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The crystal structures of 8-hydroxy-5-nitro­quinoline, C9H6N2O3, (I), and 8-hydroxy-5-nitro­quinolinium chloride, C9H7N2O3+·Cl-, (II), have been determined from X-ray powder data. In (I), the mol­ecules are linked via moderately strong hydrogen bonds to form dimers. Such a packing motif is likely to be responsible for the low solubility of (I) in water. In (II), the inversion-related cations form stacks, and anions fill the interstack channels.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101018224/sk1513sup1.cif
Contains datablocks global, I, II

rtv

Rietveld powder data file (CIF format) https://doi.org/10.1107/S0108270101018224/sk1513Isup2.rtv
Contains datablock I

rtv

Rietveld powder data file (CIF format) https://doi.org/10.1107/S0108270101018224/sk1513IIsup3.rtv
Contains datablock II

CCDC references: 180156; 180157

Comment top

Nitroxoline, or 8-hydroxy-5-nitroquinoline, (I), also known as 5NOK, shows antibacterial and fungicidal activity. In particular, it is used for the treatment of infections of the genito-urinary system. Compound (I) has low solubility in water, but its solubility increases considerably in alkalis and acids.

To date, it has not been clear whether the molecule of (I) in the crystal exists as the neutral form, or as a zwitterion resulting from proton transfer from the hydroxy group to the quinoline N atom. DFT (density functional theory) calculations for isolated molecules predict that the zwitterionic form is 31 kJ mol-1 less stable than the neutral one. This difference, while significant, is not large enough to exclude the zwitterion from consideration, since it can be overshadowed by the effects of the medium. Query. However, visible spectroscopy, together with semi-empirical calculations on the INDO-CISD level (Dick & Nickel, 1983), gives strong evidence for the presence of the neutral molecule. Recently, the INDO-CISD technique was proven to be suitable for reproducing the spectra of nitronaphthalenoles (Yatsenko et al., 2001). For (I), INDO-CISD calculations predict that the neutral form should have its ππ absorption maximum in the near-UV region, at 307 nm. The protonation of the quinoline N atom shifts this band bathochromically by 40 nm, whereas in the case of the zwitterion, this maximum is shifted to 391 nm and a new absorption band appears at 635 nm. Thus, the zwitterion should absorb light essentially in the whole of the visible region. In practice, crystals of (I) are light yellow, with no absorption maximum in the visible region, and the hydrochloride salt, (II), is deeper in colour than (I), in full agreement with the results of the calculations for the neutral form and cation, and with the spectroscopic data for solutions (Ermakov et al., 1985). \sch

The molecule of (I) is nearly planar, the dihedral angle formed by the least squares planes through the naphthalene and nitro moieties being only 6.3 (4)°. The dihedral angle formed by the planes through the naphthalene moieties of adjacent molecules is 44.8 (5)°. Details of the hydrogen bonds are given in Table 1. Molecules related by the 2 axis form dimers, as shown in Fig. 1. We have carried out the DFT optimization of one such dimer, starting from the crystallographic geometry. The resulting geometry does not significantly differ from the experimental one. After the optimization, the angle subtended by two naphthalene moieties increased to 64° and the hydroxy group is twisted by 15° with respect to the naphthalene plane, thus facilitating the hydrogen bonding: the O8—H8···N1 angle increased to 155°, the C9—N1···H8 angle became 129° (versus 135° in the crystal) and the O···N distance was 0.07 Å shorter than in the crystal. The DFT-calculated energy of the dimer is 19.8 kJ mol-1 lower than the energy of two isolated molecules of (I). This is an exaggerated estimation for the hydrogen-bonding energy in this dimer, owing to the basis-set superposition error.

The dimers in (I) form stacks along [001], with an interplanar distance of 3.446 (8) Å between two neighbouring naphthalene fragments. It is likely that, under the effect of stacking interactions, the dimers flatten in the crystal, at the cost of distortion of the hydrogen-bonding geometry.

In (II), the cations form stacks along [100] (Fig. 2), with interplanar distances of 3.341 (10) and 3.447 (10) Å. The nitro group is twisted by 12.4 (5)° with respect to the naphthalene moiety. The anions make short contacts to NH, OH and CH groups, which can be considered as hydrogen bonds (Table 2).

Table 1. Hydrogen bonds and short C—H···O contacts (Å, °) for (I)

Table 2. Hydrogen bonds and short C—H···Cl(O) contacts (Å, °) for (II)

Experimental top

Compound (I) was prepared by oxidation of 8-hydroxy-5-nitrosoquinoline by HNO3, followed by recrystallization from ethanol, giving very thin needles. The sample obtained from aqueous solution gave an identical diffraction pattern, although of lower quality. Compound (II) was prepared by recrystallization of (I) from 5% HCl.

Refinement top

The DFT and INDO-CISD calculations were performed using programs provided by Dr D. N. Laikov (Laikov, 1997) and Professor B. Dick (Dick & Nickel, 1983), respectively. The DFT calculations were carried out using the BLYP (Becke-Lee-Yang-Parr) exchange-correlation function (Becke, 1988; Lee, Yang & Parr, 1988) with a triple zeta basis set, including polarization and diffuse functions for all atoms. The orthorhombic and monoclinic cell dimensions of (I) and (II) were determined with ITO (Visser, 1969) and TREOR90 (Werner et al., 1985), respectively, and refined to M20 = 18 for (I) and 22 for (II), and F = 43 for (I) and 39 for (II), using the first 26 and 32 peak positions, respectively. The initial molecular models were built with MOPAC7 (Stewart, 1993) on the PM3 level (Stewart, 1989). In (I), the position and orientation of the molecule were determined using the grid-search procedure (Chernyshev & Schenk, 1998). In (II), the position and orientation of the cation and the position of the anion were determined using the simulated annealing procedure (Zhukov et al., 2001). The X-ray diffraction profiles and the differences between the measured and calculated profiles after the Rietveld refinement are shown in Figs. 3 and 4. The final RB values were 0.067 for (I) and 0.076 for (II). The Cl atom was refined anisotropically; the C, N and O atoms were refined isotropically and were gathered together into groups with a common Uiso parameter for each group. The H atoms were placed in geometrically calculated positions and their isotropic displacement parameters were fixed. The planarity of the naphthalene fragments and the nitro groups was restrained. The anisotropy of the diffraction-line broadening was approximated by a quartic form in hkl (Popa, 1998). The standard uncertainties obtained from the Rietveld refinement were corrected for serial correlation effects (Bérar & Lelann, 1991).

Computing details top

For both compounds, data collection: local program; cell refinement: LSPAID (Visser, 1986); program(s) used to solve structure: MRIA (Zlokazov & Chernyshev, 1992); program(s) used to refine structure: MRIA; molecular graphics: PLATON (Spek, 2001); software used to prepare material for publication: PARST (Nardelli, 1983).

Figures top
[Figure 1] Fig. 1. The hydrogen-bonded dimers in (I) showing the atom-labelling scheme.
[Figure 2] Fig. 2. The Cl···H contacts in (II); the atom-labelling scheme is the same as for (I) in Fig. 1.
[Figure 3] Fig. 3. The Rietveld plot for (I) showing the observed and difference profiles. The reflection positions are shown above the difference profile. The high-angle area is magnified by a factor of 10.
[Figure 4] Fig. 4. The Rietveld plot for (II) showing the observed and difference profiles. The reflection positions are shown above the difference profile. The high-angle area is magnified by a factor of 10.
(I) 8-hydroxy-5-nitroquinoline top
Crystal data top
C9H6N2O3F(000) = 1568
Mr = 190.16Dx = 1.549 Mg m3
Orthorhombic, Fdd2Cu Kα radiation, λ = 1.5418 Å
a = 28.049 (7) ÅT = 295 K
b = 31.198 (8) ÅParticle morphology: needle
c = 3.727 (1) Ålight yellow
V = 3261.4 (15) Å3flat sheet, 25 × 25 mm
Z = 16
Data collection top
DRON-3M
diffractometer (Burevestnik, Russia)
Data collection mode: reflection
Radiation source: X-ray sealed tubeScan method: step
Ni filtered monochromator2θmin = 7.90°, 2θmax = 70.0°, 2θstep = 0.02°
Specimen mounting: pressed as a thin layer in the specimen holder
Refinement top
Refinement on Inet92 parameters
Least-squares matrix: full with fixed elements per cycle11 restraints
Rp = 0.0350 constraints
Rwp = 0.048H-atom parameters constrained
Rexp = 0.023Weighting scheme based on measured s.u.'s
χ2 = 4.427(Δ/σ)max = 0.045
3151 data pointsBackground function: Chebyshev polynomial up to the 5th order
Excluded region(s): 7.00 - 7.88Preferred orientation correction: Spherical harmonics (Ahtee et al., 1989)
Profile function: split-type pseudo-Voigt
Crystal data top
C9H6N2O3V = 3261.4 (15) Å3
Mr = 190.16Z = 16
Orthorhombic, Fdd2Cu Kα radiation, λ = 1.5418 Å
a = 28.049 (7) ÅT = 295 K
b = 31.198 (8) Åflat sheet, 25 × 25 mm
c = 3.727 (1) Å
Data collection top
DRON-3M
diffractometer (Burevestnik, Russia)
Scan method: step
Specimen mounting: pressed as a thin layer in the specimen holder2θmin = 7.90°, 2θmax = 70.0°, 2θstep = 0.02°
Data collection mode: reflection
Refinement top
Rp = 0.0353151 data points
Rwp = 0.04892 parameters
Rexp = 0.02311 restraints
χ2 = 4.427H-atom parameters constrained
Special details top

Experimental. specimen was rotated in its plane

Refinement. H atoms were placed in calculated positions. The planarity of the naphthalene and nitro groups was restrained.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N10.04038 (10)0.45902 (13)0.11630.0660 (13)*
C20.03319 (11)0.41938 (14)0.2495 (14)0.0660 (13)*
C30.07072 (12)0.38965 (10)0.2867 (15)0.0660 (13)*
C40.11631 (12)0.39958 (12)0.1868 (13)0.0660 (13)*
C50.16940 (11)0.45789 (13)0.0708 (18)0.0660 (13)*
C60.17411 (10)0.49972 (14)0.2017 (18)0.0660 (13)*
C70.13449 (11)0.52722 (10)0.2295 (13)0.0660 (13)*
C80.09105 (12)0.51330 (14)0.1169 (16)0.0660 (13)*
C90.08603 (12)0.46949 (13)0.016 (2)0.0660 (13)*
C100.12520 (12)0.44153 (12)0.0431 (13)0.0660 (13)*
N50.21257 (11)0.43142 (12)0.0490 (19)0.0929 (12)*
O10.21057 (12)0.39570 (12)0.086 (2)0.0929 (12)*
O20.24904 (11)0.44491 (12)0.188 (2)0.0929 (12)*
O80.05370 (8)0.53875 (12)0.143 (2)0.0929 (12)*
H20.00010.41140.32230.101*
H30.06370.36050.38510.101*
H40.14230.37790.21330.101*
H60.20630.50960.28310.101*
H70.14040.55650.32910.101*
H80.02680.52610.06480.101*
Geometric parameters (Å, º) top
O1—N51.224 (6)C6—C71.408 (5)
O2—N51.221 (6)C7—C81.360 (5)
O8—C81.318 (5)C8—C91.461 (6)
N1—C21.348 (6)C9—C101.406 (5)
N1—C91.373 (5)O8—H80.900
N5—C51.468 (5)C2—H21.000
C2—C31.410 (5)C3—H31.000
C3—C41.367 (5)C4—H41.000
C4—C101.436 (6)C6—H61.000
C5—C61.399 (6)C7—H71.001
C5—C101.406 (5)
C2—N1—C9117.3 (3)N1—C9—C10124.1 (4)
O1—N5—O2121.8 (4)C8—C9—C10122.0 (3)
O1—N5—C5119.8 (4)C4—C10—C5126.6 (3)
O2—N5—C5118.3 (4)C4—C10—C9117.2 (3)
N1—C2—C3121.9 (3)C5—C10—C9116.2 (4)
C2—C3—C4121.5 (3)C8—O8—H8112
C3—C4—C10118.1 (3)N1—C2—H2118
N5—C5—C6117.8 (3)C3—C2—H2120
N5—C5—C10120.4 (4)C2—C3—H3119
C6—C5—C10121.8 (3)C4—C3—H3119
C5—C6—C7121.3 (3)C3—C4—H4120
C6—C7—C8119.3 (4)C10—C4—H4122
O8—C8—C7119.8 (4)C5—C6—H6119
O8—C8—C9120.8 (3)C7—C6—H6120
C7—C8—C9119.3 (3)C6—C7—H7117
N1—C9—C8113.9 (3)C8—C7—H7124
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O8—H8···N1i0.902.052.811 (5)141
C6—H6···O2ii1.002.423.304 (7)147
C3—H3···O2iii1.002.593.472 (6)147
Symmetry codes: (i) x, y+1, z; (ii) x+1/2, y+1, z+1/2; (iii) x1/4, y+3/4, z3/4.
(II) 8-hydroxy-5-nitroquinolinium chloride top
Crystal data top
C9H7N2O3+·ClZ = 4
Mr = 226.62F(000) = 464
Monoclinic, P21/cDx = 1.633 Mg m3
a = 7.566 (4) ÅCu Kα radiation, λ = 1.5418 Å
b = 7.467 (4) ÅT = 295 K
c = 16.334 (7) ÅParticle morphology: plate
β = 92.49 (3)°yellow
V = 921.9 (8) Å3flat sheet, 25 × 25 mm
Data collection top
DRON-3M
diffractometer (Burevestnik, Russia)
Data collection mode: reflection
Radiation source: X-ray sealed tubeScan method: step
Ni filtered monochromator2θmin = 9.40°, 2θmax = 70.0°, 2θstep = 0.02°
Specimen mounting: pressed as a thin layer in the specimen holder
Refinement top
Refinement on Inet112 parameters
Least-squares matrix: full with fixed elements per cycle11 restraints
Rp = 0.0400 constraints
Rwp = 0.056H-atom parameters constrained
Rexp = 0.030Weighting scheme based on measured s.u.'s
χ2 = 3.423(Δ/σ)max = 0.048
3251 data pointsBackground function: Chebyshev polynomial up to the 5th order
Excluded region(s): 5.00 - 9.38Preferred orientation correction: Spherical harmonics (Ahtee et al., 1989)
Profile function: split-type pseudo-Voigt
Crystal data top
C9H7N2O3+·Clβ = 92.49 (3)°
Mr = 226.62V = 921.9 (8) Å3
Monoclinic, P21/cZ = 4
a = 7.566 (4) ÅCu Kα radiation, λ = 1.5418 Å
b = 7.467 (4) ÅT = 295 K
c = 16.334 (7) Åflat sheet, 25 × 25 mm
Data collection top
DRON-3M
diffractometer (Burevestnik, Russia)
Scan method: step
Specimen mounting: pressed as a thin layer in the specimen holder2θmin = 9.40°, 2θmax = 70.0°, 2θstep = 0.02°
Data collection mode: reflection
Refinement top
Rp = 0.0403251 data points
Rwp = 0.056112 parameters
Rexp = 0.03011 restraints
χ2 = 3.423H-atom parameters constrained
Special details top

Experimental. specimen was rotated in its plane

Refinement. H atoms were placed in calculated positions. The planarity of the naphthalene and nitro groups was restrained.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N10.1586 (9)0.6092 (7)0.5789 (3)0.0479 (8)*
C20.1701 (17)0.4818 (9)0.6368 (3)0.0479 (8)*
C30.2416 (13)0.3103 (7)0.6208 (3)0.0479 (8)*
C40.3032 (10)0.2718 (7)0.5439 (3)0.0479 (8)*
C50.3476 (10)0.3879 (7)0.3982 (3)0.0479 (8)*
C60.3301 (9)0.5309 (7)0.3430 (3)0.0479 (8)*
C70.2551 (16)0.6951 (8)0.3652 (3)0.0479 (8)*
C80.1991 (17)0.7180 (8)0.4453 (3)0.0479 (8)*
C90.2180 (15)0.5725 (8)0.5031 (3)0.0479 (8)*
C100.2941 (8)0.4056 (7)0.4812 (3)0.0479 (8)*
N50.4301 (13)0.2229 (8)0.3675 (3)0.0884 (11)*
O10.4767 (14)0.1042 (8)0.4171 (3)0.0884 (11)*
O20.4452 (17)0.2071 (8)0.2944 (3)0.0884 (11)*
O80.1263 (12)0.8706 (7)0.4704 (2)0.0884 (11)*
Cl10.0019 (7)0.9048 (4)0.6691 (2)0.0603 (6)
H10.11280.71700.59070.0761*
H20.12740.50860.69250.0761*
H30.24940.21860.66550.0761*
H40.35440.15170.53130.0761*
H60.37150.51440.28630.0761*
H70.24340.79560.32490.0761*
H80.11890.95570.43650.0761*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cl10.059 (6)0.062 (3)0.060 (2)0.012 (5)0.031 (3)0.017 (3)
Geometric parameters (Å, º) top
O1—N51.242 (8)C6—C71.405 (9)
O2—N51.210 (7)C7—C81.403 (9)
O8—C81.338 (10)C8—C91.442 (8)
N1—C21.342 (8)C9—C101.425 (9)
N1—C91.363 (8)O8—H80.843
N5—C51.479 (9)N1—H10.900
C2—C31.419 (10)C2—H20.999
C3—C41.389 (8)C3—H31.001
C4—C101.430 (7)C4—H41.002
C5—C61.400 (7)C6—H60.998
C5—C101.438 (7)C7—H70.999
C2—N1—C9118.9 (6)C8—C9—C10121.6 (6)
O1—N5—O2122.5 (7)C4—C10—C5127.2 (5)
O1—N5—C5119.1 (5)C4—C10—C9116.0 (5)
O2—N5—C5118.4 (6)C5—C10—C9116.8 (5)
N1—C2—C3121.6 (6)C8—O8—H8117
C2—C3—C4119.9 (5)C2—N1—H1120
C3—C4—C10119.7 (5)C9—N1—H1121
N5—C5—C6116.5 (5)N1—C2—H2119
N5—C5—C10122.5 (5)C3—C2—H2119
C6—C5—C10121.0 (5)C2—C3—H3120
C5—C6—C7121.8 (5)C4—C3—H3120
C6—C7—C8119.3 (5)C3—C4—H4121
O8—C8—C7122.3 (5)C10—C4—H4119
O8—C8—C9118.1 (6)C5—C6—H6119
C7—C8—C9119.6 (6)C7—C6—H6120
N1—C9—C8114.6 (6)C6—C7—H7121
N1—C9—C10123.8 (5)C8—C7—H7120
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···Cl10.902.112.945 (7)154
O8—H8···Cl1i0.842.172.950 (6)154
C2—H2···Cl1ii1.002.613.515 (8)151
C4—H4···O1iii1.002.433.312 (10)147
C6—H6···O2iv1.002.433.161 (10)130
C3—H3···O2v1.002.583.170 (10)118
Symmetry codes: (i) x, y+2, z+1; (ii) x, y1/2, z+3/2; (iii) x+1, y, z+1; (iv) x+1, y+1/2, z+1/2; (v) x, y+1/2, z+1/2.

Experimental details

(I)(II)
Crystal data
Chemical formulaC9H6N2O3C9H7N2O3+·Cl
Mr190.16226.62
Crystal system, space groupOrthorhombic, Fdd2Monoclinic, P21/c
Temperature (K)295295
a, b, c (Å)28.049 (7), 31.198 (8), 3.727 (1)7.566 (4), 7.467 (4), 16.334 (7)
α, β, γ (°)90, 90, 9090, 92.49 (3), 90
V3)3261.4 (15)921.9 (8)
Z164
Radiation typeCu Kα, λ = 1.5418 ÅCu Kα, λ = 1.5418 Å
Specimen shape, size (mm)Flat sheet, 25 × 25Flat sheet, 25 × 25
Data collection
DiffractometerDRON-3M
diffractometer (Burevestnik, Russia)
DRON-3M
diffractometer (Burevestnik, Russia)
Specimen mountingPressed as a thin layer in the specimen holderPressed as a thin layer in the specimen holder
Data collection modeReflectionReflection
Scan methodStepStep
2θ values (°)2θmin = 7.90 2θmax = 70.0 2θstep = 0.022θmin = 9.40 2θmax = 70.0 2θstep = 0.02
Refinement
R factors and goodness of fitRp = 0.035, Rwp = 0.048, Rexp = 0.023, χ2 = 4.427Rp = 0.040, Rwp = 0.056, Rexp = 0.030, χ2 = 3.423
No. of data points31513251
No. of parameters92112
No. of restraints1111
H-atom treatmentH-atom parameters constrainedH-atom parameters constrained

Computer programs: local program, LSPAID (Visser, 1986), MRIA (Zlokazov & Chernyshev, 1992), MRIA, PLATON (Spek, 2001), PARST (Nardelli, 1983).

Hydrogen-bond geometry (Å, º) for (I) top
D—H···AD—HH···AD···AD—H···A
O8—H8···N1i0.902.052.811 (5)141
C6—H6···O2ii1.002.423.304 (7)147
C3—H3···O2iii1.002.593.472 (6)147
Symmetry codes: (i) x, y+1, z; (ii) x+1/2, y+1, z+1/2; (iii) x1/4, y+3/4, z3/4.
Hydrogen-bond geometry (Å, º) for (II) top
D—H···AD—HH···AD···AD—H···A
N1—H1···Cl10.902.112.945 (7)154
O8—H8···Cl1i0.842.172.950 (6)154
C2—H2···Cl1ii1.002.613.515 (8)151
C4—H4···O1iii1.002.433.312 (10)147
C6—H6···O2iv1.002.433.161 (10)130
C3—H3···O2v1.002.583.170 (10)118
Symmetry codes: (i) x, y+2, z+1; (ii) x, y1/2, z+3/2; (iii) x+1, y, z+1; (iv) x+1, y+1/2, z+1/2; (v) x, y+1/2, z+1/2.
 

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