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Crystals of the title compound, C4H8N5+·C2F3O2, are built up of singly protonated 2,4-diamino-6-methyl-1,3,5-triazin-1-ium cations and trifluoro­acetate anions. The CF3 group of the anion is disordered. The oppositely charged ions inter­act via almost linear N—H...O hydrogen bonds, forming a CF3COO...C4H8N5+ unit. Two units related by an inversion centre inter­act through a pair of N—H...N hydrogen bonds, forming planar (CF3COO...C4H8N5+...C4H8N5+·CF3COO) aggregates that are linked by a pair of N—H...O hydrogen bonds into chains running along the c axis.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270107010165/fa3075sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270107010165/fa3075Isup2.hkl
Contains datablock I

CCDC reference: 649080

Comment top

The present study is a continuation of our investigations on the characterization of the hydrogen-bonding system formed by triazine derivatives in the solid state (Perpétuo & Janczak, 2005, Janczak & Kubiak, 2005). Triazine and its derivatives, especially 2,4,6-triamino-1,3,5-triazine, i.e. melamine and its organic and inorganic complexes or salts, can develop well defined non-covalent supramolecular architectures via multiple hydrogen bonds since they contain components of complementary arrays of hydrogen-bonding sites (Desiraju, 1990; MacDonald & Whitesides, 1994; Row, 1999; Krische & Lehn, 2000; Sherrington & Taskinen, 2001). Our interest of these types of compounds arises from the posibility of obtaining materials for nonlinear optics (Janczak & Perpétuo, 2002; Marchewka et al. 2003; Perpétuo & Janczak, 2006). In order to expand the understanding of the solid-state physical-organic chemistry of compounds that form multiple N—H···N and N—H···O hydrogen-bonding systems, we present here the solid-state structure of 2,4-diamino-6-methyl-1,3,5-triazin-1-ium trifluoroacetate, (I), and compare the results with the structure predicted for isolated oppositely charged units by ab-initio fully optimized geometry calculations at the B3LYP/6–31 G(d) level (Frisch et al., 1998). The molecular orbital calculations were carried out on isolated ions corresponding to the gas phase, and results are shown in Fig. 1.

The asymetric unit of (I) consists of a 2,4-diamino-6-methyl-1,3,5-triazinium cation, singly protonated at one of the ring N atoms located between the methyl and amine groups, and a trifluoroacetate anion, which shows disorder of the CF3 group (Fig. 2). The two oppostely charged units of (I) interact via a pair of almost linear N—H···O hydrogen bonds with a graph set of R22(8), which is one of the 24 most frequently observed bimolecular cyclic hydrogen-bonded units in organic crystal structures (Steiner, 2002; Stanley et al. 2002; Raj et al., 2003). The triazine ring is essentially planar [the deviation of the N and C atoms from the mean plane is smaller than 0.0256 (2) Å], but exhibits significant distortion from the ideal hexagonal form (Table 1). The internal C—N—C angle at the protonated N atom in the ring is greater than the other two C—N—C angles within the ring. This distortion results from the steric effect of the lone-pair electrons, predicted by the valence-shell electron-pair repulsion therory (VSEPR; Gillespie, 1963, 1992)·According to the theory the lone pair of electrons on the ring N atoms occupy a wider region than the bonding pair NH, causing the internal angle of the latter to be greater than that on the non-protonated ring N atoms. As a result of the protonation of the triazine ring at one of the three ring N atoms, the internal N—C—N angle involving only non-protonated N atoms is significantly greater than the remaining two N—C—N angles involving both protonated and non-protonated N atoms (Table 1). The ab-initio gas-phase geometry calculated for the isolated singly protonated 2,4-diamino-6-methyl-1,3,5-triazin-1-ium cation (Fig. 1) shows quite similar correlation between the internal C—N—C and N—C—N angles within the ring. Thus the ring distortions result mainly from the protonation and, to a lesser degree, from the hydrogen-bonding system, interionic interactions and the crystal packing forces. Protonation of the triazine ring also disturbs the C—N bonds within the ring when compared with the neutral 2,4-diamino-6-methyl-1,3,5-triazine molecule (Aoki et al. 1994). A search of Cambridge Structural Database (Version 5.27; Allen, 2002) for crystals containing the protonated 2,4-diamino-6-methyl-1,3,5- triazine residue yields only one structure (Wijaya et al. 2004), which shows very similar ring distortions to those found in the present stucture.

The trifluoroacetate anion, CF3COO-, exhibits disorder, caused by the rotation of the CF3 group around the single C—C bond. The conformation of the trifluoroacetate ion, CF3COO-, in the crystal is described by the O1—C5—C6—F1 torsion angle of -174.1 (1)° (one rotational conformer) and by the O1—C5—C6—F21 torsion angle of -100.4 (1)° (the second rotational conformer). Molecular orbital calculations performed for the isolated CF3COO- ion show a minimum on the potential energy surface (PES) for a conformation quite similar to the first rotational conformer in the crystal (the O1—C5—C6—F1 torsion angle is -175.2°). The other minima on the PES appears when the CF3 group is rotated by about 60 or 120°; however, these conformations are different from the second rotational conformer present in the crystal. Undoubtedly, this results from the interaction with the neigbouring cations, the N—H···F hydrogen bond and the crystal-packing forces. The C—O bond lengths in the carboxylate group are intermediate between single Csp2—O (1.308–1.320 Å) and double Csp2O bond values (1.214–1.224 Å; Allen et al. 1987) indicating delocalization of the charge onto both O atoms of the COO- group. The average C—F bond length in the crystal of 1.287 Å is slightly shorter than those for the gas phase obtained by MO calculations (1.334 Å; Frisch et al., 1998). The X-ray O—C—O angle in the COO- group is smaller by about 3.5° than that in the ab-initio MO calculations (132.88°). Thus in the crystal the repulsive interactions between the O atoms of COO- as well as the steric effects of the lone pair of electrons on both O atoms are decreased as a result of the formation of the N—H···O hydrogen bonds.

An extensive set of hydrogen bonds (Table 2) links the components of (I) into a continuous framework superstructure. Each 2,4-diamino-6-methyl-1,3,5-triazin-1-ium residue is involved in seven hydrogen bonds; in five of these it acts as a donor and in the remaining two as an acceptor. One pair of almost linear N—H···N hydrogen bonds links inversion-related 2,4-diamino-6-methyl-1,3,5-triazin-1-ium cations into a planar dimer. These dimers interact with two CF3COO- anions via N—H···O hydrogen bonds, forming almost planar (CF3COO- ···C4H8N5+···C4H8N5+CF3COO-) aggregates (Fig. 3). These aggregates are alternately located in the crystal almost parallel to the (120) and (120) planes. Additionally, the aggreagates interact via N—H···O hydrogen bonds between the amine (N5) group and atom O2 of the COO- group (Fig. 3). Both O atoms of the COO- group act as acceptors in two hydrogen bonds. The ring N atom in the position para to the methyl group is not involved in any hydrogen bonds.

Related literature top

For related literature, see: Allen (2002); Allen et al. (1987); Aoki et al. (1994); Desiraju (1990); Frisch et al. (1998); Gillespie (1963, 1992); Janczak & Kubiak (2005); Janczak & Perpétuo (2002); Krische & Lehn (2000); MacDonald & Whitesides (1994); Marchewka et al. (2003); Perpétuo & Janczak (2005, 2006); Raj et al. (2003); Row (1999); Sherrington & Taskinen (2001); Stanley et al. (2002); Steiner (2002); Wijaya et al. (2004).

Experimental top

2,4-Diamino-6-methyl-1,3,5-triazine (98%) was resolved in 10% CF3COOH. After several days, colourless crystals had formed, which proved to be suitable for single-crystal X-ray diffraction analysis.

Refinement top

H atoms were positioned geometrically and treated as riding, with Uiso(H) values of 1.2Ueq(N) and 1.5Ueq(C).

Computing details top

Data collection: KM-4 CCD Software (Kuma, 2004); cell refinement: KM-4 CCD Software; data reduction: KM-4 CCD Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 1990); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. Results of the optimized molecular orbital calculations for the 2,4-diamino-6-methyl-1,3,5-triazin-1-ium cation.
[Figure 2] Fig. 2. A view of (I), showing displacement ellipsoids at the 50% probability level and H atoms as spheres of arbitrary radii. Hydrogen bonds are drawn as dashed lines. The two orientations of the CF3 group (each 50% occupancy) are shown as solid and open bonds.
[Figure 3] Fig. 3. A view of the crystal packing in (I), showing the hydrogen bonded (CF3COO- ···C4H8N5+···C4H8N5+CF3COO-) aggregates that interact via N—H···O hydrogen bonds, forming chains parallel to the c axis. H atoms of methyl groups have been omitted for clarity.
2,4-Diamino-6-methyl-1,3,5-triazin-1-ium trifluoroacetate top
Crystal data top
C4H8N5+·C2F3O2F(000) = 488
Mr = 239.17Dx = 1.546 Mg m3
Dm = 1.54 Mg m3
Dm measured by flotation
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 1182 reflections
a = 10.384 (2) Åθ = 3.0–28.5°
b = 8.187 (1) ŵ = 0.15 mm1
c = 13.013 (3) ÅT = 295 K
β = 111.75 (2)°Paralellepiped, colourless
V = 1027.5 (4) Å30.32 × 0.26 × 0.22 mm
Z = 4
Data collection top
Kuma KM-4 with CCD area-detector
diffractometer
2563 independent reflections
Radiation source: fine-focus sealed tube1548 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.026
Detector resolution: 1024x1024 with blocks 2x2 pixels mm-1θmax = 28.5°, θmin = 3.0°
ω–scanh = 1313
Absorption correction: analytical
face-indexed (SHELXTL; Sheldrick, 1990)
k = 108
Tmin = 0.953, Tmax = 0.964l = 1717
12223 measured reflections
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.053H-atom parameters constrained
wR(F2) = 0.165 w = 1/[σ2(Fo2) + (0.0849P)2]
where P = (Fo2 + 2Fc2)/3
S = 1.11(Δ/σ)max = 0.009
2563 reflectionsΔρmax = 0.29 e Å3
177 parametersΔρmin = 0.25 e Å3
6 restraintsExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.023 (4)
Crystal data top
C4H8N5+·C2F3O2V = 1027.5 (4) Å3
Mr = 239.17Z = 4
Monoclinic, P21/cMo Kα radiation
a = 10.384 (2) ŵ = 0.15 mm1
b = 8.187 (1) ÅT = 295 K
c = 13.013 (3) Å0.32 × 0.26 × 0.22 mm
β = 111.75 (2)°
Data collection top
Kuma KM-4 with CCD area-detector
diffractometer
2563 independent reflections
Absorption correction: analytical
face-indexed (SHELXTL; Sheldrick, 1990)
1548 reflections with I > 2σ(I)
Tmin = 0.953, Tmax = 0.964Rint = 0.026
12223 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0536 restraints
wR(F2) = 0.165H-atom parameters constrained
S = 1.11Δρmax = 0.29 e Å3
2563 reflectionsΔρmin = 0.25 e Å3
177 parameters
Special details top

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 (Å2) top
xyzUiso*/UeqOcc. (<1)
N10.17496 (14)0.06954 (17)0.00560 (11)0.0380 (4)
C10.21154 (16)0.0574 (2)0.11798 (14)0.0364 (4)
N20.33379 (14)0.09825 (18)0.19374 (11)0.0403 (4)
C20.42717 (17)0.1559 (2)0.15526 (13)0.0397 (4)
N30.39947 (15)0.16226 (19)0.04479 (11)0.0405 (4)
H30.46230.19270.02100.049*
C30.27180 (17)0.1199 (2)0.02753 (14)0.0376 (4)
N40.11718 (16)0.0009 (2)0.15326 (12)0.0493 (5)
H410.13570.01130.22310.059*
H420.03700.02860.10650.059*
N50.54769 (16)0.2076 (2)0.22449 (13)0.0592 (5)
H510.56630.20420.29460.071*
H520.60810.24480.19980.071*
C40.2464 (2)0.1301 (3)0.14743 (15)0.0577 (6)
H4A0.26740.02690.17250.087*
H4B0.30440.21330.15950.087*
H4C0.15080.15670.18780.087*
O10.60611 (13)0.26716 (18)0.03446 (10)0.0545 (4)
O20.74213 (16)0.3215 (2)0.13932 (12)0.0811 (6)
C50.70961 (18)0.3255 (2)0.03901 (15)0.0553 (5)
C60.8174 (2)0.4101 (3)0.00143 (18)0.0715 (6)
F10.9273 (7)0.4553 (19)0.0797 (4)0.091 (4)0.50
F20.7645 (11)0.5373 (6)0.0553 (9)0.089 (4)0.50
F30.8416 (7)0.3252 (6)0.0749 (6)0.0872 (12)0.50
F210.9279 (7)0.3213 (5)0.0217 (11)0.095 (2)0.50
F220.8648 (7)0.5386 (6)0.0601 (7)0.092 (2)0.50
F230.7725 (7)0.4749 (17)0.0943 (4)0.093 (4)0.50
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0369 (8)0.0453 (8)0.0307 (7)0.0035 (6)0.0115 (6)0.0029 (6)
C10.0327 (8)0.0406 (9)0.0356 (9)0.0009 (7)0.0125 (7)0.0007 (7)
N20.0340 (8)0.0561 (9)0.0309 (7)0.0055 (6)0.0123 (6)0.0013 (6)
C20.0345 (9)0.0501 (10)0.0364 (9)0.0031 (7)0.0153 (7)0.0053 (8)
N30.0357 (8)0.0548 (9)0.0341 (8)0.0061 (7)0.0164 (6)0.0013 (7)
C30.0400 (9)0.0391 (9)0.0354 (9)0.0007 (7)0.0160 (7)0.0008 (7)
N40.0384 (8)0.0747 (11)0.0334 (8)0.0107 (7)0.0118 (6)0.0062 (7)
N50.0385 (9)0.1018 (14)0.0379 (9)0.0178 (9)0.0150 (7)0.0081 (9)
C40.0579 (12)0.0810 (15)0.0355 (10)0.0117 (11)0.0187 (9)0.0030 (10)
O10.0413 (7)0.0832 (10)0.0396 (7)0.0152 (7)0.0156 (6)0.0042 (7)
O20.0655 (10)0.1219 (16)0.0630 (9)0.0347 (10)0.0283 (7)0.0224 (9)
C50.0493 (10)0.0692 (12)0.0504 (10)0.0047 (8)0.0184 (8)0.0059 (9)
C60.0709 (13)0.0744 (15)0.0687 (13)0.0116 (11)0.0267 (10)0.0045 (11)
F10.075 (4)0.113 (13)0.067 (2)0.020 (6)0.008 (3)0.011 (6)
F20.091 (9)0.0890 (19)0.090 (10)0.015 (3)0.035 (9)0.020 (4)
F30.086 (3)0.085 (2)0.106 (3)0.020 (2)0.033 (3)0.027 (2)
F210.082 (3)0.083 (3)0.112 (7)0.012 (2)0.052 (4)0.013 (4)
F220.106 (4)0.063 (2)0.112 (6)0.045 (2)0.065 (4)0.032 (3)
F230.095 (4)0.104 (12)0.058 (2)0.021 (6)0.008 (3)0.020 (4)
Geometric parameters (Å, º) top
N1—C31.299 (2)N5—H520.8600
N1—C11.372 (2)C4—H4A0.9600
C1—N41.316 (2)C4—H4B0.9600
C1—N21.330 (2)C4—H4C0.9600
N2—C21.332 (2)O1—C51.239 (2)
C2—N51.312 (2)O2—C51.222 (2)
C2—N31.359 (2)C5—C61.542 (3)
N3—C31.356 (2)C6—F11.273 (5)
N3—H30.8600C6—F21.277 (6)
C3—C41.485 (2)C6—F231.273 (6)
N4—H410.8600C6—F221.286 (5)
N4—H420.8600C6—F211.300 (5)
N5—H510.8600C6—F31.311 (4)
C3—N1—C1115.75 (14)C3—C4—H4B109.5
N4—C1—N2117.54 (15)H4A—C4—H4B109.5
N4—C1—N1116.80 (15)C3—C4—H4C109.5
N2—C1—N1125.66 (15)H4A—C4—H4C109.5
C1—N2—C2116.02 (14)H4B—C4—H4C109.5
N5—C2—N2119.93 (15)O2—C5—O1129.17 (18)
N5—C2—N3119.31 (15)O2—C5—C6113.89 (17)
N2—C2—N3120.76 (15)O1—C5—C6116.89 (16)
C3—N3—C2119.59 (16)F1—C6—F2107.0 (6)
C3—N3—H3120.0F23—C6—F2299.2 (5)
C2—N3—H3120.0F23—C6—F21114.0 (5)
N1—C3—N3121.78 (15)F22—C6—F21102.8 (4)
N1—C3—C4120.55 (16)F1—C6—F3113.4 (5)
N3—C3—C4117.65 (16)F2—C6—F399.0 (4)
C1—N4—H41120.0F1—C6—C5114.7 (3)
C1—N4—H42120.0F2—C6—C5110.0 (4)
H41—N4—H42120.0F23—C6—C5116.9 (3)
C2—N5—H51120.0F22—C6—C5110.0 (3)
C2—N5—H52120.0F21—C6—C5112.0 (3)
H51—N5—H52120.0F3—C6—C5111.6 (3)
C3—C4—H4A109.5
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N3—H3···O10.861.982.836 (2)179
N5—H52···O20.861.942.799 (2)178
N4—H41···O2i0.862.242.935 (2)138
N4—H42···N1ii0.862.173.024 (2)173
N5—H51···O1iii0.862.122.974 (2)172
N5—H51···F23iii0.862.553.027 (7)116
Symmetry codes: (i) x+1, y1/2, z+1/2; (ii) x, y, z; (iii) x, y+1/2, z+1/2.

Experimental details

Crystal data
Chemical formulaC4H8N5+·C2F3O2
Mr239.17
Crystal system, space groupMonoclinic, P21/c
Temperature (K)295
a, b, c (Å)10.384 (2), 8.187 (1), 13.013 (3)
β (°) 111.75 (2)
V3)1027.5 (4)
Z4
Radiation typeMo Kα
µ (mm1)0.15
Crystal size (mm)0.32 × 0.26 × 0.22
Data collection
DiffractometerKuma KM-4 with CCD area-detector
diffractometer
Absorption correctionAnalytical
face-indexed (SHELXTL; Sheldrick, 1990)
Tmin, Tmax0.953, 0.964
No. of measured, independent and
observed [I > 2σ(I)] reflections
12223, 2563, 1548
Rint0.026
(sin θ/λ)max1)0.671
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.053, 0.165, 1.11
No. of reflections2563
No. of parameters177
No. of restraints6
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.29, 0.25

Computer programs: KM-4 CCD Software (Kuma, 2004), KM-4 CCD Software, SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), SHELXTL (Sheldrick, 1990), SHELXL97.

Selected geometric parameters (Å, º) top
N1—C31.299 (2)C2—N31.359 (2)
N1—C11.372 (2)N3—C31.356 (2)
C1—N41.316 (2)C3—C41.485 (2)
C1—N21.330 (2)O1—C51.239 (2)
N2—C21.332 (2)O2—C51.222 (2)
C2—N51.312 (2)C5—C61.542 (3)
C3—N1—C1115.75 (14)C3—N3—C2119.59 (16)
N2—C1—N1125.66 (15)N1—C3—N3121.78 (15)
C1—N2—C2116.02 (14)O2—C5—O1129.17 (18)
N2—C2—N3120.76 (15)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N3—H3···O10.861.982.836 (2)179.0
N5—H52···O20.861.942.799 (2)177.6
N4—H41···O2i0.862.242.935 (2)138.2
N4—H42···N1ii0.862.173.024 (2)172.7
N5—H51···O1iii0.862.122.974 (2)171.6
N5—H51···F23iii0.862.553.027 (7)115.6
Symmetry codes: (i) x+1, y1/2, z+1/2; (ii) x, y, z; (iii) x, y+1/2, z+1/2.
 

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