Bis(melaminium) tartrate dihydrate.

In the title compound, 2C(3)H(7)N(6) (+)·C(4)H(4)O(6) (2-)·2H(2)O, in which the complete anion is generated by crystallographic twofold symmetry, there are O-H⋯O, N-H⋯O and N-H⋯N hydrogen-bonding inter-actions between neighbouring moieties, forming layers parallel to the bc plane. In addition, π-π contacts [centroid-centroid distance = 3.6541 (9) Å] between the six-membered rings of the melamine cations are observed.

Related literature

For general background, see: Row (1999 ▶); Krische & Lehn (2000 ▶); Sherrington & Taskinen (2001 ▶); Marchewka et al. (2003 ▶); Thushari et al. (2005 ▶). For related structures, see: Udaya Lakshmi et al. (2006 ▶).

Experimental

Crystal data

2C3H7N6 +·C4H4O6 2−·2H2O

M = 436.38

Monoclinic,

a = 7.6963 (9) Å

b = 21.955 (3) Å

c = 10.7405 (12) Å

β = 98.179 (6)°

V = 1796.4 (4) Å3

Z = 4

Mo Kα radiation

μ = 0.14 mm−1

T = 296 K

0.26 × 0.22 × 0.12 mm

Data collection

Bruker APEXII area-detector diffractometer

Absorption correction: multiscan (SADABS; Sheldrick, 1996 ▶) T min = 0.963, T max = 0.980

13436 measured reflections

2047 independent reflections

1712 reflections with I > 2σ(I)

R int = 0.027

Refinement

R[F 2 > 2σ(F 2)] = 0.037

wR(F 2) = 0.108

S = 1.00

2047 reflections

166 parameters

15 restraints

H atoms treated by a mixture of independent and constrained refinement

Δρmax = 0.25 e Å−3

Δρmin = −0.24 e Å−3

Data collection: APEX2 (Bruker, 2006 ▶); cell refinement: 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: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809011143/at2740sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809011143/at2740Isup2.hkl

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

2C3H7N6+·C4H4O62−·2H2O	F(000) = 920
Mr = 436.38	Dx = 1.621 Mg m−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 4811 reflections
a = 7.6963 (9) Å	θ = 1.9–27.5°
b = 21.955 (3) Å	µ = 0.14 mm−1
c = 10.7405 (12) Å	T = 296 K
β = 98.179 (6)°	Block, colourless
V = 1796.4 (4) Å3	0.26 × 0.22 × 0.12 mm
Z = 4

Bruker APEXII area-detector diffractometer	2047 independent reflections
Radiation source: fine-focus sealed tube	1712 reflections with I > 2σ(I)
graphite	Rint = 0.027
ω scans	θmax = 27.5°, θmin = 1.9°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −9→10
Tmin = 0.963, Tmax = 0.980	k = −27→28
13436 measured reflections	l = −13→13

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.037	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.108	H atoms treated by a mixture of independent and constrained refinement
S = 1.00	w = 1/[σ2(Fo2) + (0.059P)2 + 0.9299P] where P = (Fo2 + 2Fc2)/3
2047 reflections	(Δ/σ)max < 0.001
166 parameters	Δρmax = 0.25 e Å−3
15 restraints	Δρmin = −0.24 e Å−3

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.

	x	y	z	Uiso*/Ueq
O1	0.25143 (17)	0.05132 (5)	0.11300 (12)	0.0603 (3)
O2	0.17077 (17)	−0.04576 (5)	0.08785 (10)	0.0535 (3)
O3	0.15841 (13)	0.05730 (4)	0.33946 (9)	0.0394 (3)
H3	0.158 (2)	0.0508 (7)	0.4193 (11)	0.047*
N1	0.06055 (18)	0.17081 (6)	0.04393 (13)	0.0470 (3)
H1NA	0.074 (2)	0.1308 (6)	0.0459 (17)	0.056*
H1NB	−0.004 (2)	0.1902 (7)	−0.0177 (15)	0.056*
N2	0.23582 (16)	0.17105 (6)	0.23551 (12)	0.0428 (3)
H2NA	0.233 (2)	0.1306 (7)	0.2342 (16)	0.051*
N3	0.4140 (2)	0.17049 (7)	0.42646 (15)	0.0558 (4)
H3NA	0.407 (2)	0.1308 (7)	0.4247 (18)	0.067*
H3NB	0.477 (2)	0.1917 (8)	0.4890 (16)	0.067*
N4	0.32789 (15)	0.26210 (5)	0.33724 (11)	0.0373 (3)
N5	0.22621 (18)	0.35022 (5)	0.24256 (11)	0.0451 (3)
H5NA	0.157 (2)	0.3702 (8)	0.1812 (13)	0.054*
H5NB	0.282 (2)	0.3704 (8)	0.3088 (13)	0.054*
N6	0.13898 (15)	0.26268 (5)	0.13787 (10)	0.0353 (3)
C1	0.18246 (18)	0.00368 (6)	0.14673 (13)	0.0392 (3)
C2	0.09995 (16)	0.00520 (5)	0.26757 (11)	0.0308 (3)
H2A	0.1329	−0.0309	0.3157	0.037*
C3	0.23110 (16)	0.29059 (6)	0.23929 (11)	0.0338 (3)
C4	0.14503 (16)	0.20248 (6)	0.13831 (13)	0.0352 (3)
C5	0.32593 (17)	0.20212 (6)	0.33379 (13)	0.0386 (3)
O1W	0.45183 (14)	0.06665 (5)	−0.06993 (11)	0.0465 (3)
H1WA	0.391 (2)	0.0544 (8)	−0.0137 (16)	0.056*
H1WB	0.535 (2)	0.0446 (8)	−0.0730 (17)	0.056*

	U11	U22	U33	U12	U13	U23
O1	0.0750 (8)	0.0567 (7)	0.0575 (7)	0.0020 (6)	0.0378 (6)	0.0128 (6)
O2	0.0879 (8)	0.0446 (6)	0.0312 (5)	0.0254 (5)	0.0197 (5)	0.0046 (4)
O3	0.0533 (6)	0.0362 (5)	0.0272 (5)	−0.0122 (4)	0.0010 (4)	0.0008 (4)
N1	0.0582 (8)	0.0324 (6)	0.0480 (8)	−0.0069 (5)	−0.0006 (6)	−0.0048 (5)
N2	0.0496 (7)	0.0278 (6)	0.0494 (7)	0.0002 (5)	0.0013 (5)	0.0020 (5)
N3	0.0641 (8)	0.0382 (7)	0.0591 (9)	0.0069 (6)	−0.0120 (7)	0.0110 (6)
N4	0.0433 (6)	0.0337 (6)	0.0333 (6)	0.0020 (4)	0.0003 (5)	0.0027 (4)
N5	0.0658 (8)	0.0288 (6)	0.0358 (7)	−0.0001 (5)	−0.0097 (6)	0.0001 (5)
N6	0.0434 (6)	0.0308 (6)	0.0310 (6)	−0.0022 (4)	0.0033 (5)	0.0001 (4)
C1	0.0454 (7)	0.0420 (8)	0.0320 (7)	0.0151 (6)	0.0118 (5)	0.0100 (5)
C2	0.0422 (7)	0.0264 (6)	0.0236 (6)	0.0017 (5)	0.0046 (5)	0.0031 (4)
C3	0.0395 (6)	0.0329 (7)	0.0291 (6)	−0.0004 (5)	0.0048 (5)	0.0012 (5)
C4	0.0366 (6)	0.0328 (7)	0.0372 (7)	−0.0028 (5)	0.0086 (5)	−0.0003 (5)
C5	0.0383 (6)	0.0359 (7)	0.0412 (7)	0.0022 (5)	0.0044 (5)	0.0051 (6)
O1W	0.0443 (6)	0.0467 (6)	0.0496 (6)	0.0051 (4)	0.0102 (5)	0.0143 (5)

O1—C1	1.2497 (18)	N4—C5	1.3174 (18)
O2—C1	1.2530 (18)	N4—C3	1.3527 (16)
O3—C2	1.4170 (15)	N5—C3	1.3104 (18)
O3—H3	0.870 (11)	N5—H5NA	0.901 (13)
N1—C4	1.3215 (18)	N5—H5NB	0.895 (13)
N1—H1NA	0.884 (13)	N6—C4	1.3224 (18)
N1—H1NB	0.879 (13)	N6—C3	1.3583 (16)
N2—C4	1.3590 (18)	C1—C2	1.5242 (18)
N2—C5	1.3610 (18)	C2—C2i	1.531 (2)
N2—H2NA	0.889 (15)	C2—H2A	0.9600
N3—C5	1.3193 (18)	O1W—H1WA	0.858 (14)
N3—H3NA	0.872 (14)	O1W—H1WB	0.804 (13)
N3—H3NB	0.900 (14)
C2—O3—H3	111.1 (11)	O2—C1—C2	116.11 (12)
C4—N1—H1NA	117.6 (12)	O3—C2—C1	110.08 (10)
C4—N1—H1NB	119.1 (12)	O3—C2—C2i	111.37 (8)
H1NA—N1—H1NB	123.3 (16)	C1—C2—C2i	108.42 (12)
C4—N2—C5	119.39 (13)	O3—C2—H2A	109.5
C4—N2—H2NA	119.1 (11)	C1—C2—H2A	109.3
C5—N2—H2NA	121.5 (11)	C2i—C2—H2A	108.2
C5—N3—H3NA	119.1 (13)	N5—C3—N4	117.12 (12)
C5—N3—H3NB	117.1 (12)	N5—C3—N6	117.29 (12)
H3NA—N3—H3NB	123.8 (17)	N4—C3—N6	125.59 (13)
C5—N4—C3	115.95 (12)	N1—C4—N6	120.66 (13)
C3—N5—H5NA	118.9 (11)	N1—C4—N2	117.72 (13)
C3—N5—H5NB	120.3 (11)	N6—C4—N2	121.62 (12)
H5NA—N5—H5NB	120.5 (15)	N4—C5—N3	120.17 (13)
C4—N6—C3	115.71 (11)	N4—C5—N2	121.69 (12)
O1—C1—O2	125.57 (13)	N3—C5—N2	118.14 (14)
O1—C1—C2	118.30 (13)	H1WA—O1W—H1WB	110.6 (16)
O1—C1—C2—O3	−15.91 (17)	C3—N6—C4—N1	−179.76 (12)
O2—C1—C2—O3	165.79 (11)	C3—N6—C4—N2	0.99 (18)
O1—C1—C2—C2i	106.14 (12)	C5—N2—C4—N1	179.33 (13)
O2—C1—C2—C2i	−72.17 (12)	C5—N2—C4—N6	−1.4 (2)
C5—N4—C3—N5	177.80 (13)	C3—N4—C5—N3	−178.79 (13)
C5—N4—C3—N6	−2.34 (19)	C3—N4—C5—N2	1.85 (19)
C4—N6—C3—N5	−179.21 (12)	C4—N2—C5—N4	−0.1 (2)
C4—N6—C3—N4	0.93 (18)	C4—N2—C5—N3	−179.50 (13)

D—H···A	D—H	H···A	D···A	D—H···A
O3—H3···O2ii	0.87 (1)	1.80 (1)	2.6680 (14)	173 (2)
N1—H1NA···O1	0.88 (1)	2.27 (1)	3.0466 (19)	146 (2)
N1—H1NB···N4iii	0.88 (1)	2.15 (1)	3.0287 (19)	177 (2)
N2—H2NA···O3	0.89 (2)	2.09 (2)	2.8333 (16)	140 (1)
N2—H2NA···O1	0.89 (2)	2.19 (2)	2.9497 (18)	143 (1)
N3—H3NA···O1Wiv	0.87 (1)	2.26 (2)	2.8609 (18)	126 (2)
N3—H3NA···O3	0.87 (1)	2.57 (2)	3.2241 (18)	132 (2)
N3—H3NB···N6v	0.90 (1)	2.13 (1)	3.0313 (19)	176 (2)
N5—H5NA···O1Wvi	0.90 (1)	1.94 (1)	2.8148 (16)	163 (2)
N5—H5NB···O2vii	0.90 (1)	2.15 (2)	2.9581 (16)	149 (2)
O1W—H1WA···O1	0.86 (1)	1.85 (1)	2.6861 (16)	164 (2)
O1W—H1WB···O2viii	0.80 (1)	2.30 (2)	2.9738 (17)	142 (2)

Table 1

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H3⋯O2i	0.870 (11)	1.802 (12)	2.6680 (14)	173.2 (16)
N1—H1NA⋯O1	0.884 (13)	2.271 (14)	3.0466 (19)	146.3 (16)
N1—H1NB⋯N4ii	0.879 (13)	2.151 (13)	3.0287 (19)	177.3 (17)
N2—H2NA⋯O3	0.889 (15)	2.093 (15)	2.8333 (16)	140.2 (14)
N2—H2NA⋯O1	0.889 (15)	2.190 (15)	2.9497 (18)	143.2 (14)
N3—H3NA⋯O1Wiii	0.872 (14)	2.261 (19)	2.8609 (18)	125.9 (15)
N3—H3NA⋯O3	0.872 (14)	2.573 (16)	3.2241 (18)	132.2 (16)
N3—H3NB⋯N6iv	0.900 (14)	2.133 (14)	3.0313 (19)	176.2 (18)
N5—H5NA⋯O1Wv	0.901 (13)	1.940 (14)	2.8148 (16)	163.2 (15)
N5—H5NB⋯O2vi	0.895 (13)	2.153 (15)	2.9581 (16)	149.4 (15)
O1W—H1WA⋯O1	0.858 (14)	1.852 (14)	2.6861 (16)	163.8 (17)
O1W—H1WB⋯O2vii	0.804 (13)	2.297 (15)	2.9738 (17)	142.3 (17)

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