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In [beta]-phenazine, C12H9N2, the mol­ecules show a sandwich herring-bone type of packing. The experimental crystal structure shows very good agreement with that predicted earlier from systematic searches of potential packing arrangements for the known unit cell [Hammond, Roberts, Smith & Docherty (1999). J. Phys. Chem. B, 103, 7762-7770].

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270102001464/os1149sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270102001464/os1149Isup2.hkl
Contains datablock I

CCDC reference: 183031

Comment top

It is well known that phenazine crystallizes in two polymorphic forms. The structure of the stable phase (α-phenazine, m.p. 449.5 K) was first determined by Herbstein & Schmidt (1955) and later redetermined by Woźniak et al. (1991). The existence of a second polymorph was also first recognized by Herbstein & Schmidt (1955), who reported the space group and unit-cell parameters, and described the morphology of the β phase. To our knowledge, no other experimental data have been reported on the less stable polymorph to date, and β-phenazine seems to exemplify a disappearing polymorph case (Dunitz & Bernstein, 1995). Nevertheless, Hammond et al. (1999), using the systematic search method of potential packing arrangements, predicted the crystal structure of the β polymorph.

Recently, by chance, we have obtained good quality single crystals of β-phenazine, (I), from a crystallization mixture consisting of phenazine, 1,3,5-trihydroxybenzene and ethanol, by slow evaporation of the solution. In the first crop, we isolated several block-like crystals of α-phenazine and two rod-like crystals of dimensions 1 × 0.2 × 0.2 mm which, after measuring the unit-cell parameters, turned out to be the β-form. The melting point of these crystals (431 K) is 18 K lower than that of the α phase (449 K). The crystal structure of β-phenazine, (I), is presented here. \sch

The bond lengths and angles of the phenazine molecule in both polymorphic forms are very similar. In contrast with α-phenazine, for which a γ-arrangement (Desiraju & Gavezzoti, 1989) of the heteroaromatic rings has been observed, β-phenazine shows a sandwich herringbone type of packing.

The common structural motif for the two polymorphs is a chain of molecules connected via pairs of C—H···N interactions. For the α-form, H···N 2.89 Å and C—H···N 146°. For the β-form, H3···N13i 2.71 (2) Å and C3—H3···N13i 156.5 (16)°, and H8···N14ii 2.71 (2) Å and C8—H8···N14ii 153.9 (16)° [symmetry codes: (i) x, y, 1 + z; (ii) x, y, z - 1]. The interplanar distance between adjacent phenazine molecules along the chain is 1.26 Å in the α polymorph and 1.088 (3) Å in the β form. In the β-polymorph, there is an additional short C—H···N contact between molecules related by an n glide [H5···N14iii 2.60 (2) Å and C5—H5···N14iii 145.1 (16)°; symmetry code: (iii) x - 1/2, 1/2 - y, z - 1/2].

The structure determined from the single-crystal of (I) is very close to that predicted by Hammond et al. (1999), as can be seen from Fig. 2, which shows the superposition of the postulated and experimentally determined crystal structures. The ππ stack distance in the β-phenazine structure is 3.498 (3) Å (predicted distance 3.53 Å), the centroid-centroid distance within the stack is 3.80 Å (predicted 3.81 Å) and the herringbone angle is 71.4 (3)° (predicted 72.9°).

Experimental top

Good quality single crystals of β-phenazine were formed in a crystallization mixture consisting of phenazine (0.694 mmol; Fluka), 1,3,5-trihydroxybenzene (0.395 mmol; Fluka) and ethanol (10 ml) after slow evaporation of the solution.

Computing details top

Data collection: CRYSALIS (Oxford Diffraction, 2001); cell refinement: CRYSALIS; data reduction: CRYSALIS; program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: Stereochemical Workstation Operation Manual (Siemens, 1989); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. A view of the molecule of β-phenazine with 50% probability displacement ellipsoids. H atoms are shown as small spheres of arbitrary radii.
[Figure 2] Fig. 2. The superposition of the postulated (dashed lines) and experimentally determined (solid lines) crystal structures of β-phenazine.
phenazine β-polymorph top
Crystal data top
C12H8N2Dx = 1.309 Mg m3
Mr = 180.20Melting point: 431K K
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
a = 11.6418 (12) ÅCell parameters from 2800 reflections
b = 11.5449 (11) Åθ = 3.7–25.0°
c = 6.8981 (7) ŵ = 0.08 mm1
β = 99.476 (10)°T = 293 K
V = 914.48 (16) Å3Prism, yellow
Z = 40.3 × 0.2 × 0.2 mm
F(000) = 376
Data collection top
Kuma KM-4 CCD κ geometry
diffractometer
1272 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.031
Graphite monochromatorθmax = 25.0°, θmin = 3.7°
ω scansh = 1313
4500 measured reflectionsk = 138
1604 independent reflectionsl = 88
Refinement top
Refinement on F2Hydrogen site location: difference Fourier map
Least-squares matrix: fullAll H-atom parameters refined
R[F2 > 2σ(F2)] = 0.053 w = 1/[σ2(Fo2) + (0.0716P)2 + 0.0381P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.149(Δ/σ)max < 0.001
S = 1.23Δρmax = 0.14 e Å3
1604 reflectionsΔρmin = 0.12 e Å3
160 parametersExtinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.026 (7)
Primary atom site location: coordinates from J. Phys. Chem. B, 103, 7762 (1999)
Crystal data top
C12H8N2V = 914.48 (16) Å3
Mr = 180.20Z = 4
Monoclinic, P21/nMo Kα radiation
a = 11.6418 (12) ŵ = 0.08 mm1
b = 11.5449 (11) ÅT = 293 K
c = 6.8981 (7) Å0.3 × 0.2 × 0.2 mm
β = 99.476 (10)°
Data collection top
Kuma KM-4 CCD κ geometry
diffractometer
1272 reflections with I > 2σ(I)
4500 measured reflectionsRint = 0.031
1604 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0530 restraints
wR(F2) = 0.149All H-atom parameters refined
S = 1.23Δρmax = 0.14 e Å3
1604 reflectionsΔρmin = 0.12 e Å3
160 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
C10.01654 (15)0.15551 (14)0.3448 (2)0.0414 (5)
C20.06582 (15)0.14216 (14)0.5480 (2)0.0420 (5)
C30.01104 (17)0.19765 (17)0.6929 (3)0.0525 (5)
H30.0463 (17)0.1870 (16)0.830 (3)0.062 (5)*
C40.08431 (18)0.26431 (18)0.6378 (3)0.0593 (6)
H40.1228 (18)0.3008 (18)0.742 (3)0.071 (6)*
C50.13282 (18)0.27771 (18)0.4371 (3)0.0585 (6)
H50.2011 (18)0.3274 (17)0.398 (3)0.060 (6)*
C60.08454 (17)0.22539 (16)0.2958 (3)0.0520 (5)
H60.1175 (17)0.2343 (16)0.159 (3)0.058 (5)*
C70.16029 (15)0.04107 (14)0.2577 (3)0.0426 (5)
C80.21420 (19)0.01561 (16)0.1137 (3)0.0539 (5)
H80.1770 (18)0.0068 (18)0.028 (3)0.077 (7)*
C90.31299 (19)0.07804 (18)0.1679 (3)0.0629 (6)
H90.3507 (18)0.1154 (17)0.065 (3)0.065 (6)*
C100.3638 (2)0.08772 (19)0.3689 (3)0.0649 (6)
H100.4332 (19)0.1324 (17)0.401 (3)0.069 (6)*
C110.31476 (18)0.03677 (18)0.5098 (3)0.0579 (6)
H110.3486 (18)0.0399 (17)0.649 (3)0.071 (6)*
C120.21100 (15)0.02927 (14)0.4609 (3)0.0436 (5)
N130.06430 (13)0.10528 (12)0.2019 (2)0.0467 (5)
N140.16283 (13)0.07926 (12)0.6036 (2)0.0470 (5)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0444 (11)0.0378 (9)0.0400 (10)0.0048 (7)0.0011 (8)0.0015 (7)
C20.0465 (10)0.0379 (9)0.0396 (10)0.0034 (8)0.0011 (8)0.0022 (7)
C30.0609 (12)0.0550 (12)0.0408 (11)0.0038 (10)0.0057 (9)0.0013 (9)
C40.0635 (14)0.0583 (12)0.0577 (13)0.0122 (10)0.0139 (11)0.0005 (10)
C50.0543 (13)0.0551 (12)0.0639 (13)0.0122 (10)0.0030 (10)0.0056 (10)
C60.0533 (12)0.0510 (11)0.0479 (12)0.0022 (9)0.0032 (9)0.0064 (9)
C70.0485 (10)0.0378 (9)0.0406 (10)0.0071 (8)0.0052 (8)0.0019 (7)
C80.0671 (13)0.0503 (11)0.0452 (12)0.0006 (10)0.0120 (10)0.0018 (9)
C90.0723 (15)0.0594 (12)0.0616 (14)0.0065 (11)0.0242 (12)0.0050 (10)
C100.0578 (14)0.0677 (14)0.0693 (15)0.0170 (11)0.0109 (12)0.0007 (11)
C110.0552 (12)0.0658 (13)0.0497 (12)0.0100 (10)0.0005 (10)0.0027 (10)
C120.0471 (10)0.0424 (9)0.0407 (10)0.0017 (8)0.0051 (8)0.0001 (8)
N130.0520 (10)0.0448 (9)0.0407 (9)0.0020 (7)0.0003 (7)0.0018 (7)
N140.0492 (9)0.0493 (9)0.0399 (9)0.0012 (7)0.0003 (7)0.0005 (7)
Geometric parameters (Å, º) top
C1—N131.341 (2)C7—N131.343 (2)
C1—C61.421 (2)C7—C81.419 (3)
C1—C21.433 (2)C7—C121.435 (2)
C2—N141.344 (2)C8—C91.357 (3)
C2—C31.423 (2)C8—H81.01 (2)
C3—C41.353 (3)C9—C101.419 (3)
C3—H30.98 (2)C9—H90.99 (2)
C4—C51.415 (3)C10—C111.341 (3)
C4—H41.00 (2)C10—H100.95 (2)
C5—C61.346 (3)C11—C121.421 (3)
C5—H50.98 (2)C11—H110.97 (2)
C6—H60.97 (2)C12—N141.341 (2)
N13—C1—C6119.88 (16)N13—C7—C12121.42 (16)
N13—C1—C2121.68 (16)C8—C7—C12118.81 (17)
C6—C1—C2118.43 (17)C9—C8—C7120.29 (19)
N14—C2—C3119.68 (15)C9—C8—H8122.1 (13)
N14—C2—C1121.30 (16)C7—C8—H8117.6 (13)
C3—C2—C1119.02 (17)C8—C9—C10120.6 (2)
C4—C3—C2120.04 (18)C8—C9—H9119.2 (12)
C4—C3—H3122.6 (12)C10—C9—H9120.2 (12)
C2—C3—H3117.3 (12)C11—C10—C9121.0 (2)
C3—C4—C5120.9 (2)C11—C10—H10120.8 (13)
C3—C4—H4118.9 (12)C9—C10—H10118.1 (13)
C5—C4—H4120.1 (12)C10—C11—C12120.62 (19)
C6—C5—C4120.83 (19)C10—C11—H11123.0 (13)
C6—C5—H5118.6 (11)C12—C11—H11116.4 (13)
C4—C5—H5120.6 (11)N14—C12—C11119.89 (16)
C5—C6—C1120.73 (18)N14—C12—C7121.45 (16)
C5—C6—H6121.1 (12)C11—C12—C7118.66 (17)
C1—C6—H6118.2 (12)C1—N13—C7116.99 (14)
N13—C7—C8119.77 (16)C12—N14—C2117.14 (14)

Experimental details

Crystal data
Chemical formulaC12H8N2
Mr180.20
Crystal system, space groupMonoclinic, P21/n
Temperature (K)293
a, b, c (Å)11.6418 (12), 11.5449 (11), 6.8981 (7)
β (°) 99.476 (10)
V3)914.48 (16)
Z4
Radiation typeMo Kα
µ (mm1)0.08
Crystal size (mm)0.3 × 0.2 × 0.2
Data collection
DiffractometerKuma KM-4 CCD κ geometry
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
4500, 1604, 1272
Rint0.031
(sin θ/λ)max1)0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.053, 0.149, 1.23
No. of reflections1604
No. of parameters160
H-atom treatmentAll H-atom parameters refined
Δρmax, Δρmin (e Å3)0.14, 0.12

Computer programs: CRYSALIS (Oxford Diffraction, 2001), CRYSALIS, SHELXL97 (Sheldrick, 1997), Stereochemical Workstation Operation Manual (Siemens, 1989), SHELXL97.

Selected geometric parameters (Å, º) top
C1—N131.341 (2)C7—N131.343 (2)
C1—C61.421 (2)C7—C81.419 (3)
C1—C21.433 (2)C7—C121.435 (2)
C2—N141.344 (2)C8—C91.357 (3)
C2—C31.423 (2)C9—C101.419 (3)
C3—C41.353 (3)C10—C111.341 (3)
C4—C51.415 (3)C11—C121.421 (3)
C5—C61.346 (3)C12—N141.341 (2)
N13—C1—C6119.88 (16)N13—C7—C12121.42 (16)
N13—C1—C2121.68 (16)C8—C7—C12118.81 (17)
C6—C1—C2118.43 (17)C9—C8—C7120.29 (19)
N14—C2—C3119.68 (15)C8—C9—C10120.6 (2)
N14—C2—C1121.30 (16)C11—C10—C9121.0 (2)
C3—C2—C1119.02 (17)C10—C11—C12120.62 (19)
C4—C3—C2120.04 (18)N14—C12—C11119.89 (16)
C3—C4—C5120.9 (2)N14—C12—C7121.45 (16)
C6—C5—C4120.83 (19)C11—C12—C7118.66 (17)
C5—C6—C1120.73 (18)C1—N13—C7116.99 (14)
N13—C7—C8119.77 (16)C12—N14—C2117.14 (14)
 

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