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In the title compounds, C7H6ClN2O+·NO3 and C7H6ClN2O+·ClO4, the ions are connected by N—H...O hydrogen bonds and halogen inter­actions. Additionally, in the first compound, co-operative π–π stacking and halogen...π inter­actions are observed. The energies of the observed inter­actions range from a value typical for very weak inter­actions (1.80 kJ mol−1) to one typical for mildly strong inter­actions (53.01 kJ mol−1). The iminium cations exist in an equilibrium form inter­mediate between exo- and endocyclic. This study provides structural insights relevant to the biochemical activity of 2-amino-5-chloro-1,3-benzoxazole compounds.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270110029008/gd3352sup1.cif
Contains datablocks global, I, II

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270110029008/gd3352Isup2.hkl
Contains datablock I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270110029008/gd3352IIsup3.hkl
Contains datablock II

CCDC references: 796073; 796074

Comment top

Benzoxazole derivatives are important heterocyclic compounds that exhibit biological activities, including antitumour, antibacterial, DNA-damaging genotoxic and antiviral properties (Sum et al., 2003; Oksuzoglu et al., 2007; Tekiner-Gulbas et al., 2007; Jauhari et al., 2008). Recently, a novel series of benzoxazole derivatives have been developed as 5-HT3 receptor partial agonists for the treatment of diarrhoea-predominant irritable bowel syndrome (Yoshida et al., 2005). Among them, the 2-substituted benzoxazole 2-amino-5-chloro-1,3-benzoxazole (2-abox) was found to be very active as a uricosuric and muscle relaxant, but the molecular and cellular mechanisms of action are not understood (McMillen et al., 1992; Cao et al., 2001; Liu et al., 2003). Although its side effects limit its pharmaceutical usefulness, 2-abox has been used extensively in pre-clinical biological modelling studies, as a benchmark standard or as a model substrate for enzyme-catalysed oxidation (Wei et al., 2000). Since the target binding site is unknown, studies of the bonding properties of 2-abox itself can be crucial for the design of new muscle-relaxant drugs.

In the Cambridge Structural Database (CSD, Version 5.30; Allen, 2002), five 2-abox adducts were found with organic compounds containing a carboxylic acid or carboxylate moiety (Lynch, Daly & Parsons, 2000; Lynch, Singh & Parsons, 2000; Lynch et al., 2003), and two of these are proton-transfer salts. There are as yet no examples of the incorporation of this benzoxazole into salts with inorganic acids. As protonation is a common process occurring in physiological systems, and almost all drugs or bioactive molecules undergo protonation before they enter the reaction chain, knowledge of long-range interactions such as ion pairing might be helpful in the design of new drugs. In this context, the synthesis of 2-abox adducts with inorganic acids is of interest. Hence, the solid-state characterization of 2-amino-5-chloro-1,3-benzoxazol-3-ium nitrate, (I), and 2-amino-5-chloro-1,3-benzoxazol-3-ium perchlorate, (II), as well as the results of quantum mechanical calculations, are reported here.

The asymmetric units of (I) and (II) contain an inorganic anion acting as counterion, balancing the charge of the 2-amino-5-chlorobenzoxazolium cation (Figs. 1 and 2). The 2-amino-5-chlorobenzoxazolium cation is close to planarity, with maximum deviations from the weighted least-squares plane calculated for its all non-H atoms of 0.0434 (15) and 0.0119 (12) Å for atoms N2, for (I) and (II), respectively. The weighted least-squares plane defined by the atoms of the nitrate group in (I), with a maximum deviation of 0.0063 (15) Å for atom N3, is inclined at 10.30 (10)° to the plane of the cation. The bond lengths and angles (Tables 1 and 2) in the 2-amino-5-chlorobenzoxazolium cations are consistent with those in pure 2-abox (Lynch, 2004), except for the C—N and C—O distances. The C1—N2 and C1—O1 bonds are shortened [by 0.040 (3) and 0.035 (2) Å, respectively, for (I), and by 0.039 (3) and 0.035 (2) Å, respectively, for (II)], while the C1—N1 bonds are elongated by 0.021 (3) and 0.018 Å, respectively, for (I) and (II), compared with 2-abox. Similar effects can be observed for 2-abox adducts or salts with organic compounds (Lynch, Daly, & Parsons, 2000; Lynch, Singh & Parsons, 2000; Lynch et al., 2003). This lengthening (compared with 2-abox) observed in (I) and (II) is caused by protonation of the endocyclic N atom of the five-membered heterocyclic ring, together with the strong hydrogen-bond acceptor properties of the O atoms of the anion involved in intermolecular Nendocyclic—H···O hydrogen bonds. In 2-abox, this endocyclic N atom acts as a hydrogen-bond acceptor in intermolecular N—H···N hydrogen bonds. For similar 2-aminoheterocyclic compounds, shortening of the exocyclic C—N bond (compared with 2-abox) has been explained by the attraction of a more electron-accepting heterocyclic ring (Lynch & Jones, 2004). This suggests the delocalization of electron density and in consequence delocalization of the positive charge over the HN—C—NH2 moiety. Such exocyclic imines or iminium ions in equilibrium with endocyclic ones have previously been found and discussed for other compounds containing the NexoCNendo group (Lynch & Jones, 2004; Low et al., 2003; Donga et al., 2002; Trzesowska-Kruszynska & Kruszynski, 2009; Kruszynski & Trzesowska-Kruszynska, 2009).

The ions in (I) and (II) are linked by hydrogen bonds, ππ stacking and halogen interactions. The crystal structure of (I) is stabilized by amine–nitrate N—H···O hydrogen bonds (Table 3), which form an N2 = R12(4)R12(4)R21(6)[C21(6)C22(6)C22(6)] basic graph set (Bernstein et al., 1995), and in consequence form hydrogen-bonded chains along the [100] axis (Fig. 3). Noteworthy is the fact that one second-level R12(4) and one second-level R21(6) basic motifs create a binary R22(8) complex graph. The phenyl rings and nitrate anions of successive hydrogen-bonded chains are interlinked by C—H···O interactions, so forming a folded two-dimensional net parallel to (001).

As in (I), so in (II) the N—H···O hydrogen bonds create finite D motifs in terms of unitary level graphs, but on the second level the motifs are more complicated and can be expressed by an N2 = R12(4)R22(8)D[C12(4)C22(6)D][R12(4)C22(8)D] descriptor of basic graph set or, simplifying, as an N2 = C12(4)C23(12) complex graph set. The N—H···O hydrogen bonds expand the ions of (II) into a folded two-dimensional net along the (010) plane. Thus, the change from a planar nitrate group to a tetrahedral perchlorate group leads to an elaboration of the N—H···O hydrogen-bonded chain in (I) to the hydrogen-bonded net of (II), accompanied by more complex graph-set motifs.

In (I), ππ stacking interactions (Hunter & Sanders, 1990) can be observed (Table 3) between benzene rings, parallel by symmetry, of adjacent 2-amino-5-chlorobenzoxazolium ions oriented in opposite directions (Fig. 4). In this way a ππ stacked pile along the [001] axis is created. In one of the above-mentioned arrangements of interacting cations [that in which the cations are related by an inversion centre at (1/2, 1/2, 1/2)], the Cl atom is situated almost above the oxazolium ring centroid (Fig. 4), at a distance of 3.411 (3) Å, with an angle between the vector linking the ring centroid and atom Cl1 of 86.07 (2)° and a distance between the oxazolium ring plane and atom Cl1 of 3.403 Å. This contact can be considered a bonding interaction, since the Cl···π distance fulfils the criterion (Schottel et al., 2008; Imai et al., 2008) of being shorter than the sum of the Cl and C van der Waals radii (3.45 Å; Bondi, 1964). This suggests that ππ stacking interactions have a synergetic effect on forming halogen···π interactions. Usually, the existence of other cooperative interactions is required to create a weaker halogen···π contact (Escudero et al., 2009; Imai et al., 2008). There are short contacts between the cations of (II), but the possibility of ππ interactions was rejected on geometric grounds (neighbouring aromatic/delocalized bonds do not overlap sufficiently). Despite the fact that the Cl atom in (II) is situated almost above the phenyl ring centroid, the possibility of a Cl···π contact was rejected on the basis of too long a Cl···π distance, larger than the sum of the Cl and C van der Waals radii.

An interesting feature of the structures of (I) and (II) is the presence of halogen interactions. There is short intermolecular C6—Cl1···O3viii N3viii contact [Fig. 3; symmetry code: (viii) -x, y + 1/2, -z + 1/2] of 2.989 (2) Å, shorter than the sum of the van der Waals radii (3.27 Å; Bondi, 1964), with a C6—Cl1···O3viii angle of 176.1 (2)° in (I). In (II), the similar C6—Cl1···O5ixCl2ix contact [symmetry code: (ix) -x + 2, y - 1/2, -z + 1/2] is slightly longer [3.152 (2) Å] and the C6—Cl1···O5ix angle is smaller [165.2 (2)°]. A search of the CSD yielded nine compounds containing the chlorophenyl moiety in close contact with the O atom of the nitrate ion. The average intermolecular Cl···O distance from 11 hits is 3.16 (7) Å, slightly longer than that observed in (I). An analogous search carried out for a chlorophenyl moiety and a perchlorate ion gives 40 compounds, with 44 interactions and a mean distance of 3.14 (2) Å, which is the same as that in (II), within experimental error. In the other known 2-abox adducts or salts with organic compounds (Lynch, Daly & Parsons, 2000; Lynch, Singh & Parsons, 2000; Lynch et al., 2003), the Cl atom is either involved in hydrogen bonding or it forms Cl···Cl contacts, but Cl···O contacts were not observed.

The CSD was also searched for all intermolecular C—Cl···O(N) and C—Cl···O(Cl) contacts shorter than 3.27 Å (sum of the van der Waals radii; Bondi, 1964). The most common acceptor of halogen bonds is the O atom of the nitrate or perchlorate group, respectively. The number of reported Cl···O interactions decreases rapidly as the Cl···O distance shortens below 3.0 Å. Less than 5% of Cl···O interactions can be considered as relatively strong. The C—Cl···O and Cl···O(N/Cl) angles adopt values in the range 70–180°, with a single maximum of 165° for the C—Cl···O angle and multiple maxima in the range 100–170° for the Cl···O(N/Cl) angles. Examination of two-dimensional contour plots of angles versus distances reveals between one and four preferred distance–angle pairs (Fig. 5), with the most populated maxima at 3.143 Å and 163.5°, 3.152 Å and 139.4°, 3.177 Å and 165.6°, and 3.174 Å and 163.4° for Cl···O distances and C—Cl···ON, Cl···O(N), C—Cl···OCl and Cl···O(Cl) angles, respectively. The distances in (I) and (II) are shorter and the angles are larger than the most preferred ones.

The molecular electronic properties have been calculated [for (I) and (II)?] at a single point for both the diffraction-derived coordinates and the optimized structures, and these are comparable within three standard deviations, although the geometrically optimized molecules show typical elongation of the C—H bonds (0.15–0.21 Å). The total binding energies of the intermolecular interactions were calculated for molecular sets containing from one to four cation–anion pairs. The cation and anion of each pair were arranged as in the hydrogen-bonded sheets, along the halogen bonds and in the ππ stacking interactions. In order to estimate the energy of the electrostatic interactions between the anions and cations, additional computations were performed for subsets containing an odd number of cations and anions. Basis-set superposition error (BSSE) corrections were carried out using the counterpoise (CP) method (Boys & Bernardi,1970). The B3LYP functional (Becke, 1993; Lee et al., 1988) in the triple-ζ 6-311++G(3df,2p) basis set was used, as implemented in GAUSSIAN03 (Frisch et al., 2004). In all cases, the differences in electronic properties and energies originating from the different numbers of cation–anion pairs used in the calculation, and the differences between the various methods described above, are given in parentheses as standard deviations of the mean values. Where a deviation is not given, the values were the same within their range of reported precision.

As expected, the cations and anions of (I) and (II) are attracted by strong electrostatic interactions with very large binding energies of 337.23 and 344.34 kJ mol-1, respectively. The energy of the ππ stacking interaction between the 2-abox cations of (I) related by the inversion centre at (1/2, 1/2, 0), as calculated by the total self-consistent field-energy method, proves that this interaction has antibonding character (excluding the dispersion energy). The cooperative effect of the ππ stacking and halogen···π interactions between 2-abox cations related by the symmetry operator (-x + 1, -y + 1, -z + 1) is manifested by the larger value of the total binding energy, which is 3.56 (4) kJ mol-1. The energies of the Cl···O intermolecular interactions are 15.48 (8) and 6.28 (4) kJ mol-1, respectively, for (I) and (II), which is in accordance with the energies of intermolecular halogen bonds present in small molecules (Allen et al., 1997; Zou et al., 2005; Kruszynski, 2007).

Previously, it was postulated that an electric attraction exists between the N—Cl and OC groups of N-chlorosuccinimide, due to polarization of these groups (Brown, 1961), Nδ-—Clδ+···Oδ- Cδ+, and such a model of polarization was confirmed for 1,3-dibromo-5,5-dimethyl-2,4-imidazolidinedione (Kruszynski, 2007). Analysis of the atomic charges based on the Breneman radii (Breneman & Wiberg, 1990) shows that similar polarization also exists for (I) and (II). The C-bonded Cl atoms have a partial charge of 0.011 (5) A.U. for both studied compounds, and the aromatic ring C atoms are negatively charged. The anion O atoms have mean charges of -0.72 and -0.60 A.U., respectively, for NO3- and ClO4-, and the N and Cl atoms of the anions have charges of 1.20 (3) and 1.41 (1) A.U., respectively. The positive charge located on the Cl atom is relatively small but, combined with the large negative charge present on the O atoms of the anions, Cl···O interactions are electrostatically permitted.

The results of the quantum-mechanical calculations indicate that stronger hydrogen bonds are more attractive than halogen bonds. The values of the hydrogen-bond energies lie in ranges typical for similar hydrogen bonds (Desiraju & Steiner, 1999). The total energy of three N—H···O hydrogen bonds formed between a 2-abox cation and a nitrate ion (Fig. 1, Table 2) is 56.10 (8) kJ mol-1, whereas the total energy of those formed between a cation and anion related by the symmetry operator (x + 1, y, z) is 41.84 (8) kJ mol-1. As expected, the C—H···O hydrogen-bond energy is small (Table 3) and comparable with those for small-angle N—H···O hydrogen bonds. In general, bonds with very similar geometry are stronger in (II) than in (I), suggesting that the topology of the electron-density distribution in the anion significantly influences the strength of the hydrogen bonds.

The non-covalent nature of the intermolecular interactions in (I) and (II) was analysed using the natural bond orbital (NBO) method (Foster & Weinhold, 1980; Reed & Weinhold, 1985; Reed et al., 1988). In this method, the strength of the donor–acceptor charge-transfer delocalization is characterized by the second-order stabilization energy, Edel. For halogen bonds, the principal charge-transfer interactions occur between the O-atom lone pairs and the antibonding orbitals of the C—Cl bond [Edel = 12.89 (3) and 5.69 kJ mol-1, respectively, for (I) and(II)], and lateral charge-transfer interactions occur between the O-atom lone pairs and the one-centre Rydberg orbitals of the Cl atom. A similar scheme is observed for the hydrogen bonds: the hydrogen-bond acceptor lone pairs donate their lone-pair electron density primarily to the antibonding orbitals of the hydrogen-bond donor and secondarily to the Rydberg orbitals of the H atom. The origins of the observed stacking (based on NBO calculations) are the interactions of the delocalized molecular π orbitals of one molecule with the delocalized antibonding molecular π orbitals and antibonding molecular σ orbital created between the C atoms of the second aromatic ring, and vice versa. The interactions with the antibonding molecular σ orbitals contribute a larger proportion (about 70%) of the total intermolecular binding energy than those with the delocalized antibonding molecular π orbitals. This confirms the generally accepted model of stacking interactions, which postulates that the interactions appear when attractive interactions between π electrons and the σ framework outweigh unfavourable contributions such as π-electron repulsion (Hunter & Sanders, 1990).

Related literature top

For related literature, see: Allen (2002); Allen et al. (1997); Becke (1993); Bernstein et al. (1995); Bondi (1964); Boys & Bernardi (1970); Breneman & Wiberg (1990); Brown (1961); Cao et al. (2001); Desiraju & Steiner (1999); Donga et al. (2002); Escudero et al. (2009); Foster & Weinhold (1980); Frisch (2004); Hunter & Sanders (1990); Imai et al. (2008); Jauhari et al. (2008); Kruszynski (2007); Kruszynski & Trzesowska-Kruszynska (2009); Lee et al. (1988); Liu et al. (2003); Low et al. (2003); Lynch (2004); Lynch & Jones (2004); Lynch et al. (2003); Lynch, Daly & Parsons (2000); Lynch, Singh & Parsons (2000); McMillen et al. (1992); Oksuzoglu et al. (2007); Reed & Weinhold (1985); Reed et al. (1988); Schottel et al. (2008); Sum et al. (2003); Tekiner-Gulbas, Temiz-Arpaci, Yildiz & Altanlar (2007); Trzesowska-Kruszynska & Kruszynski (2009); Wei et al. (2000); Yoshida et al. (2005); Zou et al. (2005).

Experimental top

A hot ethanolic solution (4 ml) of 2-amino-5-chloro-1,3-benzoxazole (0.150 g, 1 mmol) was mixed with either 65% nitric acid (5 ml) for (I), or 60% perchloric acid for (II). The resulting solutions were allowed to cool to room temperature and, after several days, orange crystals of (I) and dark-red crystals of (II) suitable for X-ray diffraction were isolated in yields of 69 and 78%, respectively.

Refinement top

H atoms bonded to C atoms were treated as riding atoms in calculated positions, with C—H = 0.93 Å and Uiso(H) = 1.2Ueq(C). H atoms bonded to N atoms were located in difference maps and then permitted to ride at the positions deduced from the difference maps, with Uiso(H) = 1.2Ueq(N), giving the N—H distances shown in Table 3.

Computing details top

For both compounds, data collection: CrysAlis CCD (UNIL IC & Kuma 2000); cell refinement: CrysAlis RED (UNIL IC & Kuma 2000); data reduction: CrysAlis RED (UNIL IC & Kuma 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP in SHELXTL/PC (Sheldrick, 2008) and ORTEP-3 for Windows (Version 1.062; Farrugia 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top
[Figure 1] Fig. 1. A view of the asymmetric unit of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as spheres of arbitrary radii. Hydrogen bonds are indicated by dashed lines.
[Figure 2] Fig. 2. A view of the asymmetric unit of (II), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as spheres of arbitrary radii. Hydrogen bonds are indicated by dashed lines.
[Figure 3] Fig. 3. Part of the molecular packing of (I), showing the N—H···O hydrogen bonds and Cl···O halogen interactions (dashed lines). H atoms not involved in intermolecular interactions have been omitted for clarity. [Symmetry codes: (i) x + 1, y, z; (ii) -x, y + 1/2, -z + 1/2; (iii) -x, y - 1/2, -z + 1/2; (iv) x - 1, y, z.]
[Figure 4] Fig. 4. Part of the molecular packing of (II), showing the N—H···O hydrogen bonds as dashed lines. H atoms not involved in intermolecular interactions have been omitted for clarity. [Symmetry codes: (i) x, -y + 1/2, z - 1/2; (ii) x - 1, y, z.]
[Figure 5] Fig. 5. Part of the molecular packing of (I), showing the Cl···π and ππ stacking interactions (dashed lines) between 2-amino-5-chlorobenzoxazolium cations. H atoms have been omitted for clarity. [Symmetry codes: (i) -x + 1, -y + 1, -z + 1; (ii) -x + 1, -y + 1, -z.]
[Figure 6] Fig. 6. Contour plots, showing the relationship between the C—Cl···O or Cl···O(N/Cl) angles and the Cl···O distances, (a), (b) for (I), and (c), (d) for (II). The values for (I) or (II) are indicated by asterisks and the contours are frequency of occurrence.
(I) 2-amino-5-chloro-1,3-benzoxazol-3-ium nitrate top
Crystal data top
C7H6ClN2O+·NO3F(000) = 472
Mr = 231.60Dx = 1.647 Mg m3
Dm = 1.65 Mg m3
Dm measured by Berman density torsion balance
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 5086 reflections
a = 6.8900 (9) Åθ = 2–25°
b = 20.3139 (18) ŵ = 0.41 mm1
c = 7.2562 (10) ÅT = 291 K
β = 113.138 (9)°Prism, orange
V = 933.9 (2) Å30.11 × 0.09 × 0.08 mm
Z = 4
Data collection top
Kuma KM4 CCD area-detector
diffractometer
1642 independent reflections
Radiation source: fine-focus sealed tube1593 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.017
Detector resolution: 1048576 pixels mm-1θmax = 25.0°, θmin = 2.0°
ω scansh = 88
Absorption correction: numerical
(X-RED; Stoe & Cie, 1999)
k = 2424
Tmin = 0.955, Tmax = 0.968l = 88
12495 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.035Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.091H-atom parameters constrained
S = 1.17 w = 1/[σ2(Fo2) + (0.0385P)2 + 0.4685P]
where P = (Fo2 + 2Fc2)/3
1642 reflections(Δ/σ)max < 0.001
136 parametersΔρmax = 0.26 e Å3
0 restraintsΔρmin = 0.18 e Å3
Crystal data top
C7H6ClN2O+·NO3V = 933.9 (2) Å3
Mr = 231.60Z = 4
Monoclinic, P21/cMo Kα radiation
a = 6.8900 (9) ŵ = 0.41 mm1
b = 20.3139 (18) ÅT = 291 K
c = 7.2562 (10) Å0.11 × 0.09 × 0.08 mm
β = 113.138 (9)°
Data collection top
Kuma KM4 CCD area-detector
diffractometer
1642 independent reflections
Absorption correction: numerical
(X-RED; Stoe & Cie, 1999)
1593 reflections with I > 2σ(I)
Tmin = 0.955, Tmax = 0.968Rint = 0.017
12495 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0350 restraints
wR(F2) = 0.091H-atom parameters constrained
S = 1.17Δρmax = 0.26 e Å3
1642 reflectionsΔρmin = 0.18 e Å3
136 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
xyzUiso*/Ueq
N10.5489 (2)0.35377 (8)0.3667 (2)0.0397 (4)
H1N0.46720.32890.37830.048*
C10.7439 (3)0.33694 (10)0.3931 (3)0.0410 (4)
O10.8517 (2)0.38837 (7)0.3665 (2)0.0433 (3)
C20.5203 (3)0.41997 (9)0.3133 (3)0.0344 (4)
C30.7116 (3)0.44161 (9)0.3164 (3)0.0369 (4)
C40.7477 (3)0.50472 (10)0.2749 (3)0.0425 (5)
H40.87850.51810.27950.051*
C50.5789 (3)0.54785 (10)0.2255 (3)0.0415 (4)
H50.59500.59160.19670.050*
C60.3861 (3)0.52572 (9)0.2191 (3)0.0373 (4)
C70.3498 (3)0.46166 (9)0.2622 (3)0.0364 (4)
H70.21910.44780.25700.044*
Cl10.17750 (8)0.58152 (3)0.14981 (8)0.04905 (19)
N20.8331 (3)0.27981 (9)0.4382 (3)0.0555 (5)
H2N0.76200.24930.44430.067*
H2O0.95620.27820.44540.067*
N30.3018 (3)0.21879 (8)0.4348 (3)0.0467 (4)
O20.4810 (3)0.20468 (8)0.4461 (3)0.0673 (5)
O30.1794 (3)0.17656 (8)0.4409 (4)0.0795 (6)
O40.2473 (3)0.27795 (7)0.4203 (3)0.0700 (5)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0316 (8)0.0357 (8)0.0549 (10)0.0032 (6)0.0205 (7)0.0011 (7)
C10.0337 (9)0.0425 (10)0.0483 (11)0.0003 (8)0.0178 (8)0.0003 (8)
O10.0301 (7)0.0456 (8)0.0579 (8)0.0013 (6)0.0212 (6)0.0036 (6)
C20.0311 (9)0.0370 (9)0.0365 (9)0.0044 (7)0.0148 (7)0.0023 (7)
C30.0302 (9)0.0422 (10)0.0411 (10)0.0006 (8)0.0170 (8)0.0007 (8)
C40.0344 (10)0.0478 (11)0.0510 (11)0.0070 (8)0.0229 (9)0.0017 (9)
C50.0431 (10)0.0385 (10)0.0463 (11)0.0052 (8)0.0211 (9)0.0019 (8)
C60.0349 (9)0.0408 (10)0.0372 (9)0.0031 (8)0.0154 (8)0.0006 (8)
C70.0278 (9)0.0419 (10)0.0418 (10)0.0035 (7)0.0163 (8)0.0037 (8)
Cl10.0420 (3)0.0444 (3)0.0621 (3)0.0083 (2)0.0219 (2)0.0052 (2)
N20.0395 (9)0.0466 (10)0.0823 (14)0.0063 (8)0.0261 (9)0.0083 (9)
N30.0382 (9)0.0389 (9)0.0628 (11)0.0023 (7)0.0198 (8)0.0033 (8)
O20.0466 (9)0.0504 (9)0.1142 (15)0.0034 (7)0.0418 (10)0.0022 (9)
O30.0476 (9)0.0488 (9)0.1419 (18)0.0086 (8)0.0372 (11)0.0152 (10)
O40.0555 (10)0.0379 (8)0.1314 (17)0.0030 (7)0.0529 (11)0.0089 (9)
Geometric parameters (Å, º) top
N1—C11.325 (2)C5—C61.385 (3)
N1—C21.392 (2)C5—H50.9300
N1—H1N0.7849C6—C71.384 (3)
C1—N21.294 (3)C6—Cl11.7424 (19)
C1—O11.339 (2)C7—H70.9300
O1—C31.400 (2)N2—H2N0.8029
C2—C71.376 (3)N2—H2O0.8293
C2—C31.381 (3)N3—O31.216 (2)
C3—C41.362 (3)N3—O21.238 (2)
C4—C51.386 (3)N3—O41.251 (2)
C4—H40.9300
C1—N1—C2108.31 (16)C6—C5—C4119.96 (18)
C1—N1—H1N123.2C6—C5—H5120.0
C2—N1—H1N128.4C4—C5—H5120.0
N2—C1—N1128.47 (18)C7—C6—C5123.63 (17)
N2—C1—O1120.05 (17)C7—C6—Cl1118.34 (14)
N1—C1—O1111.48 (17)C5—C6—Cl1118.02 (15)
C1—O1—C3105.97 (14)C2—C7—C6115.36 (16)
C7—C2—C3121.13 (17)C2—C7—H7122.3
C7—C2—N1133.02 (16)C6—C7—H7122.3
C3—C2—N1105.85 (16)C1—N2—H2N117.9
C4—C3—C2123.50 (18)C1—N2—H2O115.1
C4—C3—O1128.14 (16)H2N—N2—H2O126.6
C2—C3—O1108.35 (16)O3—N3—O2121.47 (18)
C3—C4—C5116.40 (17)O3—N3—O4119.41 (18)
C3—C4—H4121.8O2—N3—O4119.10 (17)
C5—C4—H4121.8
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1N···O40.781.962.735 (2)172
N1—H1N···O20.782.573.152 (2)133
N2—H2N···O20.802.142.886 (2)154
N2—H2O···O4i0.832.082.908 (2)172
N2—H2O···O3i0.832.583.171 (3)129
C5—H5···O2ii0.932.493.386 (3)162
Symmetry codes: (i) x+1, y, z; (ii) x+1, y+1/2, z+1/2.
(II) 2-amino-5-chloro-1,3-benzoxazol-3-ium perchlorate top
Crystal data top
C7H6ClN2O+·ClO4F(000) = 544
Mr = 269.04Dx = 1.719 Mg m3
Dm = 1.72 Mg m3
Dm measured by Berman density torsion balance
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 7471 reflections
a = 6.1743 (8) Åθ = 2–25°
b = 17.6159 (19) ŵ = 0.63 mm1
c = 9.7682 (11) ÅT = 291 K
β = 101.869 (9)°Prism, dark red
V = 1039.7 (2) Å30.19 × 0.19 × 0.16 mm
Z = 4
Data collection top
Kuma KM4 CCD area-detector
diffractometer
1829 independent reflections
Radiation source: fine-focus sealed tube1774 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.015
Detector resolution: 1048576 pixels mm-1θmax = 25.0°, θmin = 2.3°
ω scansh = 77
Absorption correction: numerical
(X-RED; Stoe & Cie, 1999)
k = 2020
Tmin = 0.888, Tmax = 0.896l = 1111
14071 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.027Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.071H-atom parameters constrained
S = 1.06 w = 1/[σ2(Fo2) + (0.0331P)2 + 0.5515P]
where P = (Fo2 + 2Fc2)/3
1829 reflections(Δ/σ)max = 0.001
145 parametersΔρmax = 0.21 e Å3
0 restraintsΔρmin = 0.28 e Å3
Crystal data top
C7H6ClN2O+·ClO4V = 1039.7 (2) Å3
Mr = 269.04Z = 4
Monoclinic, P21/cMo Kα radiation
a = 6.1743 (8) ŵ = 0.63 mm1
b = 17.6159 (19) ÅT = 291 K
c = 9.7682 (11) Å0.19 × 0.19 × 0.16 mm
β = 101.869 (9)°
Data collection top
Kuma KM4 CCD area-detector
diffractometer
1829 independent reflections
Absorption correction: numerical
(X-RED; Stoe & Cie, 1999)
1774 reflections with I > 2σ(I)
Tmin = 0.888, Tmax = 0.896Rint = 0.015
14071 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0270 restraints
wR(F2) = 0.071H-atom parameters constrained
S = 1.06Δρmax = 0.21 e Å3
1829 reflectionsΔρmin = 0.28 e Å3
145 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
xyzUiso*/Ueq
N10.5796 (2)0.13189 (8)0.37668 (14)0.0351 (3)
H1N0.67780.16270.37500.042*
C10.4125 (3)0.14124 (9)0.44075 (17)0.0352 (4)
O10.27551 (18)0.08150 (7)0.42164 (12)0.0397 (3)
C20.5535 (3)0.06189 (9)0.30742 (17)0.0340 (4)
C30.3626 (3)0.03111 (9)0.33594 (17)0.0363 (4)
C40.2791 (3)0.03804 (10)0.2857 (2)0.0466 (4)
H40.15000.05780.30640.056*
C50.3985 (3)0.07630 (10)0.2026 (2)0.0505 (5)
H50.34900.12330.16520.061*
C60.5917 (3)0.04562 (10)0.17401 (19)0.0441 (4)
C70.6751 (3)0.02466 (10)0.22508 (18)0.0396 (4)
H70.80400.04500.20490.047*
N20.3726 (3)0.19784 (9)0.51641 (16)0.0454 (4)
H2N0.46430.23390.54000.055*
H2O0.25130.19820.54650.055*
Cl10.73543 (9)0.09620 (3)0.06840 (6)0.06225 (18)
Cl20.93001 (6)0.26774 (2)0.67693 (4)0.03332 (13)
O20.8968 (2)0.26179 (8)0.81784 (13)0.0516 (4)
O30.9519 (2)0.19304 (7)0.62246 (13)0.0474 (3)
O40.7416 (2)0.30481 (8)0.59280 (15)0.0558 (4)
O51.1251 (2)0.31039 (9)0.67481 (15)0.0593 (4)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0316 (7)0.0317 (7)0.0421 (8)0.0049 (5)0.0083 (6)0.0030 (6)
C10.0327 (8)0.0355 (8)0.0356 (8)0.0013 (7)0.0024 (7)0.0039 (7)
O10.0336 (6)0.0399 (6)0.0456 (7)0.0033 (5)0.0085 (5)0.0046 (5)
C20.0342 (8)0.0297 (8)0.0356 (8)0.0007 (6)0.0011 (6)0.0025 (6)
C30.0347 (8)0.0334 (8)0.0388 (9)0.0002 (7)0.0026 (7)0.0060 (7)
C40.0424 (10)0.0364 (9)0.0570 (11)0.0090 (8)0.0007 (8)0.0066 (8)
C50.0555 (11)0.0313 (9)0.0569 (12)0.0030 (8)0.0068 (9)0.0022 (8)
C60.0502 (10)0.0361 (9)0.0408 (9)0.0100 (8)0.0029 (8)0.0024 (7)
C70.0370 (9)0.0383 (9)0.0421 (9)0.0033 (7)0.0050 (7)0.0005 (7)
N20.0393 (8)0.0486 (9)0.0490 (9)0.0032 (7)0.0103 (7)0.0081 (7)
Cl10.0662 (3)0.0555 (3)0.0600 (3)0.0175 (2)0.0012 (3)0.0196 (2)
Cl20.0353 (2)0.0364 (2)0.0295 (2)0.00093 (15)0.00963 (15)0.00172 (14)
O20.0566 (8)0.0692 (9)0.0333 (7)0.0179 (7)0.0192 (6)0.0039 (6)
O30.0618 (8)0.0362 (7)0.0473 (7)0.0022 (6)0.0185 (6)0.0059 (5)
O40.0553 (8)0.0572 (9)0.0506 (8)0.0116 (7)0.0009 (6)0.0114 (6)
O50.0555 (8)0.0634 (9)0.0627 (9)0.0258 (7)0.0208 (7)0.0153 (7)
Geometric parameters (Å, º) top
N1—C11.322 (2)C5—C61.390 (3)
N1—C21.400 (2)C5—H50.9300
N1—H1N0.8165C6—C71.393 (2)
C1—N21.295 (2)C6—Cl11.7383 (19)
C1—O11.339 (2)C7—H70.9300
O1—C31.401 (2)N2—H2N0.8506
C2—C71.374 (2)N2—H2O0.8590
C2—C31.377 (2)Cl2—O51.4236 (14)
C3—C41.373 (2)Cl2—O41.4359 (14)
C4—C51.379 (3)Cl2—O31.4361 (13)
C4—H40.9300Cl2—O21.4366 (13)
C1—N1—C2108.38 (14)C4—C5—H5119.6
C1—N1—H1N125.6C6—C5—H5119.6
C2—N1—H1N126.0C5—C6—C7122.88 (17)
N2—C1—N1128.66 (16)C5—C6—Cl1118.95 (14)
N2—C1—O1119.75 (15)C7—C6—Cl1118.17 (15)
N1—C1—O1111.58 (14)C2—C7—C6115.33 (17)
C1—O1—C3105.80 (12)C2—C7—H7122.3
C7—C2—C3121.58 (16)C6—C7—H7122.3
C7—C2—N1132.93 (15)C1—N2—H2N122.4
C3—C2—N1105.49 (14)C1—N2—H2O118.9
C4—C3—C2123.44 (17)H2N—N2—H2O118.7
C4—C3—O1127.83 (16)O5—Cl2—O4109.88 (9)
C2—C3—O1108.73 (14)O5—Cl2—O3109.51 (8)
C3—C4—C5115.90 (17)O4—Cl2—O3109.36 (9)
C3—C4—H4122.0O5—Cl2—O2109.90 (9)
C5—C4—H4122.0O4—Cl2—O2108.85 (8)
C4—C5—C6120.87 (17)O3—Cl2—O2109.33 (8)

Experimental details

(I)(II)
Crystal data
Chemical formulaC7H6ClN2O+·NO3C7H6ClN2O+·ClO4
Mr231.60269.04
Crystal system, space groupMonoclinic, P21/cMonoclinic, P21/c
Temperature (K)291291
a, b, c (Å)6.8900 (9), 20.3139 (18), 7.2562 (10)6.1743 (8), 17.6159 (19), 9.7682 (11)
β (°) 113.138 (9) 101.869 (9)
V3)933.9 (2)1039.7 (2)
Z44
Radiation typeMo KαMo Kα
µ (mm1)0.410.63
Crystal size (mm)0.11 × 0.09 × 0.080.19 × 0.19 × 0.16
Data collection
DiffractometerKuma KM4 CCD area-detector
diffractometer
Kuma KM4 CCD area-detector
diffractometer
Absorption correctionNumerical
(X-RED; Stoe & Cie, 1999)
Numerical
(X-RED; Stoe & Cie, 1999)
Tmin, Tmax0.955, 0.9680.888, 0.896
No. of measured, independent and
observed [I > 2σ(I)] reflections
12495, 1642, 1593 14071, 1829, 1774
Rint0.0170.015
(sin θ/λ)max1)0.5950.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.035, 0.091, 1.17 0.027, 0.071, 1.06
No. of reflections16421829
No. of parameters136145
H-atom treatmentH-atom parameters constrainedH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.26, 0.180.21, 0.28

Computer programs: CrysAlis CCD (UNIL IC & Kuma 2000), CrysAlis RED (UNIL IC & Kuma 2000), SHELXS97 (Sheldrick, 2008), XP in SHELXTL/PC (Sheldrick, 2008) and ORTEP-3 for Windows (Version 1.062; Farrugia 1997), SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).

Selected bond lengths (Å) for (I) top
N1—C11.325 (2)O1—C31.400 (2)
N1—C21.392 (2)N3—O31.216 (2)
C1—N21.294 (3)N3—O21.238 (2)
C1—O11.339 (2)N3—O41.251 (2)
Selected bond lengths (Å) for (II) top
N1—C11.322 (2)Cl2—O51.4236 (14)
N1—C21.400 (2)Cl2—O41.4359 (14)
C1—N21.295 (2)Cl2—O31.4361 (13)
C1—O11.339 (2)Cl2—O21.4366 (13)
O1—C31.401 (2)
Experimental hydrogen-bond geometry (Å, °) for (I) and (II), total energy E (kJ mol-1) and principal `delocalisation' energy Edel, calculated on the natural bonding orbital basis top
D—H···AD—HH···AD···AD—H···AEEdel
(I)
N1—H1N···O40.781.962.735 (2)171.839.85 (5)27.246 (8)
N1—H1N···O20.782.573.152 (2)132.73.640 (12)3.326 (1)
N2—H2N···O20.802.142.886 (2)154.212.62 (4)8.857 (3)
N2—H2O···O4i0.832.082.908 (2)171.739.36 (6)24.233 (4)
N2—H2O···O2i0.832.583.171 (3)129.12.48 (4)2.192
C5—H5···O2ii0.932.493.386 (3)162.13.14 (8)2.410 (1)
(II)
N1—H1N···O2iii0.822.052.8527 (19)165.742.29 (2)25.878 (8)
N2—H2N···O40.852.102.932 (2)167.553.01 (8)34.116 (11)
N2—H2O···O3iv0.862.132.989 (2)177.138.38 (7)25.057 (9)
N2—H2O···O5iv0.862.553.103 (2)123.42.04 (7)1.786
C4—H4···O3v0.932.593.289 (2)132.010.29 (8)8.372
Symmetry codes: (i) x + 1, y, z; (ii) -x + 1, y + 1/2, -z + 1/2; (iii) x, -y + 1/2, z - 1/2; (iv) x - 1, y, z; (v) -x + 1, -y, -z + 1.
Experimental geometry of stacking interactions (Å, °) for (I) top
CgJ···CgKCg···CgαβCgJperp
Cg6···Cg6vi3.745 (3)025.3 (2)3.385 (3)
Cg6···Cg6vii3.737 (3)026.1 (2)3.355 (3)
Cg6 is the ring-centroid of the six-membered ring. Cg···Cg is the perpendicular distance between the first ring centroid and that of the second ring. α is the dihedral angle between planes J and K. β is athe angle between the vector linking the ring centroids and the normal to ring J. CgJperp is the perpendicular distance from the J ring centroid to ring K. Symmetry codes: (v) -x + 1, -y, -z + 1; (vi) -x + 1, -y + 1, -z; (vii) -x + 1, -y + 1, -z + 1;
 

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