Ferroelastic n-pentyl­ammonium di­hydrogenarsenate

n-Pentyl­ammonium di­hydrogenarsenate, C₅H₁₄N⁺·H₂AsO₄^- (C5ADA), is ferroelastic at room temperature. The structure is monoclinic (P2₁/n) and isostructural with n-pentyl­ammonium di­hydrogenphosphate (C5ADP). In contrast to C7ADA and C9ADA, as well as to C7ADP and C9ADP, two independent di­hydrogenarsenates in the present structure are not disordered. Similarly, as in other known members of the series (C2ADP-C10ADP and C6ADA-C9ADA), there are strong hydrogen bonds between the anions, and moderate hydrogen bonds between the anions and the cations. The hydrogen-bond distances correspond well to those observed in the di­hydrogenphosphates. There are two H atoms in the structure which are involved in asymmetric hydrogen bonds between respective oxy­gen pairs. These H atoms jump from the donor to the acceptor O atoms during ferroelastic switching. A phase transition was observed at about 380 and 371 K during heating and cooling, respectively.

Key indicators

• Single-crystal X-ray study
• T = 290 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.036
• wR factor = 0.045
• Data-to-parameter ratio = 13.3

checkCIF results

No syntax errors found


 Alert Level B:



PLAT_112  Alert B ADDSYM detects additional (pseudo)symmetry ...          ?

Author response: The structure is ferroelastic, i. e. twinned.

PLAT_113  Alert B ADDSYM suggests Pseudo/New Spacegroup ........       Pbcn

Author response: The suggested space-group is a space-group of a prototypic phase.

 Alert Level C:



GOODF_01  Alert C The least squares goodness of fit parameter lies
          outside the range 0.80 <> 2.00
          Goodness of fit given =      2.020


 0 Alert Level A = Potentially serious problem

 2 Alert Level B = Potential problem

 1 Alert Level C = Please check

---

S1. Comment

Ferroelasticity and a phase transition in the n-alkylammoniumdihydrogenphosphates (CnADP) and dihydrogenarsenates (CnADA) were discovered by Kroupa & Fuith (1993, 1994). Until now, however, the presence of phase transitions in C5ADA was not investigated. The related dihydrogenphosphate (C2ADP—C10ADP) and dihydrogenarsenate (C6ADA—C8ADA) structures have been studied previously. C2ADP, C3ADP and C4ADP were studied by Kasatani et al. (1998), C3ADP by Fábry et al. (2000a), C4ADP by Fábry et al. (2000b), C5ADP and C6ADP by Kasatani et al. (1999), C5ADP, C6ADP and C9ADP by Fábry et al. (2000), C7ADP and C8ADP by Fábry et al. (1997), and C10ADP by Oliver et al. (1998). C6ADA and C8ADA were determined by Fábry, Kroupa & Císařová (2001), while C7ADA was determined by Fábry, Krupková & Císařová (2001). All the structures are monoclinic (P2₁/n). The prototypic phases are orthorhombic (P2/b2₁/n2₁/a).

The ferroelastic switching is concomitant with the hydrogen jumps of two H atoms within the hydrogen bridges from the donor to the acceptor O atoms: O41—HO41···O42 and O22—HO22···O21.

Each structure contains a pair of symmetry independent anion molecules (dihydrogenphosphates or dihydrogenarsenates) and a pair of symmetry independent n-alkylammonium molecules. The latter ones are almost exactly displaced by (1/2, 0, 0).

It was found that C3ADP and C5ADP belong to a different structure type than C7ADP and C9ADP (Kasatani et al., 1999; Fábry et al. 2000). The preference for the different structure type, either C3ADP or C5ADP, seems to be related to the smaller number of intermolecular contacts between the n-alkylammonium chains in C3ADP and C5ADP (Fábry et al., 2000) than in C7ADP and C9ADP. This means that these chains in C3ADP and C5ADP are more loosely packed than in C7ADP and C9ADP.

Disorder of the anionic molecules was first observed in C7ADP and C9ADP. Even more prominent disorder (the proportion was more than 10°) was observed in C7ADA. This means that until now the disorder was observed only in the compounds which belong to the structure type of C7ADP. This disorder can be envisaged as stacking faults (1/2, 0, 0) or, alternatively, as the co-existence of both structure types, i.e. of C5ADP and of C7ADP. The greater prominence of the disorder in the dihydrogenarsenates is in accordance with its view as co-existence of both structure types of C5ADP and C7ADP since the structure type of C5ADP seems to be supported by a lesser number of contacts between n-alkylammonium chains. The lesser number of contacts between the n-alkylammonium chains in C3ADP and C5ADP implies more space between these molecules. On the other hand in the dihydrogenarsenates the larger size of the anions would cause the n-alkylammonium chains to be more separated, and therefore these chains would have more space around. For these reasons, it may be expected that C5ADA, (I), would be isomorphous with C5ADP and no disorder would exist in it.

The non-existence of the disorder of the dihydrogenarsenate molecules was confirmed. Figs. 1 and 2 depict the studied structure (Burnett \& Johnson, 1996). The structure is isostructural with C5ADP.

The presence of phase transition in C5ADA was also investigated by DSC [Perkin Elmer DSC 7, software PYRIS (1997); 10.7 mg of the powdered capsule were put into an Al-capsule, rate 10 K min^-1, temperature range 298–423 K], as well as by observation of the samples in the polarized light during heating and cooling. It was found by the DSC experiments that a phase transition occurs during heating at ~380 K and during cooling at ~371 K. Observation of the sample between crossed polarizers revealed that above 373 K the structure becomes gradually optically homogeneous though it does not turn into liquid. After repeated cooling, the domain pattern develops again. The domains partially recover if the temperature would not exceed 393 K. If the temperature reaches at least 393 K than the cooling results in a more dense domain pattern.

S2. Experimental

Precipitation of n-pentylamine and H₃AsO₄. 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 crystal which appeared single domained under the polarization microscope was selected for a diffractometer measurement.

S3. Refinement

The structure is ferroelastic. It can be related to the prototypic space group P2/b2₁/n2₁/a. Therefore, the sample was expected to be twinned but the twinning turned out to be insignificant. The disorder was taken into account by the refinement on separate scales for h even and odd, respectively, but it was irrelevant either. The extinction correction was negligible and for the final refinement not used. No maxima which would belong to the disordered dihydrogenarsenates were detected. All H atoms except those which are pertinent to the OH groups could be distinguished on the Fourier maps. The bond distances as well as the angles in which the H atoms were involved were restrained. The O—H, N—H and C—H bond lengths were restrained to 0.90 (3), 0.90 (2) and 0.95 (1) Å, respectively. The H—C—H and H—N—H angles were restrained to 109 (1)°.

Computing details

Data collection: COLLECT (Nonius, 1997-2000); cell refinement: HKL SCALEPACK (Otwinowski & Minor, 1997); data reduction: HKL DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: JANA2000 (Petříček & Dušek, 2000); program(s) used to refine structure: JANA2000; molecular graphics: ORTEPIII (Burnett & Johnson, 1996); software used to prepare material for publication: JANA2000.

Figures

	Fig. 1. View of the unit cell of C5ADA along the a axis.
	Fig. 2. View of the unit cell of C5ADA along the c axis.

n-pentylammonium dihydrogenarsenate

Crystal data

C5H11NH3^+·H2AsO4^−	F(000) = 944
Mr = 229.11	Dx = 1.595 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 9.3380 (3) Å	Cell parameters from 54194 reflections
b = 27.3950 (8) Å	θ = 1.0–27.5°
c = 7.4570 (8) Å	µ = 3.54 mm^−1
β = 90.568 (1)°	T = 290 K
V = 1907.5 (1) Å^3	Prism, colourless
Z = 8	0.32 × 0.10 × 0.04 mm

Data collection

Nonius KappaCCD diffractometer	4366 independent reflections
Radiation source: fine-focus sealed X-ray tube	2740 reflections with I > 3σ(I)
Graphite monochromator	Rint = 0.053
ϕ and ω scans	θmax = 27.5°, θmin = 1.5°
Absorption correction: integration Gaussian integration (Coppens, 1970)	h = −12→12
Tmin = 0.461, Tmax = 0.868	k = −35→35
27031 measured reflections	l = 0→9

Refinement

Refinement on F	52 restraints
Least-squares matrix: full with fixed elements per cycle	0 constraints
R[F^2 > 2σ(F^2)] = 0.036	All H-atom parameters refined
wR(F^2) = 0.045	Weighting scheme based on measured s.u.'s w = 1/[σ^2(Fo) + 0.0001(Fo)^2]
S = 2.02	(Δ/σ)max = 0.001
4365 reflections	Δρmax = 0.67 e Å^−3
327 parameters	Δρmin = −0.83 e Å^−3

Special details

Experimental. rotation scans:10 images collected ω scans, rotation per image 10°, 202 s exposure, crystal to detector distance 35 mm.

Refinement. The structure was intended to be refined as a twin, however the domain fraction f was refined to negative values; the trial measurement on a 4-dircle diffractometer with a point detector did not indicate existence of a second domain.

>From the similarity with other compounds of the series the twinning matrix is analogous as in other related sompounds. The components for the twinning matrix is given in _diffrn_reflns_transf_matrix_ items

The H atoms were restrained by the distfix and anglefix functions of JANA2000: The values for distfix were 0.90(0.021) 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 0.9(0.022) 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 109.47(1.00) ° for all H—N—H; H—C—H angles.

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

	x	y	z	Uiso*/Ueq
As1	0.31307 (3)	0.307442 (10)	0.25283 (3)	0.02457 (11)
O11	0.1862 (2)	0.35199 (8)	0.2262 (3)	0.0434 (9)
O21	0.3460 (2)	0.29710 (7)	0.4683 (2)	0.0384 (8)
O31	0.4509 (2)	0.32376 (7)	0.1276 (2)	0.0353 (8)
O41	0.2413 (2)	0.25415 (7)	0.1745 (2)	0.0372 (8)
As2	0.80930 (3)	0.304597 (10)	0.26180 (3)	0.02493 (12)
O12	0.6922 (3)	0.35176 (8)	0.2620 (3)	0.0430 (9)
O22	0.8455 (2)	0.29388 (8)	0.0409 (2)	0.0405 (9)
O32	0.9521 (2)	0.32228 (7)	0.3745 (2)	0.0363 (8)
O42	0.7361 (2)	0.25369 (6)	0.3420 (2)	0.0350 (8)
N1	0.9655 (3)	0.68617 (9)	0.2684 (3)	0.0323 (10)
C11	0.8867 (4)	0.63951 (12)	0.2472 (4)	0.0363 (13)
C21	0.9866 (4)	0.59597 (12)	0.2549 (4)	0.0390 (13)
C31	0.9051 (4)	0.54822 (14)	0.2469 (5)	0.0446 (15)
C41	1.0003 (5)	0.50296 (13)	0.2490 (5)	0.0472 (15)
C51	0.9154 (6)	0.45551 (15)	0.2440 (6)	0.069 (2)
N2	0.4732 (3)	0.68587 (10)	0.2308 (3)	0.0326 (10)
C12	0.3916 (4)	0.63946 (12)	0.2493 (4)	0.0343 (12)
C22	0.4886 (4)	0.59559 (12)	0.2450 (4)	0.0355 (12)
C32	0.4038 (4)	0.54833 (13)	0.2519 (5)	0.0436 (14)
C42	0.4983 (5)	0.50296 (13)	0.2507 (5)	0.0480 (15)
C52	0.4136 (6)	0.45545 (15)	0.2524 (6)	0.064 (2)
H1n1	1.002 (2)	0.6862 (9)	0.380 (2)	0.080 (14)*
H2n1	0.908 (2)	0.7118 (8)	0.256 (2)	0.033 (10)*
H3n1	1.035 (2)	0.6882 (9)	0.190 (3)	0.032 (10)*
H1c11	0.818 (2)	0.6360 (11)	0.338 (2)	0.045 (10)*
H2c11	0.840 (2)	0.6403 (12)	0.135 (2)	0.070 (12)*
H1c21	1.049 (2)	0.6013 (12)	0.157 (2)	0.057 (11)*
H2c21	1.042 (2)	0.5950 (12)	0.362 (2)	0.067 (12)*
H1c31	0.841 (2)	0.5480 (12)	0.344 (2)	0.056 (11)*
H2c31	0.852 (2)	0.5475 (11)	0.137 (2)	0.051 (11)*
H1c41	1.058 (2)	0.5036 (10)	0.144 (2)	0.038 (10)*
H2c41	1.061 (2)	0.5056 (9)	0.351 (2)	0.028 (9)*
H1c51	0.856 (2)	0.4533 (12)	0.343 (3)	0.074 (15)*
H2c51	0.985 (3)	0.4303 (12)	0.249 (3)	0.095 (17)*
H3c51	0.859 (3)	0.4522 (13)	0.136 (3)	0.111 (18)*
H1n2	0.539 (2)	0.6849 (8)	0.320 (2)	0.025 (8)*
H2n2	0.421 (3)	0.7120 (9)	0.239 (2)	0.080 (16)*
H3n2	0.517 (2)	0.6851 (8)	0.126 (2)	0.021 (8)*
H1c12	0.325 (2)	0.6390 (9)	0.152 (2)	0.021 (8)*
H2c12	0.342 (2)	0.6390 (10)	0.358 (2)	0.043 (10)*
H1c22	0.539 (2)	0.5985 (11)	0.136 (2)	0.050 (10)*
H2c22	0.554 (2)	0.5989 (11)	0.342 (2)	0.043 (10)*
H1c32	0.351 (2)	0.5509 (10)	0.360 (2)	0.042 (10)*
H2c32	0.339 (2)	0.5498 (13)	0.153 (2)	0.075 (14)*
H1c42	0.552 (2)	0.5040 (10)	0.143 (2)	0.041 (10)*
H2c42	0.562 (2)	0.5054 (10)	0.351 (2)	0.034 (9)*
H1c52	0.359 (2)	0.4523 (11)	0.356 (3)	0.067 (13)*
H2c52	0.485 (3)	0.4295 (11)	0.250 (3)	0.074 (14)*
H3c52	0.351 (2)	0.4518 (11)	0.150 (3)	0.078 (14)*
HO11	0.104 (3)	0.3383 (13)	0.284 (4)	0.067 (13)*
HO41	0.250 (4)	0.2488 (12)	0.049 (3)	0.096 (14)*
HO12	0.603 (3)	0.3402 (14)	0.239 (4)	0.070 (15)*
HO22	0.857 (5)	0.2615 (9)	0.027 (5)	0.15 (2)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
As1	0.0251 (2)	0.02775 (19)	0.02088 (18)	−0.00111 (16)	0.00106 (14)	0.00268 (12)
O11	0.0326 (18)	0.0381 (14)	0.0596 (16)	0.0062 (13)	0.0076 (13)	0.0161 (11)
O21	0.0528 (19)	0.0398 (13)	0.0226 (11)	−0.0086 (12)	−0.0046 (11)	0.0059 (8)
O31	0.0278 (15)	0.0520 (14)	0.0263 (11)	−0.0058 (12)	0.0065 (10)	0.0026 (9)
O41	0.0495 (18)	0.0381 (13)	0.0242 (12)	−0.0159 (12)	0.0048 (11)	−0.0041 (9)
As2	0.0252 (2)	0.02890 (19)	0.02063 (18)	−0.00158 (16)	−0.00088 (14)	−0.00086 (12)
O12	0.0326 (18)	0.0347 (14)	0.0617 (16)	0.0022 (13)	−0.0051 (13)	−0.0066 (10)
O22	0.062 (2)	0.0356 (14)	0.0235 (12)	−0.0058 (13)	0.0051 (11)	0.0005 (9)
O32	0.0276 (15)	0.0534 (14)	0.0278 (11)	−0.0065 (12)	−0.0020 (10)	0.0005 (9)
O42	0.0490 (17)	0.0334 (12)	0.0226 (11)	−0.0079 (11)	−0.0041 (10)	0.0027 (8)
N1	0.028 (2)	0.0341 (17)	0.0350 (17)	0.0041 (15)	0.0023 (15)	0.0010 (12)
C11	0.038 (2)	0.034 (2)	0.037 (2)	−0.0064 (19)	−0.003 (2)	−0.0010 (15)
C21	0.036 (2)	0.036 (2)	0.045 (2)	0.001 (2)	0.002 (2)	−0.0003 (16)
C31	0.047 (3)	0.041 (2)	0.046 (2)	−0.004 (2)	−0.002 (2)	−0.0032 (17)
C41	0.057 (3)	0.039 (2)	0.045 (2)	0.004 (2)	−0.003 (2)	−0.0006 (17)
C51	0.105 (5)	0.031 (2)	0.070 (3)	−0.009 (2)	−0.005 (3)	0.0051 (19)
N2	0.035 (2)	0.0341 (17)	0.0285 (17)	−0.0004 (16)	−0.0011 (15)	0.0015 (11)
C12	0.029 (2)	0.035 (2)	0.038 (2)	0.0019 (18)	0.0044 (18)	−0.0009 (15)
C22	0.033 (2)	0.033 (2)	0.041 (2)	−0.0012 (19)	−0.0003 (19)	−0.0011 (15)
C32	0.048 (3)	0.032 (2)	0.051 (2)	−0.003 (2)	−0.001 (2)	0.0012 (17)
C42	0.060 (3)	0.040 (2)	0.044 (2)	0.004 (2)	0.000 (2)	−0.0031 (17)
C52	0.087 (4)	0.039 (2)	0.065 (3)	−0.005 (2)	0.000 (3)	−0.0006 (19)

Geometric parameters (Å, º)

As1—O11	1.711 (2)	C11—H1c11	0.94 (2)
As1—O21	1.6575 (19)	C11—H2c11	0.939 (18)
As1—O31	1.659 (2)	C21—H1c21	0.95 (2)
As1—O41	1.707 (2)	C21—H2c21	0.95 (2)
As2—O12	1.693 (2)	C31—H1c31	0.95 (2)
As2—O22	1.710 (2)	C31—H2c31	0.950 (18)
As2—O32	1.642 (2)	C41—H1c41	0.953 (19)
As2—O42	1.667 (2)	C41—H2c41	0.948 (18)
O11—HO11	0.96 (3)	C51—H1c51	0.93 (2)
O41—HO41	0.95 (2)	C51—H2c51	0.95 (3)
O12—HO12	0.90 (3)	C51—H3c51	0.96 (2)
O22—HO22	0.90 (2)	N2—H1n2	0.90 (2)
N1—C11	1.483 (4)	N2—H2n2	0.87 (2)
C11—C21	1.515 (5)	N2—H3n2	0.890 (18)
C21—C31	1.514 (5)	C12—H1c12	0.953 (17)
C31—C41	1.526 (5)	C12—H2c12	0.941 (17)
C41—C51	1.523 (6)	C22—H1c22	0.949 (18)
N2—C12	1.489 (4)	C22—H2c22	0.95 (2)
C12—C22	1.505 (5)	C32—H1c32	0.949 (19)
C22—C32	1.519 (5)	C32—H2c32	0.95 (2)
C32—C42	1.525 (5)	C42—H1c42	0.950 (19)
C42—C52	1.523 (6)	C42—H2c42	0.95 (2)
N1—H1n1	0.90 (2)	C52—H1c52	0.93 (2)
N1—H2n1	0.89 (2)	C52—H2c52	0.98 (3)
N1—H3n1	0.88 (2)	C52—H3c52	0.97 (2)
O11—As1—O21	110.86 (11)	O12—As2—O22	105.42 (11)
O11—As1—O31	106.41 (11)	O12—As2—O32	107.20 (11)
O11—As1—O41	107.53 (12)	O12—As2—O42	111.77 (12)
O21—As1—O31	117.02 (11)	O22—As2—O32	112.10 (11)
O21—As1—O41	104.71 (10)	O22—As2—O42	106.71 (10)
O31—As1—O41	110.01 (10)	O32—As2—O42	113.41 (10)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	D···A	D—H···A
O11—HO11···O32^i	0.96 (3)	2.591 (3)	172 (3)
O41—HO41···O42^ii	0.95 (2)	2.489 (3)	168 (4)
O12—HO12···O31	0.90 (3)	2.574 (3)	161 (3)
O22—HO22···O21^iii	0.90 (3)	2.550 (3)	167 (5)
N1—H3n1···O22^iv	0.88 (2)	2.969 (4)	162 (2)
N1—H1n1···O32^v	0.90 (2)	2.774 (3)	168 (2)
N1—H2n1···O42^vi	0.88 (2)	2.759 (4)	160 (2)
N2—H1n2···O21^vii	0.90 (2)	2.833 (4)	162 (2)
N2—H3n2···O31^viii	0.89 (2)	2.785 (3)	161 (2)
N2—H2n2···O41^ix	0.87 (3)	2.835 (4)	157 (2)

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+2, −y+1, −z; (v) −x+2, −y+1, −z+1; (vi) −x+3/2, y+1/2, −z+1/2; (vii) −x+1, −y+1, −z+1; (viii) −x+1, −y+1, −z; (ix) −x+1/2, y+1/2, −z+1/2.