Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270109025499/sk3334sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270109025499/sk3334Isup2.hkl |
CCDC reference: 749707
The melting point was determined with an electrothermal apparatus and is uncorrected. Compound (4) was prepared following the procedure described in the literature (Kuznetsov et al., 2007). Hydroquinone was purchased from Merck and used without further purification. To a solution of hydroquinone (11.0 mg, 0.1 mmol) in acetone (10 ml) was slowly added a solution containing (4) (20.2 mg, 0.1 mmol) in acetone (10 ml), and the resulting mixture was gently heated for five minutes. Slow evaporation of the solvent at room temperature afforded a hard crystalline mass from which it was possible to break out air-stable colorless small crystals [m.p. 437–440 K (decomposition)].
The hydroxy H1O atom was located in a difference map and its postion refined isotropically [Uiso(H) = 1.2Ueq(O)]. All remaining H atoms were placed in geometrically idealized positions, with C—H distances of 0.95 or 0.99 Å [Uiso(H) = 1.2Ueq(C)].
Data collection: APEX2 (Bruker, 2005); cell refinement: APEX2 (Bruker, 2005); data reduction: APEX2 (Bruker, 2005); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).
2C11H14N4·C6H6O2 | F(000) = 548 |
Mr = 514.64 | Dx = 1.372 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.7107 Å |
Hall symbol: -P 2yn | Cell parameters from 1992 reflections |
a = 6.6421 (4) Å | θ = 2.6–30.0° |
b = 5.9519 (3) Å | µ = 0.09 mm−1 |
c = 31.5160 (18) Å | T = 100 K |
β = 90.687 (3)° | Prism, colourless |
V = 1245.84 (12) Å3 | 0.38 × 0.21 × 0.2 mm |
Z = 2 |
Bruker APEXII CCD diffractometer | 2673 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.053 |
ω and phi scans | θmax = 30.7°, θmin = 1.3° |
Absorption correction: multi-scan (SADABS; Bruker, 2005) | h = −9→9 |
Tmin = 0.90, Tmax = 0.98 | k = 0→8 |
16516 measured reflections | l = 0→45 |
3840 independent reflections |
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)] = 0.049 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.121 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.08 | w = 1/[σ2(Fo2) + (0.0522P)2 + 0.1373P] where P = (Fo2 + 2Fc2)/3 |
3840 reflections | (Δ/σ)max = 0.001 |
175 parameters | Δρmax = 0.31 e Å−3 |
0 restraints | Δρmin = −0.31 e Å−3 |
2C11H14N4·C6H6O2 | V = 1245.84 (12) Å3 |
Mr = 514.64 | Z = 2 |
Monoclinic, P21/n | Mo Kα radiation |
a = 6.6421 (4) Å | µ = 0.09 mm−1 |
b = 5.9519 (3) Å | T = 100 K |
c = 31.5160 (18) Å | 0.38 × 0.21 × 0.2 mm |
β = 90.687 (3)° |
Bruker APEXII CCD diffractometer | 3840 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2005) | 2673 reflections with I > 2σ(I) |
Tmin = 0.90, Tmax = 0.98 | Rint = 0.053 |
16516 measured reflections |
R[F2 > 2σ(F2)] = 0.049 | 0 restraints |
wR(F2) = 0.121 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.08 | Δρmax = 0.31 e Å−3 |
3840 reflections | Δρmin = −0.31 e Å−3 |
175 parameters |
x | y | z | Uiso*/Ueq | ||
C1 | 0.33750 (19) | 0.8528 (2) | 0.50431 (4) | 0.0143 (3) | |
C2 | 0.5265 (2) | 0.7955 (2) | 0.52058 (4) | 0.0151 (3) | |
H2 | 0.5453 | 0.6556 | 0.5346 | 0.018* | |
C3 | 0.3123 (2) | 1.0572 (2) | 0.48363 (4) | 0.0156 (3) | |
H3 | 0.184 | 1.0967 | 0.4723 | 0.019* | |
C4 | 0.09599 (19) | 0.5617 (2) | 0.68067 (4) | 0.0136 (3) | |
C5 | 0.1349 (2) | 0.6814 (2) | 0.71778 (4) | 0.0161 (3) | |
H5 | 0.269 | 0.6927 | 0.7284 | 0.019* | |
C6 | −0.0211 (2) | 0.7849 (2) | 0.73956 (4) | 0.0178 (3) | |
H6 | 0.0065 | 0.8649 | 0.7651 | 0.021* | |
C7 | −0.2171 (2) | 0.7710 (2) | 0.72391 (4) | 0.0178 (3) | |
H7 | −0.3237 | 0.8419 | 0.7387 | 0.021* | |
C8 | −0.2572 (2) | 0.6530 (2) | 0.68654 (4) | 0.0163 (3) | |
H8 | −0.391 | 0.6449 | 0.6757 | 0.02* | |
C9 | −0.10221 (19) | 0.5470 (2) | 0.66509 (4) | 0.0136 (3) | |
C10 | −0.1019 (2) | 0.1847 (2) | 0.62874 (4) | 0.0191 (3) | |
H10A | −0.143 | 0.1281 | 0.6569 | 0.023* | |
H10B | −0.1846 | 0.1057 | 0.6071 | 0.023* | |
C11 | 0.1736 (2) | 0.2207 (2) | 0.58177 (4) | 0.0178 (3) | |
H11A | 0.0875 | 0.1605 | 0.5586 | 0.021* | |
H11B | 0.3144 | 0.1759 | 0.5762 | 0.021* | |
C12 | 0.2945 (2) | 0.5531 (2) | 0.61631 (4) | 0.0156 (3) | |
H12A | 0.4353 | 0.5215 | 0.6082 | 0.019* | |
H12B | 0.2793 | 0.7183 | 0.6181 | 0.019* | |
C13 | 0.2444 (2) | 0.2105 (2) | 0.65594 (4) | 0.0188 (3) | |
H13A | 0.3807 | 0.1483 | 0.6514 | 0.023* | |
H13B | 0.1967 | 0.1531 | 0.6835 | 0.023* | |
C14 | −0.05507 (19) | 0.5276 (2) | 0.58892 (4) | 0.0151 (3) | |
H14A | −0.0657 | 0.693 | 0.5912 | 0.018* | |
H14B | −0.1333 | 0.4812 | 0.5635 | 0.018* | |
N1 | −0.14875 (17) | 0.42664 (18) | 0.62647 (3) | 0.0150 (2) | |
N2 | 0.11009 (18) | 0.12458 (19) | 0.62236 (4) | 0.0190 (3) | |
N3 | 0.15909 (16) | 0.46852 (18) | 0.58234 (3) | 0.0149 (2) | |
N4 | 0.26049 (16) | 0.45734 (18) | 0.65873 (3) | 0.0146 (2) | |
O1 | 0.17232 (14) | 0.71492 (17) | 0.50782 (3) | 0.0190 (2) | |
H1O | 0.189 (2) | 0.616 (3) | 0.5284 (5) | 0.023* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0153 (6) | 0.0166 (7) | 0.0111 (6) | −0.0015 (5) | 0.0005 (5) | −0.0017 (5) |
C2 | 0.0179 (7) | 0.0140 (6) | 0.0134 (6) | 0.0029 (5) | 0.0004 (5) | 0.0024 (5) |
C3 | 0.0152 (6) | 0.0187 (7) | 0.0128 (6) | 0.0020 (5) | −0.0011 (5) | 0.0015 (5) |
C4 | 0.0144 (6) | 0.0123 (6) | 0.0141 (6) | 0.0008 (5) | 0.0011 (5) | 0.0018 (5) |
C5 | 0.0155 (7) | 0.0166 (7) | 0.0163 (6) | −0.0009 (5) | −0.0019 (5) | 0.0000 (5) |
C6 | 0.0221 (7) | 0.0161 (6) | 0.0150 (6) | −0.0021 (5) | −0.0001 (5) | −0.0024 (5) |
C7 | 0.0186 (7) | 0.0174 (7) | 0.0174 (7) | −0.0001 (5) | 0.0047 (5) | −0.0022 (5) |
C8 | 0.0141 (6) | 0.0172 (7) | 0.0177 (7) | −0.0022 (5) | 0.0005 (5) | 0.0017 (5) |
C9 | 0.0168 (6) | 0.0116 (6) | 0.0125 (6) | −0.0015 (5) | −0.0017 (5) | 0.0014 (5) |
C10 | 0.0243 (7) | 0.0155 (7) | 0.0177 (7) | −0.0049 (5) | 0.0007 (6) | −0.0018 (5) |
C11 | 0.0216 (7) | 0.0172 (7) | 0.0147 (6) | 0.0018 (5) | 0.0002 (5) | −0.0035 (5) |
C12 | 0.0148 (6) | 0.0179 (7) | 0.0142 (6) | −0.0011 (5) | −0.0003 (5) | −0.0010 (5) |
C13 | 0.0238 (7) | 0.0157 (7) | 0.0168 (7) | 0.0053 (5) | −0.0025 (5) | 0.0010 (5) |
C14 | 0.0156 (6) | 0.0172 (7) | 0.0124 (6) | 0.0013 (5) | −0.0009 (5) | 0.0006 (5) |
N1 | 0.0173 (6) | 0.0149 (6) | 0.0129 (5) | −0.0021 (4) | −0.0006 (4) | −0.0014 (4) |
N2 | 0.0267 (7) | 0.0148 (6) | 0.0156 (6) | 0.0011 (5) | −0.0009 (5) | −0.0011 (5) |
N3 | 0.0158 (6) | 0.0152 (6) | 0.0137 (5) | 0.0011 (4) | −0.0010 (4) | 0.0003 (4) |
N4 | 0.0152 (5) | 0.0156 (6) | 0.0130 (5) | 0.0021 (4) | −0.0004 (4) | −0.0012 (4) |
O1 | 0.0176 (5) | 0.0212 (5) | 0.0181 (5) | −0.0057 (4) | −0.0021 (4) | 0.0069 (4) |
C1—O1 | 1.3755 (16) | C10—N1 | 1.4750 (17) |
C1—C3 | 1.3893 (18) | C10—H10A | 0.99 |
C1—C2 | 1.3924 (18) | C10—H10B | 0.99 |
C2—C3i | 1.3918 (18) | C11—N2 | 1.4677 (18) |
C2—H2 | 0.95 | C11—N3 | 1.4785 (18) |
C3—C2i | 1.3918 (18) | C11—H11A | 0.99 |
C3—H3 | 0.95 | C11—H11B | 0.99 |
C4—C5 | 1.3912 (18) | C12—N4 | 1.4733 (17) |
C4—C9 | 1.4023 (18) | C12—N3 | 1.4783 (17) |
C4—N4 | 1.4407 (16) | C12—H12A | 0.99 |
C5—C6 | 1.3933 (19) | C12—H12B | 0.99 |
C5—H5 | 0.95 | C13—N2 | 1.4678 (18) |
C6—C7 | 1.389 (2) | C13—N4 | 1.4754 (17) |
C6—H6 | 0.95 | C13—H13A | 0.99 |
C7—C8 | 1.3945 (19) | C13—H13B | 0.99 |
C7—H7 | 0.95 | C14—N1 | 1.4717 (17) |
C8—C9 | 1.3894 (18) | C14—N3 | 1.4822 (17) |
C8—H8 | 0.95 | C14—H14A | 0.99 |
C9—N1 | 1.4428 (16) | C14—H14B | 0.99 |
C10—N2 | 1.4689 (19) | O1—H1O | 0.884 (17) |
O1—C1—C3 | 117.93 (11) | N3—C11—H11A | 109.4 |
O1—C1—C2 | 122.73 (12) | N2—C11—H11B | 109.4 |
C3—C1—C2 | 119.35 (12) | N3—C11—H11B | 109.4 |
C3i—C2—C1 | 120.13 (12) | H11A—C11—H11B | 108 |
C3i—C2—H2 | 119.9 | N4—C12—N3 | 115.26 (11) |
C1—C2—H2 | 119.9 | N4—C12—H12A | 108.5 |
C1—C3—C2i | 120.52 (12) | N3—C12—H12A | 108.5 |
C1—C3—H3 | 119.7 | N4—C12—H12B | 108.5 |
C2i—C3—H3 | 119.7 | N3—C12—H12B | 108.5 |
C5—C4—C9 | 119.37 (12) | H12A—C12—H12B | 107.5 |
C5—C4—N4 | 119.34 (11) | N2—C13—N4 | 115.67 (11) |
C9—C4—N4 | 121.29 (11) | N2—C13—H13A | 108.4 |
C4—C5—C6 | 120.59 (12) | N4—C13—H13A | 108.4 |
C4—C5—H5 | 119.7 | N2—C13—H13B | 108.4 |
C6—C5—H5 | 119.7 | N4—C13—H13B | 108.4 |
C7—C6—C5 | 119.87 (12) | H13A—C13—H13B | 107.4 |
C7—C6—H6 | 120.1 | N1—C14—N3 | 115.56 (11) |
C5—C6—H6 | 120.1 | N1—C14—H14A | 108.4 |
C6—C7—C8 | 119.91 (13) | N3—C14—H14A | 108.4 |
C6—C7—H7 | 120 | N1—C14—H14B | 108.4 |
C8—C7—H7 | 120 | N3—C14—H14B | 108.4 |
C9—C8—C7 | 120.30 (13) | H14A—C14—H14B | 107.5 |
C9—C8—H8 | 119.8 | C9—N1—C14 | 112.78 (10) |
C7—C8—H8 | 119.8 | C9—N1—C10 | 113.65 (10) |
C8—C9—C4 | 119.95 (12) | C14—N1—C10 | 110.28 (10) |
C8—C9—N1 | 118.91 (12) | C11—N2—C13 | 108.29 (11) |
C4—C9—N1 | 121.14 (11) | C11—N2—C10 | 108.09 (11) |
N2—C10—N1 | 115.67 (11) | C13—N2—C10 | 113.05 (11) |
N2—C10—H10A | 108.4 | C12—N3—C11 | 108.01 (10) |
N1—C10—H10A | 108.4 | C12—N3—C14 | 113.25 (10) |
N2—C10—H10B | 108.4 | C11—N3—C14 | 107.53 (10) |
N1—C10—H10B | 108.4 | C4—N4—C12 | 113.22 (10) |
H10A—C10—H10B | 107.4 | C4—N4—C13 | 113.76 (11) |
N2—C11—N3 | 111.02 (10) | C12—N4—C13 | 110.04 (10) |
N2—C11—H11A | 109.4 | C1—O1—H1O | 111.2 (10) |
O1—C1—C2—C3i | −179.44 (12) | N2—C10—N1—C14 | 47.05 (15) |
C3—C1—C2—C3i | 0.5 (2) | N3—C11—N2—C13 | −60.98 (14) |
O1—C1—C3—C2i | 179.45 (11) | N3—C11—N2—C10 | 61.83 (14) |
C2—C1—C3—C2i | −0.5 (2) | N4—C13—N2—C11 | 54.80 (15) |
C9—C4—C5—C6 | 0.43 (19) | N4—C13—N2—C10 | −64.94 (15) |
N4—C4—C5—C6 | 179.71 (12) | N1—C10—N2—C11 | −54.74 (14) |
C4—C5—C6—C7 | −0.8 (2) | N1—C10—N2—C13 | 65.12 (15) |
C5—C6—C7—C8 | 0.2 (2) | N4—C12—N3—C11 | −54.78 (14) |
C6—C7—C8—C9 | 0.7 (2) | N4—C12—N3—C14 | 64.19 (14) |
C7—C8—C9—C4 | −1.0 (2) | N2—C11—N3—C12 | 60.99 (14) |
C7—C8—C9—N1 | −179.89 (12) | N2—C11—N3—C14 | −61.55 (13) |
C5—C4—C9—C8 | 0.45 (19) | N1—C14—N3—C12 | −64.71 (14) |
N4—C4—C9—C8 | −178.81 (12) | N1—C14—N3—C11 | 54.54 (14) |
C5—C4—C9—N1 | 179.31 (11) | C5—C4—N4—C12 | −115.32 (13) |
N4—C4—C9—N1 | 0.05 (19) | C9—C4—N4—C12 | 63.94 (16) |
C8—C9—N1—C14 | 115.04 (13) | C5—C4—N4—C13 | 118.07 (13) |
C4—C9—N1—C14 | −63.82 (15) | C9—C4—N4—C13 | −62.66 (15) |
C8—C9—N1—C10 | −118.50 (13) | N3—C12—N4—C4 | −80.82 (14) |
C4—C9—N1—C10 | 62.63 (16) | N3—C12—N4—C13 | 47.73 (15) |
N3—C14—N1—C9 | 81.18 (14) | N2—C13—N4—C4 | 80.50 (14) |
N3—C14—N1—C10 | −47.06 (15) | N2—C13—N4—C12 | −47.75 (15) |
N2—C10—N1—C9 | −80.71 (14) |
Symmetry code: (i) −x+1, −y+2, −z+1. |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1O···N3 | 0.884 (17) | 1.924 (18) | 2.7711 (15) | 159.9 (15) |
Experimental details
Crystal data | |
Chemical formula | 2C11H14N4·C6H6O2 |
Mr | 514.64 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 100 |
a, b, c (Å) | 6.6421 (4), 5.9519 (3), 31.5160 (18) |
β (°) | 90.687 (3) |
V (Å3) | 1245.84 (12) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.09 |
Crystal size (mm) | 0.38 × 0.21 × 0.2 |
Data collection | |
Diffractometer | Bruker APEXII CCD diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 2005) |
Tmin, Tmax | 0.90, 0.98 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 16516, 3840, 2673 |
Rint | 0.053 |
(sin θ/λ)max (Å−1) | 0.717 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.049, 0.121, 1.08 |
No. of reflections | 3840 |
No. of parameters | 175 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.31, −0.31 |
Computer programs: APEX2 (Bruker, 2005), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997), WinGX (Farrugia, 1999).
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1O···N3 | 0.884 (17) | 1.924 (18) | 2.7711 (15) | 159.9 (15) |
We are interested in investigating the structures and properties, as well as the reactivity, of aminal (aminoacetal) cages by reacting them with electrophiles and nucleophiles. These cyclic polyamines are able to play a role as hydrogen acceptors using the lone pair of an N atom in a hydrogen bond, and have been used as model systems for proton transfer studies. For instance, there are several reports (MacLean et al., 1999; Mak et al., 1977; Tse et al., 1977; Ghosh et al., 2005, and references 11–13 and 15 therein) on the preparation of adducts between hexamethylenetetramine (urotropine), (1), and phenols. In contrast, the analogue 1,3,6,8-tetraazatricyclo[4.4.1.13,8]dodecane (TATD), (2), has been shown to be highly reactive with a variety of phenols (Rivera et al., 2006, 2005, 1993). In addition, we were able to crystallize the 1:1 adduct of (2) and hydroquinone (Rivera, Ríos-Motta et al., 2007). Whereas these two aminals maintain similar hydrogen-bonding patterns with the hydroxyl groups of hydroquinone, the O—H bond exhibits dramatic changes in length. A comparison of the influence of the lone pair orbital hybridizations (LPOs) on O—H···N length (Rivera, Ríos-Motta et al., 2007) shows that the major sp3 character of the N atoms in (1) causes this molecule to possess a slightly shorter hydrogen-bond distance. In connection with our previous work on the synthesis of 1,3,6,8-tetraazatricyclo[4.3.1.13,8]undecane (TATU), (3) (Rivera et al., 2004), where a competition between hydrogen bonding and interactions between p-electron systems may occur and which offers the opportunity to study LPOs owing to the presence of two non-equivalent N atoms, we have recently studied the formation of a 1:1 complex of (3) with hydroquinone. The X-ray data showed that, contrary to the crystal structures of (2), the hydroquinone molecule hydrogen bonds to those N atoms with higher sp3 character (Rivera, González-Salas et al., 2007).
Recent work from the Kuznetsov group on a three-component condensation of formaldehyde with a mixture of ammonia and o-phenylenediamine, which resulted in the preparation of the new cage amine 1,5:3,7-dimethano-1,3,5,7-benzotetrazonine (4) (Kuznetsov et al., 2007), caught our attention for two reasons. First, a previous publication from our laboratory reported the synthesis of an analogous compound, (3), but following our methodology (Rivera et al., 2004) all attempts to prepare benzoTATU, (4), were unsuccessful. Second, from the viewpoint of crystal engineering, (4) can provide different hydrogen-bonding interactions since it contains two types of non-equivalent hydrogen-bonding acceptor atoms, and a possible competition between N atoms can occur. Thus, the results from the Kuznetzov group encouraged us to extend our investigation to determine the relationship between nitrogen lone pair hybridization and hydrogen-bond systems in aminal cages.
The reaction of (4) with hydroquinone yielded a colorless adduct, (I), whose structure contains two molecules of (4) linked to one hydroquinone molecule by O—H···N hydrogen bonds, which hold the molecules together in the crystal lattice. A view of the molecular structure indicating the atomic numbering is shown in Fig. 1 and a packing diagram is given in Fig. 2.
The asymmetric unit of complex (I) contains one molecule of (4) and one-half of a hydroquinone molecule, which is related to the other half by a inversion center, and the monoclinic unit cell contains two adducts. In contrast, the crystal structures of the urotropine (Mak et al. 1977), TATD (Rivera, Ríos-Motta et al., 2007) and TATU hydroquinone adducts (Rivera, González-Salas et al., 2007) show 1:1 molecular complexes. The lattices of these three hydroquinone adducts form infinite hydrogen-bonded networks, in which the aminal cages act as a twofold acceptor of hydrogen bonds, leading to the formation of zigzag chains. Previous X-ray structural investigation of (4) showed that the bond angles around the N atoms are close to sp3 geometry, ranging from 107.1 to 113.6° (the average value was 110.8°; Kuznetsov et al., 2007). On the basis of these X-ray data, the authors suggested that the non-bonding electron pairs on the N atoms directly attached to the benzene ring cannot efficiently delocalize into the aromatic ring. According to these results, the tetrahedral disposition of all nitrogen lone pairs in the aminal cage molecule makes this an attractive candidate as a hydrogen-bond acceptor, and some or all of them may, in principle, form hydrogen-bonded adducts. Thus, we expected that, with the use of hydroquinone, it should be possible to generate an infinite hydrogen-bonding network. However, a search on the packing diagram of the 4 hydroquinone:4 adduct (Fig. 2), using the Mercury software (Macrae et al., 2006), shows that although th hydroxyl groups of hydroquinone form hydrogen bonds with N atoms of two molecules of (4), the aminal cage is involved in a single intermolecular O—H···N hydrogen bond. Contrary to the case of (3) (Rivera, González-Salas et al., 2007), this observation suggests that the common hydrogen-bond network between polyamine and hydroquinone is broken as a consequence of the presence of a benzene ring moiety in the structure of (4). It appears that this group reduces the overall basicity of the aminal cage. Indeed, anilines are weaker bases than aliphatic amines, as a result of electron pair delocalization of the nitrogen non-bonding electron pair into the aromatic ring.
Our recent studies on the influence of the nitrogen lone pair hybridization on O—H···N hydrogen bonds and O—H bond lengths, carried out for structures determined by X-ray crystallography of 1:1 adducts between aminal cages and hydroquinone (Rivera, González-Salas et al., 2007), showed that the hydrogen bond is sensitive to the sp3 character of the N atom. As a continuation of these studies, we found that the current adduct presents slightly longer hydrogen bonds and a different relative orientation of the aromatic rings than those in the crystal structure of the TATU:hydroquinone adduct.