N,N-Dimethyl­anilinium 2,4,6-trinitro­phenolate

Nagarajan Vembu; Frank R Fronczek

doi:10.1107/S1600536808041743

. 2008 Dec 13;65(Pt 1):o111–o112. doi: 10.1107/S1600536808041743

N,N-Dimethylanilinium 2,4,6-trinitrophenolate

Nagarajan Vembu ^a,^*, Frank R Fronczek ^b

PMCID: PMC2968034 PMID: 21581574

Abstract

In the title compound, C₈H₁₂N⁺·C₆H₂N₃O₇ ⁻, there are N—H⋯O and C—H⋯O interactions which generate R ₂ ¹(5), R ₂ ¹(6) and R ₁ ²(6) ring motifs. The supramolecular aggregation is completed by the presence of edge-to-face and offset face-to-face π–π interactions with centroid–centroid distances of 3.673 and 3.697 Å, respectively.

Related literature

For a detailed account of the design of organic polar crystals, see: Pecaut & Bagieu-Beucher (1993 ▶). For hydrogen bonding in nitrophenol complexes, see: In et al. (1997 ▶); Zadrenko et al. (1997 ▶); Mizutani et al. (1998 ▶). For the supramolecular architecture of molecular complexes of trinitrophenols, see: Botoshansky et al. (1994 ▶); Vembu et al. (2003 ▶). For details of the monoclinic polymorph of the title compound, see: Takayanagi et al. (1996 ▶). For hydrogen-bonding criteria, see: Desiraju & Steiner (1999 ▶); Desiraju (1989 ▶); Jeffrey (1997 ▶). For graph-set notation, see: Bernstein et al. (1995 ▶); Etter (1990 ▶).

Experimental

Crystal data

C₈H₁₂N⁺·C₆H₂N₃O₇ ⁻
M _r = 350.29
Orthorhombic,
a = 15.9960 (10) Å
b = 9.1491 (6) Å
c = 10.3899 (9) Å
V = 1520.55 (19) Å³
Z = 4
Cu Kα radiation
μ = 1.08 mm⁻¹
T = 90.0 (5) K
0.26 × 0.24 × 0.08 mm

Data collection

Bruker Kappa APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.767, T _max = 0.919
16980 measured reflections
2823 independent reflections
2755 reflections with I > 2σ(I)
R _int = 0.033

Refinement

R[F ² > 2σ(F ²)] = 0.023
wR(F ²) = 0.060
S = 1.03
2823 reflections
283 parameters
1 restraint
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.14 e Å⁻³
Δρ_min = −0.16 e Å⁻³
Absolute structure: Flack (1983 ▶), 1309 Friedel pairs
Flack parameter: 0.07 (12)

Data collection: APEX2 (Bruker, 2006 ▶); cell refinement: APEX2 and SAINT (Bruker, 2006 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: PLATON (Spek, 2003 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808041743/sj2565sup1.cif

e-65-0o111-sup1.cif^{(19.9KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808041743/sj2565Isup2.hkl

e-65-0o111-Isup2.hkl^{(138.6KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N7—H7⋯O16	0.892 (17)	1.825 (18)	2.7128 (14)	172.8 (16)
N7—H7⋯O19	0.892 (17)	2.578 (16)	3.0517 (15)	114.0 (12)
C2—H2⋯O16	0.931 (18)	2.341 (17)	3.0464 (16)	132.4 (13)
C2—H2⋯O24	0.931 (18)	2.498 (17)	3.3444 (17)	151.4 (14)
C8—H8A⋯O19	1.001 (18)	2.411 (18)	3.1171 (18)	126.9 (13)
C9—H9C⋯O19	0.997 (18)	2.592 (17)	3.2311 (17)	121.9 (12)
C9—H9B⋯O21ⁱ	0.974 (19)	2.571 (19)	3.5074 (17)	161.3 (14)
C9—H9B⋯O25ⁱⁱ	0.974 (19)	2.476 (18)	3.0794 (18)	119.9 (13)
C4—H4⋯O21ⁱⁱⁱ	0.924 (19)	2.466 (18)	3.1776 (16)	134.0 (14)
C14—H14⋯O19^iv	0.941 (18)	2.564 (18)	3.4988 (16)	172.3 (14)
C9—H9C⋯O22^v	0.997 (18)	2.502 (18)	3.3283 (16)	140.0 (13)

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) .

Acknowledgments

NV thanks the University Grants Commission (UGC), Government of India, for a minor research project grant [MRP-2219/06(UGC-SERO)].

supplementary crystallographic information

Comment

The design of organic polar crystals for quadratic non-linear optical applications is supported by the observation that the organic molecules containing π-electron systems asymmetrized by electron donor and acceptor groups are highly polarizable entities in which problems of transparency and crystal growth may arise from their molecular crystal packing (Pecaut & Bagieu-Beucher, 1993). It is known that nitrophenols act not only as π-acceptors to form various π-stacking complexes with other aromatic molecules, but also as acidic ligands to form salts through specific electrostatic or H-bonding interactions (In et al., 1997). The bonding of electron-donor acceptor complexes strongly depends on the nature of the partners. The linkage could involve not only electrostatic interactions, but also the formation of molecular complexes (Zadrenko et al., 1997). It has been reported that proton transferred thermochromic complexes were formed between phenols and amines in apolar solvents at low temperature if an appropriate H-bonding network between the phenols and amines was present to stabilize it (Mizutani et al., 1998). Pyridinium picrate has been reported in two crystalline phases and it appears in both phases as an internally linked H-bonded ion pair. These two phases are referred to as molecular crystals rather than salts based on their structural arrangements (Botoshansky et al., 1994). A similar structural arrangement has also been reported for 4-dimethylaminopyridinium picrate (Vembu et al., 2003). The monoclinic polymorph of the title compound (CSD Reference Code: REYDEE) has been reported previously (Takayanagi et al., 1996). We have structurally elucidated the orthorhombic polymorph of the title compound as a forerunner to assessing its optical properties and report its structure here.

The asymmetric unit of (I) contains one N,N-Dimethylanilinium cation, and one 2,4,6-trinitrophenolate anion. (Fig.1). The crystal structure of (I) is stabilized by N—H···O and C—H···O interactions. The range of H···O distances (Table 1) found in (I) agrees with those found for N—H···O (Jeffrey, 1997) and C—H···O hydrogen bonds (Desiraju & Steiner, 1999). The N7—H7···O16 and N7—H7···O19 interactions form a pair of bifurcated donor bonds that link the N,N-dimethylanilinium cation and 2,4,6-trinitrophenolate anion and also form a motif of graph set R²₁(6) (Bernstein et al., 1995; Etter, 1990). Another pair of bifurcated donor bonds consists of the C2—H2···O16 and C2—H2···O24 interactions that also link the cation and the anion and form a R²₁(6) motif. The C8—H8A···O19 and C9—H9C···O19 interactions constitute a pair of bifurcated bonds forming a R¹₂(6) motif that link the cation and the anion. The N7—H7···O19 and C8—H8A···O19 interactions constitute a pair of bifurcated acceptor bonds that form a R¹₂(5) motif. The above two motifs, R¹₂(6) and R¹₂(5), together form a R¹₂(5) motif by the interplay of the trifurcated acceptor bonds formed by N7—H7···O19, C9—H8A···O19 and C9—H9C···O19 interactions. There are five intermolecular C—H···O interactions (Table 1) that contribute to the supramolecular aggregation of the title compound. The intramolecular N—H···O interactions mentioned above also contribute to the formation of cooperative H-bonded network (Fig. 2). There is an offset π···π stacking interaction, Cg1···Cg2 (x, -1+y, z) at 3.697Å with α = 3.19, β = 24.88 and γ = 24.00 and the two perpendicular distances being 3.377 and 3.354Å. There is also an edge to face π···π stacking interaction, Cg1···Cg2 (1.5-x, -0.5+y, 0.5+z) at 3.673Å with α=13.75, β=25.68 and γ=12.78 and the two perpendicular distances being 3.582 and 3.310Å. Cg1 and Cg2 are the centroids of the C1···C6 and C10···.C15 rings.

The interplay of strong N—H···O and weak C—H···O, π···π interactions with different strengths, directional preferences and distance presents a complex mosaic of interactions. The three dimensional arrangement of the 2,4,6-trinitrophenolate and N,N-dimethylanilinium moieties in the unit cell, shows that the title compound is an internally linked hydrogen bonded ion pair and hence can be regarded as a molecular crystal rather than a salt.

Experimental

2,4,6-Trinitrophenol (5.2 mmol) dissolved in aqueous ethanol (25 ml) was added dropwise to N,N-dimethylaniline (5.7 mmol) in aqueous ethanol (25 ml). The above solution was constantly stirred at room temperature for 2 hrs. The precipitated product was filtered and recrystallized from aqueous ethanol. Yield 75% (3.9 mmol).