Melaminium sulfate

Bao-Yong Zhu; De-Liang Cui; Hai-Peng Jing

doi:10.1107/S1600536807067463

. 2008 Jan 4;64(Pt 2):o351. doi: 10.1107/S1600536807067463

Melaminium sulfate

Bao-Yong Zhu ^a, De-Liang Cui ^a, Hai-Peng Jing ^a,^*

PMCID: PMC2960347 PMID: 21201383

Abstract

In the title compound, C₃H₈N₆ ²⁺·SO₄ ²⁻, the melaminium cations and sulfate anions are interconnected by N—H⋯N and N—H⋯O hydrogen bonds, forming a layer in the (101) plane. The layers are connected through multiple hydrogen bonds and π–π stacking interactions (centroid–centroid distance of about 3.4 Å).

Related literature

For related literature, see: Janczak & Perpétuo (2001a ▶,b ▶); Martin & Pinkerton (1995 ▶); Dewar et al. (1985 ▶).

Experimental

Crystal data

C₃H₈N₆ ²⁺·SO₄ ²⁻
M _r = 224.21
Monoclinic,
a = 18.5787 (3) Å
b = 8.6272 (2) Å
c = 12.7945 (4) Å
β = 129.739 (1)°
V = 1576.94 (7) Å³
Z = 8
Mo Kα radiation
μ = 0.42 mm⁻¹
T = 293 (2) K
0.32 × 0.27 × 0.26 mm

Data collection

Bruker APEXII CCD diffractometer
Absorption correction: multi-scan (APEX2; Bruker, 2005 ▶) T _min = 0.878, T _max = 0.900
3793 measured reflections
1794 independent reflections
1672 reflections with I > 2σ(I)
R _int = 0.013

Refinement

R[F ² > 2σ(F ²)] = 0.031
wR(F ²) = 0.088
S = 1.00
1794 reflections
136 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.48 e Å⁻³
Δρ_min = −0.45 e Å⁻³

Data collection: APEX2 (Bruker, 2005 ▶); cell refinement: APEX2; data reduction: APEX2; program(s) used to solve structure: SIR97 (Altomare et al., 1999 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997 ▶); molecular graphics: SHELXTL (Bruker, 1997 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536807067463/bt2656sup1.cif

e-64-0o351-sup1.cif^{(14.8KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536807067463/bt2656Isup2.hkl

e-64-0o351-Isup2.hkl^{(88.5KB, 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
N6—H6⋯O2ⁱ	0.87 (3)	1.76 (3)	2.622 (2)	171 (3)
N5—H5⋯O4ⁱⁱ	0.85 (3)	1.76 (3)	2.608 (2)	176 (3)
N3—H3B⋯O2ⁱ	0.86	2.59	3.244 (2)	134
N3—H3B⋯O1ⁱⁱⁱ	0.86	2.44	2.944 (2)	118
N3—H3A⋯N4^iv	0.86	2.14	3.000 (2)	176
N2—H2B⋯O3ⁱ	0.86	1.97	2.822 (2)	172
N2—H2A⋯O3^v	0.86	2.02	2.836 (2)	159
N1—H1B⋯O2ⁱⁱ	0.86	1.99	2.838 (2)	169
N1—H1A⋯O1^vi	0.86	2.43	2.992 (2)	123
N1—H1A⋯O1^vii	0.86	2.11	2.887 (2)	151

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

Acknowledgments

We thank Professor Wen-Tao Yu and Mr Jian-Dong Fan for the data collection and helpful discussions. This work was supported by the Science and Technology Research Program of the Ministry of Education, China (grant No. 305010).

supplementary crystallographic information

Comment

Salts of melamine and its derivatives can develop supramolecular structures via hydrogen bonding by self assembly. Monoprotonated melaminium sulfate hydrate, (C₃H₇N₆)₂ SO₄.H₂O, has been structurally investigated (Janczak & Perpétuo, 2001b). We present here the solid state structure of anhydrous diprotonated melaminium salt.

The internal C—N—C angle at the protonated N atoms [C2—N6—C3 120.35 (15) ° and C2—N5—C1 120.25 (15) °] is significantly larger than the C—N—C angle at the non-protonated N atom [C1—N4—C3 116.79 (15) °]. These differences are due to the steric effect of the lone-pair electrons and are fully consistent with the valence-shell electron-pair repulsion theory (Janczak & Perpétuo, 2001a). The two shortest bonds [N4—C3 1.333 (2) Å and N4—C1 1.338 (2) Å] are those furthest from the protonated ring N atoms. The two longest bonds [N6—C3 1.367 (2) Å and N5—C1 1.373 (2) Å] are those connected to the shortest bonds. This has the effect of opening up the ring bond angles at atoms C1 and C3, thus creating the largest bond angles in the ring [N4—C3—N6 122.4 (1) ° and N4—C1—N5 122.1 (1) °]. A semi-empirical calculation, with the AM1 parameter set (Dewar et al., 1985) on the melaminium residue diprotonated at two ring N atoms, results in almost the same geometrical features as being found in the title compound. The distortion of the aromatic ring is quite similar to that reported for the melaminium diperchlorate monohydrate salt (Martin & Pinkerton, 1995), as well as for melaminium bis(4-hydroxybenzene-sulfonate) dihydrate (Janczak & Perpétuo, 2001a).

The melaminium residue is involved in eleven hydrogen bonds, two N—H···N bonds with the neighbouring melaminium residue and nine N—H···O bonds with six neighbouring SO₄^2- anions. Two of the SO₄^2- anions are acceptors of two and three hydrogen bonds, respectively, while the other four are acceptors of one hydrogen bond each (Fig. 2). The H atoms at the protonated N atoms of the melaminium residue are involved in almost linear N—H···O hydrogen bonds.

Each SO₄^2- ion is involved as an acceptor in nine hydrogen bonds connecting to six melaminium residues. The O1 and O2 atoms are the most interesting ones as they all accept three hydrogen atoms each. O3 forms two hydrogen bonds with melaminium residues via the H atoms of the amino groups, and O4 forms only one hydrogen bond via H5 atom at the protonated N atom of the melaminium residue.

The melaminium residues are interconnected by two almost linear N—H···N hydrogen bonds and five N—H···O hydrogen bonds. The distance between the centroids of the aromatic rings in adjacent layers (symmetry operator 2 - x, +y, 1.5 - z) is about 3.4 Å, which is much shorter than the maximum distance for the π-π stacking interaction (3.8 Å for centroid-centroid distance), indicating strong π-π stacking interactions. The two-dimensional layers are extensively interconnected by multiple hydrongen bonds with sulfate anions and π-π stacking interactions (Fig. 3).

Experimental

0.126 g (0.001 mol) of melamine was dissolved in 50 ml hot water. To this solution 4 ml 98% sulfate acid was slowly added. After several days, colorless crystals of (I) appeared.