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In the title compound, 3,4-dioxo-2-(pyridinium-1-yl)cyclo­but-1-enolate, C9H5NO3, mol­ecules are connected three-dimensionally through nonclassical C—H...O and π–π inter­actions [3.220 (3) Å] between the oppositely charged squarate and pyridinium fragments. Classical hydrogen-bonding inter­actions are not observed. In the unit cell, only half an independent molecule is present and a twofold rotation axis passes through the pyridinium ring and the opposite CO group.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536807028887/is2179sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536807028887/is2179Isup2.hkl
Contains datablock I

CCDC reference: 654997

Key indicators

  • Single-crystal X-ray study
  • T = 290 K
  • Mean [sigma](C-C) = 0.003 Å
  • R factor = 0.053
  • wR factor = 0.133
  • Data-to-parameter ratio = 15.0

checkCIF/PLATON results

No syntax errors found



Alert level C PLAT369_ALERT_2_C Long C(sp2)-C(sp2) Bond C1 - C2 ... 1.53 Ang. PLAT369_ALERT_2_C Long C(sp2)-C(sp2) Bond C1 - C2_a ... 1.53 Ang. PLAT480_ALERT_4_C Long H...A H-Bond Reported HC5 .. O2 .. 2.64 Ang. PLAT720_ALERT_4_C Number of Unusual/Non-Standard Label(s) ........ 3
0 ALERT level A = In general: serious problem 0 ALERT level B = Potentially serious problem 4 ALERT level C = Check and explain 0 ALERT level G = General alerts; check 0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data 2 ALERT type 2 Indicator that the structure model may be wrong or deficient 0 ALERT type 3 Indicator that the structure quality may be low 2 ALERT type 4 Improvement, methodology, query or suggestion 0 ALERT type 5 Informative message, check

Comment top

The title compound, (I), has been synthesized as part of our synthetic and structural investigations of new organic materials with nonlinear and electro-optical properties (Chemla & Zyss, 1987; Wolff & Wortmann, 1999). We already analyzed the crystal structures of a number of pyridinium-betaines of squaric acid (Kolev et al., 2001, 2002, 2004; Kolev, Yancheva et al., 2005; Kolev, Wortmann et al., 2005), but without the essential member of the family, the unsubstituted compound, (I), their characterization remains incomplete. In order to provide relevant information on the changes observed upon substitution, we report its characteristic features.

The molecular features of (I) are similar to those in Kolev et al. (2001, 2002, 2004), Kolev, Yancheva et al. (2005), Kolev, Wortmann et al. (2005) and Uçar et al. (2005) with positive and negative charges situated on the pyridinium and squarate moiety, respectively (Scheme 1). The "semicarbonyl" C2—O1 bond length of 1.221 (2) Å shows the complete delocalization of the negative charge. In all reported structures the semi-carbonyl bond lengths, within the squarate fragment, are apparently unaffected by the substitution and their values vary around 1.22 Å. The C=O double bond length is also constant in reported structures with typical values around 1.201 Å. The pyridinium ring in (I) is planar with r.m.s deviation of 0.002 (2) Å and has partially quinoidal character reflected by the shorter C5—C6 and C8—C9 distances, most expressed in the 4-dimethylamino derivative (Kolev et al., 2002).

The C(Sq)—N(py) bond length bond length of 1.403 (4) Å is also unaffected by the presence of different substitutes. From the studied compounds only in 3-acetoxy-2-(acetylamino)pyridinium-1-squarate (Uçar et al., 2005) this value differs slightly and has a value of 1.422 (5) Å.

The dihedral angle between the squarate and pyridinium mean planes also show minor variations within the series of 3- and 4-substituted compounds, but differ significantly from the values for the 2-(3-benzoyl-1-pyridinio)-3,4-dioxocyclobutenolate derivative (Kolev, Yancheva et al., 2005), which is a sign that the conjugation between the molecular fragments is strongly decreased by the substitution at 2- and 3-position.

Similarly to the substituted pyridinium-betaines of squaric acid in the crystal structure of (I) molecules are connected through non-classical C—H···O hydrogen bonds (Table1) and π···π interactions between the oppositely charged squarate and pyridinium fragments [Cg1···O1iii 3.220 (3) Å; Cg1 is the controid of the pyridinium ring; symmetry code: (iii) x, 1 - y, 1/2 + z]. A side-to-side C4—HC4···O1i [symmetry code: (i) -x, 1 - y, -z] interaction of squarate and pyridinium fragments build up straight chains replicating along the c axis. A bifurcated head-to-tail C5—HC5···O2ii [symmetry code: (i) -1/2 + x, -1/2 + y, 1/2 - z] interaction connects three-dimensionally the chains.

Practically in all derivatives of (I) the squarate carbonyl O atom forms a bifurcated bond. The only observed exception is for 3-benzoylpyridinium betaine of squaric acid (Kolev, Yancheva et al., 2005) and could be explained by the steric effect of the phenyl substitute.

Related literature top

For related literature, see: Chemla & Zyss (1987); Kolev et al. (2001, 2002, 2004); Kolev, Wortmann et al. (2005); Kolev, Yancheva et al. (2005); Schmidt et al. (1984); Uçar et al. (2005); Wolff & Wortmann (1999).

Experimental top

The title compound was synthesized according to Schmidt et al. (1984). Crystal suitable for X-ray diffraction has been obtained after slow evaporation from water/ethanol mixture (1:1) at room temperature.

Refinement top

Hydrogen atoms were located in a difference map. All H atoms were constrained to ride on their parent atoms, with Uiso(H) = 1.2Ueq(C).

Structure description top

The title compound, (I), has been synthesized as part of our synthetic and structural investigations of new organic materials with nonlinear and electro-optical properties (Chemla & Zyss, 1987; Wolff & Wortmann, 1999). We already analyzed the crystal structures of a number of pyridinium-betaines of squaric acid (Kolev et al., 2001, 2002, 2004; Kolev, Yancheva et al., 2005; Kolev, Wortmann et al., 2005), but without the essential member of the family, the unsubstituted compound, (I), their characterization remains incomplete. In order to provide relevant information on the changes observed upon substitution, we report its characteristic features.

The molecular features of (I) are similar to those in Kolev et al. (2001, 2002, 2004), Kolev, Yancheva et al. (2005), Kolev, Wortmann et al. (2005) and Uçar et al. (2005) with positive and negative charges situated on the pyridinium and squarate moiety, respectively (Scheme 1). The "semicarbonyl" C2—O1 bond length of 1.221 (2) Å shows the complete delocalization of the negative charge. In all reported structures the semi-carbonyl bond lengths, within the squarate fragment, are apparently unaffected by the substitution and their values vary around 1.22 Å. The C=O double bond length is also constant in reported structures with typical values around 1.201 Å. The pyridinium ring in (I) is planar with r.m.s deviation of 0.002 (2) Å and has partially quinoidal character reflected by the shorter C5—C6 and C8—C9 distances, most expressed in the 4-dimethylamino derivative (Kolev et al., 2002).

The C(Sq)—N(py) bond length bond length of 1.403 (4) Å is also unaffected by the presence of different substitutes. From the studied compounds only in 3-acetoxy-2-(acetylamino)pyridinium-1-squarate (Uçar et al., 2005) this value differs slightly and has a value of 1.422 (5) Å.

The dihedral angle between the squarate and pyridinium mean planes also show minor variations within the series of 3- and 4-substituted compounds, but differ significantly from the values for the 2-(3-benzoyl-1-pyridinio)-3,4-dioxocyclobutenolate derivative (Kolev, Yancheva et al., 2005), which is a sign that the conjugation between the molecular fragments is strongly decreased by the substitution at 2- and 3-position.

Similarly to the substituted pyridinium-betaines of squaric acid in the crystal structure of (I) molecules are connected through non-classical C—H···O hydrogen bonds (Table1) and π···π interactions between the oppositely charged squarate and pyridinium fragments [Cg1···O1iii 3.220 (3) Å; Cg1 is the controid of the pyridinium ring; symmetry code: (iii) x, 1 - y, 1/2 + z]. A side-to-side C4—HC4···O1i [symmetry code: (i) -x, 1 - y, -z] interaction of squarate and pyridinium fragments build up straight chains replicating along the c axis. A bifurcated head-to-tail C5—HC5···O2ii [symmetry code: (i) -1/2 + x, -1/2 + y, 1/2 - z] interaction connects three-dimensionally the chains.

Practically in all derivatives of (I) the squarate carbonyl O atom forms a bifurcated bond. The only observed exception is for 3-benzoylpyridinium betaine of squaric acid (Kolev, Yancheva et al., 2005) and could be explained by the steric effect of the phenyl substitute.

For related literature, see: Chemla & Zyss (1987); Kolev et al. (2001, 2002, 2004); Kolev, Wortmann et al. (2005); Kolev, Yancheva et al. (2005); Schmidt et al. (1984); Uçar et al. (2005); Wolff & Wortmann (1999).

Computing details top

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Bruno et al., 2002); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. View of the molecule and the atom-numbering scheme of (I) showing 50% probability displacement ellipsoids. H atoms are shown as small spheres of arbitrary radii [symmetry code: (i) 1 - x, y,1/2 - z].
[Figure 2] Fig. 2. A view of the molecular packing in (I). All H atoms not involved in the short contact interactions have been omitted for clarity [symmetry codes: (i) -x,1 - y,-z; (ii) -1/2 + x, -1/2 + y, 1/2 - z; (iii) x, 1 - y, 1/2 + z].
3,4-dioxo-2-(pyridinium-1-yl)cyclobut-1-enolate top
Crystal data top
C9H5NO3Dx = 1.497 Mg m3
Mr = 175.14Melting point: not measured K
Orthorhombic, PbcnMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2n 2abCell parameters from 22 reflections
a = 5.0654 (2) Åθ = 19.3–19.6°
b = 18.8003 (17) ŵ = 0.12 mm1
c = 8.1609 (4) ÅT = 290 K
V = 777.17 (9) Å3Prism, yellow
Z = 40.40 × 0.36 × 0.36 mm
F(000) = 360
Data collection top
Enraf–Nonius CAD-4
diffractometer
Rint = 0.070
Radiation source: fine-focus sealed tubeθmax = 27.9°, θmin = 2.2°
Graphite monochromatorh = 06
Non–profiled ω/2θ scansk = 2424
3425 measured reflectionsl = 1010
942 independent reflections3 standard reflections every 120 min
559 reflections with I > 2σ(I) intensity decay: 5%
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)] = 0.053Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.134H-atom parameters constrained
S = 1.04 w = 1/[σ2(Fo2) + (0.0456P)2 + 0.3645P]
where P = (Fo2 + 2Fc2)/3
942 reflections(Δ/σ)max < 0.001
63 parametersΔρmax = 0.15 e Å3
0 restraintsΔρmin = 0.20 e Å3
Crystal data top
C9H5NO3V = 777.17 (9) Å3
Mr = 175.14Z = 4
Orthorhombic, PbcnMo Kα radiation
a = 5.0654 (2) ŵ = 0.12 mm1
b = 18.8003 (17) ÅT = 290 K
c = 8.1609 (4) Å0.40 × 0.36 × 0.36 mm
Data collection top
Enraf–Nonius CAD-4
diffractometer
Rint = 0.070
3425 measured reflections3 standard reflections every 120 min
942 independent reflections intensity decay: 5%
559 reflections with I > 2σ(I)
Refinement top
R[F2 > 2σ(F2)] = 0.0530 restraints
wR(F2) = 0.134H-atom parameters constrained
S = 1.04Δρmax = 0.15 e Å3
942 reflectionsΔρmin = 0.20 e Å3
63 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
C10.50000.64018 (18)0.25000.0465 (8)
C20.3375 (4)0.58204 (12)0.1671 (3)0.0408 (5)
C30.50000.53134 (15)0.25000.0356 (6)
C40.3121 (4)0.42083 (12)0.1638 (3)0.0411 (5)
HC40.17790.44990.11940.061 (7)*
C50.3098 (5)0.34857 (13)0.1636 (3)0.0491 (6)
HC50.17060.32010.10320.059*
C60.50000.31182 (18)0.25000.0531 (9)
HC60.50000.26090.25000.064*
N10.50000.45673 (12)0.25000.0349 (6)
O10.1529 (3)0.58096 (9)0.0708 (2)0.0557 (5)
O20.50000.70389 (12)0.25000.0725 (9)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0433 (18)0.0490 (18)0.0471 (18)0.0000.0043 (16)0.000
C20.0356 (11)0.0494 (13)0.0373 (11)0.0003 (10)0.0020 (10)0.0018 (10)
C30.0325 (15)0.0415 (15)0.0330 (14)0.0000.0009 (13)0.000
C40.0336 (10)0.0505 (13)0.0391 (11)0.0035 (11)0.0031 (10)0.0002 (10)
C50.0430 (12)0.0530 (14)0.0512 (13)0.0102 (12)0.0009 (12)0.0054 (11)
C60.051 (2)0.0440 (17)0.065 (2)0.0000.007 (2)0.000
N10.0297 (12)0.0429 (14)0.0319 (12)0.0000.0000 (11)0.000
O10.0484 (9)0.0637 (11)0.0549 (10)0.0019 (9)0.0204 (8)0.0061 (8)
O20.080 (2)0.0418 (13)0.096 (2)0.0000.0218 (18)0.000
Geometric parameters (Å, º) top
C1—O21.198 (4)C4—N11.363 (2)
C1—C21.526 (3)C4—HC40.9436
C2—O11.221 (2)C5—C61.379 (3)
C2—C31.430 (3)C5—HC51.0133
C3—N11.403 (4)C6—HC60.9571
C4—C51.359 (3)
O2—C1—C2135.73 (12)N1—C4—HC4114.5
O2—C1—C2i135.73 (12)C4—C5—C6119.6 (2)
C2—C1—C2i88.5 (2)C4—C5—HC5122.3
O1—C2—C3137.2 (2)C6—C5—HC5118.0
O1—C2—C1135.2 (2)C5i—C6—C5119.9 (3)
C3—C2—C187.55 (16)C5i—C6—HC6120.1
N1—C3—C2i131.82 (11)C5—C6—HC6120.1
N1—C3—C2131.82 (11)C4—N1—C4i120.6 (3)
C2i—C3—C296.4 (2)C4—N1—C3119.69 (13)
C5—C4—N1120.1 (2)C4i—N1—C3119.69 (13)
C5—C4—HC4124.9
O2—C1—C2—O10.9 (3)N1—C4—C5—C60.6 (3)
C2i—C1—C2—O1179.1 (3)C4—C5—C6—C5i0.28 (15)
O2—C1—C2—C3180.0C5—C4—N1—C4i0.29 (16)
C2i—C1—C2—C30.0C5—C4—N1—C3179.71 (16)
O1—C2—C3—N10.9 (3)C2i—C3—N1—C4177.06 (15)
C1—C2—C3—N1180.0C2—C3—N1—C42.94 (15)
O1—C2—C3—C2i179.1 (3)C2i—C3—N1—C4i2.94 (15)
C1—C2—C3—C2i0.0C2—C3—N1—C4i177.06 (15)
Symmetry code: (i) x+1, y, z+1/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C4—HC4···O1ii0.942.363.036 (3)129
C5—HC5···O2iii1.012.643.218 (3)116
Symmetry codes: (ii) x, y+1, z; (iii) x1/2, y1/2, z+1/2.

Experimental details

Crystal data
Chemical formulaC9H5NO3
Mr175.14
Crystal system, space groupOrthorhombic, Pbcn
Temperature (K)290
a, b, c (Å)5.0654 (2), 18.8003 (17), 8.1609 (4)
V3)777.17 (9)
Z4
Radiation typeMo Kα
µ (mm1)0.12
Crystal size (mm)0.40 × 0.36 × 0.36
Data collection
DiffractometerEnraf–Nonius CAD-4
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
3425, 942, 559
Rint0.070
(sin θ/λ)max1)0.659
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.053, 0.134, 1.04
No. of reflections942
No. of parameters63
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.15, 0.20

Computer programs: CAD-4 EXPRESS (Enraf–Nonius, 1994), CAD-4 EXPRESS, XCAD4 (Harms & Wocadlo, 1995), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Bruno et al., 2002), WinGX (Farrugia, 1999).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C4—HC4···O1i0.942.363.036 (3)128.5
C5—HC5···O2ii1.012.643.218 (3)116.4
Symmetry codes: (i) x, y+1, z; (ii) x1/2, y1/2, z+1/2.
 

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