2,4–Dimethylanilinium dihydrogenphosphate, C
8H
12N
+.H
2PO
4−, (I), is monoclinic (
P2
1/
c). The ions are held together by O—H
O and N—H
O hydrogen bonds. In addition there is one C
methyl—H
O hydrogen bond. The dihydrogenphosphates and the —NH
3 groups are arranged in sheets which are parallel to the (010) plane. In each sheet there are centrosymmetric pairs of dihydrogenphosphates held by O—H
O bonds. These pairs of dihydrogenphosphates are arranged in columns that are parallel to the unit-cell
b axis. These columns are held together
via —NH
3 groups through N—H
O bonds. Each hydrogen from an —NH
3 group is donated to a different dihydrogenphosphate ion. The differential scanning calorimetry experiment showed anomaly during heating at ∼442 K.
Supporting information
CCDC reference: 176017
Key indicators
- Single-crystal X-ray study
- T = 290 K
- Mean (C-C) = 0.004 Å
- R factor = 0.034
- wR factor = 0.041
- Data-to-parameter ratio = 11.1
checkCIF results
No syntax errors found
ADDSYM reports no extra symmetry
Precipitation of 2,4-dimethylaniline and H3PO4. The precipitate was filtered
off, dried and dissolved in 96% ethanol from which the single crystals were
grown by slow evaporation at room temperature.
The O—H, N—H, C(sp2)-H and C(sp3) bond lengths were
restrained to 0.85 (2), 0.90 (3), 0.97 (1) and 0.95 (1) Å, respectively. The
angles between the H atoms pertinent to the respective methyl groups were
restrained to the values 109.5 (1)°.
Cell refinement: KM4B8; data reduction: JANA2000 (Petříček & Dušek, 2000); program(s) used to solve structure: JANA2000; program(s) used to refine structure: JANA2000; molecular graphics: ORTEPIII (Burnett & Johnson, 1996).
Crystal data top
(C8H9NH3)(H2PO4) | F(000) = 464 |
Mr = 219.2 | Dx = 1.394 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.710688 Å |
a = 13.009 (3) Å | Cell parameters from 68 reflections |
b = 4.688 (1) Å | θ = 6.1–18.1° |
c = 17.607 (4) Å | µ = 0.25 mm−1 |
β = 103.60 (2)° | T = 290 K |
V = 1043.7 (4) Å3 | Prism, colourless |
Z = 4 | 0.24 × 0.19 × 0.14 mm |
Data collection top
KUMA4 diffractometer | Rint = 0.055 |
ω–2θ scans | θmax = 26.0°, θmin = 1.6° |
Absorption correction: gaussian Gaussian integration (Coppens, 1965) | h = −16→15 |
Tmin = 0.942, Tmax = 0.967 | k = −5→5 |
3969 measured reflections | l = 0→21 |
2050 independent reflections | 3 standard reflections every 200 reflections |
1258 reflections with I > 3σ(I) | intensity decay: 2.1% |
Refinement top
Refinement on F | 0 constraints |
Least-squares matrix: full with fixed elements per cycle | All H-atom parameters refined |
R[F2 > 2σ(F2)] = 0.034 | Weighting scheme based on measured s.u.'s w = 1/(σ2(F) + 0.0001F2) |
wR(F2) = 0.041 | (Δ/σ)max = 0.0001 |
S = 1.75 | Δρmax = 0.57 e Å−3 |
2050 reflections | Δρmin = −0.92 e Å−3 |
184 parameters | Extinction correction: Becker & Coppens (1974) type 2 |
20 restraints | Extinction coefficient: 0.00063 (3) |
Crystal data top
(C8H9NH3)(H2PO4) | V = 1043.7 (4) Å3 |
Mr = 219.2 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 13.009 (3) Å | µ = 0.25 mm−1 |
b = 4.688 (1) Å | T = 290 K |
c = 17.607 (4) Å | 0.24 × 0.19 × 0.14 mm |
β = 103.60 (2)° | |
Data collection top
KUMA4 diffractometer | 1258 reflections with I > 3σ(I) |
Absorption correction: gaussian Gaussian integration (Coppens, 1965) | Rint = 0.055 |
Tmin = 0.942, Tmax = 0.967 | 3 standard reflections every 200 reflections |
3969 measured reflections | intensity decay: 2.1% |
2050 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.034 | 20 restraints |
wR(F2) = 0.041 | All H-atom parameters refined |
S = 1.75 | Δρmax = 0.57 e Å−3 |
2050 reflections | Δρmin = −0.92 e Å−3 |
184 parameters | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
P | 0.08037 (4) | 0.05703 (11) | 0.11655 (3) | 0.02769 (18) | |
O1 | −0.03598 (12) | 0.1746 (3) | 0.08557 (9) | 0.0351 (5) | |
O2 | 0.15871 (13) | 0.3039 (3) | 0.11068 (11) | 0.0468 (6) | |
O3 | 0.10080 (12) | −0.1884 (3) | 0.06608 (8) | 0.0366 (5) | |
O4 | 0.09002 (12) | −0.0155 (3) | 0.20150 (8) | 0.0390 (5) | |
N | 0.14708 (15) | 0.4949 (4) | 0.28896 (12) | 0.0331 (7) | |
C1 | 0.26217 (16) | 0.4775 (4) | 0.31971 (12) | 0.0295 (7) | |
C2 | 0.30343 (18) | 0.3005 (4) | 0.38333 (12) | 0.0332 (7) | |
C3 | 0.4134 (2) | 0.2859 (5) | 0.40772 (14) | 0.0435 (9) | |
C4 | 0.48118 (18) | 0.4390 (5) | 0.37308 (14) | 0.0429 (8) | |
C5 | 0.4361 (2) | 0.6158 (5) | 0.31124 (16) | 0.0484 (10) | |
C6 | 0.3272 (2) | 0.6360 (5) | 0.28401 (15) | 0.0421 (9) | |
C7 | 0.2329 (2) | 0.1319 (6) | 0.42350 (18) | 0.0523 (10) | |
C8 | 0.6008 (2) | 0.4085 (9) | 0.4009 (2) | 0.0716 (14) | |
H1n | 0.1115 (15) | 0.523 (4) | 0.3265 (11) | 0.026 (5)* | |
H2n | 0.1225 (19) | 0.330 (4) | 0.2625 (14) | 0.053 (7)* | |
H3n | 0.131 (2) | 0.660 (5) | 0.2576 (15) | 0.066 (8)* | |
H1c3 | 0.4446 (18) | 0.161 (4) | 0.4508 (10) | 0.055 (7)* | |
H1c5 | 0.4814 (15) | 0.718 (4) | 0.2844 (12) | 0.055 (7)* | |
H1c6 | 0.2939 (16) | 0.757 (4) | 0.2407 (9) | 0.046 (7)* | |
H1c7 | 0.1708 (13) | 0.053 (4) | 0.3903 (13) | 0.091 (11)* | |
H2c7 | 0.273 (2) | −0.019 (4) | 0.4512 (14) | 0.112 (13)* | |
H3c7 | 0.212 (2) | 0.256 (5) | 0.4597 (13) | 0.126 (15)* | |
H1c8 | 0.621 (2) | 0.232 (3) | 0.3819 (16) | 0.16 (2)* | |
H2c8 | 0.632 (2) | 0.562 (4) | 0.3789 (15) | 0.125 (16)* | |
H3c8 | 0.623 (2) | 0.415 (5) | 0.4564 (6) | 0.102 (12)* | |
H1o | −0.056 (2) | 0.189 (6) | 0.0360 (10) | 0.064 (9)* | |
H2o | 0.132 (2) | 0.466 (4) | 0.0963 (19) | 0.092 (12)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
P | 0.0308 (3) | 0.0229 (2) | 0.0296 (3) | 0.0037 (2) | 0.0074 (2) | 0.0038 (2) |
O1 | 0.0317 (9) | 0.0438 (9) | 0.0300 (10) | 0.0080 (7) | 0.0074 (7) | 0.0027 (7) |
O2 | 0.0372 (9) | 0.0283 (9) | 0.0749 (13) | 0.0035 (8) | 0.0135 (9) | 0.0126 (9) |
O3 | 0.0481 (10) | 0.0273 (8) | 0.0347 (9) | 0.0099 (7) | 0.0101 (7) | 0.0032 (7) |
O4 | 0.0509 (10) | 0.0347 (9) | 0.0303 (9) | 0.0048 (7) | 0.0075 (7) | 0.0043 (6) |
N | 0.0335 (11) | 0.0350 (13) | 0.0322 (11) | 0.0007 (8) | 0.0106 (9) | 0.0011 (9) |
C1 | 0.0308 (11) | 0.0310 (12) | 0.0279 (11) | −0.0010 (9) | 0.0092 (9) | −0.0052 (9) |
C2 | 0.0392 (13) | 0.0329 (12) | 0.0278 (12) | −0.0002 (10) | 0.0086 (10) | 0.0006 (9) |
C3 | 0.0417 (15) | 0.0514 (16) | 0.0353 (15) | 0.0092 (12) | 0.0050 (12) | 0.0023 (11) |
C4 | 0.0335 (13) | 0.0575 (14) | 0.0373 (13) | 0.0026 (12) | 0.0074 (10) | −0.0133 (13) |
C5 | 0.0439 (16) | 0.0549 (17) | 0.0534 (17) | −0.0101 (13) | 0.0253 (13) | −0.0038 (13) |
C6 | 0.0429 (15) | 0.0440 (14) | 0.0418 (15) | 0.0022 (12) | 0.0147 (12) | 0.0085 (11) |
C7 | 0.0492 (17) | 0.0524 (17) | 0.0562 (18) | 0.0014 (14) | 0.0144 (14) | 0.0200 (14) |
C8 | 0.0338 (16) | 0.113 (3) | 0.066 (2) | −0.0019 (19) | 0.0069 (15) | −0.016 (2) |
Geometric parameters (Å, º) top
P—O1 | 1.583 (2) | C3—C4 | 1.385 (3) |
P—O2 | 1.562 (2) | C3—H1c3 | 0.97 (2) |
P—O3 | 1.515 (2) | C4—C5 | 1.384 (3) |
P—O4 | 1.510 (2) | C4—C8 | 1.525 (3) |
O1—H1o | 0.85 (2) | C5—C6 | 1.388 (3) |
O2—H2o | 0.85 (2) | C5—H1c5 | 0.97 (2) |
N—H1n | 0.90 (2) | C6—H1c6 | 0.97 (2) |
N—H2n | 0.92 (2) | C7—H1c7 | 0.95 (2) |
N—H3n | 0.95 (2) | C7—H2c7 | 0.95 (2) |
C1—N | 1.470 (2) | C7—H3c7 | 0.95 (2) |
C1—C2 | 1.396 (2) | C8—H1c8 | 0.95 (2) |
C1—C6 | 1.383 (3) | C8—H2c8 | 0.95 (2) |
C2—C3 | 1.395 (3) | C8—H3c8 | 0.95 (1) |
C2—C7 | 1.508 (4) | | |
| | | |
O1—P—O2 | 107.77 (9) | H1n—N—H3n | 103 (2) |
O1—P—O3 | 110.36 (9) | H2n—N—H3n | 113 (2) |
O1—P—O4 | 105.7 (1) | C2—C3—H1c3 | 119 (1) |
O2—P—O3 | 108.5 (1) | C4—C3—H1c3 | 118 (1) |
O2—P—O4 | 109.2 (1) | C4—C5—H1c5 | 119 (1) |
O3—P—O4 | 115.14 (9) | C6—C5—H1c5 | 119 (1) |
N—C1—C2 | 119.7 (2) | C1—C6—H1c6 | 118 (1) |
N—C1—C6 | 118.8 (2) | C5—C6—H1c6 | 123 (1) |
C1—C2—C3 | 116.7 (2) | C2—C7—H1c7 | 116 (1) |
C1—C2—C7 | 121.8 (2) | C2—C7—H2c7 | 108 (2) |
C2—C3—C4 | 123.5 (2) | C2—C7—H3c7 | 107 (2) |
C3—C4—C5 | 117.5 (2) | H1c7—C7—H2c7 | 109 (2) |
C1—C6—C5 | 119.4 (2) | H1c7—C7—H3c7 | 109 (2) |
C3—C4—C8 | 121.2 (2) | H2c7—C7—H3c7 | 109 (2) |
C4—C5—C6 | 121.4 (2) | C4—C8—H1c8 | 108 (2) |
P—O1—H1o | 114 (2) | C4—C8—H2c8 | 108 (2) |
P—O2—H2o | 117 (2) | C4—C8—H3c8 | 112 (2) |
C1—N—H1n | 113 (1) | H1c8—C8—H2c8 | 110 (2) |
C1—N—H2n | 110 (2) | H1c8—C8—H3c8 | 110 (2) |
C1—N—H3n | 109 (2) | H2c8—C8—H3c8 | 110 (2) |
H1n—N—H2n | 109 (2) | | |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1o···O3i | 0.85 (2) | 1.76 (2) | 2.605 (2) | 175 (2) |
O2—H2o···O3ii | 0.85 (3) | 1.72 (2) | 2.563 (2) | 170 (3) |
N—H1n···O1iii | 0.90 (2) | 2.14 (2) | 3.030 (2) | 169 (2) |
N—H2n···O4 | 0.92 (2) | 1.94 (2) | 2.848 (2) | 172 (2) |
N—H3n···O4ii | 0.95 (2) | 1.82 (2) | 2.766 (2) | 175 (2) |
C7—H1c7···O1iv | 0.95 (2) | 2.60 (2) | 3.315 (3) | 132 (2) |
Symmetry codes: (i) −x, −y, −z; (ii) x, y+1, z; (iii) −x, y+1/2, −z+1/2; (iv) −x, y−1/2, −z+1/2. |
Experimental details
Crystal data |
Chemical formula | (C8H9NH3)(H2PO4) |
Mr | 219.2 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 290 |
a, b, c (Å) | 13.009 (3), 4.688 (1), 17.607 (4) |
β (°) | 103.60 (2) |
V (Å3) | 1043.7 (4) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.25 |
Crystal size (mm) | 0.24 × 0.19 × 0.14 |
|
Data collection |
Diffractometer | KUMA4 diffractometer |
Absorption correction | Gaussian Gaussian integration (Coppens, 1965) |
Tmin, Tmax | 0.942, 0.967 |
No. of measured, independent and observed [I > 3σ(I)] reflections | 3969, 2050, 1258 |
Rint | 0.055 |
(sin θ/λ)max (Å−1) | 0.617 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.034, 0.041, 1.75 |
No. of reflections | 2050 |
No. of parameters | 184 |
No. of restraints | 20 |
H-atom treatment | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.57, −0.92 |
Selected geometric parameters (Å, º) topP—O1 | 1.583 (2) | C2—C3 | 1.395 (3) |
P—O2 | 1.562 (2) | C2—C7 | 1.508 (4) |
P—O3 | 1.515 (2) | C3—C4 | 1.385 (3) |
P—O4 | 1.510 (2) | C4—C5 | 1.384 (3) |
C1—N | 1.470 (2) | C4—C8 | 1.525 (3) |
C1—C2 | 1.396 (2) | C5—C6 | 1.388 (3) |
C1—C6 | 1.383 (3) | | |
| | | |
O1—P—O2 | 107.77 (9) | O2—P—O3 | 108.5 (1) |
O1—P—O3 | 110.36 (9) | O2—P—O4 | 109.2 (1) |
O1—P—O4 | 105.7 (1) | O3—P—O4 | 115.14 (9) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1o···O3i | 0.85 (2) | 1.76 (2) | 2.605 (2) | 175 (2) |
O2—H2o···O3ii | 0.85 (3) | 1.72 (2) | 2.563 (2) | 170 (3) |
N—H1n···O1iii | 0.90 (2) | 2.14 (2) | 3.030 (2) | 169 (2) |
N—H2n···O4 | 0.92 (2) | 1.94 (2) | 2.848 (2) | 172 (2) |
N—H3n···O4ii | 0.95 (2) | 1.82 (2) | 2.766 (2) | 175 (2) |
C7—H1c7···O1iv | 0.95 (2) | 2.60 (2) | 3.315 (3) | 132 (2) |
Symmetry codes: (i) −x, −y, −z; (ii) x, y+1, z; (iii) −x, y+1/2, −z+1/2; (iv) −x, y−1/2, −z+1/2. |
The main purpose of this structural study was a determination of arrangement of arylammoniums and dihydrogenphosphates which are held together by hydrogen bonds. R—NH3+ cations (R=aryl, alkyl or H) can bind in various ways to [H2PO4]- anions. Some of these structures show interesting phase transitions and physical properties which are influenced by hydrogen bonding. Examples include [NH4]+[H2PO4]- (e.g. Baur, 1973) or n-alkylammoniumdihydrogenphosphates (Kroupa & Fuith, 1993, 1994; Fábry et al. 2000).
A search in the Cambridge Structure Database System (Allen \& Kennard, 1993) yielded the structure SOMHUX (2-Methyl-4-nitroanilinium dihydrogenmonophosphate) determined by Masse & Levy, 1991. The latter structure is orthorhombic (Pbca) and contains layers of dihydrogenphosphates. Symmetry and structural similarity to room-temperature phases of n-alkylammonium dihydrogenphosphates which also contain layers of dihydrogenphosphates and which are closely related to the prototypic orthorhombic phase (Pbna) made us to think about possibility of phase transitions in other related compounds. Therefore similarly substituted anilines were chosen for investigation, among them 2,4-dimethylaniline.
It was found that in the studied compound there are also sheets of dihydrogenphosphates. These sheets are interconnected by ammonium groups (Fig. 1). Each hydrogen from the ammonium group is donated to a different dihydrogenphosphate ion. In all the compounds the H atoms are ordered at room temperature. The N—H···O contacts are in the interval 2.71 (SOMHUX) – 3.04 Å (e.g. WINKUZ01) while the pertinent angles fall into the interval 153 (FUQNAG) – 177° (SOMHUX). The O—H···O bond lengths are shorter, being in the interval 2.49 (WOBZES) – 2.63 Å (SOMHUX) while the angles fall into the interval 157 (SOMHUX) – 177° (e.g. FUQMOT). (Cambridge Structural Database REFCODES are given in parentheses.)
Despite these similarities, the aforementioned compounds differ in how the sheets composed of dihydrogenphosphates and ammonium groups are interbonded by hydrogen bonds. In the title compound, there are columns of aggregated dihydrogenphosphates parallel to (100) and directed along [010] (Fig. 1). These columns are held together by N—H···O hydrogen bonds while in n-alkylammoniumdihydrogenphosphates as well as in SOMHUX the O—H···O hydrogen-bond network itself makes sheets of H2PO4-. (In the latter compounds, these sheets are also different.)
It is interesting that there is one C—H···O contact that should be considered as a hydrogen bond according to the criteria given by Desiraju & Steiner (1999). The angle between the planes C2—C7-H1c7 and C2—C7—O1 (-x,-1/2 + y,1/2 - z) is only 15 (1)° thus indicating attraction of the hydrogen H1c7 to the atom O1. (The distance C7···O1(-x,1/2 + y,1/2 - z) is 3.586 (3) Å; the distance H1c7···O1(-x,1/2 + y,1/2 - z) is 3.48 (2) Å pointing to a possible electrostatic interaction.) The interatomic distances and angles are otherwise normal.
The differential scanning calorimetry experiments [Perkin Elmer DSC 7 using PYRIS software (Perkin-Elmer,1997)] showed interesting behaviour. During heating an anomaly ocurred between 441 and 443 K (aluminium pans, m=9.35 mg, scanning rate 10 K/min, ΔH = 21 J/g). Interestingly, cooling caused no corresponding anomaly. An immediate heating of the sample after it had been cooled down to room temperature did not bring about to the anomaly at \sim442 K.
Nevertheless, after several hours since the last cooling the repeated heating caused partial or full restoration of the anomaly at ~442 K. The degree of restoration depended on time it had elapsed since the last cooling. Both phenomena (i.e. no anomaly during cooling as well as relaxation necessary for restoration of the anomaly at ~442 K) indicate a structural change with much faster kinetics on heating than on cooling.