Ferroelastic n-propyl­ammonium dihydrogenphosphate

n-Propyl­ammonium di­hydrogenphosphate, C₃H₇NH₃⁺·­H₂PO₄^-, crystals are ferroelastic at room temperature. The phase transition into the prototypic phase takes place at approximately 378 K. All atoms except two H atoms are linked by the lost symmetry operations derived from the prototypic space group P2/b2₁/n2₁/a. Each of these two different H atoms is involved in an asymmetric hydrogen bond between an oxy­gen pair. Ferroelastic switching is concomitant with jumps of these H atoms from the donor to the acceptor O atoms. The compound belongs to the structural family of n-alkyl­ammonium di­hydrogenphosphate and in particular to the structure type of pentyl­ammonium di­hydrogenphosphate, which differs by localization of alternating layers from the rest of the known alkyl­ammonium di­hydrogenphosphates. The crystal was slightly twinned; the proportion of the minor domain was approximately 3.5%.

S1. Comment

The title compound, (I), belongs to the series of n-alkylammonium dihydrogenphosphates which show ferroelasticity, as well as a number of interesting phase transitions. (Hereafter the denomination CnADP will be applied for n-alkylammonium dihydrogenphosphates.) Among other factors these phase transitions depend on parity of the carbons in an alkylammonium chain and some of them show hysteresis effects (Kroupa & Fuith, 1993, 1994). Up to now, several structures have been determined: C2ADP and C3ADP (Kasatani et al., 1998), C4ADP (Kasatani et al., 1998; Fábry. Císařová & Kroupa, 2000), C5ADP and C6ADP (Kasatani et al., 1999; Fábry, Petříček et al., 2000), C7ADP and C8ADP (Fábry et al., 1997), C9ADP (Fábry, Petříček et al., 2000) and C10ADP (Oliver et al., 1998). All these compounds crystallize in the space group P2₁/n. The prototypic space group of all these compounds is P2/b2₁/n2₁/a. In all the compounds, there exists a couple of H atoms which are involved in asymmetric O···O hydrogen bonds. The ferroelastic switching is accompanied by hopping of these H atoms from donor towards acceptor O atoms.

The structures which were determined until now are similar. Each unit cell contains two double layers of dihydrogenphosphates which are mutually bonded by hydrogen bonds, among them being these with hopping H atoms. In addition, the double layers of dihydrogenphosphates are bonded by hydrogen bonds to n-alkylammonium groups via NH₃ groups. The n-alkyl chains are separated from each other by van der Waals distances (Weast & Astle, 1980) and are oriented with their methyl group on the outside of the double layers.

It was also found that the packing of n-alkylammonium chains depends on the parity of carbons.

Despite their similarity the structures of C3ADP and C5ADP belong to a different structure type in contrast to the rest of the compounds. This difference concerns the mutual position of the alternating double layers of dihydrogenphosphates which are situated among the n-alkylammonium chains.

In C7ADP and C9ADP, there were observed stacking faults which halve the a axis. These stacking faults can be viewed as a disorder of dihydrogenphosphates or as a co-existence of both structure types: that of C5ADP and of C7ADP. The aim of the present study was to redetermine the structure of C3ADP as well as to find out whether the dihydrogenphosphates are disordered as was observed in C7ADP and C9ADP.

All important structural features of C3ADP (twinning, hydrogen bonding, hopping of H atoms, packing of n-alkylammonium chains ets.) are analogous to the structures which are referenced above.

No disorder of dihydrogenphosphates which can be interpreted as stacking faults halving the periodicity along the a axis was observed.

S2. Experimental

The title compound was obtained by crystallization of n-propylamine and H₃PO₄ from methanol. A crystal which appeared single domained under the polarization microscope was selected for a diffractometer measurement.

S3. Refinement

The structure is a superstucture, as well as a ferroelastic structure, which can be related to the prototypic space group P2/b2₁/n2₁/a. Therefore, the crystal was expected to be twinned though a sample was chosen which seemed to be single domained when viewed under the polarization microscope. The domain proportion f was a refined parameter which converged to the value 0.037 (5). All the H atoms were refined; N—H 0.87 (2)–0.92 (2), C—H 0.94 (2)–0.98 (2) and O—H 0.80 (2)–0.86 (2) Å.

Computing details

Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: JANA2000 (Petříček & Dušek, 2000); program(s) used to solve structure: SHELX86 (Sheldrick, 1986); program(s) used to refine structure: JANA2000; software used to prepare material for publication: JANA2000.

n-butylammonium dihydrogenphosphate

Crystal data

C3H10N^+·H2PO4^−	F(000) = 672
Mr = 157.1	Dx = 1.442 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 9.131 (2) Å	Cell parameters from 25 reflections
b = 22.090 (5) Å	θ = 9–18°
c = 7.175 (3) Å	µ = 0.33 mm^−1
β = 90.67 (3)°	T = 150 K
V = 1447.1 (8) Å^3	Plate, colourless
Z = 8	0.56 × 0.32 × 0.15 mm

Data collection

Enraf-Nonius CAD-4 MACHIII-PC diffractometer	θmax = 25°
ω–2θ scans	h = −10→10
2750 measured reflections	k = 0→26
2544 independent reflections	l = 0→8
1602 reflections with I > 3σ(I)	3 standard reflections every 60 min
Rint = 0.022	intensity decay: 5.2%

Refinement

Refinement on F	0 constraints
Least-squares matrix: full with fixed elements per cycle	All H-atom parameters refined
R[F^2 > 2σ(F^2)] = 0.034	w = 1/[σ^2(Fo) + 0.0001(Fo)^2]
wR(F^2) = 0.039	(Δ/σ)max = 0.01
S = 1.39	Δρmax = 0.64 e Å^−3
2544 reflections	Δρmin = −0.59 e Å^−3
261 parameters	Extinction correction: type I, Lorentz. iso. (Becker & Coppens, 1974)
40 restraints	Extinction coefficient: 0.00014 (2)

Special details

Refinement. The structure was refined as a twin. The domain proportion f determined from the refinement: 0.037 (5).

The twinning matrix is given in _diffrn_reflns_transf_matrix_ items

The H atoms except of those which are bonded to the O atoms were restrained by the distfix and anglefix functions of JANA2000: The values for distfix were 0.85(0.022) A ng. for O—H distances. The values for distfix were 0.90(0.022) A ng. for N—H distances. The values for distfix were 0.95(0.03) A ng. for methyl-H distances. The values for distfix were 0.95(0.013) A ng. for methylene-H distances. The values for anglefix were 109.4 (1) °.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
P1	0.31326 (6)	0.31915 (2)	0.25997 (7)	0.0128 (2)
P2	0.80954 (6)	0.31525 (2)	0.26426 (7)	0.0133 (2)
O11	0.1928 (2)	0.36875 (7)	0.2323 (2)	0.0200 (5)
O21	0.3438 (2)	0.30805 (6)	0.4638 (2)	0.0187 (5)
O31	0.4421 (1)	0.33835 (7)	0.1449 (2)	0.0179 (5)
O41	0.2483 (2)	0.25796 (7)	0.1850 (2)	0.0180 (5)
O12	0.6978 (2)	0.36826 (7)	0.2660 (2)	0.0207 (5)
O22	0.8430 (2)	0.30330 (7)	0.0536 (2)	0.0197 (5)
O32	0.9443 (1)	0.33563 (7)	0.3673 (2)	0.0191 (5)
O42	0.7426 (2)	0.25777 (7)	0.3412 (2)	0.0176 (5)
N1	0.9620 (2)	0.67237 (9)	0.2650 (3)	0.0175 (6)
C11	0.8835 (2)	0.6137 (1)	0.2464 (3)	0.0196 (7)
C21	0.9882 (3)	0.5611 (1)	0.2524 (4)	0.0270 (8)
C31	0.9084 (4)	0.5014 (1)	0.2402 (5)	0.040 (1)
N2	0.4712 (2)	0.67201 (9)	0.2232 (3)	0.0173 (6)
C12	0.3869 (2)	0.6146 (1)	0.2443 (3)	0.0182 (7)
C22	0.4877 (3)	0.5606 (1)	0.2441 (4)	0.0271 (8)
C32	0.4031 (4)	0.5018 (1)	0.2634 (5)	0.040 (1)
H1n1	1.003 (2)	0.6730 (9)	0.383 (2)	0.034 (7)*
H2n1	0.902 (2)	0.7036 (8)	0.251 (2)	0.033 (7)*
H3n1	1.031 (2)	0.6750 (9)	0.182 (2)	0.030 (7)*
H1c11	0.815 (2)	0.613 (1)	0.346 (2)	0.021 (6)*
H2c11	0.831 (2)	0.613 (1)	0.131 (2)	0.019 (6)*
H1c21	1.051 (2)	0.567 (1)	0.150 (2)	0.049 (9)*
H2c21	1.045 (2)	0.563 (1)	0.365 (2)	0.042 (8)*
H1c31	0.845 (2)	0.497 (1)	0.345 (3)	0.06 (1)*
H2c31	0.979 (2)	0.470 (1)	0.240 (3)	0.048 (8)*
H3c31	0.851 (2)	0.499 (1)	0.128 (3)	0.047 (9)*
H1n2	0.538 (2)	0.6749 (8)	0.315 (2)	0.016 (6)*
H2n2	0.407 (2)	0.7026 (8)	0.231 (2)	0.028 (7)*
H3n2	0.516 (2)	0.6728 (9)	0.111 (2)	0.036 (7)*
H1c12	0.318 (1)	0.6142 (9)	0.144 (2)	0.004 (5)*
H2c12	0.337 (2)	0.617 (1)	0.360 (2)	0.018 (6)*
H1c22	0.539 (2)	0.562 (1)	0.130 (2)	0.040 (8)*
H2c22	0.556 (2)	0.563 (1)	0.344 (2)	0.032 (7)*
H1c32	0.353 (2)	0.503 (1)	0.383 (3)	0.042 (8)*
H2c32	0.469 (3)	0.468 (1)	0.260 (3)	0.054 (9)*
H3c32	0.332 (2)	0.498 (1)	0.167 (3)	0.050 (9)*
Ho11	0.115 (2)	0.357 (1)	0.266 (3)	0.015 (6)*
Ho41	0.248 (3)	0.256 (1)	0.065 (2)	0.049 (9)*
Ho12	0.617 (2)	0.359 (1)	0.224 (3)	0.035 (8)*
Ho22	0.838 (3)	0.2656 (8)	0.026 (4)	0.040 (8)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
P1	0.0112 (3)	0.0153 (3)	0.0119 (3)	−0.0004 (3)	0.0012 (2)	0.0008 (2)
P2	0.0111 (3)	0.0173 (3)	0.0114 (3)	0.0004 (3)	0.0003 (2)	−0.0003 (2)
O11	0.0100 (8)	0.0202 (8)	0.0300 (9)	−0.0008 (8)	0.0042 (7)	0.0070 (7)
O21	0.0227 (8)	0.0221 (8)	0.0113 (7)	−0.0025 (7)	−0.0015 (6)	−0.0003 (6)
O31	0.0107 (7)	0.0256 (9)	0.0174 (8)	−0.0036 (6)	0.0020 (6)	0.0010 (6)
O41	0.0227 (8)	0.0189 (8)	0.0125 (8)	−0.0044 (7)	0.0021 (7)	−0.0004 (7)
O12	0.0137 (9)	0.0203 (8)	0.028 (1)	0.0011 (8)	−0.0029 (7)	−0.0035 (7)
O22	0.0296 (9)	0.0174 (9)	0.0122 (8)	−0.0023 (7)	0.0029 (6)	−0.0004 (7)
O32	0.0134 (7)	0.0262 (9)	0.0178 (8)	−0.0022 (6)	−0.0005 (6)	0.0001 (6)
O42	0.0204 (8)	0.0198 (8)	0.0125 (8)	−0.0037 (7)	0.0008 (6)	0.0008 (6)
N1	0.0134 (9)	0.021 (1)	0.018 (1)	0.0009 (8)	0.0019 (9)	0.0013 (8)
C11	0.017 (1)	0.024 (1)	0.018 (1)	−0.002 (1)	0.001 (1)	−0.002 (1)
C21	0.025 (1)	0.023 (1)	0.033 (2)	0.003 (1)	0.003 (1)	−0.002 (1)
C31	0.044 (2)	0.023 (2)	0.053 (2)	0.002 (1)	0.002 (2)	0.000 (1)
N2	0.017 (1)	0.021 (1)	0.014 (1)	0.0028 (9)	0.0010 (9)	0.0003 (8)
C12	0.015 (1)	0.020 (1)	0.020 (1)	−0.001 (1)	0.003 (1)	0.003 (1)
C22	0.025 (1)	0.025 (1)	0.032 (2)	0.001 (1)	0.002 (1)	0.003 (1)
C32	0.048 (2)	0.023 (2)	0.049 (2)	−0.002 (1)	−0.002 (2)	0.004 (1)

Geometric parameters (Å, º)

P1—O11	1.564 (2)	N2—H1n2	0.90 (2)
P1—O21	1.505 (2)	N2—H2n2	0.90 (2)
P1—O31	1.507 (2)	N2—H3n2	0.90 (2)
P1—O41	1.569 (2)	C12—H1c12	0.95 (1)
P2—O12	1.553 (2)	C12—H2c12	0.96 (1)
P2—O22	1.568 (2)	C22—H1c22	0.95 (1)
P2—O32	1.498 (2)	C22—H2c22	0.94 (2)
P2—O42	1.516 (2)	C32—H1c32	0.98 (2)
N1—C11	1.486 (3)	C32—H2c32	0.96 (2)
C11—C21	1.505 (3)	C32—H3c32	0.95 (2)
C21—C31	1.510 (4)	O11—Ho11	0.80 (2)
N1—H1n1	0.92 (2)	O41—Ho41	0.86 (2)
N1—H2n1	0.89 (2)	O12—Ho12	0.82 (2)
N1—H3n1	0.87 (2)	O22—Ho22	0.86 (2)
C11—H1c11	0.96 (1)	O11—O32^i	2.583 (2)
C11—H2c11	0.95 (1)	O21—O22^ii	2.543 (2)
C21—H1c21	0.95 (2)	O31—O12	2.568 (2)
C21—H2c21	0.96 (2)	O41—O42^iii	2.491 (2)
C31—H1c31	0.96 (2)	O21—N2^iv	2.829 (2)
C31—H2c31	0.95 (2)	O31—N2^v	2.775 (2)
C31—H3c31	0.96 (2)	O41—N2^vi	2.844 (2)
N2—C12	1.492 (3)	O22—N1^vii	2.963 (2)
C12—C22	1.508 (3)	O32—N1^viii	2.770 (2)
C22—C32	1.517 (4)	O42—N1^ix	2.756 (2)
O11—P1—O21	111.07 (9)	O12—P2—O22	105.69 (9)
O11—P1—O31	106.63 (9)	O12—P2—O32	107.79 (9)
O11—P1—O41	107.30 (8)	O12—P2—O42	111.13 (9)
O21—P1—O31	116.18 (8)	O22—P2—O32	110.98 (9)
O21—P1—O41	104.94 (8)	O22—P2—O42	107.09 (8)
O31—P1—O41	110.45 (8)	O32—P2—O42	113.87 (8)

Symmetry codes: (i) x−1, y, z; (ii) x−1/2, −y+1/2, z+1/2; (iii) x−1/2, −y+1/2, z−1/2; (iv) −x+1, −y+1, −z+1; (v) −x+1, −y+1, −z; (vi) −x+1/2, y−1/2, −z+1/2; (vii) −x+2, −y+1, −z; (viii) −x+2, −y+1, −z+1; (ix) −x+3/2, y−1/2, −z+1/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	D···A	D—H···A
N1—H3n1···O22^vii	0.87 (2)	2.963 (2)	165 (2)
N1—H1n1···O32^viii	0.92 (2)	2.770 (2)	169 (2)
N1—H2n1···O42^x	0.89 (2)	2.756 (2)	164 (2)
N2—H1n2···O21^iv	0.90 (2)	2.829 (2)	169 (2)
N2—H3n2···O31^v	0.90 (2)	2.775 (2)	163 (2)
N2—H2n2···O41^xi	0.90 (2)	2.844 (2)	164 (2)
O11—Ho11···O32^i	0.80 (2)	2.583 (2)	173 (2)
O41—Ho41···O42^iii	0.86 (2)	2.491 (2)	173 (3)
O12—Ho12···O31	0.86 (2)	2.568 (2)	177 (3)
O22—Ho22···O21^xii	0.82 (2)	2.543 (2)	175 (3)

Symmetry codes: (i) x−1, y, z; (iii) x−1/2, −y+1/2, z−1/2; (iv) −x+1, −y+1, −z+1; (v) −x+1, −y+1, −z; (vii) −x+2, −y+1, −z; (viii) −x+2, −y+1, −z+1; (x) −x+3/2, y+1/2, −z+1/2; (xi) −x+1/2, y+1/2, −z+1/2; (xii) x+1/2, −y+1/2, z−1/2.