
Supporting information
![]() | Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536807029856/tk2167sup1.cif |
![]() | Structure factor file (CIF format) https://doi.org/10.1107/S1600536807029856/tk2167Isup2.hkl |
CCDC reference: 655025
Dicyclohexylamine (0.17 g, 1 mmol) and 4-hydroxybenzoic acid (0.14 g, 1 mmol) were dissolved in ethanol (25 ml). The mixture was heated to dissolve the reactants. Colorless plates of the salt separated from the solution after several days.
All hydrogen atoms were located in difference Fourier maps, and were refined with distance restraints C–H = 0.95±0.01 Å and N–H = O–H = 0.85±0.01 Å. The temperature factors were refined freely.
4-Hydroxybenzoic acid is an excellent counterion for the engineering of ammonium salts that exhibit second-harmonic generation, as noted from the SHG activity of (S)-ethylphenylammonium 4-hydroxybenzoate (Aakeröy et al., 1993). The anion is capable of mutiple hydrogen bonding interactions, this feature is crucial to chemical stability. We have previously used the sterically crowded dicyclohexylammonium cation in the synthesis of monocarboxylates (Ng, 1996; Ng, 1997; Ng, 1998; Ng & Hook, 1999; Ng et al., 1999, 2001; Subramanian et al., 2000) but these monocarboxylates do not have hydrogen-bond donor sites. Our studies are now extended to a study of dicyclohexylammonium 4-hydroxybenzoate, which exists as a hydrogen-bonded dimeric ion-pair that is linked across a center-of-inversion (Fig. 1). The ammonium hydrogen serves as as donor to a single-bond carboxyl oxygen atom of one anion as well as to the double-bond carbonyl oxygen atom of the symmetry-related anion. The carboxylate –CO2 unit has localized bonds: the hydrogen bond to the negatively-charged oxygen atom is significantly longer than that to the neutral oxygen atom. The hydroxy group engages in linking adjacent dimeric ion-pairs into a layer motif (Table 1, Fig. 2). The layer has a honeycomb-like topology (Fig. 3) but is buckled.
The crystal structures of polymethyleneiminium 4-hydroxybenzoates, [(CH2)nNH2] [C7H5O3] (n = 4, 5 and 6) have been reported; the hexamethyleneiminiums exists in two modifications (Moritani et al., 1987). The compounds, whose carboxylate groups are also localized, adopt chain motif instead, a motif that is also adopted by dicyclohexylammonium trifluoroacetate (Ng et al., 1999).
For crystal structures of dicyclohexylammonium salts of monocarboxylic acids, see Ng (1996, 1997, 1998), Ng et al. (1999, 2001), Ng & Hook (1999), Subramanian et al. (2000). For crystal structures of other ammonium salts of 4-hydroxybenzoic acid, see Moritani et al. (1987). For related literature, see: Aakeröy et al. (1993); Subramanian et al. (2000).
Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: X-SEED (Barbour, 2001) and OLEX (Dolomanov et al., 2003); software used to prepare material for publication: publCIF (Westrip, 2007).
2C12H24N+·2C7H5O3− | F(000) = 696 |
Mr = 638.86 | Dx = 1.156 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2yn | Cell parameters from 9647 reflections |
a = 9.4779 (2) Å | θ = 2.4–34.6° |
b = 11.0650 (3) Å | µ = 0.08 mm−1 |
c = 17.5816 (4) Å | T = 173 K |
β = 95.431 (1)° | Plate, colorless |
V = 1835.56 (8) Å3 | 0.35 × 0.30 × 0.06 mm |
Z = 2 |
Bruker APEX2 area-detector diffractometer | 4227 reflections with I > 2σ(I) |
Radiation source: medium-focus sealed tube | Rint = 0.033 |
Graphite monochromator | θmax = 30.0°, θmin = 2.6° |
φ and ω scans | h = −13→13 |
32008 measured reflections | k = −15→15 |
5346 independent reflections | l = −24→24 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.045 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.135 | All H-atom parameters refined |
S = 1.04 | w = 1/[σ2(Fo2) + (0.0739P)2 + 0.5355P] where P = (Fo2 + 2Fc2)/3 |
5346 reflections | (Δ/σ)max = 0.001 |
324 parameters | Δρmax = 0.52 e Å−3 |
29 restraints | Δρmin = −0.19 e Å−3 |
2C12H24N+·2C7H5O3− | V = 1835.56 (8) Å3 |
Mr = 638.86 | Z = 2 |
Monoclinic, P21/n | Mo Kα radiation |
a = 9.4779 (2) Å | µ = 0.08 mm−1 |
b = 11.0650 (3) Å | T = 173 K |
c = 17.5816 (4) Å | 0.35 × 0.30 × 0.06 mm |
β = 95.431 (1)° |
Bruker APEX2 area-detector diffractometer | 4227 reflections with I > 2σ(I) |
32008 measured reflections | Rint = 0.033 |
5346 independent reflections |
R[F2 > 2σ(F2)] = 0.045 | 29 restraints |
wR(F2) = 0.135 | All H-atom parameters refined |
S = 1.04 | Δρmax = 0.52 e Å−3 |
5346 reflections | Δρmin = −0.19 e Å−3 |
324 parameters |
x | y | z | Uiso*/Ueq | ||
O1 | 0.3950 (1) | 0.6161 (1) | 0.3722 (1) | 0.0201 (2) | |
O2 | 0.2552 (1) | 0.6278 (1) | 0.4673 (1) | 0.0238 (2) | |
O3 | 0.0294 (1) | 1.0816 (1) | 0.2716 (1) | 0.0224 (2) | |
N1 | 0.6664 (1) | 0.5639 (1) | 0.4429 (1) | 0.0159 (2) | |
C1 | 0.7400 (1) | 0.5365 (1) | 0.3728 (1) | 0.0193 (2) | |
C2 | 0.9009 (1) | 0.5378 (2) | 0.3891 (1) | 0.0312 (3) | |
C3 | 0.9688 (2) | 0.5083 (2) | 0.3159 (1) | 0.0472 (5) | |
C4 | 0.9177 (2) | 0.3876 (2) | 0.2818 (1) | 0.0439 (4) | |
C5 | 0.7560 (1) | 0.3837 (1) | 0.2691 (1) | 0.0305 (3) | |
C6 | 0.6884 (1) | 0.4135 (1) | 0.3423 (1) | 0.0224 (2) | |
C7 | 0.7084 (1) | 0.6764 (1) | 0.4870 (1) | 0.0163 (2) | |
C8 | 0.6200 (1) | 0.6816 (1) | 0.5551 (1) | 0.0185 (2) | |
C9 | 0.6546 (1) | 0.7949 (1) | 0.6030 (1) | 0.0210 (2) | |
C10 | 0.6305 (1) | 0.9076 (1) | 0.5536 (1) | 0.0222 (2) | |
C11 | 0.7201 (1) | 0.9028 (1) | 0.4858 (1) | 0.0227 (2) | |
C12 | 0.6889 (1) | 0.7891 (1) | 0.4374 (1) | 0.0201 (2) | |
C13 | 0.2947 (1) | 0.6642 (1) | 0.4052 (1) | 0.0165 (2) | |
C14 | 0.2207 (1) | 0.7721 (1) | 0.3683 (1) | 0.0152 (2) | |
C15 | 0.2559 (1) | 0.8142 (1) | 0.2979 (1) | 0.0182 (2) | |
C16 | 0.1924 (1) | 0.9166 (1) | 0.2646 (1) | 0.0194 (2) | |
C17 | 0.0917 (1) | 0.9792 (1) | 0.3017 (1) | 0.0178 (2) | |
C18 | 0.0528 (1) | 0.9369 (1) | 0.3717 (1) | 0.0190 (2) | |
C19 | 0.1173 (1) | 0.8343 (1) | 0.4046 (1) | 0.0176 (2) | |
H3o | 0.063 (2) | 1.096 (2) | 0.228 (1) | 0.052 (6)* | |
H1n | 0.577 (1) | 0.571 (1) | 0.428 (1) | 0.019 (3)* | |
H2n | 0.680 (2) | 0.503 (1) | 0.473 (1) | 0.036 (4)* | |
H1 | 0.709 (2) | 0.597 (1) | 0.337 (1) | 0.022 (4)* | |
H21 | 0.929 (2) | 0.481 (1) | 0.429 (1) | 0.036 (4)* | |
H22 | 0.933 (2) | 0.615 (1) | 0.409 (1) | 0.038 (5)* | |
H31 | 1.069 (1) | 0.507 (2) | 0.327 (1) | 0.061 (6)* | |
H32 | 0.949 (3) | 0.570 (2) | 0.278 (1) | 0.077 (8)* | |
H41 | 0.946 (2) | 0.323 (1) | 0.318 (1) | 0.049 (6)* | |
H42 | 0.959 (2) | 0.372 (2) | 0.235 (1) | 0.054 (6)* | |
H51 | 0.727 (2) | 0.304 (1) | 0.253 (1) | 0.044 (5)* | |
H52 | 0.728 (2) | 0.445 (1) | 0.232 (1) | 0.029 (4)* | |
H61 | 0.587 (1) | 0.414 (1) | 0.334 (1) | 0.024 (4)* | |
H62 | 0.713 (2) | 0.355 (1) | 0.381 (1) | 0.034 (4)* | |
H7 | 0.807 (1) | 0.667 (1) | 0.505 (1) | 0.020 (3)* | |
H81 | 0.635 (2) | 0.610 (1) | 0.585 (1) | 0.023 (4)* | |
H82 | 0.522 (1) | 0.685 (2) | 0.536 (1) | 0.030 (4)* | |
H91 | 0.753 (1) | 0.795 (1) | 0.625 (1) | 0.026 (4)* | |
H92 | 0.595 (1) | 0.796 (1) | 0.645 (1) | 0.024 (4)* | |
H101 | 0.651 (2) | 0.979 (1) | 0.583 (1) | 0.028 (4)* | |
H102 | 0.532 (1) | 0.911 (1) | 0.533 (1) | 0.022 (4)* | |
H111 | 0.818 (1) | 0.906 (1) | 0.506 (1) | 0.026 (4)* | |
H112 | 0.706 (2) | 0.975 (1) | 0.455 (1) | 0.028 (4)* | |
H121 | 0.594 (1) | 0.790 (1) | 0.413 (1) | 0.024 (4)* | |
H122 | 0.751 (1) | 0.787 (2) | 0.398 (1) | 0.028 (4)* | |
H15 | 0.324 (1) | 0.769 (1) | 0.272 (1) | 0.026 (4)* | |
H16 | 0.218 (2) | 0.947 (2) | 0.217 (1) | 0.028 (4)* | |
H18 | −0.017 (1) | 0.981 (1) | 0.395 (1) | 0.029 (4)* | |
H19 | 0.096 (2) | 0.807 (1) | 0.453 (1) | 0.026 (4)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0204 (4) | 0.0178 (4) | 0.0214 (4) | 0.0044 (3) | −0.0021 (3) | −0.0041 (3) |
O2 | 0.0307 (4) | 0.0195 (4) | 0.0211 (4) | 0.0056 (3) | 0.0024 (3) | 0.0052 (3) |
O3 | 0.0265 (4) | 0.0160 (4) | 0.0247 (4) | 0.0036 (3) | 0.0019 (3) | 0.0053 (3) |
N1 | 0.0173 (4) | 0.0147 (4) | 0.0156 (4) | 0.0007 (3) | 0.0007 (3) | −0.0009 (3) |
C1 | 0.0183 (5) | 0.0226 (5) | 0.0172 (5) | 0.0011 (4) | 0.0027 (4) | −0.0052 (4) |
C2 | 0.0187 (5) | 0.0415 (8) | 0.0334 (7) | −0.0008 (5) | 0.0019 (5) | −0.0174 (6) |
C3 | 0.0210 (6) | 0.0725 (13) | 0.0499 (9) | −0.0063 (7) | 0.0127 (6) | −0.0310 (9) |
C4 | 0.0272 (7) | 0.0609 (11) | 0.0439 (9) | 0.0101 (7) | 0.0050 (6) | −0.0269 (8) |
C5 | 0.0275 (6) | 0.0362 (7) | 0.0280 (6) | 0.0029 (5) | 0.0029 (5) | −0.0136 (6) |
C6 | 0.0225 (5) | 0.0226 (6) | 0.0216 (5) | 0.0022 (4) | 0.0001 (4) | −0.0066 (4) |
C7 | 0.0191 (5) | 0.0139 (5) | 0.0157 (5) | −0.0006 (4) | −0.0001 (4) | −0.0019 (4) |
C8 | 0.0255 (5) | 0.0151 (5) | 0.0148 (5) | 0.0004 (4) | 0.0020 (4) | 0.0001 (4) |
C9 | 0.0287 (6) | 0.0180 (5) | 0.0163 (5) | 0.0008 (4) | 0.0014 (4) | −0.0020 (4) |
C10 | 0.0284 (6) | 0.0148 (5) | 0.0234 (5) | 0.0006 (4) | 0.0037 (4) | −0.0017 (4) |
C11 | 0.0290 (6) | 0.0153 (5) | 0.0242 (6) | −0.0032 (4) | 0.0049 (4) | 0.0005 (4) |
C12 | 0.0262 (5) | 0.0171 (5) | 0.0170 (5) | −0.0025 (4) | 0.0028 (4) | 0.0017 (4) |
C13 | 0.0177 (5) | 0.0127 (5) | 0.0182 (5) | −0.0005 (4) | −0.0030 (4) | −0.0019 (4) |
C14 | 0.0154 (4) | 0.0128 (5) | 0.0169 (5) | −0.0005 (4) | −0.0005 (3) | −0.0002 (4) |
C15 | 0.0182 (5) | 0.0187 (5) | 0.0177 (5) | 0.0004 (4) | 0.0025 (4) | −0.0010 (4) |
C16 | 0.0216 (5) | 0.0201 (5) | 0.0166 (5) | −0.0007 (4) | 0.0017 (4) | 0.0027 (4) |
C17 | 0.0187 (5) | 0.0136 (5) | 0.0204 (5) | −0.0015 (4) | −0.0019 (4) | 0.0013 (4) |
C18 | 0.0188 (5) | 0.0160 (5) | 0.0227 (5) | 0.0018 (4) | 0.0045 (4) | −0.0005 (4) |
C19 | 0.0190 (5) | 0.0161 (5) | 0.0179 (5) | −0.0007 (4) | 0.0035 (4) | 0.0013 (4) |
O1—C13 | 1.276 (1) | C1—H1 | 0.95 (1) |
O2—C13 | 1.254 (1) | C2—H21 | 0.96 (1) |
O3—C17 | 1.362 (1) | C2—H22 | 0.96 (1) |
N1—C1 | 1.503 (1) | C3—H31 | 0.95 (1) |
N1—C7 | 1.501 (1) | C3—H32 | 0.96 (1) |
C1—C2 | 1.525 (2) | C4—H41 | 0.97 (1) |
C1—C6 | 1.526 (2) | C4—H42 | 0.96 (1) |
C2—C3 | 1.528 (2) | C5—H51 | 0.96 (1) |
C3—C4 | 1.524 (2) | C5—H52 | 0.96 (1) |
C4—C5 | 1.529 (2) | C6—H61 | 0.96 (1) |
C5—C6 | 1.528 (2) | C6—H62 | 0.95 (1) |
C7—C12 | 1.523 (2) | C7—H7 | 0.96 (1) |
C7—C8 | 1.526 (2) | C9—H91 | 0.97 (1) |
C9—C10 | 1.525 (2) | C9—H92 | 0.97 (1) |
C9—C8 | 1.528 (2) | C10—H101 | 0.96 (1) |
C10—C11 | 1.528 (2) | C10—H102 | 0.97 (1) |
C11—C12 | 1.532 (2) | C11—H111 | 0.96 (1) |
C13—C14 | 1.500 (2) | C11—H112 | 0.97 (1) |
C14—C15 | 1.393 (2) | C8—H81 | 0.95 (1) |
C14—C19 | 1.399 (2) | C8—H82 | 0.96 (1) |
C15—C16 | 1.386 (2) | C12—H121 | 0.96 (1) |
C16—C17 | 1.390 (2) | C12—H122 | 0.96 (1) |
C17—C18 | 1.399 (2) | C15—H15 | 0.97 (1) |
C18—C19 | 1.390 (2) | C16—H16 | 0.96 (1) |
O3—H3o | 0.87 (1) | C18—H18 | 0.95 (1) |
N1—H1n | 0.87 (1) | C19—H19 | 0.95 (1) |
N1—H2n | 0.86 (1) | ||
C1—N1—C7 | 118.0 (1) | C5—C4—H41 | 107 (1) |
N1—C1—C2 | 112.2 (1) | C3—C4—H42 | 111 (1) |
N1—C1—C6 | 108.0 (1) | C5—C4—H42 | 111 (1) |
C2—C1—C6 | 110.9 (1) | H41—C4—H42 | 108 (2) |
C1—C2—C3 | 109.5 (1) | C6—C5—H51 | 108 (1) |
C4—C3—C2 | 112.0 (2) | C4—C5—H51 | 109 (1) |
C3—C4—C5 | 111.1 (1) | C6—C5—H52 | 108 (1) |
C6—C5—C4 | 111.4 (1) | C4—C5—H52 | 107 (1) |
C1—C6—C5 | 110.1 (1) | H51—C5—H52 | 114 (2) |
N1—C7—C12 | 111.8 (1) | C1—C6—H61 | 110 (1) |
N1—C7—C8 | 107.4 (1) | C5—C6—H61 | 111 (1) |
C12—C7—C8 | 111.9 (1) | C1—C6—H62 | 108 (1) |
C10—C9—C8 | 110.2 (1) | C5—C6—H62 | 111 (1) |
C9—C10—C11 | 110.6 (1) | H61—C6—H62 | 107 (1) |
C10—C11—C12 | 111.6 (1) | N1—C7—H7 | 106 (1) |
C7—C8—C9 | 111.0 (1) | C12—C7—H7 | 110 (1) |
C7—C12—C11 | 110.4 (1) | C8—C7—H7 | 110 (1) |
O1—C13—O2 | 124.0 (1) | C10—C9—H91 | 108 (1) |
O2—C13—C14 | 117.7 (1) | C8—C9—H91 | 111 (1) |
O1—C13—C14 | 118.3 (1) | C10—C9—H92 | 111 (1) |
C15—C14—C19 | 118.5 (1) | C8—C9—H92 | 109 (1) |
C15—C14—C13 | 120.6 (1) | H91—C9—H92 | 108 (1) |
C19—C14—C13 | 120.9 (1) | C9—C10—H101 | 111 (1) |
C16—C15—C14 | 121.2 (1) | C11—C10—H101 | 111 (1) |
C15—C16—C17 | 119.9 (1) | C9—C10—H102 | 109 (1) |
O3—C17—C16 | 121.6 (1) | C11—C10—H102 | 107 (1) |
O3—C17—C18 | 118.6 (1) | H101—C10—H102 | 108 (1) |
C16—C17—C18 | 119.7 (1) | C10—C11—H111 | 108 (1) |
C19—C18—C17 | 119.9 (1) | C12—C11—H111 | 111 (1) |
C18—C19—C14 | 120.8 (1) | C10—C11—H112 | 110 (1) |
C17—O3—H3o | 108 (1) | C12—C11—H112 | 111 (1) |
C7—N1—H1n | 107 (1) | H111—C11—H112 | 105 (1) |
C1—N1—H1n | 106 (1) | C7—C8—H81 | 109 (1) |
C7—N1—H2n | 108 (1) | C9—C8—H81 | 112 (1) |
C1—N1—H2n | 107 (1) | C7—C8—H82 | 109 (1) |
H1n—N1—H2n | 110 (2) | C9—C8—H82 | 108 (1) |
N1—C1—H1 | 106 (1) | H81—C8—H82 | 108 (1) |
C2—C1—H1 | 111 (1) | C7—C12—H121 | 109 (1) |
C6—C1—H1 | 109 (1) | C11—C12—H121 | 111 (1) |
C1—C2—H21 | 110 (1) | C7—C12—H122 | 111 (1) |
C3—C2—H21 | 111 (1) | C11—C12—H122 | 109 (1) |
C1—C2—H22 | 110 (1) | H121—C12—H122 | 107 (1) |
C3—C2—H22 | 110 (1) | C16—C15—H15 | 120 (1) |
H21—C2—H22 | 106 (2) | C14—C15—H15 | 119 (1) |
C4—C3—H31 | 110 (1) | C15—C16—H16 | 121 (1) |
C2—C3—H31 | 109 (1) | C17—C16—H16 | 119 (1) |
C4—C3—H32 | 108 (2) | C19—C18—H18 | 122 (1) |
C2—C3—H32 | 112 (2) | C17—C18—H18 | 118 (1) |
H31—C3—H32 | 106 (2) | C18—C19—H19 | 121 (1) |
C3—C4—H41 | 109 (1) | C14—C19—H19 | 119 (1) |
C7—N1—C1—C2 | 52.8 (1) | N1—C7—C12—C11 | 175.0 (1) |
C7—N1—C1—C6 | 175.3 (1) | C8—C7—C12—C11 | 54.5 (1) |
N1—C1—C2—C3 | 179.5 (1) | C10—C11—C12—C7 | −55.0 (1) |
C6—C1—C2—C3 | 58.7 (2) | O2—C13—C14—C15 | −177.6 (1) |
C1—C2—C3—C4 | −56.6 (2) | O1—C13—C14—C15 | 3.4 (2) |
C2—C3—C4—C5 | 54.6 (2) | O2—C13—C14—C19 | 3.9 (2) |
C3—C4—C5—C6 | −54.1 (2) | O1—C13—C14—C19 | −175.1 (1) |
N1—C1—C6—C5 | 177.8 (1) | C19—C14—C15—C16 | 1.1 (2) |
C2—C1—C6—C5 | −58.9 (1) | C13—C14—C15—C16 | −177.4 (1) |
C4—C5—C6—C1 | 56.3 (2) | C14—C15—C16—C17 | 0.0 (2) |
C1—N1—C7—C12 | 57.7 (1) | C15—C16—C17—O3 | 178.5 (1) |
C1—N1—C7—C8 | −179.2 (1) | C15—C16—C17—C18 | −1.3 (2) |
C8—C9—C10—C11 | −57.5 (1) | O3—C17—C18—C19 | −178.4 (1) |
C9—C10—C11—C12 | 57.0 (1) | C16—C17—C18—C19 | 1.5 (2) |
N1—C7—C8—C9 | −179.3 (1) | C17—C18—C19—C14 | −0.4 (2) |
C12—C7—C8—C9 | −56.2 (1) | C15—C14—C19—C18 | −1.0 (2) |
C10—C9—C8—C7 | 57.1 (1) | C13—C14—C19—C18 | 177.6 (1) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1n···O1 | 0.87 (1) | 1.96 (1) | 2.808 (1) | 164 (1) |
N1—H2n···O2i | 0.86 (1) | 1.85 (1) | 2.706 (1) | 169 (2) |
O3—H3o···O1ii | 0.87 (1) | 1.86 (1) | 2.719 (1) | 170 (2) |
Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x+1/2, y+1/2, −z+1/2. |
Experimental details
Crystal data | |
Chemical formula | 2C12H24N+·2C7H5O3− |
Mr | 638.86 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 173 |
a, b, c (Å) | 9.4779 (2), 11.0650 (3), 17.5816 (4) |
β (°) | 95.431 (1) |
V (Å3) | 1835.56 (8) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.08 |
Crystal size (mm) | 0.35 × 0.30 × 0.06 |
Data collection | |
Diffractometer | Bruker APEX2 area-detector |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 32008, 5346, 4227 |
Rint | 0.033 |
(sin θ/λ)max (Å−1) | 0.703 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.045, 0.135, 1.04 |
No. of reflections | 5346 |
No. of parameters | 324 |
No. of restraints | 29 |
H-atom treatment | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.52, −0.19 |
Computer programs: APEX2 (Bruker, 2004), SAINT (Bruker, 2004), SAINT, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), X-SEED (Barbour, 2001) and OLEX (Dolomanov et al., 2003), publCIF (Westrip, 2007).
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1n···O1 | 0.87 (1) | 1.96 (1) | 2.808 (1) | 164 (1) |
N1—H2n···O2i | 0.86 (1) | 1.85 (1) | 2.706 (1) | 169 (2) |
O3—H3o···O1ii | 0.87 (1) | 1.86 (1) | 2.719 (1) | 170 (2) |
Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x+1/2, y+1/2, −z+1/2. |
4-Hydroxybenzoic acid is an excellent counterion for the engineering of ammonium salts that exhibit second-harmonic generation, as noted from the SHG activity of (S)-ethylphenylammonium 4-hydroxybenzoate (Aakeröy et al., 1993). The anion is capable of mutiple hydrogen bonding interactions, this feature is crucial to chemical stability. We have previously used the sterically crowded dicyclohexylammonium cation in the synthesis of monocarboxylates (Ng, 1996; Ng, 1997; Ng, 1998; Ng & Hook, 1999; Ng et al., 1999, 2001; Subramanian et al., 2000) but these monocarboxylates do not have hydrogen-bond donor sites. Our studies are now extended to a study of dicyclohexylammonium 4-hydroxybenzoate, which exists as a hydrogen-bonded dimeric ion-pair that is linked across a center-of-inversion (Fig. 1). The ammonium hydrogen serves as as donor to a single-bond carboxyl oxygen atom of one anion as well as to the double-bond carbonyl oxygen atom of the symmetry-related anion. The carboxylate –CO2 unit has localized bonds: the hydrogen bond to the negatively-charged oxygen atom is significantly longer than that to the neutral oxygen atom. The hydroxy group engages in linking adjacent dimeric ion-pairs into a layer motif (Table 1, Fig. 2). The layer has a honeycomb-like topology (Fig. 3) but is buckled.
The crystal structures of polymethyleneiminium 4-hydroxybenzoates, [(CH2)nNH2] [C7H5O3] (n = 4, 5 and 6) have been reported; the hexamethyleneiminiums exists in two modifications (Moritani et al., 1987). The compounds, whose carboxylate groups are also localized, adopt chain motif instead, a motif that is also adopted by dicyclohexylammonium trifluoroacetate (Ng et al., 1999).