A 1:1 adduct of hexa­methylene­tetramine and 4-hydroxy-3-methoxy­benz­aldehyde

In the title complex, C₆H₁₂N₄·C₈H₈O₃, the hexa­methyl­ene­tetramine mol­ecule accepts a single intermolecular O—H...N hydrogen bond from the hydroxy group of the 4-hydroxy-3-methoxy­benz­aldehyde moiety. The non-centrosymmetric crystal structure is built from alternating molecular sheets of 4-hydroxy-3-methoxy­benz­aldehyde and hexa­methyl­ene­tetramine mol­ecules, and is stabilized by intermolecular O—H...N, C—H...O and C—H...π interactions.

S1. Comment

Phenols usually crystallize with hexamethylenetetramine (HMT) to form O—H···N hydrogen-bonded adducts, in which the HMT acts as a mono-, bis- or tris-acceptor of hydrogen bonds (Jordan & Mak, 1970; Mak et al., 1977, 1978; Mahmoud & Wallwork, 1979; Coupar, Ferguson et al., 1997; Coupar, Glidewell & Ferguson, 1997). In only a few examples has HMT been found to act as an N—H···O hydrogen-bond donor, i.e. in the adducts of HMT with 2,4-dinitrophenol–water and with 2,4,6-trinitrophenol; in these, the nitrophenol molecules transfer the hydroxy H atom to the HMT moiety, thus forming an ion pair (Usman et al., 2001, 2002). This unusual behaviour of HMT in the solid state is due to these two nitrophenols being stronger acids compared with the other substituted phenols investigated. In order to further confirm this behaviour of HMT in the solid state, we have selected a very weak acid, 4-hydroxy-3-methoxybenzaldehyde (HMBA), to co-crystallize with HMT.

As expected, the H-atom transfer process was not observed in the title adduct, (I). The bond lengths and angles in (I) have normal values (Allen et al., 1987). The average values of the N—C bond lengths, and the C—-N–C and N—C—N bond angles in the HMT moiety are 1.470 (4) Å, 107.9 (2)° and 112.5 (2)°, respectively, and are comparable with those of uncomplexed HMT obtained by neutron diffraction at 130 K [average C—N 1.469 (2) Å, N—C—N 107.88 (9)° and C—N—C 112.58 (8)°; Kampermann et al., 1994] or with those of HMT in the adduct with 1,1,1-tris(hydroxyphenyl)ethane [average C—N is 1.467 (5) Å; Coupar, Ferguson et al., 1997]. The bond lengths and angles within the HMBA moiety agree with those of free HMBA (Velavan et al., 1995), with the maximum difference being a deviation of 0.015 Å in the length of the C13—O2 bond.

In the title adduct, the HMBA molecule is nearly planar, with the O2 atom of the carboxylic acid group deviating by 0.145 (3) Å from the plane of the HMBA ring. The four six-membered N—C—N—C—N—C rings of the HMT moiety adopt chair conformations whose puckering parameters (Cremer & Pople, 1975) are listed in Table 3, and the absolute value of the mean deviation of all atoms from their mean-ring planes is 0.236 (3) Å.

In the title adduct, the two components are connected by an intermolecular O1—H1···N4 hydrogen bond, with the HMT moiety acting as a mono-acceptor and the HMBA molecule acting as a mono-donor in the conventional intermolecular hydrogen bond between the hydroxy group of the HMBA molecule and one of the amine N atoms of the HMT moiety, as was also observed in the HMT–phenol adducts studied previously (Wallwork, 1962; Mahmoud & Wallwork, 1979; Coupar, Ferguson et al., 1997; Coupar, Glidewell & Ferguson, 1997). The N···O distance in the title adduct is slightly shorter than the average value (2.78 Å) found for O—H···N hydrogen bonds in other HMT–phenol adducts (Wallwork, 1962; Mahmoud & Wallwork, 1979; Coupar, Ferguson et al., 1997; Coupar, Glidewell & Ferguson, 1997). The O1 atom actually facilitates a bifurcated hydrogen-bonding system, as it is also involved in an intramolecular O1—H1···O3 interaction which forms a closed five-membered H1—O1—C7—C12—O3 ring.

In the crystal structure of the title adduct, there are two intermolecular C—H···O interactions which link the HMBA moieties into molecular sheets that extend in the b and c directions. The HMT molecules are linked by O—H···N hydrogen-bonding interactions to these molecular sheets of HMBA and are alternately stacked along the a axis. Fig. 2 shows the packing diagram of the title adduct viewed down the b axis, and indicates the intermolecular interactions. Three intermolecular C—H···π interactions involving the centroid of the aromatic ring of the HMBA were also observed (C_g is the centroid of ring C7—C12). All these interactions (see Table 2) stabilize the acentric packing in the title adduct.

S2. Experimental

Hexamethylenetetramine (1.40 g, 10 mmol) and 4-hydroxy-3-methoxybenzaldehyde (1.52 g, 10 mmol) were thoroughly mixed and then dissolved in ethanol (50 ml) with the addition of a few drops of water. The resultant mixture was warmed until a clear solution was obtained. The solution was filtered and left to evaporate slowly in air. Yellow single crystals suitable for X-ray data collection were obtained from the solution after a few days (m.p. 352 K).

S3. Refinement

The H atoms attached to atoms O1 and C13, which are involved in hydrogen bonds, were located in a difference Fourier map and were refined isotropically. After checking their presence in the difference map, the positions of all remaining H atoms were geometrically idealized and allowed to ride on their parent C atoms, with C—H distances in the range 0.93–0.97 Å. Due to the absence of any significant anomalous scatters, the 1661 Friedel equivalents were merged before the final refinements. The choice of the absolute structure was chosen arbitrarily.

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 1997); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL, PARST (Nardelli, 1995) and PLATON (Spek, 1990).

Figures

	Fig. 1. The structure of the title adduct showing 50% probability displacement ellipsoids and the atom-numbering scheme.
	Fig. 2. Packing diagram of the title adduct viewed down the b axis. The dashed lines denote the intermolecular hydrogen bonding interactions.

Hexamethylenetetramine-4-hydroxy-3-methoxybenzaldehyde

Crystal data

C6H12N4·C8H8O3	Dx = 1.342 Mg m^−3
Mr = 292.34	Melting point: 352 K
Orthorhombic, Pca21	Mo Kα radiation, λ = 0.71073 Å
a = 27.1214 (3) Å	Cell parameters from 4976 reflections
b = 7.1327 (1) Å	θ = 2.9–28.3°
c = 7.4776 (1) Å	µ = 0.10 mm^−1
V = 1446.53 (3) Å^3	T = 183 K
Z = 4	Block, colorless
F(000) = 624	0.32 × 0.24 × 0.12 mm

Data collection

Siemens SMART CCD area-detector diffractometer	1870 independent reflections
Radiation source: fine-focus sealed tube	1441 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.077
Detector resolution: 8.33 pixels mm^-1	θmax = 28.3°, θmin = 2.9°
ω scans	h = −35→33
Absorption correction: empirical (using intensity measurements) (SADABS; Sheldrick, 1996)	k = −7→9
Tmin = 0.970, Tmax = 0.989	l = −9→9
8042 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.049	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.113	w = 1/[σ^2(Fo^2) + (0.0562P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.94	(Δ/σ)max < 0.001
1870 reflections	Δρmax = 0.24 e Å^−3
200 parameters	Δρmin = −0.26 e Å^−3
1 restraint	Extinction correction: SHELXTL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.030 (4)

Special details

Experimental. The data collection covered over a hemisphere of reciprocal space by a combination of three sets of exposures; each set had a different ϕ angle (0, 88 and 180°) for the crystal and each exposure of 30 s covered 0.3° in ω. The crystal-to-detector distance was 4 cm and the detector swing angle was -35°. Crystal decay was monitored by repeating fifty initial frames at the end of data collection and analysing the intensity of duplicate reflections, and was found to be negligible.

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
N1	0.47535 (8)	0.3756 (3)	0.6221 (3)	0.0304 (5)
N2	0.40811 (8)	0.3651 (3)	0.8404 (4)	0.0303 (5)
N3	0.47249 (7)	0.1258 (3)	0.8451 (4)	0.0313 (5)
N4	0.41215 (7)	0.1310 (3)	0.6020 (3)	0.0245 (5)
C1	0.50360 (9)	0.2521 (4)	0.7393 (5)	0.0338 (6)
H1A	0.5233	0.3280	0.8198	0.041*
H1B	0.5260	0.1778	0.6672	0.041*
C2	0.44119 (11)	0.4846 (3)	0.7354 (4)	0.0343 (6)
H2A	0.4602	0.5629	0.8160	0.041*
H2B	0.4216	0.5664	0.6599	0.041*
C3	0.44570 (10)	0.2580 (4)	0.5021 (4)	0.0299 (6)
H3A	0.4675	0.1837	0.4277	0.036*
H3B	0.4263	0.3379	0.4242	0.036*
C4	0.37993 (8)	0.2472 (4)	0.7168 (4)	0.0294 (6)
H4A	0.3595	0.3265	0.6417	0.035*
H4B	0.3582	0.1660	0.7849	0.035*
C5	0.44293 (10)	0.0138 (3)	0.7209 (4)	0.0300 (6)
H5A	0.4218	−0.0697	0.7887	0.036*
H5B	0.4647	−0.0628	0.6485	0.036*
C6	0.43873 (10)	0.2436 (4)	0.9518 (4)	0.0332 (7)
H6A	0.4176	0.1633	1.0231	0.040*
H6B	0.4579	0.3204	1.0332	0.040*
O2	0.24422 (11)	−0.7869 (3)	0.4360 (4)	0.0626 (8)
O3	0.32498 (6)	−0.1490 (3)	0.6078 (3)	0.0324 (5)
O1	0.38307 (7)	−0.0747 (3)	0.3227 (3)	0.0375 (5)
C7	0.35748 (8)	−0.2367 (3)	0.3297 (4)	0.0269 (6)
C8	0.36169 (9)	−0.3623 (4)	0.1876 (4)	0.0336 (7)
H8	0.3820	−0.3339	0.0911	0.040*
C9	0.33566 (9)	−0.5292 (4)	0.1902 (4)	0.0331 (6)
H9	0.3394	−0.6140	0.0966	0.040*
C10	0.30433 (8)	−0.5712 (4)	0.3297 (4)	0.0277 (6)
C11	0.29899 (8)	−0.4437 (4)	0.4721 (4)	0.0247 (5)
H11	0.2774	−0.4701	0.5653	0.030*
C12	0.32581 (8)	−0.2799 (3)	0.4733 (4)	0.0237 (5)
C13	0.27700 (11)	−0.7489 (4)	0.3307 (5)	0.0372 (7)
C14	0.29172 (11)	−0.1858 (5)	0.7514 (4)	0.0434 (8)
H14A	0.2915	−0.0812	0.8321	0.065*
H14B	0.3021	−0.2964	0.8141	0.065*
H14C	0.2591	−0.2046	0.7046	0.065*
H13	0.2876 (10)	−0.843 (4)	0.230 (4)	0.033 (8)*
H1	0.3848 (16)	−0.004 (6)	0.439 (8)	0.092 (15)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0330 (11)	0.0260 (12)	0.0321 (12)	−0.0085 (9)	0.0009 (11)	0.0014 (10)
N2	0.0335 (11)	0.0262 (11)	0.0311 (12)	0.0049 (9)	0.0017 (11)	−0.0092 (10)
N3	0.0310 (11)	0.0280 (12)	0.0349 (13)	0.0033 (9)	−0.0046 (11)	0.0055 (11)
N4	0.0268 (10)	0.0200 (10)	0.0265 (12)	−0.0038 (8)	0.0031 (10)	−0.0026 (9)
C1	0.0221 (12)	0.0379 (14)	0.0413 (16)	−0.0022 (11)	−0.0032 (13)	0.0014 (12)
C2	0.0471 (16)	0.0173 (12)	0.0385 (16)	−0.0017 (12)	−0.0063 (13)	−0.0032 (13)
C3	0.0391 (15)	0.0281 (14)	0.0225 (13)	−0.0055 (11)	0.0022 (12)	0.0013 (11)
C4	0.0243 (12)	0.0301 (13)	0.0339 (15)	0.0032 (11)	−0.0013 (13)	−0.0058 (11)
C5	0.0325 (13)	0.0188 (12)	0.0387 (17)	0.0023 (11)	0.0028 (12)	0.0033 (13)
C6	0.0397 (15)	0.0363 (16)	0.0236 (14)	−0.0048 (12)	−0.0014 (12)	−0.0004 (12)
O2	0.0854 (18)	0.0466 (13)	0.0557 (16)	−0.0291 (13)	0.0236 (15)	−0.0217 (13)
O3	0.0345 (10)	0.0301 (10)	0.0325 (11)	−0.0067 (8)	0.0142 (9)	−0.0122 (8)
O1	0.0379 (10)	0.0424 (11)	0.0321 (12)	−0.0170 (9)	0.0072 (10)	−0.0108 (10)
C7	0.0188 (11)	0.0340 (14)	0.0278 (14)	−0.0027 (10)	−0.0020 (11)	−0.0072 (12)
C8	0.0267 (12)	0.0467 (17)	0.0274 (15)	−0.0059 (12)	0.0047 (12)	−0.0130 (13)
C9	0.0279 (13)	0.0402 (15)	0.0311 (15)	0.0010 (12)	−0.0017 (13)	−0.0148 (13)
C10	0.0235 (11)	0.0277 (13)	0.0318 (14)	0.0034 (9)	−0.0054 (12)	−0.0094 (12)
C11	0.0197 (11)	0.0268 (13)	0.0277 (14)	0.0024 (9)	−0.0008 (11)	−0.0040 (11)
C12	0.0198 (11)	0.0256 (12)	0.0258 (14)	0.0043 (9)	−0.0018 (10)	−0.0086 (11)
C13	0.0428 (16)	0.0333 (15)	0.0356 (17)	−0.0032 (12)	−0.0021 (15)	−0.0100 (14)
C14	0.0520 (18)	0.0375 (16)	0.0406 (18)	−0.0097 (14)	0.0250 (15)	−0.0179 (14)

Geometric parameters (Å, º)

N1—C1	1.460 (4)	C6—H6A	0.9700
N1—C3	1.468 (3)	C6—H6B	0.9700
N1—C2	1.477 (4)	O1—C7	1.349 (3)
N2—C6	1.461 (4)	O2—C13	1.218 (4)
N2—C4	1.465 (3)	O3—C12	1.372 (3)
N2—C2	1.465 (4)	O3—C14	1.426 (3)
N3—C5	1.464 (4)	O1—H1	1.00 (5)
N3—C1	1.466 (4)	C7—C8	1.395 (4)
N3—C6	1.477 (4)	C7—C12	1.409 (4)
N4—C5	1.479 (3)	C8—C9	1.384 (4)
N4—C4	1.479 (3)	C8—H8	0.9300
N4—C3	1.486 (3)	C9—C10	1.379 (4)
C1—H1A	0.9700	C9—H9	0.9300
C1—H1B	0.9700	C10—C11	1.408 (4)
C2—H2A	0.9700	C10—C13	1.468 (4)
C2—H2B	0.9700	C11—C12	1.376 (3)
C3—H3A	0.9700	C11—H11	0.9300
C3—H3B	0.9700	C13—H13	1.05 (3)
C4—H4A	0.9700	C14—H14A	0.9600
C4—H4B	0.9700	C14—H14B	0.9600
C5—H5A	0.9700	C14—H14C	0.9600
C5—H5B	0.9700
C1—N1—C3	108.0 (2)	N3—C5—H5B	109.1
C1—N1—C2	107.6 (2)	N4—C5—H5B	109.1
C3—N1—C2	107.9 (2)	H5A—C5—H5B	107.8
C6—N2—C4	108.4 (2)	N2—C6—N3	112.4 (2)
C6—N2—C2	107.6 (2)	N2—C6—H6A	109.1
C4—N2—C2	108.4 (2)	N3—C6—H6A	109.1
C5—N3—C1	107.9 (2)	N2—C6—H6B	109.1
C5—N3—C6	108.29 (19)	N3—C6—H6B	109.1
C1—N3—C6	107.4 (2)	H6A—C6—H6B	107.9
C5—N4—C4	107.6 (2)	C12—O3—C14	115.9 (2)
C5—N4—C3	107.54 (19)	C7—O1—H1	115 (3)
C4—N4—C3	108.16 (19)	O1—C7—C8	118.6 (3)
N1—C1—N3	113.13 (18)	O1—C7—C12	122.0 (2)
N1—C1—H1A	109.0	C8—C7—C12	119.4 (2)
N3—C1—H1A	109.0	C9—C8—C7	120.0 (3)
N1—C1—H1B	109.0	C9—C8—H8	120.0
N3—C1—H1B	109.0	C7—C8—H8	120.0
H1A—C1—H1B	107.8	C10—C9—C8	120.8 (3)
N2—C2—N1	112.66 (18)	C10—C9—H9	119.6
N2—C2—H2A	109.1	C8—C9—H9	119.6
N1—C2—H2A	109.1	C9—C10—C11	119.7 (2)
N2—C2—H2B	109.1	C9—C10—C13	120.2 (3)
N1—C2—H2B	109.1	C11—C10—C13	120.1 (3)
H2A—C2—H2B	107.8	C12—C11—C10	119.9 (2)
N1—C3—N4	112.1 (2)	C12—C11—H11	120.0
N1—C3—H3A	109.2	C10—C11—H11	120.0
N4—C3—H3A	109.2	O3—C12—C11	125.0 (2)
N1—C3—H3B	109.2	O3—C12—C7	114.8 (2)
N4—C3—H3B	109.2	C11—C12—C7	120.2 (2)
H3A—C3—H3B	107.9	O2—C13—C10	124.3 (3)
N2—C4—N4	112.31 (18)	O2—C13—H13	121.4 (16)
N2—C4—H4A	109.1	C10—C13—H13	114.3 (16)
N4—C4—H4A	109.1	O3—C14—H14A	109.5
N2—C4—H4B	109.1	O3—C14—H14B	109.5
N4—C4—H4B	109.1	H14A—C14—H14B	109.5
H4A—C4—H4B	107.9	O3—C14—H14C	109.5
N3—C5—N4	112.44 (18)	H14A—C14—H14C	109.5
N3—C5—H5A	109.1	H14B—C14—H14C	109.5
N4—C5—H5A	109.1
C3—N1—C1—N3	−58.4 (3)	C2—N2—C6—N3	−59.0 (3)
C2—N1—C1—N3	57.9 (3)	C5—N3—C6—N2	−57.7 (3)
C5—N3—C1—N1	58.3 (3)	C1—N3—C6—N2	58.6 (3)
C6—N3—C1—N1	−58.3 (3)	O1—C7—C8—C9	−179.6 (3)
C6—N2—C2—N1	58.6 (3)	C12—C7—C8—C9	−1.3 (4)
C4—N2—C2—N1	−58.5 (3)	C7—C8—C9—C10	1.8 (4)
C1—N1—C2—N2	−57.8 (3)	C8—C9—C10—C11	−0.5 (4)
C3—N1—C2—N2	58.5 (3)	C8—C9—C10—C13	−179.9 (3)
C1—N1—C3—N4	58.1 (3)	C9—C10—C11—C12	−1.4 (4)
C2—N1—C3—N4	−58.0 (3)	C13—C10—C11—C12	178.0 (2)
C5—N4—C3—N1	−58.1 (3)	C14—O3—C12—C11	−3.0 (4)
C4—N4—C3—N1	57.8 (3)	C14—O3—C12—C7	177.6 (2)
C6—N2—C4—N4	−58.6 (3)	C10—C11—C12—O3	−177.5 (2)
C2—N2—C4—N4	57.9 (3)	C10—C11—C12—C7	1.9 (3)
C5—N4—C4—N2	58.3 (3)	O1—C7—C12—O3	−2.9 (3)
C3—N4—C4—N2	−57.6 (3)	C8—C7—C12—O3	178.8 (2)
C1—N3—C5—N4	−58.1 (3)	O1—C7—C12—C11	177.6 (2)
C6—N3—C5—N4	57.9 (3)	C8—C7—C12—C11	−0.6 (4)
C4—N4—C5—N3	−58.1 (3)	C9—C10—C13—O2	−170.4 (3)
C3—N4—C5—N3	58.2 (3)	C11—C10—C13—O2	10.2 (5)
C4—N2—C6—N3	58.0 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O3	1.01 (6)	2.30 (5)	2.703 (3)	102 (3)
O1—H1···N4	1.01 (6)	1.72 (5)	2.671 (3)	156 (4)
C13—H13···O2^i	1.05 (3)	2.40 (3)	3.019 (5)	117 (2)
C14—H14A···O2^ii	0.96	2.44	3.309 (4)	151
C3—H3B···Cg^iii	0.96	3.26	4.147 (3)	153
C14—H14C···Cg^iv	0.96	2.97	3.713 (3)	135

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