A three-dimensional hydrogen-bonded network in bis­(4-hydroxy­anilinium) selenate(VI) dihydrate

The title compound, 2C₆H₈NO⁺·SeO₄^2-·2H₂O, contains 4-hy­droxy­anilinium cations, selenate(VI) anions and water mol­ecules. One of the two independent cations is nearly planar (excluding the ammonium H atoms), while the other is markedly nonplanar, with the hydr­oxy and ammonium groups displaced from the plane of the benzene ring. This results from the anti­parallel orientation of the cations, which inter­act through oppositely polarized ammonium and hydr­oxy groups. Ionic and hydrogen-bonding inter­actions join the oppositely charged units into a three-dimensional network. This work demonstrates the usefulness of 4-amino­phenol in the crystal engineering of organic-inorganic hybrid compounds.

S1. Comment

In recent years, studies on the self-assembly of acid–base hydrogen-bond interactions and molecular recognition in the solid state have shown a great variety of physical and chemical properties in this class of materials. These hybrid crystals are potentially good materials exhibiting nonlinear optical properties (Chemla & Zyss, 1987; Marchewka et al., 2003): the anionic acid part is responsible for favourable chemical and mechanical properties due to the formation of strongly directional hydrogen bonds, while the organic base is mainly responsible for nonlinear optical properties due to its relatively high hyperpolarizability (Bhattacharya et al., 1994; Blagden & Seddon, 1999; Głowiak et al., 2001). Continuing our studies on the characterization of acid–base hybrid crystals (Janczak & Perpétuo, 2007), we report here the structure of bis(4-hydroxyanilinium) selenate(VI) dihydrate, (I).

The asymmetric unit of (I) consists of two 4-hydroxyanilinium cations (denoted 4AP⁺), one selenate(VI) anion and two water molecules (Fig. 1). One of the water molecules (O6) acts as a hydrogen-bond donor to two anions, while the other water molecule (O7) acts as a donor to an anion and a cation (Table 1). Additionally, water atom O7 acts as an acceptor from both ammonium cations (denoted M1 and M2), while water atom O6 acts as an acceptor from one cation only.

The two independent cations exhibit different geometries: M2 is almost planar (excluding the ammonium H atoms), while M1 is nonplanar. In M1, the O and N atoms are displaced from the ring plane by 0.167 (2) and 0.187 (2)Å, respectively, while in M2 the respective displacements are less than 0.006 (2)Å. Thus, in M1 the C—N and C—O bonds are inclined to the benzene ring by 7.3 (1)°. This nonplanar conformation of M1 results from an antiparallel orientation of the dipolar 4AP⁺ units that interact via oppositely charged ammonium and hydroxy groups, forming a centrosymmetric dimer.

Considering the geometry of the N—H···O hydrogen bond in the (4AP⁺)₂ dimer, it was observed that the H···O distance of 2.542 (2)Å is longer than the 1.2–2.2Å range typically observed for N—H···O hydrogen bonds (Jeffrey, 1997). However, the H···O distance in (I) is slightly shorter than the sum of the van der Waals radii of H and O atoms (r_H = 1.10Å and r_O = 1.55Å; Bondi, 1964; Rowland & Taylor, 1996); thus, the N—H···O interaction between the ammonium and hydroxy groups in the (4AP⁺)₂ dimer is significant and is responsible for the inclination of both groups to the plane of the benzene ring. In addition, ammonium atom H11 is involved in a three-centre hydrogen bond, where the N—H···(O)₂ contacts are generally longer than in a two-centre system.

Extensive N—H···O and O—H···O hydrogen bonding (Table 1) links the oppositely charged 4AP⁺ and SeO₄^2- units, forming stacks along [001], while the water molecules interconnect the stacks into a three-dimensional network (Fig. 2). The nonplanar M1 4AP⁺ cations that form dimers are arranged in stacks, forming layers parallel to (100) (at x = 0, 1/2, etc.). The planar M2 4AP⁺ cations form layers at x = 1/4 and 3/4. The benzene rings of the nonplanar M1 4AP⁺ cations are almost parallel to (001), while the planar M2 4AP⁺ units are inclined by ~22° to this plane. Between the phenyl rings of the 4AP⁺ cations there are weak π–π interactions with an interplanar spacing of 3.320 (2)Å for the M1···M1ⁱ dimer [symmetry code: -x, 1-y, 1-z)]. The ring-centroid separation is 3.552 (2)Å and the corresponding ring-centroid offset is 1.262 (2)Å. By contrast, the rings of planar 4AP⁺ (M2) units are inclined to each other so that no effective π–π interactions can occur. It is commonly accepted that interactions between stacks of aromatic rings with approximately parallel molecular planes occur if the planes are separated by 3.3–3.8Å (Filippini & Gavezzotti, 1993; Janiak, 2000). The layers of M1 and M2 cations are interconnected by layers of anions and water molecules at x = 1/8, 3/8, 5/8 and 7/8 (Fig. 2), forming a three-dimensional network.

Related literature

For related literature, see: Bhattacharya et al. (1994); Blagden & Seddon (1999); Bondi (1964); Filippini & Gavezzotti (1993); Głowiak et al. (2001); Janczak & Perpétuo (2007); Janiak (2000); Jeffrey (1997); Marchewka et al. (2003); Rowland & Taylor (1996).

S2. Experimental

An aqueous solution of 4-aminophenol (Aldrich, 99% purity) in selenic acid was prepared and held at a temperature of 360 K. When the solution became homogeneous, it was cooled to 295 K. After several days at room temperature, crystals of (I) suitable for X-ray diffraction analysis were obtained.

S3. Refinement

All H atoms were located in difference maps and then treated as riding, with C—H distances of 0.93Å, N—H distances of 0.89Å and O—H distances of 0.82Å, and with U_iso(H) = kU_eq(carrier), where k = 1.2 for the aryl rings and 1.5 otherwise.

Computing details

Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis CCD (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg & Putz, 2006); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. A view of molecular structure of (I), showing the atom-labelling scheme. Displacemnt ellipsoids are shown at the 50% probability level and H atoms as spheres of arbitrary radii. Dashed lines indicate hydrogen-bond contacts. M1 and M2 denote nonplanar and planar 4AP^+ cations, respectively.
	Fig. 2. A view of hydrogen-bonded three-dimensional network of (I), showing layers of planar and nonplanar 4AP^+ cations at x = 1/4, 3/4 and at x = 0, 1/2, respectively, and layers of SeO4^2- and water molecules at x = 1/8, 3/8, 5/8 and 7/8.

bis(4-hydroxyanilinium) selenate(VI) dihydrate

Crystal data

2C6H8NO^+·SeO4^2^−·2H2O	F(000) = 1632
Mr = 399.26	Dx = 1.592 Mg m^−3 Dm = 1.59 Mg m^−3 Dm measured by floatation
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 1276 reflections
a = 37.632 (6) Å	θ = 2.8–28.3°
b = 6.520 (1) Å	µ = 2.30 mm^−1
c = 14.431 (3) Å	T = 295 K
β = 109.82 (1)°	Paralellepiped, colourless
V = 3331.0 (10) Å^3	0.32 × 0.24 × 0.18 mm
Z = 8

Data collection

Kuma KM-4 with CCD area-detector diffractometer	4283 independent reflections
Radiation source: fine-focus sealed tube	3056 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.025
Detector resolution: 1024x1024 with blocks 2x2 pixels mm^-1	θmax = 29.3°, θmin = 2.8°
ω scans	h = −50→49
Absorption correction: numerical (CrysAlis RED; Oxford Diffraction, 2006)	k = −7→8
Tmin = 0.532, Tmax = 0.684	l = −19→19
21626 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.023	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.051	H-atom parameters constrained
S = 1.00	w = 1/[σ^2(Fo^2) + (0.0243P)^2] where P = (Fo^2 + 2Fc^2)/3
4283 reflections	(Δ/σ)max = 0.003
222 parameters	Δρmax = 0.38 e Å^−3
0 restraints	Δρmin = −0.44 e Å^−3

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.

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 (Ų)

	x	y	z	Uiso*/Ueq
Se1	0.119226 (4)	0.05390 (2)	0.343974 (11)	0.03802 (6)
O1	0.11338 (3)	−0.19164 (16)	0.32617 (8)	0.0391 (3)
O2	0.15030 (4)	0.09187 (17)	0.45385 (8)	0.0496 (3)
O3	0.13604 (4)	0.15035 (19)	0.26340 (8)	0.0537 (3)
O4	0.07984 (3)	0.16144 (19)	0.33716 (10)	0.0569 (4)
C1	0.03000 (4)	0.5844 (2)	0.38550 (11)	0.0295 (4)
C2	0.01693 (5)	0.7790 (3)	0.39182 (12)	0.0410 (4)
H2	0.0325	0.8918	0.3963	0.049*
C3	−0.01944 (5)	0.8059 (3)	0.39147 (13)	0.0454 (5)
H3	−0.0285	0.9371	0.3956	0.055*
C4	−0.04233 (5)	0.6374 (3)	0.38495 (11)	0.0380 (4)
C5	−0.02976 (5)	0.4437 (3)	0.37226 (12)	0.0414 (4)
H5	−0.0458	0.3313	0.3633	0.050*
C6	0.00647 (5)	0.4182 (2)	0.37298 (12)	0.0380 (4)
H6	0.0151	0.2881	0.3650	0.046*
N1	0.06968 (4)	0.5508 (2)	0.39750 (10)	0.0358 (3)
H11	0.0834	0.5512	0.4613	0.054*
H12	0.0776	0.6504	0.3672	0.054*
H13	0.0722	0.4304	0.3713	0.054*
O5	−0.07735 (3)	0.6505 (2)	0.39405 (9)	0.0534 (3)
H51	−0.0818	0.7703	0.4035	0.080*
C21	0.19413 (4)	0.5924 (2)	0.29990 (11)	0.0304 (4)
C22	0.21590 (5)	0.4428 (3)	0.35961 (12)	0.0399 (4)
H22	0.2053	0.3167	0.3656	0.048*
C23	0.25369 (5)	0.4807 (3)	0.41090 (13)	0.0427 (4)
H23	0.2686	0.3796	0.4510	0.051*
C24	0.26920 (5)	0.6676 (3)	0.40257 (12)	0.0382 (4)
C25	0.24715 (5)	0.8183 (3)	0.34261 (13)	0.0470 (5)
H25	0.2577	0.9446	0.3367	0.056*
C26	0.20951 (5)	0.7802 (3)	0.29159 (12)	0.0406 (4)
H26	0.1945	0.8814	0.2516	0.049*
O25	0.30616 (3)	0.71280 (19)	0.45165 (10)	0.0600 (4)
H251	0.3165	0.6140	0.4851	0.090*
N21	0.15430 (3)	0.55421 (19)	0.24509 (9)	0.0319 (3)
H211	0.1484	0.4270	0.2569	0.048*
H212	0.1501	0.5693	0.1809	0.048*
H213	0.1402	0.6430	0.2641	0.048*
O6	0.10040 (5)	0.0306 (3)	0.07158 (11)	0.0757 (5)
H61	0.1149	0.0550	0.1272	0.113*
H62	0.1164	−0.0120	0.049	0.113*
O7	0.14738 (4)	0.45667 (19)	0.54609 (10)	0.0468 (3)
H71	0.1533	0.3660	0.5151	0.070*
H72	0.1626	0.5430	0.5421	0.070*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Se1	0.03949 (9)	0.03369 (8)	0.04013 (8)	−0.00110 (7)	0.00916 (6)	−0.00102 (7)
O1	0.0472 (8)	0.0329 (6)	0.0448 (8)	−0.0045 (5)	0.0273 (6)	−0.0040 (5)
O2	0.0525 (8)	0.0455 (8)	0.0359 (7)	0.0048 (6)	−0.0046 (6)	−0.0072 (5)
O3	0.0689 (10)	0.0487 (7)	0.0500 (7)	−0.0217 (7)	0.0296 (7)	−0.0004 (6)
O4	0.0474 (7)	0.0435 (8)	0.0779 (10)	0.0082 (6)	0.0189 (7)	−0.0122 (7)
C1	0.0263 (8)	0.0331 (10)	0.0287 (8)	0.0012 (7)	0.0087 (6)	−0.0030 (6)
C2	0.0405 (10)	0.0352 (10)	0.0493 (11)	0.0018 (8)	0.0184 (9)	−0.0066 (8)
C3	0.0421 (11)	0.0427 (11)	0.0527 (12)	−0.0095 (9)	0.0195 (9)	−0.0100 (9)
C4	0.0300 (9)	0.0501 (11)	0.0311 (9)	−0.0060 (9)	0.0058 (7)	−0.0109 (8)
C5	0.0332 (10)	0.0477 (11)	0.0394 (9)	0.0044 (9)	0.0074 (8)	0.0026 (8)
C6	0.0383 (10)	0.0349 (10)	0.0396 (9)	0.0027 (8)	0.0117 (8)	0.0047 (7)
N1	0.0281 (7)	0.0362 (8)	0.0438 (8)	−0.0013 (7)	0.0133 (6)	−0.0033 (7)
O5	0.0361 (7)	0.0653 (9)	0.0592 (8)	−0.0046 (7)	0.0129 (6)	−0.0106 (7)
C21	0.0258 (9)	0.0337 (10)	0.0312 (8)	−0.0002 (7)	0.0092 (7)	0.0006 (7)
C22	0.0346 (9)	0.0328 (9)	0.0474 (10)	0.0028 (8)	0.0075 (8)	−0.0054 (8)
C23	0.0356 (10)	0.0363 (10)	0.0486 (10)	−0.0011 (8)	0.0043 (8)	−0.0141 (8)
C24	0.0319 (9)	0.0392 (10)	0.0394 (10)	0.0041 (8)	0.0067 (7)	−0.0042 (8)
C25	0.0371 (11)	0.0331 (10)	0.0630 (12)	0.0066 (8)	0.0071 (9)	−0.0116 (9)
C26	0.0333 (10)	0.0319 (9)	0.0513 (11)	−0.0026 (8)	0.0076 (8)	−0.0117 (8)
O25	0.0410 (7)	0.0471 (8)	0.0730 (10)	0.0090 (6)	−0.0054 (7)	−0.0196 (7)
N21	0.0273 (7)	0.0299 (7)	0.0375 (7)	−0.0010 (6)	0.0094 (6)	−0.0020 (6)
O6	0.0627 (11)	0.1041 (13)	0.0626 (9)	−0.0155 (10)	0.0228 (8)	−0.0242 (9)
O7	0.0532 (9)	0.0432 (8)	0.0483 (8)	−0.0131 (7)	0.0227 (6)	−0.0094 (6)

Geometric parameters (Å, º)

Se1—O4	1.6123 (12)	C21—C22	1.374 (2)
Se1—O1	1.6245 (11)	C21—C26	1.377 (2)
Se1—O3	1.6269 (12)	C21—N21	1.460 (2)
Se1—O2	1.6387 (13)	C22—C23	1.385 (2)
C1—C6	1.372 (2)	C22—H22	0.9300
C1—C2	1.375 (2)	C23—C24	1.374 (2)
C1—N1	1.460 (2)	C23—H23	0.9300
C2—C3	1.378 (2)	C24—O25	1.3620 (19)
C2—H2	0.9300	C24—C25	1.384 (2)
C3—C4	1.380 (2)	C25—C26	1.379 (2)
C3—H3	0.9300	C25—H25	0.9300
C4—O5	1.3709 (19)	C26—H26	0.9300
C4—C5	1.382 (2)	O25—H251	0.8200
C5—C6	1.370 (2)	N21—H211	0.8900
C5—H5	0.9300	N21—H212	0.8900
C6—H6	0.9300	N21—H213	0.8900
N1—H11	0.8900	O6—H61	0.8200
N1—H12	0.8900	O6—H62	0.8200
N1—H13	0.8900	O7—H71	0.8200
O5—H51	0.8200	O7—H72	0.8200
O4—Se1—O1	110.27 (6)	H12—N1—H13	109.5
O4—Se1—O3	111.14 (7)	C4—O5—H51	109.5
O1—Se1—O3	109.42 (6)	C22—C21—C26	120.49 (15)
O4—Se1—O2	109.44 (7)	C22—C21—N21	120.20 (14)
O1—Se1—O2	108.41 (5)	C26—C21—N21	119.31 (14)
O3—Se1—O2	108.08 (7)	C21—C22—C23	119.63 (15)
C6—C1—C2	120.52 (16)	C21—C22—H22	120.2
C6—C1—N1	119.06 (14)	C23—C22—H22	120.2
C2—C1—N1	120.33 (14)	C24—C23—C22	120.10 (16)
C1—C2—C3	119.66 (16)	C24—C23—H23	120.0
C1—C2—H2	120.2	C22—C23—H23	120.0
C3—C2—H2	120.2	O25—C24—C23	122.39 (15)
C2—C3—C4	119.65 (17)	O25—C24—C25	117.49 (15)
C2—C3—H3	120.2	C23—C24—C25	120.12 (15)
C4—C3—H3	120.2	C26—C25—C24	119.70 (16)
O5—C4—C3	122.83 (18)	C26—C25—H25	120.2
O5—C4—C5	116.93 (16)	C24—C25—H25	120.2
C3—C4—C5	120.20 (16)	C21—C26—C25	119.96 (15)
C6—C5—C4	119.61 (16)	C21—C26—H26	120.0
C6—C5—H5	120.2	C25—C26—H26	120.0
C4—C5—H5	120.2	C24—O25—H251	109.5
C5—C6—C1	120.11 (16)	C21—N21—H211	109.5
C5—C6—H6	119.9	C21—N21—H212	109.5
C1—C6—H6	119.9	H211—N21—H212	109.5
C1—N1—H11	109.5	C21—N21—H213	109.5
C1—N1—H12	109.5	H211—N21—H213	109.5
H11—N1—H12	109.5	H212—N21—H213	109.5
C1—N1—H13	109.5	H61—O6—H62	97
H11—N1—H13	109.5	H71—O7—H72	98

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H11···O7	0.89	2.38	3.045 (2)	131
N1—H11···O5^i	0.89	2.54	3.204 (2)	132
N1—H12···O1^ii	0.89	1.94	2.781 (2)	157
N1—H13···O4	0.89	1.87	2.752 (2)	171
O5—H51···O6^iii	0.82	1.92	2.726 (2)	170
O25—H251···O2^iv	0.82	1.84	2.641 (2)	165
N21—H211···O3	0.89	1.87	2.757 (2)	172
N21—H212···O7^v	0.89	1.92	2.795 (2)	167
N21—H213···O1^ii	0.89	1.90	2.776 (2)	170
O6—H61···O3	0.82	1.95	2.748 (2)	163
O6—H62···O2^vi	0.82	2.24	3.035 (2)	166
O7—H71···O2	0.82	1.98	2.746 (2)	156
O7—H72···O25^vii	0.82	1.96	2.768 (2)	168

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