Melaminium iodide monohydrate

In the title melaminium salt, 2,4,6-triamino-1,3,5-triazin-1-ium iodide monohydrate, C₃H₇N₆⁺·I⁻·H₂O, the components are linked via N—H...O, N—H...N, O—H...I and N—H...I hydrogen bonds. All of the H atoms of the melaminium cation are involved in hydrogen bonds. The melaminium cations are inter­connected by four N—H...N hydrogen bonds, forming ribbons along [111]. The water mol­ecules connected by N—H...O hydrogen bonds also form part of these ribbons. The ribbons are inter­connected by other hydrogen bonds (O—H...I and N—H...I), as well as by π–π inter­actions [centroid–centroid distance = 3.6597 (17) Å].

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](N-C) = 0.004 Å
• R factor = 0.026
• wR factor = 0.067
• Data-to-parameter ratio = 18.9

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT420_ALERT_2_C D-H Without Acceptor       N4     -   H4B    ...          ?
PLAT910_ALERT_3_C Missing # of FCF Reflections Below Th(Min) .....          1
PLAT042_ALERT_1_C Calc. and Reported MoietyFormula Strings  Differ          ?
PLAT480_ALERT_4_C Long H...A H-Bond Reported H4B    ..  I1      ..       3.20 Ang.
PLAT480_ALERT_4_C Long H...A H-Bond Reported H1A    ..  I1      ..       3.13 Ang.
PLAT480_ALERT_4_C Long H...A H-Bond Reported H1A    ..  I1      ..       3.39 Ang.
PLAT731_ALERT_1_C Bond    Calc     0.83(5), Rep   0.831(18) ......       2.78 su-Ra
              O1   -H1A     1.555   1.555
PLAT731_ALERT_1_C Bond    Calc     0.82(4), Rep   0.822(18) ......       2.22 su-Ra
              O1   -H1B     1.555   1.555
PLAT735_ALERT_1_C D-H     Calc     0.83(5), Rep   0.831(18) ......       2.78 su-Ra
              O1   -H1A     1.555   1.555
PLAT735_ALERT_1_C D-H     Calc     0.83(5), Rep   0.831(18) ......       2.78 su-Ra
              O1   -H1A     1.555   1.555
PLAT735_ALERT_1_C D-H     Calc     0.82(4), Rep   0.822(18) ......       2.22 su-Ra
              O1   -H1B     1.555   1.555
PLAT912_ALERT_4_C Missing # of FCF Reflections Above STh/L=  0.600          3

Alert level G
PLAT860_ALERT_3_G Note: Number of Least-Squares Restraints .......          3
PLAT154_ALERT_1_G The su's on the Cell Angles are Equal  (x 10000)       3000 Deg.
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
  12 ALERT level C = Check and explain
   4 ALERT level G = General alerts; check

   9 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
   2 ALERT type 3 Indicator that the structure quality may be low
   4 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

The melamine molecule and its organic and inorganic complexes or salts can develop supramolecular structures via multiple hydrogen-bonding systems by self-assembly of components which contain abundant hydrogen-bonding sites (Janczak et al., 2001; Athikomrattanakul et al., 2007). The present study is a part of systematic investigation of ferroelectric materials (Fu et al., 2009; Hang et al., 2009) that include metal-organic coordination compounds with organic ligands or are related to the structures with both organic and inorganic building fragments.

The compound was characterized by the X-ray powder diffraction (XRPD) at room temperature. The pattern calculated from the single-crystal X-ray data was in a good agreement with the observed at to the peak positions but with different peak intensities.

The structure is composed of the melaminium cations, iodide anions and the water molecules (Fig. 1). The melaminium cation is protonated at only one melamine site. The six-membered melaminium ring exhibits distortions from the regular hexagonal form. The internal C—N—C angle at the protonated N atom (119.5 (2)°) is greater than the other two C—N—C angles of the ring (115.5 (2)°) and the internal N—C—N angles involving the unprotonated ring N atoms (126.1 (2)°) are obviously larger than those containing protonated and unprotonated N atoms (121.4 (2)°) .

Fig. 2 shows a view down the b axis. The melaminium cations are interconnected by four N-H···N hydrogen bonds, forming ribbons parallel to (1 1 1). The water molecules connected by N-H···O hydrogen bonds (Tab. 1) form also a part of these ribbons. The ribbons are interconnected by other hydrogen bonds that involve I^- as well as by π-electron ring - π-electron ring interactions with the distance between the centroids of the neighbour melaminium rings (1-x,1-y,1-z) equal to 3.6597 (17) Å. The hydrogen bonds are summarized in Tab. 1. It is of interest that water oxygens despite of being quite close to each other are not interconnected by the hydrogen bond. The distance between the water oxygens is 2.9643 (40) Å [Symmetry code: 1-x, 1-y, -z]. The H atom of the protonated ring N atom (H2a) is donated to the water molecule, being involved in a strong N-H···O hydrogen bond. The other amine H atoms are involved in N—H···I and N—H···N hydrogen bonds. I^- anions that take part in the electrostatic equilibrium with the melaminium cations are also involved in O—H···I hydrogen bonds.

Related literature

For similar singly protonated melaminium salts, see: Janczak et al. (2001); Athikomrattanakul et al. (2007). For ferroelectric materials, see: Fu et al. (2009); Hang et al. (2009). For impedance studies, see: Uthrakumar et al. (2008).

S2. Experimental

Melamine (0.252 g, 0.002 mol) was dissolved in 25 ml of water at 323 K. 0.569 g of 45% (weight concentration) solution of HI was added to the solution. (This amount corresponded to about 0.002 mol of pure HI.) The temperature was maintained at 323 K for one hour while stirring the mixture. Then the solution was let to cool down to room temperature. After several days, the title salt, C₃H₇N₆⁺.I^-.H₂O, crystallized from the solution. The crystals were colourless, prismatic and of the average size about 0.2×0.3×0.4 mm.

S3. Refinement

All the hydrogens were discernible in the difference electron density maps. The positions of the H atoms of the melamine cations were refined using a riding model with N—H = 0.86 Å and U_iso(H) = 1.2U_eq(N). The coordinates of the water hydrogens have been refined under restrains 0.82 (2)Å; U_iso(H) = 1.2U_eq(O). (The constrained and the restrained values fit well to the trial refinement with the freely refined hydrogen parameters.)

Dielectric studies (capacitance and dielectric loss measurements) were performed on powder samples which have been pressed into tablets with conducting carbon glue deposited on their faces. The automatic impedance TongHui2828 Analyzer has been used (Uthrakumar et al., 2008). In the measured temperature range from 80 to 450 K (m.p. > 470 K), the temperature dependence of the relative permittivity at 1 MHz varied smoothly from 3.9 to 5.2 in the title compound. No dielectric anomaly has been observed.

Computing details

Data collection: CrystalClear (Rigaku, 2005); cell refinement: CrystalClear (Rigaku, 2005); data reduction: CrystalClear (Rigaku, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: PRPKAPPA (Ferguson, 1999).

Figures

	Fig. 1. The title molecules with the atomic numbering scheme. The displacement ellipsoids are drawn at the 30% probability level.
	Fig. 2. A view of the structure along the b axis. The dashed lines depict the hydrogen bonds.

2,4,6-triamino-1,3,5-triazin-1-ium iodide monohydrate

Crystal data

C3H7N6^+·I^−·H2O	Z = 2
Mr = 272.06	F(000) = 260
Triclinic, P1	Dx = 2.050 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 6.0655 (12) Å	Cell parameters from 4510 reflections
b = 7.0370 (14) Å	θ = 3.2–27.5°
c = 11.413 (2) Å	µ = 3.59 mm^−1
α = 104.02 (3)°	T = 293 K
β = 93.95 (3)°	Prism, colourless
γ = 109.08 (3)°	0.40 × 0.30 × 0.20 mm
V = 440.80 (19) Å^3

Data collection

Rigaku SCXmini diffractometer	2006 independent reflections
Radiation source: fine-focus sealed tube	1896 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.029
Detector resolution: 13.6612 pixels mm^-1	θmax = 27.5°, θmin = 3.2°
ω scans	h = −7→7
Absorption correction: multi-scan (CrystalClear; Rigaku, 2005)	k = −9→9
Tmin = 0.285, Tmax = 0.487	l = −14→14
4551 measured reflections

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)] = 0.026	Hydrogen site location: difference Fourier map
wR(F^2) = 0.067	H atoms treated by a mixture of independent and constrained refinement
S = 1.11	w = 1/[σ^2(Fo^2) + (0.0285P)^2 + 0.1083P] where P = (Fo^2 + 2Fc^2)/3
2006 reflections	(Δ/σ)max = 0.008
106 parameters	Δρmax = 0.47 e Å^−3
3 restraints	Δρmin = −0.61 e Å^−3
30 constraints

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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
N1	0.1770 (4)	0.3970 (4)	0.3846 (2)	0.0392 (5)
N2	0.4296 (4)	0.2565 (4)	0.2773 (2)	0.0433 (5)
H2A	0.5039	0.2463	0.2159	0.052*
N3	0.3428 (4)	0.1720 (4)	0.4600 (2)	0.0402 (5)
N4	0.2758 (6)	0.4725 (5)	0.2059 (3)	0.0567 (7)
H4A	0.1912	0.5504	0.2121	0.068*
H4B	0.3504	0.4576	0.1449	0.068*
N6	0.1007 (5)	0.3160 (4)	0.5631 (2)	0.0510 (6)
H6A	0.1161	0.2533	0.6175	0.061*
H6B	0.0144	0.3925	0.5713	0.061*
O1	0.6721 (6)	0.1912 (5)	0.0884 (3)	0.0817 (9)
H1A	0.707 (10)	0.091 (5)	0.051 (5)	0.123*
H1B	0.731 (10)	0.301 (5)	0.070 (5)	0.123*
C1	0.2911 (5)	0.3752 (4)	0.2904 (3)	0.0401 (6)
C2	0.2097 (5)	0.2947 (4)	0.4671 (2)	0.0375 (5)
C3	0.4499 (5)	0.1533 (4)	0.3622 (3)	0.0414 (6)
I1	0.89281 (4)	0.76920 (3)	0.134131 (16)	0.05182 (10)
N5	0.5833 (5)	0.0365 (5)	0.3468 (3)	0.0562 (7)
H5A	0.6010	−0.0276	0.4000	0.067*
H5B	0.6525	0.0246	0.2835	0.067*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0500 (13)	0.0449 (12)	0.0330 (11)	0.0251 (10)	0.0130 (10)	0.0164 (10)
N2	0.0505 (13)	0.0533 (13)	0.0369 (12)	0.0275 (11)	0.0152 (10)	0.0170 (11)
N3	0.0489 (12)	0.0450 (12)	0.0339 (12)	0.0243 (10)	0.0076 (10)	0.0133 (10)
N4	0.0751 (18)	0.0785 (19)	0.0448 (15)	0.0473 (16)	0.0294 (14)	0.0350 (14)
N6	0.0732 (17)	0.0630 (16)	0.0401 (13)	0.0427 (14)	0.0239 (12)	0.0264 (12)
O1	0.093 (2)	0.086 (2)	0.080 (2)	0.0379 (18)	0.0513 (17)	0.0311 (18)
C1	0.0445 (14)	0.0427 (14)	0.0369 (14)	0.0182 (12)	0.0088 (11)	0.0136 (11)
C2	0.0415 (13)	0.0382 (13)	0.0330 (13)	0.0148 (11)	0.0054 (11)	0.0095 (11)
C3	0.0424 (14)	0.0453 (14)	0.0375 (14)	0.0186 (12)	0.0035 (11)	0.0099 (12)
I1	0.06273 (16)	0.06633 (16)	0.03972 (14)	0.03312 (12)	0.01791 (10)	0.02193 (11)
N5	0.0674 (17)	0.0751 (18)	0.0485 (16)	0.0474 (15)	0.0192 (13)	0.0240 (14)

Geometric parameters (Å, º)

N1—C1	1.322 (3)	N4—H4B	0.8600
N1—C2	1.357 (3)	N6—C2	1.321 (4)
N2—C1	1.357 (3)	N6—H6A	0.8600
N2—C3	1.366 (4)	N6—H6B	0.8600
N2—H2A	0.8600	O1—H1A	0.831 (18)
N3—C3	1.330 (4)	O1—H1B	0.822 (18)
N3—C2	1.354 (3)	C3—N5	1.321 (4)
N4—C1	1.325 (4)	N5—H5A	0.8600
N4—H4A	0.8600	N5—H5B	0.8600
C1—N1—C2	115.6 (2)	N1—C1—N4	120.5 (3)
C1—N2—C3	119.5 (2)	N1—C1—N2	121.9 (2)
C1—N2—H2A	120.3	N4—C1—N2	117.6 (3)
C3—N2—H2A	120.3	N6—C2—N3	117.0 (2)
C3—N3—C2	115.5 (2)	N6—C2—N1	117.0 (2)
C1—N4—H4A	120.0	N3—C2—N1	126.1 (2)
C1—N4—H4B	120.0	N5—C3—N3	120.1 (3)
H4A—N4—H4B	120.0	N5—C3—N2	118.5 (3)
C2—N6—H6A	120.0	N3—C3—N2	121.4 (2)
C2—N6—H6B	120.0	C3—N5—H5A	120.0
H6A—N6—H6B	120.0	C3—N5—H5B	120.0
H1A—O1—H1B	115 (3)	H5A—N5—H5B	120.0

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2A···O1	0.86	1.87	2.724 (4)	172
N4—H4A···I1^i	0.86	2.95	3.764 (3)	159
N4—H4B···I1^ii	0.86	3.20	3.758 (3)	125
N6—H6A···I1^iii	0.86	2.88	3.647 (3)	149
N6—H6B···N1^iv	0.86	2.15	3.009 (3)	173
O1—H1A···I1^v	0.83 (2)	3.13 (4)	3.760 (4)	134 (5)
O1—H1A···I1^vi	0.83 (2)	3.39 (5)	3.778 (3)	112 (4)
O1—H1B···I1	0.82 (2)	3.00 (3)	3.732 (4)	150 (5)
N5—H5A···N3^vii	0.86	2.15	3.013 (4)	177
N5—H5B···I1^v	0.86	2.97	3.698 (3)	143

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