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The title compound, alternatively known as 3-acetoxy-2-(acetylamino)pyridinium betaine of squaric acid, C13H10N2O6, has been synthesized. The bond distances within the squarate ring indicate two possible resonance structures. The mean planes of the pyridinium and squarate systems are inclined at an angle of 24.0 (2)° with respect to one another due to a strong intramolecular hydrogen-bonding interaction between the amide NH group and a squarate O atom. In the extended structure, there are additional weak π–π and π–ring interactions, which also stabilize the crystal structure.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270104031841/dn1073sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270104031841/dn1073Isup2.hkl
Contains datablock I

CCDC reference: 268100

Comment top

Over the past decade, extensive studies have been made of the synthesis of nonlinear optical (NLO) materials based on organic compounds, because of their potential application in various fields, such as telecommunications, optical data storage and optical information processing (Chemla & Zyss, 1987; Prasad & Williams, 1991). Because of their notable chemical flexibility, which allows for molecular engineering of the nonlinear optical response, and their fast electronic responses, organic materials are particularly interesting candidates for the elaboration of optimized NLO materials. Their nonlinearity is based on the presence of molecular units containing a strongly delocalized π-electron system, with donor and acceptor groups located at opposite ends of the molecule (Nalwa et al., 1997; Wolff & Wortmann, 1999). Among such materials, the substituted betaines play an important role because of their dipolar structure (Schmidt et al., 1984; Kolev et al., 2004). The conversion of the N atom of (2-acetylamino-3-carbetoxy)pyridine into the corresponding pyridinium betaine provides a way of enhancing the charge-transfer transition at the molecular level, a requisite for a design of efficient second- and third-order nonlinear optical materials. As part of our ongoing research on squaric acid (H2SQ; Uçar et al., 2004), the title compound, (I), has been synthesized and its crystal structure (Fig. 1) is reported. The reaction mechanism for the title compound is shown in the scheme.

The C—C distances in the squarate ring systems of (I) reflect partial double-bond character for C1—C2 [1.432 (6) Å] and C1—C4 [1.412 (6) Å], and single-bond character for C2—C3 [1.516 (6) Å] and C3—C4 [1.513 (6) Å]. These lengths represent average values for the two possible resonance structures. The bond distances of the semi-carbonyl bonds are O1—C2 1.228 (5) Å and O3—C4 1.244 (5) Å, and these bond lengths indicate that the negative charge is located partially on atoms O1 and O3. A strong donor effect is observed for the carbetoxy group. Conjugation between it and the positively charged strong acceptor atom N1 results in a shortening of C3—O2 [1.203 (5) Å].

The pyridinium and squarate planes are essentially planar (r.m.s. deviations 0.0195 and 0.0070 Å, respectively), and the largest deviations from these mean planes are 0.030 (3) Å for atom C8 and 0.012 (4) Å for atom C2. The dihedral angle between the mean planes of the pyridinium and squarate ring systems is 23.79 (15)°, whereas this angle is 5.3 (2)° in the related 4-methoxypyridinium-3-squarate compound (Kolev et al., 2004). This is apparently due to the strong intramolecular hydrogen-bonding interaction between atom H2 of the amide N atom and the squarate atom O3 (Table 2), and the steric hindrance of the substituted groups.

The most striking feature of this structure is the occurrence of C—H···O interactions. Indeed, the C5, C6, and C7 carbon atoms of the pyridine ring form intermolecular hydrogen bonds with the O2 and O3 oxygen atoms of symmetry related squarate rings. These C—H···O hydrogen bonds build then a double chain of molecules extending along [010] as shown in Fig. 2. Although, two symmetry related pyridine ring of neighbouring molecules are oriented in such a way that the perpendicular distance between them is 3.06 Å, the centroid to centroid distance, 4.82 Å, is too long to consider a π-π interaction. Indeed, the angle between the ring normal of the pyridine plane and the centroid vector is 50.6° indicating that the two rings are too much slipped to each other to allow a π-π interaction (Janiak, 2000).

Experimental top

The title compound was prepared according to the method of Schmidt et al., 1984). Squaric acid (1 g, 8.7 mmol) was dissolved in acetic anhydride (50 ml) by continuous stirring and heating under reflux. A solution of 2-amino-3-hydroxypyridine (0.957 g, 8.7 mmol) dissolved in acetic anhydride (10 ml) was then added. After a few minutes, the solution turned dark yellow. A yellow precipate was obtained from this dark-yellow solution after heating for 60 min and evaporating half the solvent. The product was filtered off after cooling and recrystallized from methanol (yield 85%).

Refinement top

All H atoms were located from difference maps and then treated as riding atoms, with C—H distances of 0.93 (for CH[pyridine] H), 0.96 (for CH3 H) and N—H distance of 0.86 Å, and with Uiso(H) values of 1.2Ueq(for C[pyridine] and N) and 1.5Ueq(for CH3).

Computing details top

Data collection: X-AREA (Stoe & Cie, 2002); cell refinement: X-AREA; data reduction: X-RED32 (Stoe & Cie, 2002); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPIII (Burnett & Johnson, 1996); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.
[Figure 2] Fig. 2. The three-dimensional structure of (I). Dashed lines indicate the hydrogen bonds, as well as the ππ and π–ring interactions. Displacement ellipsoids are drawn at the 10% probability level. [Symmetry codes: (iii) −x, 2 − y, 1 - z; (iv) −x, 1 − y, 2 − z].
3-Acetoxy-2-(acetylamino)pyridinium-1-squarate top
Crystal data top
C13H10N2O6Z = 2
Mr = 290.23F(000) = 300
Triclinic, P1Dx = 1.486 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 8.8959 (16) ÅCell parameters from 5022 reflections
b = 8.9014 (16) Åθ = 2.5–26.0°
c = 8.9288 (16) ŵ = 0.12 mm1
α = 88.895 (15)°T = 293 K
β = 87.795 (15)°Plate, yellow
γ = 66.667 (14)°0.28 × 0.20 × 0.08 mm
V = 648.7 (2) Å3
Data collection top
Stoe IPDS 2
diffractometer
2477 independent reflections
Radiation source: fine-focus sealed tube1366 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.087
Detector resolution: 6.67 pixels mm-1θmax = 25.8°, θmin = 2.5°
ω scansh = 1010
Absorption correction: integration
(X-RED32; Stoe & Cie, 2002)
k = 1010
Tmin = 0.970, Tmax = 0.992l = 1010
8629 measured reflections
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.069H-atom parameters constrained
wR(F2) = 0.154 w = 1/[σ2(Fo2) + (0.0569P)2 + 0.2421P]
where P = (Fo2 + 2Fc2)/3
S = 1.02(Δ/σ)max = 0.002
2475 reflectionsΔρmax = 0.22 e Å3
193 parametersΔρmin = 0.20 e Å3
0 restraintsExtinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.027 (5)
Crystal data top
C13H10N2O6γ = 66.667 (14)°
Mr = 290.23V = 648.7 (2) Å3
Triclinic, P1Z = 2
a = 8.8959 (16) ÅMo Kα radiation
b = 8.9014 (16) ŵ = 0.12 mm1
c = 8.9288 (16) ÅT = 293 K
α = 88.895 (15)°0.28 × 0.20 × 0.08 mm
β = 87.795 (15)°
Data collection top
Stoe IPDS 2
diffractometer
2477 independent reflections
Absorption correction: integration
(X-RED32; Stoe & Cie, 2002)
1366 reflections with I > 2σ(I)
Tmin = 0.970, Tmax = 0.992Rint = 0.087
8629 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0690 restraints
wR(F2) = 0.154H-atom parameters constrained
S = 1.02Δρmax = 0.22 e Å3
2475 reflectionsΔρmin = 0.20 e Å3
193 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
C10.1598 (5)0.4645 (4)0.7452 (4)0.0387 (9)
C20.1712 (5)0.4275 (5)0.9028 (5)0.0463 (10)
C30.1503 (6)0.2713 (5)0.8675 (5)0.0507 (11)
C40.1389 (5)0.3220 (4)0.7035 (4)0.0397 (9)
C50.1245 (5)0.7430 (5)0.7549 (4)0.0468 (10)
H50.08750.74360.85370.056*
C60.1368 (5)0.8782 (5)0.6964 (5)0.0494 (11)
H60.11340.96950.75630.059*
C70.1841 (5)0.8817 (5)0.5472 (5)0.0457 (10)
H70.19320.97480.50640.055*
C80.2171 (5)0.7469 (4)0.4614 (4)0.0390 (9)
C90.2157 (5)0.6018 (4)0.5227 (4)0.0362 (9)
C100.3865 (5)0.3874 (4)0.3475 (4)0.0395 (9)
C110.3994 (6)0.2277 (5)0.2900 (5)0.0591 (13)
H11A0.49850.17920.23000.089*
H11B0.30690.24380.23010.089*
H11C0.40120.15660.37280.089*
C120.3697 (6)0.7824 (5)0.2508 (5)0.0490 (11)
C130.3782 (7)0.7723 (7)0.0848 (5)0.0763 (16)
H13A0.31300.87750.04340.114*
H13B0.33710.69340.05400.114*
H13C0.48990.73970.04950.114*
N10.1660 (4)0.6046 (3)0.6706 (3)0.0367 (8)
N20.2535 (4)0.4586 (4)0.4465 (3)0.0396 (8)
H20.18920.40840.46120.048*
O10.1876 (4)0.4925 (4)1.0171 (3)0.0620 (9)
O20.1430 (5)0.1577 (4)0.9380 (4)0.0777 (11)
O30.1200 (4)0.2617 (3)0.5851 (3)0.0484 (8)
O40.2387 (3)0.7502 (3)0.3077 (3)0.0443 (7)
O50.4594 (4)0.8134 (4)0.3293 (4)0.0637 (9)
O60.4830 (4)0.4497 (3)0.3171 (3)0.0520 (8)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.037 (2)0.039 (2)0.039 (2)0.0132 (18)0.0002 (17)0.0025 (17)
C20.047 (3)0.041 (2)0.046 (2)0.012 (2)0.003 (2)0.0028 (19)
C30.059 (3)0.043 (2)0.048 (2)0.017 (2)0.000 (2)0.001 (2)
C40.036 (2)0.034 (2)0.047 (2)0.0125 (18)0.0041 (18)0.0040 (17)
C50.055 (3)0.042 (2)0.040 (2)0.016 (2)0.006 (2)0.0129 (18)
C60.057 (3)0.035 (2)0.056 (3)0.018 (2)0.001 (2)0.0090 (19)
C70.044 (3)0.033 (2)0.061 (3)0.0161 (19)0.009 (2)0.0017 (19)
C80.037 (2)0.036 (2)0.043 (2)0.0123 (18)0.0070 (18)0.0048 (17)
C90.029 (2)0.039 (2)0.039 (2)0.0120 (17)0.0048 (17)0.0028 (17)
C100.042 (3)0.039 (2)0.033 (2)0.010 (2)0.0028 (19)0.0001 (16)
C110.073 (3)0.047 (2)0.050 (3)0.015 (2)0.009 (2)0.011 (2)
C120.051 (3)0.045 (2)0.050 (3)0.017 (2)0.001 (2)0.0083 (19)
C130.088 (4)0.091 (4)0.050 (3)0.036 (3)0.000 (3)0.014 (3)
N10.039 (2)0.0355 (17)0.0356 (18)0.0148 (15)0.0004 (15)0.0049 (13)
N20.042 (2)0.0369 (17)0.0437 (18)0.0194 (15)0.0002 (16)0.0062 (14)
O10.085 (2)0.0593 (19)0.0426 (17)0.0285 (17)0.0102 (16)0.0039 (14)
O20.124 (3)0.0492 (19)0.061 (2)0.037 (2)0.008 (2)0.0074 (16)
O30.060 (2)0.0484 (16)0.0481 (17)0.0326 (15)0.0007 (14)0.0068 (13)
O40.0462 (18)0.0460 (16)0.0414 (16)0.0187 (14)0.0060 (13)0.0059 (12)
O50.062 (2)0.071 (2)0.069 (2)0.0384 (18)0.0017 (17)0.0003 (16)
O60.0434 (19)0.0526 (17)0.0569 (18)0.0162 (15)0.0017 (15)0.0035 (13)
Geometric parameters (Å, º) top
C1—C41.411 (5)C8—C91.398 (5)
C1—N11.422 (5)C9—N21.370 (4)
C1—C21.437 (5)C9—N11.374 (5)
C2—O11.224 (4)C10—O61.212 (5)
C2—C31.515 (6)C10—N21.389 (5)
C3—O21.202 (5)C10—C111.480 (5)
C3—C41.519 (6)C11—H11A0.9600
C4—O31.242 (4)C11—H11B0.9600
C5—C61.344 (6)C11—H11C0.9600
C5—N11.369 (5)C12—O51.195 (5)
C5—H50.9300C12—O41.383 (5)
C6—C71.385 (6)C12—C131.484 (6)
C6—H60.9300C13—H13A0.9600
C7—C81.361 (5)C13—H13B0.9600
C7—H70.9300C13—H13C0.9600
C8—O41.380 (4)N2—H20.8600
C4—C1—N1136.4 (3)N1—C9—C8117.3 (3)
C4—C1—C295.5 (3)O6—C10—N2122.3 (3)
N1—C1—C2128.1 (3)O6—C10—C11124.8 (4)
O1—C2—C1137.0 (4)N2—C10—C11112.9 (4)
O1—C2—C3135.2 (4)C10—C11—H11A109.5
C1—C2—C387.8 (3)C10—C11—H11B109.5
O2—C3—C2136.2 (4)H11A—C11—H11B109.5
O2—C3—C4135.7 (4)C10—C11—H11C109.5
C2—C3—C488.1 (3)H11A—C11—H11C109.5
O3—C4—C1136.4 (4)H11B—C11—H11C109.5
O3—C4—C3135.0 (3)O5—C12—O4122.5 (4)
C1—C4—C388.6 (3)O5—C12—C13127.4 (5)
C6—C5—N1120.8 (4)O4—C12—C13110.1 (4)
C6—C5—H5119.6C12—C13—H13A109.5
N1—C5—H5119.6C12—C13—H13B109.5
C5—C6—C7120.2 (4)H13A—C13—H13B109.5
C5—C6—H6119.9C12—C13—H13C109.5
C7—C6—H6119.9H13A—C13—H13C109.5
C8—C7—C6119.0 (4)H13B—C13—H13C109.5
C8—C7—H7120.5C5—N1—C9121.0 (3)
C6—C7—H7120.5C5—N1—C1116.6 (3)
C7—C8—O4122.0 (3)C9—N1—C1122.3 (3)
C7—C8—C9121.5 (4)C9—N2—C10125.8 (3)
O4—C8—C9116.2 (3)C9—N2—H2117.1
N2—C9—N1117.1 (3)C10—N2—H2117.1
N2—C9—C8125.6 (3)C8—O4—C12117.8 (3)
C4—C1—C2—O1178.6 (5)O4—C8—C9—N28.5 (5)
N1—C1—C2—O10.3 (8)C7—C8—C9—N15.4 (5)
C4—C1—C2—C30.3 (3)O4—C8—C9—N1168.8 (3)
N1—C1—C2—C3179.2 (4)C6—C5—N1—C92.3 (6)
O1—C2—C3—O20.3 (10)C6—C5—N1—C1175.8 (4)
C1—C2—C3—O2179.2 (6)N2—C9—N1—C5179.5 (4)
O1—C2—C3—C4178.7 (5)C8—C9—N1—C51.9 (5)
C1—C2—C3—C40.3 (3)N2—C9—N1—C12.6 (5)
N1—C1—C4—O31.3 (8)C8—C9—N1—C1179.9 (3)
C2—C1—C4—O3180.0 (5)C4—C1—N1—C5154.9 (4)
N1—C1—C4—C3179.0 (5)C2—C1—N1—C523.5 (6)
C2—C1—C4—C30.3 (3)C4—C1—N1—C927.1 (7)
O2—C3—C4—O31.1 (9)C2—C1—N1—C9154.6 (4)
C2—C3—C4—O3179.9 (5)N1—C9—N2—C10137.6 (4)
O2—C3—C4—C1179.2 (6)C8—C9—N2—C1045.2 (5)
C2—C3—C4—C10.3 (3)O6—C10—N2—C91.2 (6)
N1—C5—C6—C73.2 (6)C11—C10—N2—C9176.6 (3)
C5—C6—C7—C80.3 (6)C7—C8—O4—C1263.5 (5)
C6—C7—C8—O4169.2 (4)C9—C8—O4—C12122.4 (4)
C6—C7—C8—C94.6 (6)O5—C12—O4—C83.0 (6)
C7—C8—C9—N2177.3 (4)C13—C12—O4—C8177.0 (3)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N2—H2···O30.861.962.733 (4)149
C5—H5···O2i0.932.603.449 (6)151
C6—H6···O2ii0.932.453.343 (5)161
C7—H7···O3ii0.932.483.222 (4)137
Symmetry codes: (i) x, y+1, z+2; (ii) x, y+1, z.

Experimental details

Crystal data
Chemical formulaC13H10N2O6
Mr290.23
Crystal system, space groupTriclinic, P1
Temperature (K)293
a, b, c (Å)8.8959 (16), 8.9014 (16), 8.9288 (16)
α, β, γ (°)88.895 (15), 87.795 (15), 66.667 (14)
V3)648.7 (2)
Z2
Radiation typeMo Kα
µ (mm1)0.12
Crystal size (mm)0.28 × 0.20 × 0.08
Data collection
DiffractometerStoe IPDS 2
diffractometer
Absorption correctionIntegration
(X-RED32; Stoe & Cie, 2002)
Tmin, Tmax0.970, 0.992
No. of measured, independent and
observed [I > 2σ(I)] reflections
8629, 2477, 1366
Rint0.087
(sin θ/λ)max1)0.613
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.069, 0.154, 1.02
No. of reflections2475
No. of parameters193
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.22, 0.20

Computer programs: X-AREA (Stoe & Cie, 2002), X-AREA, X-RED32 (Stoe & Cie, 2002), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 1997), ORTEPIII (Burnett & Johnson, 1996), WinGX (Farrugia, 1999).

Selected geometric parameters (Å, º) top
C1—C41.411 (5)C3—O21.202 (5)
C1—N11.422 (5)C3—C41.519 (6)
C1—C21.437 (5)C4—O31.242 (4)
C2—O11.224 (4)C10—O61.212 (5)
C2—C31.515 (6)
C1—C2—C387.8 (3)C5—C6—C7120.2 (4)
O2—C3—C2136.2 (4)
C2—C1—N1—C523.5 (6)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N2—H2···O30.861.962.733 (4)149.2
C5—H5···O2i0.932.603.449 (6)151.4
C6—H6···O2ii0.932.453.343 (5)161.3
C7—H7···O3ii0.932.483.222 (4)136.7
Symmetry codes: (i) x, y+1, z+2; (ii) x, y+1, z.
 

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