Dimethyl­ammonium terephthalate

The asymmetric unit of the title compound, C₂H₈N⁺·C₈H₅O₄⁻, comprises half each of a dimethyl­ammonium cation and a terephthalate anion. The cation lies on a twofold rotation axis, and the anion on an inversion centre. The crystal packing is stabilized by a bifurcated N—H...O hydrogen bond and a linear, apparently symmetric, O—H...O hydrogen bond. Experimental evidence suggests that the latter inter­action might be a (disordered) asymmetric hydrogen bond.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.047
• wR factor = 0.137
• Data-to-parameter ratio = 18.2

checkCIF/PLATON results

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Alert level C
PLAT042_ALERT_1_C Calc. and Rep. MoietyFormula Strings Differ ....          ?
PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor ....       3.77
PLAT720_ALERT_4_C Number of Unusual/Non-Standard Label(s) ........          2

Alert level G
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported _diffrn_ambient_temperature .        293 K

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   3 ALERT level C = Check and explain
   2 ALERT level G = General alerts; check

   3 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 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
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

The ionic title compound, (I), was isolated as a side-product in the synthesis of metal-organic framework materials. The asymmetric unit comprises one half-dimethylammonium cation and one half-terephthalate anion. In the terephthalate anions, the two carboxyl groups are essentially coplanar with the phenyl ring.

In addition to the ionic interactions, the crystal structure is held together by a network of two types of hydrogen bonds. The first one is a bifurcated one involving N1—H1NA in the amine anion and both O atoms in the carboxyl group (Table 1). The nature of the second type of hydrogen bond is ambiguous. Certainly there exists a short hydrogen bond interaction between the O1-carboxyl group and its crystallographically equivalent one, the O1···O1ⁱ distance of 2.467 (2) Å [symmetry code: (i) -x + 2, -y, -z + 2] falls within the normal range for symmetric hydrogen bonds (Cobbledick & Small, 1972; Catti & Ferraris, 1976), but a slightly better refinement was obtained by allowing the hydrogen to move off the center of symmetry. Two alternative structural models have been studied. Placing atom H1 on the inversion center gives a symmetric structure. Full-matrix least-squares refinement converged to a stable solution. The residual difference Fourier map has a largest peak and hole of 0.214 and -0.189 e Å^-3, respectively. The final R was 0.0474. The crystallographic symmetry constrains the hydrogen-bond angle to 180 ° and the O1—H1 distance to 1.232 (1) Å. A second structural model is one with the half occupied H1-atom site displaced from the inversion center towards O1. A Fourier map section in the O1/C1/O2 plane (MAPVIEW; Farrugia, 1999) showed a broad peak centered at the crystallographic inversion center and slightly elongated (nearly) along the O···Oⁱ direction, a fact which might support this latter hypothesis. Free refinement of the x, y, z and U_iso parameters for the H1 atom converged to an asymmetric hydrogen-bonding model, which is the one finally reported here, with a largest Fourier peak and hole of 0.212 and -0.176 e Å^-3 and the final R of 0.0470, respectively. This type of hydrogen bonding geometry is closely comparable to what reported in similar structures (Kalsbeek & Larsen, 1991; Kaduk, 2000). Nevertheless, the limited data quality and resolution mean that we cannot unambiguously determine the nature of this hydrogen bonding interaction.

The terephthalate anions link each other by the O—H···O short hydrogen-bond into a 1-D polymeric chain. Then the terephthalate anions and dimethylammonium cations are connected by N—H···O hydrogen-bonds into 3-D supermolecule structure (Table 1).

Related literature

For related literature, see: Catti & Ferraris (1976); Cobbledick & Small (1972); Farrugia (1999); Kaduk (2000); Kalsbeek & Larsen (1991).

S2. Experimental

The title compound (I) was synthesized via solvent-thermal method under autogenous pressure. A mixture of terephthalic acid (0.332 g, 2 mmol), zinc acetate dihydrate (0.11 g, 0.5 mmol), N¹,N¹,N²,N²-tetrakis(pyridin-4-ylmethyl)ethane-1,2-diamine (0.212 g, 0.5 mmol) and DMF 12 ml was sealed in a Teflon-lined stainless steel Parr vessel, which was heated at 453 K for 72 h. After slow cooling to ambient temperature, colorless blockshaped crystals of the title compound were separated mechanically as a side-product. Analysis found: C 56.8, H 6.2, N 6.5%; C₁₀H₁₃NO₄ requires: C 56.86, H 6.20, N 6.63%.

S3. Refinement

The H1 atom was located in difference Fourier maps. the other H atoms were visible in difference Fourier maps but were placed in calculated positions with C—H= 0.93 Å (CH), C—H= 0.96 Å (CH₃) and N—H= 0.90 Å (NH₂), U_iso(H)= 1.5 times U_eq(C) for CH₃ and U_iso(H)= 1.2 times U_eq(C) or U_eq(N) for CH or NH₂. All other non-H atoms were refined anisotropically. The maximum positive peak of 0.212 e Å^-3 in the final difference electron density map is located 0.74 Å from atom C3.

Computing details

Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL-Plus (Sheldrick, 1990); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. A view of of (I) with the atomic labeling scheme. Displacement ellipsoids are shown at the 30% probability level. The O1···O1^i interaction is presented as an asymmetric, disordered H-bond, drawn in broken lines. Symmetry codes: (i) -x + 2, -y, -z + 2; (ii) 1.5 - x, 1/2 - y, 1 - z], (iii) - x, y, 1/2 - z].

Dimethylammonium terephthalate

Crystal data

C2H8N^+·C8H5O4^−	F(000) = 448
Mr = 211.21	Dx = 1.251 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71069 Å
Hall symbol: -C 2yc	Cell parameters from 588 reflections
a = 16.804 (5) Å	θ = 3.6–22.8°
b = 7.885 (4) Å	µ = 0.10 mm^−1
c = 10.484 (5) Å	T = 293 K
β = 126.161 (5)°	Block, colourless
V = 1121.5 (9) Å^3	0.48 × 0.40 × 0.38 mm
Z = 4

Data collection

Bruker SMART APEX2 CCD diffractometer	1345 independent reflections
Radiation source: fine-focus sealed tube	985 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.036
φ and ω scans	θmax = 28.2°, θmin = 3.0°
Absorption correction: multi-scan (SADABS; Bruker, 2004)	h = −19→22
Tmin = 0.958, Tmax = 0.966	k = −6→10
3305 measured reflections	l = −13→13

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.047	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.137	H atoms treated by a mixture of independent and constrained refinement
S = 1.05	w = 1/[σ^2(Fo^2) + (0.0616P)^2 + 0.4384P] where P = (Fo^2 + 2Fc^2)/3
1345 reflections	(Δ/σ)max < 0.001
74 parameters	Δρmax = 0.21 e Å^−3
1 restraint	Δρmin = −0.18 e Å^−3

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.

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 (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
C1	0.88542 (10)	0.1522 (2)	0.82777 (15)	0.0429 (4)
C2	0.73871 (12)	0.3105 (2)	0.61160 (16)	0.0528 (5)
H2	0.7306	0.3520	0.6863	0.063*
C3	0.81474 (9)	0.20024 (19)	0.65670 (14)	0.0390 (4)
C4	0.82574 (12)	0.1401 (2)	0.54521 (17)	0.0532 (5)
H4	0.8769	0.0656	0.5750	0.064*
C5	0.0816 (3)	0.3853 (4)	0.2722 (3)	0.1501 (16)
H5A	0.0569	0.4584	0.1830	0.225*
H5B	0.1292	0.3086	0.2817	0.225*
H5C	0.1121	0.4524	0.3665	0.225*
H1	0.983 (4)	0.011 (8)	0.960 (5)	0.082 (15)*	0.50
N1	0.0000	0.2885 (3)	0.2500	0.0755 (8)
H1NA	0.0247	0.2208	0.3346	0.091*	0.50
H1NB	−0.0247	0.2208	0.1654	0.091*	0.50
O1	0.94143 (8)	0.02566 (16)	0.85670 (11)	0.0537 (4)
O2	0.88617 (10)	0.23126 (18)	0.92810 (12)	0.0756 (5)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0390 (7)	0.0493 (8)	0.0237 (6)	0.0042 (6)	0.0094 (5)	0.0071 (6)
C2	0.0541 (9)	0.0687 (11)	0.0268 (7)	0.0241 (8)	0.0190 (7)	0.0103 (7)
C3	0.0337 (7)	0.0454 (8)	0.0231 (6)	0.0054 (6)	0.0085 (5)	0.0078 (5)
C4	0.0488 (9)	0.0680 (11)	0.0295 (7)	0.0285 (8)	0.0158 (6)	0.0145 (7)
C5	0.212 (4)	0.136 (3)	0.0814 (19)	−0.100 (3)	0.075 (2)	−0.0276 (17)
N1	0.118 (2)	0.0552 (13)	0.0380 (10)	0.000	0.0376 (12)	0.000
O1	0.0473 (6)	0.0667 (8)	0.0266 (5)	0.0200 (5)	0.0103 (5)	0.0140 (5)
O2	0.0919 (10)	0.0798 (10)	0.0252 (5)	0.0354 (8)	0.0181 (6)	0.0076 (5)

Geometric parameters (Å, º)

C1—O2	1.2164 (19)	C5—N1	1.462 (3)
C1—O1	1.2791 (19)	C5—H5A	0.9600
C1—C3	1.5024 (18)	C5—H5B	0.9600
C2—C3	1.378 (2)	C5—H5C	0.9600
C2—C4^i	1.3877 (19)	N1—H1NA	0.9000
C2—H2	0.9300	N1—H1NB	0.9000
C3—C4	1.371 (2)	O1—H1	0.88 (4)
C4—H4	0.9300
O2—C1—O1	124.34 (12)	N1—C5—H5B	109.5
O2—C1—C3	120.03 (14)	H5A—C5—H5B	109.5
O1—C1—C3	115.63 (13)	N1—C5—H5C	109.5
C3—C2—C4^i	120.05 (14)	H5A—C5—H5C	109.5
C3—C2—H2	120.0	H5B—C5—H5C	109.5
C4^i—C2—H2	120.0	C5—N1—C5^ii	117.1 (4)
C4—C3—C2	119.32 (12)	C5—N1—H1NA	108.0
C4—C3—C1	121.42 (13)	C5^ii—N1—H1NA	108.0
C2—C3—C1	119.24 (13)	C5—N1—H1NB	108.0
C3—C4—C2^i	120.63 (14)	C5^ii—N1—H1NB	108.0
C3—C4—H4	119.7	H1NA—N1—H1NB	107.3
C2^i—C4—H4	119.7	C1—O1—H1	109 (4)
N1—C5—H5A	109.5
C4^i—C2—C3—C4	0.0 (3)	O2—C1—C3—C2	−12.7 (2)
C4^i—C2—C3—C1	178.31 (15)	O1—C1—C3—C2	166.73 (15)
O2—C1—C3—C4	165.59 (17)	C2—C3—C4—C2^i	0.0 (3)
O1—C1—C3—C4	−14.9 (2)	C1—C3—C4—C2^i	−178.28 (15)

Symmetry codes: (i) −x+3/2, −y+1/2, −z+1; (ii) −x, y, −z+1/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O1^iii	0.88 (4)	1.59 (4)	2.467 (2)	176 (6)
N1—H1NA···O2^iv	0.90	2.01	2.7630 (17)	140
N1—H1NA···O1^v	0.90	2.48	3.107 (3)	127

Symmetry codes: (iii) −x+2, −y, −z+2; (iv) −x+1, y, −z+3/2; (v) x−1, −y, z−1/2.