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The planar electron-rich heterocyclic di­amine 2,3-di­amino­phenazine (DAP), C12H10N4, is of particular interest to both chemists and biochemists because of its rich organic chemistry and intense luminescence. In this paper, we report the first structure of DAP in its non-protonated form and describe the intriguing crystal packing, which features π–π, hydrogen- and T-bonded interactions.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270100014712/bm1429sup1.cif
Contains datablocks global, DAP

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270100014712/bm1429DAPsup2.hkl
Contains datablock DAP

CCDC reference: 158272

Comment top

The planar electron-rich heterocyclic diamine 2,3-diaminophenazine (DAP) is a compound which has long been of interest initially because of its chemical and physical properties and more recently because of its mutagenic and genotoxic behaviour. The fact that DAP has a rich and varied chemistry is demonstrated by the vast number of organic transformations that have been published in the literature. In addition, the compound has been well characterized spectroscopically by NMR, absorption and most notably by emission techniques, where the remarkable luminescence of DAP has been intensively studied and exploited in analytical and biochemical applications. \sch

DAP is known to luminesce strongly both in strongly polar organic solvents (Zheng et al., 1997) and in aqueous buffer solution especially when embedded within a micelle structure (Mekler & Bystryak, 1992). Indeed, it is the luminescence of DAP that sparked our interest in the molecule, especially as probes-containing phenazine have shown potential in the exploration of nucleic acid structure. Further, DAP has been shown to damage DNA (Watanabe et al., 1996) and so may have some role to play as a chemotherapeutic agent. The compound has found useful application in analytical chemistry as a catalymetric analyte, where it is used as a marker in fluorimetric determinations of laccose activity (Huang et al., 1998) and in immunoassay determination of enzyme-catalysed reactions such as the oxidation of 1,2-phenylenediamine (o-PD) by horseradish peroxidase (Jiao et al., 1998).

Synthetically, DAP is prepared by the catalysed, autosensitized or photochemical oxidation cyclization of o-PD. The oxidation has been catalysed by various oxidants, including silver oxide, lead(IV) oxide, ferric chloride, cupric chloride and perchlorate and by cobalt perchlorate (Crank & Makin, 1989). The oxidation takes place in two one-electron transfer steps - a mechanism which may have relevance when studying the biological functions of metal-containing proteins (Loveless et al., 1981). The fact that the heterocycle is produced in high yield in neutral or acid conditions, but not in basic conditions, perhaps explains why only structures of the protonated molecule (as its chloride or perchlorate salts) have been previously published (Brownstein & Enright, 1995; Peng & Liaw, 1986). These studies have shown that the heterocycle protonates at the phenazine nitrogen although spectroscopic evidence suggests that the more basic amine nitrogen atoms are protonated in solution. When one of the phenazine nitrogen atoms is protonated the cation may exist in six resonance forms which, when the individual π bond strengths are considered, explains the lack of symmetry of the bond lengths in the structures of protonated DAP. In contrast, the structure of DAP (Fig. 1.) shows a high degree of symmetry both in bond lengths and angles on each side of the molecular C2 axis (Table 1). In the solid state, the structure of DAP is essentially planar, however a small degree of bending is discernable. This curvature may be attributed to the geometry of the central pyrazine ring which displays some distortions from that of an ideal aromatic ring (Table 1).

The crystal packing of DAP (Fig. 2) is particularly interesting and as the molecule is replete with numerous π-bonding and hydrogen-bond donor and acceptor sites it may be expected that it can act as a particularly versatile supramolecular tecton. Indeed, it is found that DAP forms infinite π-π stacks in the x and z directions, a feature which is a consequence of the orthorhombic crystal system. The average arene-arene non-bonded distance is 3.64 Å. The infinite π stacks are connected in three dimensions by way of intermolecular hydrogen bonds (Table 2). The hydrogen bonds connect the amine H1A and H16A and the aromatic H3 and H14 protons of one molecule and the pyrazine nitrogen atoms (N5 and N12) of its nearest neighbour. In addition, there are T-bonded interactions which feature the terminal benzene ring (C6 to C11) of one molecule and the amine protons (H1B and H16B) of its nearest neighbour. The typical NH—π distance is 2.71 Å. The cumulative effect of these intermolecular interactions is to create a particularly attractive three dimensional supramolecular network.

Experimental top

2,3-Diaminophenazine was prepared by addition of a stoichiometric quantity of copper(II) hydroxide to an aqueous suspension of 1,2-phenylenediamine·The resultant brown precipitate was collected by filtration and subsequently crystallized by slow diffusion of acetonitrile vapour into a methanolic solution of the title compound.

Refinement top

H atoms were placed geometrically with C'-H and N—H distances of 0.93 and 0.86 Å, respectively, and Uiso(H) = 1.2Ueq(C', N).

Computing details top

Data collection: SMART (Bruker, 1999); cell refinement: SAINT (Bruker, 1999); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 1997); program(s) used to refine structure: SHELXTL; molecular graphics: ORTEP-32 for Windows (Farrugia, 1998).

Figures top
[Figure 1] Fig. 1. Molecular structure of DAP showing 50% probability displacement ellipsoids.
[Figure 2] Fig. 2. Diagram demonstrating the hydrogen- and T-bonding interactions within the crystal packing of DAP.
Phenazine-2,3-diamine top
Crystal data top
C12H10N4Dx = 1.442 Mg m3
Mr = 210.24Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, P212121Cell parameters from 1452 reflections
a = 4.8355 (8) Åθ = 2.1–26.4°
b = 11.583 (2) ŵ = 0.09 mm1
c = 17.304 (3) ÅT = 293 K
V = 969.2 (3) Å3Trigonal prism, brown
Z = 40.3 × 0.25 × 0.2 mm
F(000) = 440
Data collection top
Bruker AXS SMART CCD area detector
diffractometer
985 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.032
Graphite monochromatorθmax = 26.4°, θmin = 2.1°
ω–2θ scansh = 46
3272 measured reflectionsk = 1413
1182 independent reflectionsl = 218
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)] = 0.041Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.115H-atom parameters constrained
S = 1.05 w = 1/[σ2(Fo2) + (0.0785P)2 + 0.0252P]
where P = (Fo2 + 2Fc2)/3
1182 reflections(Δ/σ)max < 0.001
145 parametersΔρmax = 0.19 e Å3
0 restraintsΔρmin = 0.19 e Å3
Crystal data top
C12H10N4V = 969.2 (3) Å3
Mr = 210.24Z = 4
Orthorhombic, P212121Mo Kα radiation
a = 4.8355 (8) ŵ = 0.09 mm1
b = 11.583 (2) ÅT = 293 K
c = 17.304 (3) Å0.3 × 0.25 × 0.2 mm
Data collection top
Bruker AXS SMART CCD area detector
diffractometer
985 reflections with I > 2σ(I)
3272 measured reflectionsRint = 0.032
1182 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0410 restraints
wR(F2) = 0.115H-atom parameters constrained
S = 1.05Δρmax = 0.19 e Å3
1182 reflectionsΔρmin = 0.19 e Å3
145 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
N10.6437 (5)0.40416 (18)0.61117 (11)0.0326 (6)
H1A0.67720.33120.61090.039*
H1B0.72400.44810.64440.039*
C20.4623 (5)0.45044 (19)0.55864 (13)0.0225 (5)
C30.3303 (5)0.38408 (18)0.50493 (12)0.0235 (5)
H30.37270.30590.50200.028*
C40.1325 (5)0.42995 (18)0.45394 (12)0.0215 (5)
N50.0064 (4)0.36121 (15)0.40245 (11)0.0233 (5)
C60.1894 (5)0.4090 (2)0.35679 (12)0.0227 (5)
C70.3380 (5)0.3399 (2)0.30386 (13)0.0276 (6)
H70.29760.26160.30010.033*
C80.5403 (5)0.3862 (2)0.25808 (14)0.0301 (6)
H80.63730.33910.22400.036*
C90.6025 (5)0.5054 (2)0.26237 (13)0.0294 (6)
H90.73960.53640.23090.035*
C100.4629 (5)0.5750 (2)0.31218 (13)0.0276 (6)
H100.50600.65310.31430.033*
C110.2523 (5)0.53033 (19)0.36109 (13)0.0237 (5)
N120.1178 (4)0.60103 (16)0.41102 (10)0.0243 (5)
C130.0689 (5)0.55304 (18)0.45788 (12)0.0213 (5)
C140.2120 (5)0.62085 (18)0.51267 (13)0.0240 (5)
H140.17450.69950.51550.029*
C150.4038 (5)0.57448 (18)0.56162 (12)0.0226 (5)
N160.5416 (5)0.64086 (16)0.61467 (11)0.0295 (5)
H16A0.50820.71360.61770.035*
H16B0.66160.60970.64490.035*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0369 (13)0.0217 (10)0.0391 (11)0.0029 (11)0.0099 (11)0.0002 (9)
C20.0197 (12)0.0202 (11)0.0276 (11)0.0006 (11)0.0048 (10)0.0026 (9)
C30.0239 (12)0.0161 (10)0.0304 (11)0.0015 (11)0.0023 (11)0.0032 (9)
C40.0214 (12)0.0161 (10)0.0268 (11)0.0003 (11)0.0064 (11)0.0009 (9)
N50.0236 (11)0.0186 (9)0.0277 (9)0.0005 (10)0.0017 (9)0.0009 (8)
C60.0212 (12)0.0227 (11)0.0240 (11)0.0006 (11)0.0055 (10)0.0028 (9)
C70.0277 (13)0.0218 (11)0.0332 (12)0.0016 (11)0.0019 (12)0.0038 (10)
C80.0271 (13)0.0319 (12)0.0313 (12)0.0020 (12)0.0019 (11)0.0040 (11)
C90.0254 (13)0.0322 (13)0.0306 (12)0.0013 (11)0.0015 (12)0.0073 (10)
C100.0287 (13)0.0243 (11)0.0299 (12)0.0029 (12)0.0003 (11)0.0041 (10)
C110.0235 (13)0.0193 (11)0.0283 (11)0.0027 (11)0.0053 (11)0.0012 (9)
N120.0250 (11)0.0187 (9)0.0290 (10)0.0000 (10)0.0017 (9)0.0010 (8)
C130.0201 (13)0.0163 (10)0.0275 (11)0.0001 (10)0.0022 (10)0.0025 (9)
C140.0241 (12)0.0151 (10)0.0328 (11)0.0001 (11)0.0047 (11)0.0006 (9)
C150.0229 (12)0.0192 (11)0.0255 (11)0.0027 (11)0.0037 (11)0.0011 (9)
N160.0343 (12)0.0201 (10)0.0342 (11)0.0011 (10)0.0059 (10)0.0012 (8)
Geometric parameters (Å, º) top
N1—C21.372 (3)C7—C81.368 (3)
C2—C31.365 (3)C8—C91.415 (3)
C2—C151.465 (3)C9—C101.359 (3)
C3—C41.406 (3)C10—C111.421 (3)
C4—N51.342 (3)C11—N121.357 (3)
C4—C131.460 (3)N12—C131.335 (3)
N5—C61.352 (3)C13—C141.412 (3)
C6—C71.413 (3)C14—C151.366 (3)
C6—C111.439 (3)C15—N161.371 (3)
C3—C2—N1122.0 (2)C10—C9—C8120.4 (2)
C3—C2—C15119.1 (2)C9—C10—C11121.2 (2)
N1—C2—C15118.9 (2)N12—C11—C10120.2 (2)
C2—C3—C4122.2 (2)N12—C11—C6121.4 (2)
N5—C4—C3120.12 (19)C10—C11—C6118.4 (2)
N5—C4—C13121.0 (2)C13—N12—C11117.37 (19)
C3—C4—C13118.9 (2)N12—C13—C14120.50 (19)
C4—N5—C6117.59 (18)N12—C13—C4121.4 (2)
N5—C6—C7120.2 (2)C14—C13—C4118.1 (2)
N5—C6—C11121.2 (2)C15—C14—C13122.02 (19)
C7—C6—C11118.6 (2)C14—C15—N16121.7 (2)
C8—C7—C6121.1 (2)C14—C15—C2119.7 (2)
C7—C8—C9120.3 (2)N16—C15—C2118.7 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1A···N5i0.862.393.154 (3)148
N1—H1B···C9ii0.862.793.586 (3)154
N16—H16A···N12iii0.862.293.119 (3)163
N16—H16B···C8ii0.862.683.474 (3)154
C3—H3···N5i0.932.633.371 (3)137
C14—H14···N12iii0.932.823.578 (3)139
Symmetry codes: (i) x1/2, y+1/2, z+1; (ii) x1/2, y+1, z+1/2; (iii) x1/2, y+3/2, z+1.

Experimental details

Crystal data
Chemical formulaC12H10N4
Mr210.24
Crystal system, space groupOrthorhombic, P212121
Temperature (K)293
a, b, c (Å)4.8355 (8), 11.583 (2), 17.304 (3)
V3)969.2 (3)
Z4
Radiation typeMo Kα
µ (mm1)0.09
Crystal size (mm)0.3 × 0.25 × 0.2
Data collection
DiffractometerBruker AXS SMART CCD area detector
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
3272, 1182, 985
Rint0.032
(sin θ/λ)max1)0.625
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.041, 0.115, 1.05
No. of reflections1182
No. of parameters145
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.19, 0.19
Absolute structure parameternot determined

Computer programs: SMART (Bruker, 1999), SAINT (Bruker, 1999), SAINT, SHELXTL (Sheldrick, 1997), SHELXTL, ORTEP-32 for Windows (Farrugia, 1998).

Selected geometric parameters (Å, º) top
N1—C21.372 (3)C11—N121.357 (3)
C4—N51.342 (3)N12—C131.335 (3)
N5—C61.352 (3)C15—N161.371 (3)
C3—C2—N1122.0 (2)C13—N12—C11117.37 (19)
N1—C2—C15118.9 (2)C14—C15—N16121.7 (2)
C4—N5—C6117.59 (18)N16—C15—C2118.7 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1A···N5i0.862.393.154 (3)148
N1—H1B···C9ii0.862.793.586 (3)154
N16—H16A···N12iii0.862.293.119 (3)163
N16—H16B···C8ii0.862.683.474 (3)154
C3—H3···N5i0.932.633.371 (3)137
C14—H14···N12iii0.932.823.578 (3)139
Symmetry codes: (i) x1/2, y+1/2, z+1; (ii) x1/2, y+1, z+1/2; (iii) x1/2, y+3/2, z+1.
 

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