Cocrystallization of melaminium levulinate monohydrate

Crystals of 2,4,6-tri­amino-1,3,5-triazin-1-ium levulinate (4-oxo­pentanoate) monohydrate, C₃H₇N₆⁺·C₅H₇O₃^-·H₂O, are formed via self-assembled hydrogen bonding by cocrystallization of mel­amine and levulinic acid. Two N-H...N hydrogen bonds and four N-H...O hydrogen bonds connect two melaminium entities such that each of two pairs of N-H...O bonds bridges two H atoms belonging to the amine groups of two different melaminium cations via the carbonyl O atom of one levulinate mol­ecule.

S1. Comment

One of the primary objectives of crystal engineering is the construction of self-assembled hydrogen-bonded molecular materials (Desiraju, 1996; Philip & Stoddart, 1996). Currently, many research groups are involved in synthesizing one-, two- and three-dimensional clustered self-assembled hydrogen-bonding superlattice structures of? molecular materials (Whitesides, et al., 1991; Mathias, et al., 1994; Zerkowski, et al., 1990; Ghadiri, et al., 1993; Kimizuka, et al., 1995; Lange, et al., 1997). In addition, others are synthesizing metal-ion-incorporated systems (Goddgame, et al., 1999; Zhang, et al., 1999). Various studies have been carried out using melamine and its derivatives as versatile components, because the presence of amino groups in these compounds means that they can easily form several types of self-organized superlattices with suitable hydrogen-bonding donor and acceptor molecules (Janczak & Perpétuo, 2001a, 2001b, 2001c, 201 d; Perpétuo & Janczak, 2002). The combination of levulinic acid with melamine leads to the formation of a 1:1 adduct of 2,4,6-triamino-1,3,5-triazin-1-ium levulinate monohydrate, C₃H₇N₆⁺·C₅H₇O₃⁻·H₂O, (I), the crystal structure of which is reported here.

The asymmetric unit of (I) consists of two oppositely charged ions, viz. a protonated melaminium and a levulinate ion, and one water molecule (Fig. 1). Two melaminium entities are directly connected to one another via hydrogen bonding. In this unit, two N6—H···N3 hydrogen bonds, two N5—H···O3 hydrogen bonds and two N6—H···O3 hydrogen bonds bridge two H atoms of each amine group from two melaminium entities via the carbonyl O atom on one levulinate ion. In addition, there are also two N4—H···O1W and two O1W—H···O1 hydrogen bonds. A bridging water molecule and a bridging carbonyl O atom between melaminium and levulinate entities form large pores (0L and 0R in Fig. 1). On the other hand, two water molecules, O1wⁱⁱ and O1wⁱⁱⁱ in Fig. 1, are used to bridge melaminium and levulinate entities in the next row along the b axis.

The six-membered aromatic ring of the melaminium ion exhibits slight distortions from the ideal hexagonal form (Janczak & Perpétuo, 2001c) and from the structure of neutral melamine (Hughes, 1941). The C2—N2—C1 angle (Table 1) at the protonated N atom of the melaminium entity is 4° larger than the C1—N1—C3 angle at the non-protonated N atom. Also, the N1—C3—N3 angle involving the non-protonated ring N atoms is about 5° larger than the N3—C2—N2 angle, involving protonated and non-protonated N atoms. The contraction of the C1—N1—C3 and C2—N3—C3 angles from 120 to about 115° appears to be correlated with expansion of the N1—C3—N3 angle to about 127°, while the N1—C1—N2 and N3—C2—N2 angles are both close to ideal, as is the C2—N2—C1 angle. On the other hand, the C2—N2—C1 and C1—N1—C3 angles are 3° higher than the equivalent angle (116°) of the neutral melamine (Hughes, 1941). The N1—C3—N3 and N3—C2—N2 angles are similar to those of neutral melamine.

S2. Experimental

An aqueous solution (50 ml) of levulinic acid (0.22 g, 2 mmol) was added to melamine (0.26 g, 2 mmol) dissolved in hot water (100 ml). The resulting solution was cooled slowly to ambient temperature and filtered. Colorless crystals of the melamine–levulinic acid adduct, (I), appeared after the solution had been left to stand for several days in the presence of air at room temperature.

S3. Refinement

H atoms on atoms N2 and O1W were located in a difference map and their parameters were refined isotropically. All other H atoms were positioned geometrically and constrained to ride on their parent atoms, with U_iso(H) values of 1.2 U_eq(C,N) (CH₂ and NH₂) or 1.5 U_eq(C) (CH₃).

Computing details

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

Fig. 1. The molecular structure and unit-cell contents of (I), showing the atom-numbering scheme and 30% probability displacement ellipsoids. Pores formed by hydrogen bonds between melaminium cations and levulinate anions are designated 0L and 0R. [Symmetry codes: (i) 1 − x, −y, 1 − z; (ii) −x, −1/2 + y, 1/2 − z; (iii) x, 1/2 − y, 1/2 + z.]

(I)

Crystal data

C3H7N6^+·C5H7O3^−·H2O	F(000) = 552
Mr = 260.27	Dx = 1.413 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 23 reflections
a = 10.538 (2) Å	θ = 11.3–13.9°
b = 16.214 (3) Å	µ = 0.11 mm^−1
c = 7.1988 (14) Å	T = 293 K
β = 95.85 (3)°	Block, colorless
V = 1223.6 (4) Å^3	0.46 × 0.43 × 0.36 mm
Z = 4

Data collection

Enraf–Nonius CAD-4 diffractometer	θmax = 27.5°, θmin = 2.3°
Non–profiled ω/2θ scans	h = −13→13
5931 measured reflections	k = −21→21
2806 independent reflections	l = 0→9
1899 reflections with I > 2σ(I)	3 standard reflections every 400 reflections
Rint = 0.030	intensity decay: 1%

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F^2 > 2σ(F^2)] = 0.048	w = 1/[σ^2(Fo^2) + (0.0639P)^2 + 0.3261P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.137	(Δ/σ)max < 0.001
S = 1.02	Δρmax = 0.28 e Å^−3
2806 reflections	Δρmin = −0.19 e Å^−3
175 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	0.08998 (12)	0.85856 (8)	0.2432 (2)	0.0446 (4)
O2	0.21430 (13)	0.96730 (9)	0.2963 (3)	0.0629 (5)
O3	0.54437 (13)	0.75146 (9)	0.4039 (3)	0.0652 (5)
N1	0.21102 (14)	0.58793 (10)	0.3006 (2)	0.0420 (4)
N2	0.10962 (14)	0.46023 (10)	0.3375 (2)	0.0383 (4)
H2	0.044 (2)	0.4266 (14)	0.312 (3)	0.054 (6)*
N3	0.32997 (14)	0.46890 (9)	0.4192 (2)	0.0393 (4)
N4	−0.00394 (15)	0.57231 (10)	0.2184 (3)	0.0498 (5)
H4NA	−0.0096	0.6232	0.1847	0.06*
H4NB	−0.0708	0.5416	0.2088	0.06*
N5	0.22286 (15)	0.34767 (10)	0.4542 (3)	0.0491 (5)
H5NA	0.2933	0.3242	0.4955	0.059*
H5NB	0.1529	0.32	0.4449	0.059*
N6	0.42457 (15)	0.59376 (11)	0.3864 (3)	0.0493 (5)
H6NA	0.4226	0.6449	0.3549	0.059*
H6NB	0.4955	0.5713	0.4295	0.059*
C1	0.10664 (16)	0.54157 (11)	0.2846 (3)	0.0371 (4)
C2	0.22207 (16)	0.42632 (11)	0.4048 (3)	0.0364 (4)
C3	0.31790 (16)	0.54923 (12)	0.3685 (3)	0.0383 (4)
C4	0.19804 (17)	0.89259 (11)	0.2881 (3)	0.0380 (4)
C5	0.31025 (17)	0.83492 (12)	0.3312 (3)	0.0451 (5)
H5A	0.291	0.7969	0.4286	0.054*
H5B	0.3216	0.8027	0.2206	0.054*
C6	0.43350 (17)	0.87891 (12)	0.3933 (3)	0.0408 (5)
H6A	0.452	0.9168	0.2954	0.049*
H6B	0.4211	0.9115	0.503	0.049*
C7	0.54735 (17)	0.82440 (11)	0.4384 (3)	0.0397 (5)
C8	0.66599 (19)	0.86456 (13)	0.5261 (3)	0.0528 (6)
H8A	0.7318	0.8238	0.5496	0.079*
H8B	0.6493	0.8898	0.6418	0.079*
H8C	0.6932	0.9059	0.4435	0.079*
O1W	−0.00947 (14)	0.73341 (10)	0.0286 (3)	0.0490 (4)
H1W	0.044 (3)	0.7687 (18)	0.081 (4)	0.076 (9)*
H2W	0.025 (3)	0.7124 (19)	−0.062 (5)	0.084 (10)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0296 (7)	0.0375 (7)	0.0647 (9)	0.0007 (5)	−0.0051 (6)	−0.0016 (7)
O2	0.0366 (8)	0.0325 (8)	0.1163 (15)	0.0012 (6)	−0.0087 (9)	0.0025 (8)
O3	0.0367 (7)	0.0356 (8)	0.1187 (15)	0.0026 (6)	−0.0143 (9)	−0.0072 (9)
N1	0.0329 (8)	0.0350 (8)	0.0567 (11)	−0.0048 (6)	−0.0017 (7)	0.0028 (7)
N2	0.0254 (7)	0.0334 (8)	0.0546 (10)	−0.0045 (6)	−0.0030 (7)	0.0015 (7)
N3	0.0266 (7)	0.0369 (8)	0.0535 (10)	−0.0039 (6)	−0.0008 (7)	−0.0014 (7)
N4	0.0322 (8)	0.0359 (9)	0.0784 (13)	−0.0024 (6)	−0.0081 (8)	0.0102 (9)
N5	0.0274 (8)	0.0345 (8)	0.0827 (13)	−0.0014 (6)	−0.0076 (8)	0.0066 (9)
N6	0.0334 (8)	0.0406 (9)	0.0719 (13)	−0.0113 (7)	−0.0046 (8)	0.0054 (8)
C1	0.0315 (9)	0.0344 (9)	0.0443 (11)	−0.0017 (7)	−0.0014 (8)	0.0000 (8)
C2	0.0287 (8)	0.0342 (9)	0.0456 (11)	−0.0014 (7)	0.0001 (8)	−0.0029 (8)
C3	0.0306 (9)	0.0392 (10)	0.0446 (11)	−0.0059 (7)	0.0020 (8)	−0.0035 (8)
C4	0.0306 (9)	0.0340 (10)	0.0487 (12)	0.0016 (7)	−0.0001 (8)	0.0028 (8)
C5	0.0302 (9)	0.0340 (10)	0.0692 (14)	0.0019 (7)	−0.0040 (9)	0.0021 (9)
C6	0.0336 (9)	0.0360 (10)	0.0511 (12)	0.0032 (7)	−0.0034 (8)	−0.0014 (9)
C7	0.0297 (9)	0.0352 (10)	0.0530 (13)	−0.0011 (7)	−0.0019 (8)	0.0018 (9)
C8	0.0380 (11)	0.0482 (12)	0.0691 (15)	−0.0040 (9)	−0.0104 (10)	−0.0005 (11)
O1W	0.0401 (8)	0.0422 (9)	0.0637 (11)	0.0027 (6)	0.0002 (7)	−0.0095 (7)

Geometric parameters (Å, º)

O1—C4	1.277 (2)	N6—C3	1.331 (2)
O2—C4	1.224 (2)	N6—H6NA	0.86
O3—C7	1.208 (2)	N6—H6NB	0.86
N1—C1	1.328 (2)	C4—C5	1.515 (2)
N1—C3	1.337 (2)	C5—C6	1.509 (3)
N2—C2	1.351 (2)	C5—H5A	0.97
N2—C1	1.372 (2)	C5—H5B	0.97
N2—H2	0.89 (2)	C6—C7	1.499 (3)
N3—C2	1.325 (2)	C6—H6A	0.97
N3—C3	1.355 (2)	C6—H6B	0.97
N4—C1	1.312 (2)	C7—C8	1.492 (3)
N4—H4NA	0.86	C8—H8A	0.96
N4—H4NB	0.86	C8—H8B	0.96
N5—C2	1.324 (2)	C8—H8C	0.96
N5—H5NA	0.86	O1W—H1W	0.86 (3)
N5—H5NB	0.86	O1W—H2W	0.85 (3)
C1—N1—C3	115.18 (16)	O2—C4—C5	119.90 (16)
C2—N2—C1	119.03 (15)	O1—C4—C5	116.27 (16)
C2—N2—H2	117.6 (15)	C6—C5—C4	113.53 (16)
C1—N2—H2	122.6 (15)	C6—C5—H5A	108.9
C2—N3—C3	115.05 (15)	C4—C5—H5A	108.9
C1—N4—H4NA	120	C6—C5—H5B	108.9
C1—N4—H4NB	120	C4—C5—H5B	108.9
H4NA—N4—H4NB	120	H5A—C5—H5B	107.7
C2—N5—H5NA	120	C7—C6—C5	115.54 (16)
C2—N5—H5NB	120	C7—C6—H6A	108.4
H5NA—N5—H5NB	120	C5—C6—H6A	108.4
C3—N6—H6NA	120	C7—C6—H6B	108.4
C3—N6—H6NB	120	C5—C6—H6B	108.4
H6NA—N6—H6NB	120	H6A—C6—H6B	107.5
N4—C1—N1	120.93 (17)	O3—C7—C8	121.16 (17)
N4—C1—N2	117.41 (16)	O3—C7—C6	121.95 (16)
N1—C1—N2	121.66 (16)	C8—C7—C6	116.88 (17)
N5—C2—N3	119.94 (16)	C7—C8—H8A	109.5
N5—C2—N2	118.02 (16)	C7—C8—H8B	109.5
N3—C2—N2	122.03 (17)	H8A—C8—H8B	109.5
N6—C3—N1	116.90 (17)	C7—C8—H8C	109.5
N6—C3—N3	116.09 (17)	H8A—C8—H8C	109.5
N1—C3—N3	127.00 (16)	H8B—C8—H8C	109.5
O2—C4—O1	123.83 (17)	H1W—O1W—H2W	107 (3)
C3—N1—C1—N4	−179.5 (2)	C1—N1—C3—N3	0.8 (3)
C3—N1—C1—N2	1.0 (3)	C2—N3—C3—N6	178.32 (18)
C2—N2—C1—N4	179.46 (18)	C2—N3—C3—N1	−2.5 (3)
C2—N2—C1—N1	−1.0 (3)	O2—C4—C5—C6	3.6 (3)
C3—N3—C2—N5	−178.75 (19)	O1—C4—C5—C6	−176.85 (19)
C3—N3—C2—N2	2.5 (3)	C4—C5—C6—C7	179.74 (19)
C1—N2—C2—N5	−179.69 (19)	C5—C6—C7—O3	9.4 (3)
C1—N2—C2—N3	−0.9 (3)	C5—C6—C7—C8	−171.4 (2)
C1—N1—C3—N6	179.95 (18)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2···O1^i	0.89 (2)	1.80 (2)	2.689 (2)	179 (2)
O1W—H1W···O1	0.86 (3)	1.90 (3)	2.697 (2)	154 (3)
O1W—H2W···O1^ii	0.85 (3)	1.99 (3)	2.825 (2)	168 (3)

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