter­actions.

2. Structural commentary

The mol­ecular structure of the title compound is shown in Fig. 1. This salt is isomorphous with the previously examined Cs analog (Domashevskaya et al., 1989), which is slightly unusual when considering the very different nature and ionic radii of the cations.

Figure 1 The mol­ecular structure of the title compound with displacement ellipsoids drawn at the 50% probability level. Dotted blue lines indicate N—H⋯O hydrogen bonds [symmetry codes: (i) −x, −y, z − ; (ii) −x, −y, z + ].

The main geometries of the (nccm)⁻ (or C₃H₂N₃O₂⁻) anion reveal a highly conjugated structure. The nitroso­cyano­methanide O1/N1/C1/C2/N2 fragment itself is planar within 0.004 Å, being almost coplanar also with the C3/N3/O2 amide fragment [dihedral angle = 3.93 (14)°]. The nitroso group adopts a trans–anti configuration with respect to the carbamoyl C=O group, which is the most favorable either for neutral or anionic ONC(CN)—COR species (Ponomareva et al., 1997; Ponomarova & Domasevitch, 2012). When compared with the parameters for neutral H(nccm) (Arulsamy & Bohle, 2000), the deprotonation results in a perceptible lengthening of the double bonds. For example, the carbonyl O2—C3 bond in the title compound is 1.252 (2) Å versus 1.228 (3) Å for H(nccm), but the same elongation is relevant also to the N1—C1 bond [1.303 (2) Å], which is significantly longer than in the latter case [1.275 (3) Å].

This is accompanied by a shortening of the N1—O1 bonds, which are particularly sensitive to the protolytic effects. These effects can be precisely traced by gradual shortening of the nitroso bonds for the series H(nccm) [1.356 (2) Å; Arulsamy & Bohle, 2000] > H(nccm)₂⁻ in the Rb(18-crown-6)⁺ salt [1.322 (3) Å; Domasevitch et al., 1998] > (nccm)⁻ in the title salt [1.3117 (19) Å] > (nccm)⁻ in the NMe₄⁺ salt [1.293 (2) Å; Izgorodina et al., 2010], in line with the strength of the N—O⋯H bonding. Thus, with relatively strong multiple hydrogen bonds sustained by the nitroso O atoms, the N—O bond order in the title compound is still greater than for the symmetrical hydrogen dioximate anion H(nccm)₂⁻ [which is structurally similar to more common hydrogen carboxyl­ates (Speakman, 1972)], but is lower than in NMe₄(nccm) (one N—H⋯O bond) and also Cs(nccm) [1.297 (8) Å; Domashevskaya et al., 1989] showing only distal ion–dipole inter­actions of the nitroso group. Such an evolution is clearly reflected in the positions of the ν(NO) bands in the IR spectra (cm⁻¹): they are 1098 for H(nccm); 1140 for H(nccm)₂⁻; 1212 for the title compound; 1253 for NMe₄(nccm) and 1290 for Cs(nccm), demonstrating the systematic blue shift as the N—O bond order increases.

3. Supra­molecular features

Beyond Coulombic attraction forces, the primary kinds of inter­actions for the assembly of the present three-dimensional framework are relatively strong and directional N—H⋯O and N—H⋯N hydrogen bonds (Table 1). In spite of the high number of hydrogen-bond donors and their multiple inter­actions with a set of closely separated acceptors of different nature, this directional and well-defined bonding facilitates the identification of supra­molecular synthons. This is reminiscent of the behavior of the methanide analogs in NH₄[C(CN)₂(CONH₂)] and NH₄[ONC(CN)₂] (Arulsamy et al., 1999), but is contrary to the structures of comparable nitro­somalono­amides. For example, ammonium violurate exhibits rather weak and bifurcated hydrogen bonding (Nichol & Clegg, 2007). Also, the cationic ammine in the salt [Ag(NH₃)₂](nccm) (Gerasimchuk et al., 2010) supports only a few weaker and less directional hydrogen bonds.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N4—H3⋯O1	0.89 (2)	2.07 (2)	2.848 (2)	145 (2)
N4—H4⋯O1^i	0.92 (2)	1.78 (2)	2.688 (3)	167 (2)
N4—H5⋯O1^ii	0.89 (2)	2.35 (3)	3.000 (3)	129 (3)
N4—H5⋯O2^iii	0.89 (2)	2.46 (3)	3.021 (2)	122 (3)
N4—H6⋯O2^iv	0.93 (2)	2.19 (2)	3.017 (2)	148 (2)
N3—H1⋯O2^v	0.92 (3)	2.02 (3)	2.903 (2)	161 (2)
N3—H2⋯N2^vi	0.85 (3)	2.24 (3)	3.004 (3)	149 (3)
Symmetry codes: (i) ; (ii) ; (iii) ; (iv) ; (v) ; (vi) .

Both types of O atoms, i.e., the nitroso (O1) and carbamoyl (O2) groups, accept three N—H⋯O bonds. However, their bonding preferences are markedly different. All the bonds with the O1 acceptor are sustained with the NH₄⁺ cations (Fig. 1), but the principal inter­actions with O2 correspond to the mutual amide/amide type. They represent the strongest bond accepted by O2 [N3⋯O2^v = 2.903 (2) Å; N3—H1⋯O^v = 161 (2)°; symmetry code (v) −x, −y + 1, z + ], as compared with two weaker bonds arising from the distal NH₄⁺ cations [N4⋯O2 = 3.017 (2), 3.021 (2) A, Fig. 2, Table 1].

Figure 2 Fragment of the crystal structure showing chains, propagating down the c-axis direction, of ammonium/nitroso rhombs sharing opposite edges [symmetry codes: (i) −x, −y, z − ; (ii) −x, −y, z + ; (viii) x, y, z − 1].

An important result from the multiple NH₄⁺⋯ON inter­actions is the assembly of infinite chains running along the c-axis direction in the crystal, with the [(NH₄)₂(O)₂] rhombs sharing their opposite edges (Fig. 2). Two such N—H⋯O bonds are relatively strong [N⋯O = 2.688 (3) and 2.848 (2) Å, Table 1], whereas N4⋯O1ⁱⁱ [3.000 (3) Å, symmetry code (ii) −x, −y, x + ] exists as a branch of a weaker bifurcated N4—H5⋯(O1,O2) inter­action with the nitroso and carbamoyl acceptors. The present motif is noticeably different from the bonding of NH₄⁺ cations and nitro­sodicyamomethanide, with the ionic pairs assembled via both the O and N atoms of the nitroso groups and only two N—H⋯O inter­actions retained at N⋯O distances of 2.822 (2), 2.881 (2) Å, which are comparable to the two strongest bonds in the title salt (Arulsamy et al., 1999). Such a discrimination of the nitroso N atom in (nccm)⁻ may be attributed to its lower accessibility, which is in line with the higher steric demands of the carbamoyl group. At the same time, one of the carbamoyl H atoms (which is trans-positioned to the C=O bond) is also less accessible and it selectively maintains weaker N—H⋯N bonding to the nitrile acceptor [N3⋯N2^vi = 3.004 (3) Å; symmetry code (vi) x − , −y + , z + 1], very similar to the structure of parent H(nccm) (Arulsamy & Bohle, 2000).

One can suppose that the incorporation of tetra­hedral NH₄⁺ donors itself favors the generation of three-dimensional structures. This is reflected by the formation of one-dimensional helicate motifs as a result of the mutual bonding of the carbamoyl groups (Figs. 3 and 4), instead of the more common amide dimers (McMahon et al., 2005) seen in the NMe₄⁺ salt (Izgorodina et al., 2010) and metal complexes of (nccm)⁻ (Domasevitch et al., 1996). As well, because of the abundance of hydrogen-bond donors, the nitroso O atoms accept auxillary weaker bonds [i.e., N4⋯O1ⁱⁱ = 3.000 (3) Å], which deliver an extension of the anti­cipated discrete pattern based upon single rhombs of [(NH₄)₂(O)₂]. In this view, the hydrogen-bonding preferences of the (nccm)⁻ anion in the title compound could also be applicable to a series of substituted ammonium salts. With fewer N—H donors [NH₄⁺ > RNH₃⁺ > R₂NH₂⁺], the possible thinning of the hydrogen-bond shell may result in the elimination of the weakest of the present inter­actions, such as both NH₄⁺⋯O2 bonds and one of the NH₄⁺⋯O1 bonds. Therefore, three kinds of supra­molecular synthons, in the form of centrosymmetric amide/amide and ammonium/nitroso dimers as well as the nitrile/amide bonding may be particularly prevalent for crystal engineering with the (nccm)⁻ anion (Fig. 5).

Figure 3 Mutual bonding of CONH2 groups, which yields 21 helices propagating along the c-axis direction. Stacking inter­actions [e.g. N2⋯C1^viii] are indicated with thin lines [symmetry codes: (v) −x, −y + 1, z + ; (vii) −x, −y + 1, − + z; (viii) x, y, z − 1].

Figure 4 Structure of the title compound, viewed in a projection onto the ab plane, showing the co-existence and inter­play of the three main supra­molecular motifs in the form of ammonium/nitroso chains, amide/amide chains (both of which are situated across 21 axes and are orthogonal to the drawing plane) and amide–nitrile mutual bonding [symmetry codes: (iv) −x + , y − , z − ; (v) −x, −y + 1, z + ; (ix) x + , −y + , z].

Figure 5 The hydrogen-bonding capacity of the (nccm)^− anion. (a) Two kinds of mutual inter­actions marked in black and red and bonding with NH4^+ cations marked in blue; (b–d) three types of supra­molecular synthons identified for the the title compound taking into account a set of strongest inter­actions: ammonium/nitroso chain (b), amide/amide chains (c) and mutual amide/nitrile bonding (d).

The columnar packing of (nccm)⁻ anions yields slipped stacks down the c-axis direction, with an inter­planar distance of 3.32 Å (Figs. 2 and 3). This feature is similar to the structures of cyano­methanide species examined by Chesman et al. (2014), which typically support stacks at 3.15–3.30 Å. However, the overlaps of the (nccm)⁻ skeletons are minor [as indicated by a large slippage angle of 54.9 (2)°] and actually only the nitrile fragment is involved in the stacking with the methanide fragment. The shortest contact between translation-related anions is N2⋯C1^viii = 3.357 (2) Å [symmetry code: (viii) x, y, z – 1]. This stacking is less significant for (nccm)⁻ salts due to the prevalent role of hydrogen bonding, which is a primary anion–anion inter­action for carbamoyl-substituted methanides (Chesman et al., 2014).

4. Hirshfeld analysis

The supra­molecular inter­actions in the title structure were further investigated by Hirshfeld surface analysis (Spackman & Byrom, 1997; McKinnon et al., 2004; Hirshfeld, 1977; Spackman & McKinnon, 2002) performed with CrystalExplorer17 (Turner et al., 2017). The Hirshfeld surface of the individual (nccm)⁻ anion mapped over d_norm, using a fixed color scale of −0.71 (red) to 1.05 a.u. (blue), reveals a set of red spots associated with the inter­action sites (Fig. 6). The most intense spot (−0.708 a.u.) reflects the very short NH₄⁺-O-nitroso bond, whereas a group of six almost equally prominent spots (−0.393 to −0.519 a.u.) correspond to the mutual amide/amide, amide/nitrile, one NH₄⁺-O-nitroso and one NH₄⁺-O-carbamoyl bonds. A third spot in the region of the nitroso-O acceptor is less intense (−0.288 a.u.), while the additional NH₄⁺—O-carbamoyl bond has only a minor indication of −0.081 a.u.

Figure 6 The Hirshfeld surface of the (nccm)^− anion mapped over dnorm in the color range −0.71 (red) to 1.05 a.u. (blue), in the environment of the hydrogen-bonded ammonium cations and one (out of three) (nccm)^− anion.

The two-dimensional fingerprint plots (Fig. 7) are consistent with the prevalence of hydrogen bonding in the structure. For the individual NH₄⁺ cations, as much as 57.3% of their surface are H⋯O contacts. The H⋯N contacts account for only 20.1% (H⋯H and H⋯C are 20.1% and 2.5%, respectively), which suggests a rather high selectivity in the bonding of NH₄⁺ cations to the O-acceptor sites. The plots for the anion are even more informative. The short separations are overwhelmingly hydrogen-bond contacts, accounting for 64.1% of the surface. The O⋯H/H⋯O fraction of 34.5% appears on the plot as a pair of sharp spikes pointing to the lower left, with the upper spike representing entirely H⋯O of the amide/amide synthon (the shortest contact is 2.0 Å), while the more intense and longer lower spike is due to a reciprocal O⋯H bond superimposed with points from stronger and more numerous O⋯H (NH₄⁺) contacts (the shortest is 1.7 Å). In the case of N⋯H/H⋯N type (29.6%), two spikes are shorter (2.2 Å) and nearly symmetrical, indicating the mutual character of this weaker bonding. Although the C⋯H/H⋯C contacts of the anion (9.0%) are mostly mutual, the plot also features a small but relatively sharp spike from C⋯NH₄⁺ contacts (2.8 Å), which has a complementary donor part at the plot for individual NH₄⁺ cations (not shown here). This very distal inter­action may be rationalized as an NH⋯π(C≡N) bond, with the distances N4⋯Cg(C2≡N2) = 3.584 (3); H⋯Cg(C2≡N2) = 2.89 (3) Å and N4H⋯Cg(C2≡N2) = 136 (3)° (Cg is the mid-point of the C2—N2 bond). A similar contact was observed for NH₄{ONC(CN)₂} (Arulsamy et al., 1999). Stacking inter­actions in the title compound are also important. They contribute in total 18.8% of the contacts represented by the N⋯C/C⋯N, N⋯N, C⋯C and N⋯O/O⋯N types, all of which have a very similar nature and metrics (the shortest is N⋯C = 3.3 Å). In summary, the results of Hirshfeld surface analysis effectively illustrate the predominant roles of multiple ammonium/nitroso, mutual amide/amide and amide-nitrile inter­actions as the main supra­molecular synthons.

Figure 7 Two-dimensional fingerprint plots for the anions of the title compound, and delineated into the principal contributions of O⋯H/H⋯O, N⋯H/H⋯N, C⋯H/H⋯C, H⋯H, N⋯C/C⋯N, N⋯N, C⋯C and N⋯O/O⋯N contacts. Other minor contributors are C⋯O/O⋯C contacts (0.3%).

5. Synthesis and crystallization

The 2-cyano-2-iso­nitro­soacetamide H(nccm) was prepared by nitro­sation of cyano­acetamide (Gerasimchuk et al., 2010). It is a relatively weak acid (pK_α = 5.03; Klaus et al., 2015) and therefore the compound NH₄(nccm) is unstable, readily losing ammonia in air within a period of several days. When slowly evaporated, its aqueous or methano­lic solutions lose ammonia first and then H(nccm) crystallizes.

For the preparation of the title compound, 0.339 g of H(nccm) (3 mmol) was dissolved in 10 ml of methanol at 303–313 K and 0.6 ml of 25% aqueous ammonia (8 mmol) were added to form a clear pale-yellow solution. It was placed, in an open vial, inside the larger stoppered flask containing mixture of 50 ml of 2-propanol and 1 ml of 25% aqueous ammonia. Slow inter­diffusion of the solvents through the gaseous phase resulted in the precipitation of large pale-yellow NH₄(nccm) crystals over a period of 30 d. The yield was 0.250 g (64%). Analysis (%) calculated for C₃H₆N₄O₂: C 27.69, H 4.65, N 43.07; found: C 28.01, H 4. 85, N 42.68. IR (KBr, cm⁻¹): 500 w, 668 s, 766 m, 1022 s, 1092 s, 1144 s, 1172 s, 1212 s, 1402 s, 1600 s, 1686 vs, 2218 m, 3170 br, 3302 br, 3450 s.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. All hydrogen atoms were located and then refined isotropically. Soft similarity restraints were applied to four N—H bond lengths and six H—N—H bond angles of the ammonium cations.

Table 2
Experimental details

Crystal data
Chemical formula	NH4^+·C3H2N3O2^−
Mr	130.12
Crystal system, space group	Orthorhombic, Pna21
Temperature (K)	173
a, b, c (Å)	10.7174 (5), 13.8944 (7), 4.0643 (2)
V (Å^3)	605.22 (5)
Z	4
Radiation type	Mo Kα
μ (mm^−1)	0.12
Crystal size (mm)	0.37 × 0.30 × 0.21
Data collection
Diffractometer	Bruker APEXII CCD
No. of measured, independent and observed [I > 2σ(I)] reflections	7798, 1420, 1304
Rint	0.031
(sin θ/λ)max (Å^−1)	0.663
Refinement
R[F^2 > 2σ(F^2)], wR(F^2), S	0.032, 0.081, 1.10
No. of reflections	1420
No. of parameters	106
No. of restraints	22
H-atom treatment	All H-atom parameters refined
Δρmax, Δρmin (e Å^−3)	0.19, −0.14
Computer programs: SMART-NT (Bruker, 1998), SAINT-NT (Bruker, 1999), SHELXS97 (Sheldrick, 2008), SHELXL2014/7 (Sheldrick, 2015), DIAMOND (Brandenburg, 1999) and WinGX (Farrugia, 2012).

Supporting information

Computing details

Data collection: SMART-NT (Bruker, 1998); cell refinement: SAINT-NT (Bruker, 1999); data reduction: SAINT-NT (Bruker, 1999); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2015); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: WinGX (Farrugia, 2012).

Ammonium carbamoyl(cyano)(nitroso)methanide

Crystal data

NH4^+·C3H2N3O2^−	Dx = 1.428 Mg m^−3
Mr = 130.12	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pna21	Cell parameters from 2828 reflections
a = 10.7174 (5) Å	θ = 2.4–25.3°
b = 13.8944 (7) Å	µ = 0.12 mm^−1
c = 4.0643 (2) Å	T = 173 K
V = 605.22 (5) Å^3	Prism, yellow
Z = 4	0.37 × 0.30 × 0.21 mm
F(000) = 272

Data collection

Bruker APEXII CCD diffractometer	1304 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.031
Graphite monochromator	θmax = 28.1°, θmin = 2.4°
φ and ω scans	h = −14→14
7798 measured reflections	k = −18→18
1420 independent reflections	l = −5→5

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.032	Hydrogen site location: difference Fourier map
wR(F^2) = 0.081	All H-atom parameters refined
S = 1.10	w = 1/[σ^2(Fo^2) + (0.0439P)^2 + 0.0604P] where P = (Fo^2 + 2Fc^2)/3
1420 reflections	(Δ/σ)max < 0.001
106 parameters	Δρmax = 0.19 e Å^−3
22 restraints	Δρmin = −0.14 e Å^−3

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
O1	−0.01669 (13)	0.10947 (9)	0.7570 (4)	0.0365 (4)
O2	0.12729 (11)	0.42081 (9)	0.7040 (4)	0.0306 (3)
N1	−0.02966 (14)	0.20089 (10)	0.8299 (5)	0.0285 (4)
N2	0.23276 (19)	0.19606 (15)	0.3518 (6)	0.0472 (5)
N3	−0.05305 (16)	0.38965 (12)	0.9758 (5)	0.0319 (4)
N4	0.17308 (17)	−0.03313 (12)	0.7032 (5)	0.0367 (4)
C1	0.05333 (15)	0.25999 (12)	0.7110 (5)	0.0242 (4)
C2	0.15514 (18)	0.22726 (14)	0.5109 (6)	0.0301 (4)
C3	0.04438 (16)	0.36355 (12)	0.7975 (5)	0.0243 (4)
H1	−0.057 (2)	0.4525 (18)	1.043 (8)	0.045 (7)*
H2	−0.104 (3)	0.346 (2)	1.039 (8)	0.054 (8)*
H3	0.1437 (19)	0.0263 (14)	0.727 (7)	0.046 (7)*
H4	0.125 (2)	−0.0681 (17)	0.557 (6)	0.052 (8)*
H5	0.177 (3)	−0.066 (2)	0.891 (7)	0.15 (2)*
H6	0.251 (2)	−0.0308 (18)	0.605 (7)	0.068 (10)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0414 (8)	0.0202 (6)	0.0479 (11)	−0.0014 (5)	0.0053 (8)	−0.0033 (6)
O2	0.0263 (6)	0.0245 (6)	0.0410 (8)	−0.0038 (5)	0.0026 (6)	0.0051 (6)
N1	0.0318 (8)	0.0209 (7)	0.0329 (9)	−0.0005 (6)	0.0012 (7)	−0.0016 (7)
N2	0.0415 (10)	0.0541 (11)	0.0459 (13)	0.0128 (8)	0.0116 (10)	−0.0012 (9)
N3	0.0315 (8)	0.0215 (8)	0.0427 (11)	−0.0039 (6)	0.0089 (8)	−0.0041 (7)
N4	0.0406 (9)	0.0299 (8)	0.0396 (10)	0.0044 (7)	−0.0045 (10)	−0.0042 (9)
C1	0.0248 (8)	0.0222 (8)	0.0256 (8)	0.0024 (6)	−0.0012 (8)	0.0010 (7)
C2	0.0298 (9)	0.0287 (9)	0.0318 (10)	0.0030 (7)	0.0013 (9)	0.0043 (8)
C3	0.0234 (8)	0.0224 (8)	0.0270 (10)	−0.0008 (6)	−0.0034 (7)	0.0027 (7)

Geometric parameters (Å, º)

O1—N1	1.3117 (19)	N4—H3	0.89 (2)
O2—C3	1.252 (2)	N4—H4	0.924 (19)
N1—C1	1.303 (2)	N4—H5	0.89 (2)
N2—C2	1.140 (3)	N4—H6	0.93 (2)
N3—C3	1.322 (3)	C1—C2	1.435 (3)
N3—H1	0.92 (3)	C1—C3	1.484 (2)
N3—H2	0.85 (3)
C1—N1—O1	117.00 (15)	H5—N4—H6	110 (2)
C3—N3—H1	117.6 (17)	N1—C1—C2	121.97 (16)
C3—N3—H2	118 (2)	N1—C1—C3	118.61 (16)
H1—N3—H2	124 (3)	C2—C1—C3	119.38 (15)
H3—N4—H4	111.2 (17)	N2—C2—C1	176.0 (2)
H3—N4—H5	114 (2)	O2—C3—N3	123.56 (17)
H4—N4—H5	108 (2)	O2—C3—C1	119.90 (16)
H3—N4—H6	109.6 (18)	N3—C3—C1	116.54 (15)
H4—N4—H6	104.0 (17)
O1—N1—C1—C2	−0.4 (3)	C2—C1—C3—O2	−2.1 (3)
O1—N1—C1—C3	−177.92 (16)	N1—C1—C3—N3	−4.0 (3)
N1—C1—C3—O2	175.4 (2)	C2—C1—C3—N3	178.45 (19)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N4—H3···O1	0.89 (2)	2.07 (2)	2.848 (2)	145 (2)
N4—H4···O1^i	0.92 (2)	1.78 (2)	2.688 (3)	167 (2)
N4—H5···O1^ii	0.89 (2)	2.35 (3)	3.000 (3)	129 (3)
N4—H5···O2^iii	0.89 (2)	2.46 (3)	3.021 (2)	122 (3)
N4—H6···O2^iv	0.93 (2)	2.19 (2)	3.017 (2)	148 (2)
N3—H1···O2^v	0.92 (3)	2.02 (3)	2.903 (2)	161 (2)
N3—H2···N2^vi	0.85 (3)	2.24 (3)	3.004 (3)	149 (3)

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