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
CCDC references: 180156; 180157
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.
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).
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).
(I) 8-hydroxy-5-nitroquinoline
top
Crystal data top
C9H6N2O3 | F(000) = 1568 |
Mr = 190.16 | Dx = 1.549 Mg m−3 |
Orthorhombic, Fdd2 | Cu Kα radiation, λ = 1.5418 Å |
a = 28.049 (7) Å | T = 295 K |
b = 31.198 (8) Å | Particle morphology: needle |
c = 3.727 (1) Å | light yellow |
V = 3261.4 (15) Å3 | flat sheet, 25 × 25 mm |
Z = 16 | |
Data collection top
DRON-3M diffractometer (Burevestnik, Russia) | Data collection mode: reflection |
Radiation source: X-ray sealed tube | Scan method: step |
Ni filtered monochromator | 2θmin = 7.90°, 2θmax = 70.0°, 2θstep = 0.02° |
Specimen mounting: pressed as a thin layer in the specimen holder | |
Refinement top
Refinement on Inet | 92 parameters |
Least-squares matrix: full with fixed elements per cycle | 11 restraints |
Rp = 0.035 | 0 constraints |
Rwp = 0.048 | H-atom parameters constrained |
Rexp = 0.023 | Weighting scheme based on measured s.u.'s |
χ2 = 4.427 | (Δ/σ)max = 0.045 |
3151 data points | Background function: Chebyshev polynomial up to the 5th order |
Excluded region(s): 7.00 - 7.88 | Preferred orientation correction: Spherical harmonics (Ahtee et al., 1989) |
Profile function: split-type pseudo-Voigt | |
Crystal data top
C9H6N2O3 | V = 3261.4 (15) Å3 |
Mr = 190.16 | Z = 16 |
Orthorhombic, Fdd2 | Cu Kα radiation, λ = 1.5418 Å |
a = 28.049 (7) Å | T = 295 K |
b = 31.198 (8) Å | flat 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 holder | 2θmin = 7.90°, 2θmax = 70.0°, 2θstep = 0.02° |
Data collection mode: reflection | |
Refinement top
Rp = 0.035 | 3151 data points |
Rwp = 0.048 | 92 parameters |
Rexp = 0.023 | 11 restraints |
χ2 = 4.427 | H-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 | x | y | z | Uiso*/Ueq | |
N1 | 0.04038 (10) | 0.45902 (13) | −0.1163 | 0.0660 (13)* | |
C2 | 0.03319 (11) | 0.41938 (14) | −0.2495 (14) | 0.0660 (13)* | |
C3 | 0.07072 (12) | 0.38965 (10) | −0.2867 (15) | 0.0660 (13)* | |
C4 | 0.11631 (12) | 0.39958 (12) | −0.1868 (13) | 0.0660 (13)* | |
C5 | 0.16940 (11) | 0.45789 (13) | 0.0708 (18) | 0.0660 (13)* | |
C6 | 0.17411 (10) | 0.49972 (14) | 0.2017 (18) | 0.0660 (13)* | |
C7 | 0.13449 (11) | 0.52722 (10) | 0.2295 (13) | 0.0660 (13)* | |
C8 | 0.09105 (12) | 0.51330 (14) | 0.1169 (16) | 0.0660 (13)* | |
C9 | 0.08603 (12) | 0.46949 (13) | −0.016 (2) | 0.0660 (13)* | |
C10 | 0.12520 (12) | 0.44153 (12) | −0.0431 (13) | 0.0660 (13)* | |
N5 | 0.21257 (11) | 0.43142 (12) | 0.0490 (19) | 0.0929 (12)* | |
O1 | 0.21057 (12) | 0.39570 (12) | −0.086 (2) | 0.0929 (12)* | |
O2 | 0.24904 (11) | 0.44491 (12) | 0.188 (2) | 0.0929 (12)* | |
O8 | 0.05370 (8) | 0.53875 (12) | 0.143 (2) | 0.0929 (12)* | |
H2 | 0.0001 | 0.4114 | −0.3223 | 0.101* | |
H3 | 0.0637 | 0.3605 | −0.3851 | 0.101* | |
H4 | 0.1423 | 0.3779 | −0.2133 | 0.101* | |
H6 | 0.2063 | 0.5096 | 0.2831 | 0.101* | |
H7 | 0.1404 | 0.5565 | 0.3291 | 0.101* | |
H8 | 0.0268 | 0.5261 | 0.0648 | 0.101* | |
Geometric parameters (Å, º) top
O1—N5 | 1.224 (6) | C6—C7 | 1.408 (5) |
O2—N5 | 1.221 (6) | C7—C8 | 1.360 (5) |
O8—C8 | 1.318 (5) | C8—C9 | 1.461 (6) |
N1—C2 | 1.348 (6) | C9—C10 | 1.406 (5) |
N1—C9 | 1.373 (5) | O8—H8 | 0.900 |
N5—C5 | 1.468 (5) | C2—H2 | 1.000 |
C2—C3 | 1.410 (5) | C3—H3 | 1.000 |
C3—C4 | 1.367 (5) | C4—H4 | 1.000 |
C4—C10 | 1.436 (6) | C6—H6 | 1.000 |
C5—C6 | 1.399 (6) | C7—H7 | 1.001 |
C5—C10 | 1.406 (5) | | |
| | | |
C2—N1—C9 | 117.3 (3) | N1—C9—C10 | 124.1 (4) |
O1—N5—O2 | 121.8 (4) | C8—C9—C10 | 122.0 (3) |
O1—N5—C5 | 119.8 (4) | C4—C10—C5 | 126.6 (3) |
O2—N5—C5 | 118.3 (4) | C4—C10—C9 | 117.2 (3) |
N1—C2—C3 | 121.9 (3) | C5—C10—C9 | 116.2 (4) |
C2—C3—C4 | 121.5 (3) | C8—O8—H8 | 112 |
C3—C4—C10 | 118.1 (3) | N1—C2—H2 | 118 |
N5—C5—C6 | 117.8 (3) | C3—C2—H2 | 120 |
N5—C5—C10 | 120.4 (4) | C2—C3—H3 | 119 |
C6—C5—C10 | 121.8 (3) | C4—C3—H3 | 119 |
C5—C6—C7 | 121.3 (3) | C3—C4—H4 | 120 |
C6—C7—C8 | 119.3 (4) | C10—C4—H4 | 122 |
O8—C8—C7 | 119.8 (4) | C5—C6—H6 | 119 |
O8—C8—C9 | 120.8 (3) | C7—C6—H6 | 120 |
C7—C8—C9 | 119.3 (3) | C6—C7—H7 | 117 |
N1—C9—C8 | 113.9 (3) | C8—C7—H7 | 124 |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O8—H8···N1i | 0.90 | 2.05 | 2.811 (5) | 141 |
C6—H6···O2ii | 1.00 | 2.42 | 3.304 (7) | 147 |
C3—H3···O2iii | 1.00 | 2.59 | 3.472 (6) | 147 |
Symmetry codes: (i) −x, −y+1, z; (ii) −x+1/2, −y+1, z+1/2; (iii) x−1/4, −y+3/4, z−3/4. |
(II) 8-hydroxy-5-nitroquinolinium chloride
top
Crystal data top
C9H7N2O3+·Cl− | Z = 4 |
Mr = 226.62 | F(000) = 464 |
Monoclinic, P21/c | Dx = 1.633 Mg m−3 |
a = 7.566 (4) Å | Cu Kα radiation, λ = 1.5418 Å |
b = 7.467 (4) Å | T = 295 K |
c = 16.334 (7) Å | Particle morphology: plate |
β = 92.49 (3)° | yellow |
V = 921.9 (8) Å3 | flat sheet, 25 × 25 mm |
Data collection top
DRON-3M diffractometer (Burevestnik, Russia) | Data collection mode: reflection |
Radiation source: X-ray sealed tube | Scan method: step |
Ni filtered monochromator | 2θmin = 9.40°, 2θmax = 70.0°, 2θstep = 0.02° |
Specimen mounting: pressed as a thin layer in the specimen holder | |
Refinement top
Refinement on Inet | 112 parameters |
Least-squares matrix: full with fixed elements per cycle | 11 restraints |
Rp = 0.040 | 0 constraints |
Rwp = 0.056 | H-atom parameters constrained |
Rexp = 0.030 | Weighting scheme based on measured s.u.'s |
χ2 = 3.423 | (Δ/σ)max = 0.048 |
3251 data points | Background function: Chebyshev polynomial up to the 5th order |
Excluded region(s): 5.00 - 9.38 | Preferred orientation correction: Spherical harmonics (Ahtee et al., 1989) |
Profile function: split-type pseudo-Voigt | |
Crystal data top
C9H7N2O3+·Cl− | β = 92.49 (3)° |
Mr = 226.62 | V = 921.9 (8) Å3 |
Monoclinic, P21/c | Z = 4 |
a = 7.566 (4) Å | Cu Kα radiation, λ = 1.5418 Å |
b = 7.467 (4) Å | T = 295 K |
c = 16.334 (7) Å | flat 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 holder | 2θmin = 9.40°, 2θmax = 70.0°, 2θstep = 0.02° |
Data collection mode: reflection | |
Refinement top
Rp = 0.040 | 3251 data points |
Rwp = 0.056 | 112 parameters |
Rexp = 0.030 | 11 restraints |
χ2 = 3.423 | H-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 | x | y | z | Uiso*/Ueq | |
N1 | 0.1586 (9) | 0.6092 (7) | 0.5789 (3) | 0.0479 (8)* | |
C2 | 0.1701 (17) | 0.4818 (9) | 0.6368 (3) | 0.0479 (8)* | |
C3 | 0.2416 (13) | 0.3103 (7) | 0.6208 (3) | 0.0479 (8)* | |
C4 | 0.3032 (10) | 0.2718 (7) | 0.5439 (3) | 0.0479 (8)* | |
C5 | 0.3476 (10) | 0.3879 (7) | 0.3982 (3) | 0.0479 (8)* | |
C6 | 0.3301 (9) | 0.5309 (7) | 0.3430 (3) | 0.0479 (8)* | |
C7 | 0.2551 (16) | 0.6951 (8) | 0.3652 (3) | 0.0479 (8)* | |
C8 | 0.1991 (17) | 0.7180 (8) | 0.4453 (3) | 0.0479 (8)* | |
C9 | 0.2180 (15) | 0.5725 (8) | 0.5031 (3) | 0.0479 (8)* | |
C10 | 0.2941 (8) | 0.4056 (7) | 0.4812 (3) | 0.0479 (8)* | |
N5 | 0.4301 (13) | 0.2229 (8) | 0.3675 (3) | 0.0884 (11)* | |
O1 | 0.4767 (14) | 0.1042 (8) | 0.4171 (3) | 0.0884 (11)* | |
O2 | 0.4452 (17) | 0.2071 (8) | 0.2944 (3) | 0.0884 (11)* | |
O8 | 0.1263 (12) | 0.8706 (7) | 0.4704 (2) | 0.0884 (11)* | |
Cl1 | −0.0019 (7) | 0.9048 (4) | 0.6691 (2) | 0.0603 (6) | |
H1 | 0.1128 | 0.7170 | 0.5907 | 0.0761* | |
H2 | 0.1274 | 0.5086 | 0.6925 | 0.0761* | |
H3 | 0.2494 | 0.2186 | 0.6655 | 0.0761* | |
H4 | 0.3544 | 0.1517 | 0.5313 | 0.0761* | |
H6 | 0.3715 | 0.5144 | 0.2863 | 0.0761* | |
H7 | 0.2434 | 0.7956 | 0.3249 | 0.0761* | |
H8 | 0.1189 | 0.9557 | 0.4365 | 0.0761* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Cl1 | 0.059 (6) | 0.062 (3) | 0.060 (2) | −0.012 (5) | −0.031 (3) | 0.017 (3) |
Geometric parameters (Å, º) top
O1—N5 | 1.242 (8) | C6—C7 | 1.405 (9) |
O2—N5 | 1.210 (7) | C7—C8 | 1.403 (9) |
O8—C8 | 1.338 (10) | C8—C9 | 1.442 (8) |
N1—C2 | 1.342 (8) | C9—C10 | 1.425 (9) |
N1—C9 | 1.363 (8) | O8—H8 | 0.843 |
N5—C5 | 1.479 (9) | N1—H1 | 0.900 |
C2—C3 | 1.419 (10) | C2—H2 | 0.999 |
C3—C4 | 1.389 (8) | C3—H3 | 1.001 |
C4—C10 | 1.430 (7) | C4—H4 | 1.002 |
C5—C6 | 1.400 (7) | C6—H6 | 0.998 |
C5—C10 | 1.438 (7) | C7—H7 | 0.999 |
| | | |
C2—N1—C9 | 118.9 (6) | C8—C9—C10 | 121.6 (6) |
O1—N5—O2 | 122.5 (7) | C4—C10—C5 | 127.2 (5) |
O1—N5—C5 | 119.1 (5) | C4—C10—C9 | 116.0 (5) |
O2—N5—C5 | 118.4 (6) | C5—C10—C9 | 116.8 (5) |
N1—C2—C3 | 121.6 (6) | C8—O8—H8 | 117 |
C2—C3—C4 | 119.9 (5) | C2—N1—H1 | 120 |
C3—C4—C10 | 119.7 (5) | C9—N1—H1 | 121 |
N5—C5—C6 | 116.5 (5) | N1—C2—H2 | 119 |
N5—C5—C10 | 122.5 (5) | C3—C2—H2 | 119 |
C6—C5—C10 | 121.0 (5) | C2—C3—H3 | 120 |
C5—C6—C7 | 121.8 (5) | C4—C3—H3 | 120 |
C6—C7—C8 | 119.3 (5) | C3—C4—H4 | 121 |
O8—C8—C7 | 122.3 (5) | C10—C4—H4 | 119 |
O8—C8—C9 | 118.1 (6) | C5—C6—H6 | 119 |
C7—C8—C9 | 119.6 (6) | C7—C6—H6 | 120 |
N1—C9—C8 | 114.6 (6) | C6—C7—H7 | 121 |
N1—C9—C10 | 123.8 (5) | C8—C7—H7 | 120 |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···Cl1 | 0.90 | 2.11 | 2.945 (7) | 154 |
O8—H8···Cl1i | 0.84 | 2.17 | 2.950 (6) | 154 |
C2—H2···Cl1ii | 1.00 | 2.61 | 3.515 (8) | 151 |
C4—H4···O1iii | 1.00 | 2.43 | 3.312 (10) | 147 |
C6—H6···O2iv | 1.00 | 2.43 | 3.161 (10) | 130 |
C3—H3···O2v | 1.00 | 2.58 | 3.170 (10) | 118 |
Symmetry codes: (i) −x, −y+2, −z+1; (ii) −x, y−1/2, −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 formula | C9H6N2O3 | C9H7N2O3+·Cl− |
Mr | 190.16 | 226.62 |
Crystal system, space group | Orthorhombic, Fdd2 | Monoclinic, P21/c |
Temperature (K) | 295 | 295 |
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, 90 | 90, 92.49 (3), 90 |
V (Å3) | 3261.4 (15) | 921.9 (8) |
Z | 16 | 4 |
Radiation type | Cu Kα, λ = 1.5418 Å | Cu Kα, λ = 1.5418 Å |
Specimen shape, size (mm) | Flat sheet, 25 × 25 | Flat sheet, 25 × 25 |
|
Data collection |
Diffractometer | DRON-3M diffractometer (Burevestnik, Russia) | DRON-3M diffractometer (Burevestnik, Russia) |
Specimen mounting | Pressed as a thin layer in the specimen holder | Pressed as a thin layer in the specimen holder |
Data collection mode | Reflection | Reflection |
Scan method | Step | Step |
2θ values (°) | 2θmin = 7.90 2θmax = 70.0 2θstep = 0.02 | 2θmin = 9.40 2θmax = 70.0 2θstep = 0.02 |
|
Refinement |
R factors and goodness of fit | Rp = 0.035, Rwp = 0.048, Rexp = 0.023, χ2 = 4.427 | Rp = 0.040, Rwp = 0.056, Rexp = 0.030, χ2 = 3.423 |
No. of data points | 3151 | 3251 |
No. of parameters | 92 | 112 |
No. of restraints | 11 | 11 |
H-atom treatment | H-atom parameters constrained | H-atom parameters constrained |
Hydrogen-bond geometry (Å, º) for (I) top
D—H···A | D—H | H···A | D···A | D—H···A |
O8—H8···N1i | 0.90 | 2.05 | 2.811 (5) | 141 |
C6—H6···O2ii | 1.00 | 2.42 | 3.304 (7) | 147 |
C3—H3···O2iii | 1.00 | 2.59 | 3.472 (6) | 147 |
Symmetry codes: (i) −x, −y+1, z; (ii) −x+1/2, −y+1, z+1/2; (iii) x−1/4, −y+3/4, z−3/4. |
Hydrogen-bond geometry (Å, º) for (II) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···Cl1 | 0.90 | 2.11 | 2.945 (7) | 154 |
O8—H8···Cl1i | 0.84 | 2.17 | 2.950 (6) | 154 |
C2—H2···Cl1ii | 1.00 | 2.61 | 3.515 (8) | 151 |
C4—H4···O1iii | 1.00 | 2.43 | 3.312 (10) | 147 |
C6—H6···O2iv | 1.00 | 2.43 | 3.161 (10) | 130 |
C3—H3···O2v | 1.00 | 2.58 | 3.170 (10) | 118 |
Symmetry codes: (i) −x, −y+2, −z+1; (ii) −x, y−1/2, −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. |
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 π–π 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)