N,N,N',N'-Tetra­methyl­ethyl­ene­diammonium-succinate-succinic acid (1/1/1)

In the title compound, C₆H₁₈N₂²⁺·C₄H₄O₄^2-·C₄H₆O₄, the components lie on centres of symmetry in space group , such that the asymmetric unit contains three half-mol­ecules. Despite the different mode (with respect to other di­carboxylic acids) adopted by the intermolecular self-interaction of succinic acid derivatives, the overall structure of the title compound consists of anionic layers that are typical of the packing structures exhibited by other di­carboxylic acid analogues.

S1. Comment

In the course of a wide-ranging study concerning the solid-state aggregation of anions derived from dicarboxylic acids crystallized with solvents and/or positively charged counter-ions, we have crystallized and solved the structure of an interesting supramolecular solid, (I), formed by succinic acid with an alkyl diammonium succinate. Many studies of the behaviour in the solid state of dicarboxylic acids have been carried out (MacDonald et al. 2001; Thalladi et al., 2000) in order to investigate their trend towards self-aggregation, which stems from the hydrogen interactions (Aakeroy & Seddon, 1993), that these systems are able to develop among themselves. Therefore, dicarboxylic acids provide? suitable substrates for crystal engineering (Desiraiju, 1995, 2003). Succinic acid can be considered the first in the series of dicarboxylic acids whose the two functional groups do not interact sterically with one another unless they are constrained in the symmetric cis conformation (e.g. Sobota & Szafert, 1996). Recently, the structure of this acid (related to its physical behaviour) was analyzed and compared with corresponding superior homologues? (Pedireddi et al., 1998; Thalladi et al. 2000). Moreover, its importance is evident when comsidering the many reported structures with nitrogenated compounds (Kalsbeek, 1991; Kalsbeek & Larsen, 1991; MacDonald et al., 2001; Büyükgüngör & Mustafa, 2002) and amino acids thought to be present in prebiotic conditions (Prasad & Vijayan, 1993; Prasad & Vijayan, 1991). Linear polyamines also form, in aqueous solution, fairly stable complexes with carboxylic ligands, such as dicarboxylates (malonates, succinates, etc.; De Robertis et al., 2001, and references therein), and these interactions can be considered as useful models for the binding of polyanions by polyammonium cations in natural systems.

The asymmetric unit of (I) contains one-half of a succinic acid molecule, one-half of a succinate anion and one-half of an N,N,N',N'-tetramethyletylenediammonium cation (Fig. 1). As expected, the succinic fragments are planar [the maximum deviations are for atoms C2, by 0.001 (1) Å, and C4, by 0.004 (1) Å], but they are also coplanar [the angle between their mean planes is 8.82 (5)°]. This disposition is driven by the stable planar conformation of the succinic derivatives, combined with the development of directional hydrogen-bonding interactions employing the lone pairs of carboxylate atoms O3 and O4 (anti towards the OH donors and syn towards NH). Succinic acid and succinate molecules, bound via an intermolecular hydrogen bond (H1C···O3 = 1.70 Å), alternate along one-dimensional ribbons parallel to the ab crystallographic plane and along the [110] direction (Fig. 2).

In the carboxy moieties, O-atom lone pairs and/or H atoms can be placed on the same side as the other O atom (syn) or on the opposite side (anti), so it is straightforward to infer that hydrogen-bonding interactions can be developed towards these two possible directions, either for O-donors or for O-acceptors. Usually the syn positions are less sterically hindered and thus are often exploited by strong molecular interactions and/or synthons (Fleishman et al., 2003). A search of the Cambridge Structural Database (Allen, 2002) for any ammonium succinate showns that this dicarboxylic acid often self-assesembles along one-dimensional ribbons or strands (planar or not), obtained through different hydrogen-bonding pathways, viz. anti–anti (three examples), syn–syn (14 examples) and syn–anti (four examples). The structure of (I) confirms that succinic derivates are able to self-aggregate via anti–anti (Fig. 2) interactions, unlike all of the previously reported dicarboxylic acids (MacDonald & al., 2001), which adopt the more common syn–syn hydrogen bond for self-aggregation. We suggest that, in this way, succinate networks free their stronger O-donor syn sites, which are then able to bind tightly to specific guest counter-ions. To our knowledge, there is only one pecedent, in which the acid presents two highly symmetric ionization states that lead to this particular ribbon network (YOWDET; Prasad & Vijayan, 1990). Therefore, we are currently studying the possible influence of different counter-ions on the succinic self-assembly mode. In (I), counteri-ons bear positively charged mono-hydrogenated N atoms, which lie close to the mean plane of the succinate molecule [the deviation from the plane is 0.272 (1) Å], so we might infer that this interaction between the two oppositely charged ions is directional. This strong hydrogen bond (H1···O4 = 1.82 Å), together with some weaker bonds (Table 2), holds the succinic ribbons side-by-side, such that they appear as supermolecular layers. These layers are, in turn, connected along the third dimension by ethylenediammonic chains (see Fig. 3).

S2. Experimental

Crystals of (I) were obtained by stirring, at room temperature, a 50 mM solution (6 ml) of N,N,N',N'-tetramethyletylenediammine with the same volume of an equimolecular (1:1 ratio) aqueous succinic acid solution. The final stoichiometry of the crystal was 1:2, probably as a result of the acid and base strengths; diammonium salts usually crystallize with semi-carboxylate ions of dicarboxylic acids (Barnes & Weakley, 2000), resulting in the overall ratio 1:2. The mother solution, containing the remaining ammine, was filtered, and samples suitable for X-ray analysis were selected from the dried crystals.

S3. Refinement

All non-H atoms were located by the SIR97 software for structural solution, whereas H atoms were located in difference Fourier maps. H atoms were then placed in idealized positions (O—H = 0.82 Å, N—H = 0.91 Å and C–H = 0.96 Å) and allowed to ride on their parent atoms, with fixed isotropic displacement parameters (0.05 Ų).

Computing details

Data collection: XSCANS (Siemens, 1989); cell refinement: XSCANS; data reduction: XPREPW (Bruker, 1997); program(s) used to solve structure: SIR97 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XPW (Bruker, 1997); software used to prepare material for publication: PARST97 (Nardelli, 1995) and WinGX (Farrugia, 1999).

Figures

	Fig. 1. A view of the entire molecules of (I) (30% probability displacement ellipsoids).
	Fig. 2. A view of the centrosymmetric molecular ribbons composed of succinate and succinic acid molecules.
	Fig. 3. The three-dimensional packing of the crystal structure of (I).

N,N,N',N'-Tetramethyldiammonium–succinate–succinic acid (1/1/1)

Crystal data

C6H18N2^2+·C4H6O4^2^−·C4H4O4	Z = 1
Mr = 352.38	F(000) = 190
Triclinic, P1	Dx = 1.372 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 5.6370 (4) Å	Cell parameters from 46 reflections
b = 8.7100 (8) Å	θ = 7.1–17.4°
c = 8.8431 (6) Å	µ = 0.11 mm^−1
α = 96.219 (7)°	T = 298 K
β = 93.414 (6)°	Irregular, colourless
γ = 97.604 (7)°	0.40 × 0.32 × 0.18 mm
V = 426.63 (6) Å^3

Data collection

Siemens P4 diffractometer	Rint = 0.015
2θ/ω scans	θmax = 30°, θmin = 2.3°
Absorption correction: empirical (using intensity measurements) (North et al., 1968)	h = −7→1
Tmin = 0.273, Tmax = 0.299	k = −12→12
3194 measured reflections	l = −12→12
2495 independent reflections	3 standard reflections every 197 reflections
1926 reflections with I > 2σ(I)	intensity decay: 1%

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.042	w = 1/[σ^2(Fo^2) + (0.0553P)^2 + 0.073P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.117	(Δ/σ)max < 0.001
S = 1.06	Δρmax = 0.32 e Å^−3
2495 reflections	Δρmin = −0.21 e Å^−3
109 parameters

Special details

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.60797 (19)	0.31233 (14)	1.15237 (12)	0.0532 (3)
H1C	0.5554	0.2808	1.0645	0.05*
O2	0.90969 (19)	0.47454 (13)	1.26932 (11)	0.0473 (3)
C1	0.8808 (2)	0.44766 (15)	0.99564 (13)	0.0327 (3)
H1B	0.8929	0.3500	0.9345	0.05*
H1A	0.7590	0.4970	0.9449	0.05*
C2	0.8032 (2)	0.41383 (15)	1.15107 (14)	0.0327 (3)
O3	0.41548 (18)	0.20430 (14)	0.89223 (11)	0.0532 (3)
O4	0.10688 (16)	0.07705 (11)	0.74727 (10)	0.0385 (2)
C3	0.1199 (2)	0.05140 (15)	1.01490 (13)	0.0336 (3)
H3A	0.2352	−0.0079	1.0586	0.05*
H3B	0.1038	0.1385	1.0900	0.05*
C4	0.2185 (2)	0.11487 (14)	0.87434 (13)	0.0299 (3)
N1	0.38054 (17)	0.19377 (11)	0.53328 (10)	0.0261 (2)
H1	0.3057	0.1659	0.6166	0.05*
C7	0.2093 (2)	0.26764 (15)	0.43874 (15)	0.0346 (3)
H7A	0.0707	0.1928	0.4044	0.05*
H7B	0.2862	0.3025	0.3521	0.05*
H7C	0.1610	0.3551	0.4989	0.05*
C5	0.4401 (2)	0.04896 (13)	0.44679 (13)	0.0292 (2)
H5A	0.5468	0.0765	0.3689	0.05*
H5B	0.2944	−0.0115	0.3965	0.05*
C6	0.5959 (2)	0.30841 (15)	0.58824 (15)	0.0358 (3)
H6A	0.7044	0.2598	0.6491	0.05*
H6B	0.5479	0.3958	0.6487	0.05*
H6C	0.6745	0.3437	0.5024	0.05*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0452 (6)	0.0763 (8)	0.0306 (5)	−0.0228 (5)	0.0061 (4)	0.0091 (5)
O2	0.0485 (6)	0.0621 (6)	0.0262 (5)	−0.0070 (5)	−0.0011 (4)	0.0018 (4)
C1	0.0294 (6)	0.0411 (6)	0.0247 (5)	−0.0059 (5)	0.0009 (4)	0.0045 (5)
C2	0.0305 (6)	0.0399 (6)	0.0268 (5)	0.0003 (5)	0.0034 (4)	0.0054 (5)
O3	0.0420 (5)	0.0742 (7)	0.0337 (5)	−0.0307 (5)	0.0021 (4)	0.0109 (5)
O4	0.0367 (5)	0.0518 (6)	0.0229 (4)	−0.0112 (4)	0.0032 (3)	0.0070 (4)
C3	0.0303 (6)	0.0443 (7)	0.0232 (5)	−0.0100 (5)	0.0030 (4)	0.0079 (5)
C4	0.0284 (6)	0.0347 (6)	0.0255 (5)	−0.0036 (5)	0.0062 (4)	0.0057 (4)
N1	0.0286 (5)	0.0274 (4)	0.0215 (4)	−0.0003 (4)	0.0050 (3)	0.0035 (3)
C7	0.0356 (6)	0.0355 (6)	0.0338 (6)	0.0073 (5)	0.0020 (5)	0.0065 (5)
C5	0.0342 (6)	0.0293 (5)	0.0234 (5)	0.0040 (4)	0.0005 (4)	0.0015 (4)
C6	0.0361 (6)	0.0324 (6)	0.0348 (6)	−0.0077 (5)	0.0016 (5)	0.0017 (5)

Geometric parameters (Å, º)

O1—C2	1.319 (1)	N1—C6	1.487 (1)
O1—H1C	0.82	N1—C5	1.491 (1)
O2—C2	1.206 (1)	N1—C7	1.493 (2)
C1—C1^i	1.514 (2)	N1—H1	0.91
C1—C2	1.514 (2)	C7—H7A	0.96
C1—H1B	0.97	C7—H7B	0.96
C1—H1A	0.97	C7—H7C	0.96
O3—C4	1.260 (1)	C5—C5^iii	1.523 (2)
O4—C4	1.244 (1)	C5—H5A	0.97
C3—C3^ii	1.511 (2)	C5—H5B	0.97
C3—C4	1.520 (1)	C6—H6A	0.96
C3—H3A	0.97	C6—H6B	0.96
C3—H3B	0.97	C6—H6C	0.96
C2—O1—H1C	109.5	C6—N1—H1	107.6
C1^i—C1—C2	112.76 (12)	C5—N1—H1	107.6
C1^i—C1—H1B	109	C7—N1—H1	107.6
C2—C1—H1B	109	N1—C7—H7A	109.5
C1^i—C1—H1A	109	N1—C7—H7B	109.5
C2—C1—H1A	109	H7A—C7—H7B	109.5
H1B—C1—H1A	107.8	N1—C7—H7C	109.5
O2—C2—O1	120.2 (1)	H7A—C7—H7C	109.5
O2—C2—C1	123.4 (1)	H7B—C7—H7C	109.5
O1—C2—C1	116.3 (1)	N1—C5—C5^iii	110.72 (11)
C3^ii—C3—C4	114.43 (12)	N1—C5—H5A	109.5
C3^ii—C3—H3A	108.7	C5^iii—C5—H5A	109.5
C4—C3—H3A	108.7	N1—C5—H5B	109.5
C3^ii—C3—H3B	108.7	C5^iii—C5—H5B	109.5
C4—C3—H3B	108.7	H5A—C5—H5B	108.1
H3A—C3—H3B	107.6	N1—C6—H6A	109.5
O4—C4—O3	122.3 (1)	N1—C6—H6B	109.5
O4—C4—C3	120.1 (1)	H6A—C6—H6B	109.5
O3—C4—C3	117.5 (1)	N1—C6—H6C	109.5
C6—N1—C5	113.13 (9)	H6A—C6—H6C	109.5
C6—N1—C7	110.20 (9)	H6B—C6—H6C	109.5
C5—N1—C7	110.34 (9)
C1^i—C1—C2—O2	6.0 (2)	C3^ii—C3—C4—O3	178.5 (1)
C1^i—C1—C2—O1	−174.2 (1)	C6—N1—C5—C5^iii	70.7 (1)
C3^ii—C3—C4—O4	−2.3 (2)	C7—N1—C5—C5^iii	−165.33 (12)

Symmetry codes: (i) −x+2, −y+1, −z+2; (ii) −x, −y, −z+2; (iii) −x+1, −y, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O4	0.91	1.82	2.710 (1)	166
N1—H1···O3	0.91	2.45	3.159 (1)	134
O1—H1C···O3	0.82	1.70	2.514 (1)	173
C5—H5B···O4^iv	0.97	2.49	3.424 (1)	161
C7—H7C···O2^v	0.96	2.48	3.392 (2)	158

Symmetry codes: (iv) −x, −y, −z+1; (v) −x+1, −y+1, −z+2.