1,2,3-Trihydroxy­benzene–1,3,5-triazine (1/1)

In the title mol­ecular co-crystal, C₆H₆O₃·C₃H₃N₃, two hydrogen-bonded R₄⁴(18) tetra­meric arrangements of mol­ecules involving symmetry-related O—H...N hydrogen bonds link mol­ecules of 1,2,3-trihydroxy­benzene and 1,3,5-triazine to form an infinite double-chain motif. The one-dimensional array associates with neighbouring strands, via C—H...O inter­actions, to form supramolecular sheets that are stacked together by π–π inter­actions in a three-dimensional assembly.

Key indicators

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.050
• wR factor = 0.107
• Data-to-parameter ratio = 14.5

checkCIF/PLATON results

No syntax errors found



Alert level B
ABSTM02_ALERT_3_B  The ratio of expected to reported Tmax/Tmin(RR') is < 0.75
            Tmin and Tmax reported:      0.666     0.977
            Tmin(prime) and Tmax expected:      0.968     0.977
            RR(prime) =      0.688
            Please check that your absorption correction is appropriate.
PLAT061_ALERT_3_B Tmax/Tmin Range Test RR' too Large .............       0.69

   0 ALERT level A = In general: serious problem
   2 ALERT level B = Potentially serious problem
   0 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion

---

S1. Comment

Understanding the nature of non-covalent interactions is essential for the development of crystal engineering, in order to facilitate the rational design of supramolecular structures (Desiraju, 1989, 2005; Braga, 2003). As an extension of our studies of supramolecular synthons and crystal packing in molecular co-crystals formed by `acidic' and `basic' components, we now report the crystal structure of a (1/1) adduct, (I), of pyrogallol (1,2,3-trihydroxybenzene) and 1,3,5-triazine.

In the crystal structure of a (1/1) complex of pyrogallol and pyrimidine (Dobrzańska, 2005), two distinct synthons were identified, namely a heterosynthon formed via O—H···N hydrogen bonds and a homosynthon formed via weaker poorly directed O—H···O hydrogen bonds, coded as R⁴₄(18) and R₂²(10) graph sets, respectively. The crystal structure was stabilized by offset π–π and C—H···π interactions, resulting in a herringbone packing mode. The same heterosynthon was also found in another co-crystal, of pyrogallol and hexamethylenetetramine, where a three-dimensional supramolecular framework was generated by C—H···π (arene) interactions (Tremayne & Glidewell, 2000).

The title co-crystal was prepared in order to investigate the effect on the hydrogen-bonding motif of introducing an additional N acceptor site in the heterocyclic ring. The asymmetric unit consists of one molecule of each of pyrogallol and 1,3,5-triazine (Fig. 1). The molecules are held together by hydrogen-bonded O1—H1···N1, O2—H2···N3ⁱ and O3—H3···N2ⁱⁱ interactions (symmetry codes as in Table 1). This facilitates the formation of an infinite double-chain along [010] consisting of R₄⁴(18) tetrameric arrangements. The one-dimensional hydrogen-bonded chains of supramolecular heterosynthons are further linked to one another via C5—H5···O1ⁱⁱⁱ [symmetry code: (iii) 3/2 − x, 1/2 + y, 3/2 − z] interactions [C···O = 3.448 (3) Å], to form supramolecular sheets (Fig. 2). Moreover, benzene and triazine rings from adjacent parallel sheets interact via offset π–π interactions (centroid···centroid distances 3.418 and 3.621 Å), to form a three-dimensional assembly (Fig. 3).

Only R₄⁴(18) heterosynthons formed via O—H···N hydrogen bonding are present in the structure of (I), and this motif seems to be favoured in supramolecular structures comprising pyrogallol and compounds containing two or more N acceptor sites.

S2. Experimental

Colourless crystals of (I) suitable for single-crystal X-ray diffraction were obtained by slow evaporation of an ethanolic solution of 1,2,3-trihydroxybenzene and 1,3,5-triazine (1:1 molar ratio) at room temperature.

S3. Refinement

H atoms were positioned geometrically, with C—H = 0.95 Å and O—H = 0.84 Å, and were constrained to ride on their parent atoms, with U_iso(H) = 1.2 times U_eq(C,O).

Computing details

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2002); 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 (Atwood & Barbour, 2003; Barbour, 2001); software used to prepare material for publication: X-SEED.

Figures

	Fig. 1. The asymmetric unit of (I), with atom labels and 50% probability displacement ellipsoids.
	Fig. 2. A perspective view of a two-dimensional supramolecular sheet in the structure of (I). Hydrogen bonds are shown as dashed lines (N—H···N indicated in red and C—H···O in yellow).
	Fig. 3. A capped-stick representation, showing the offset π–π interactions in the crystal packing of (I) (dashed blue lines). Dashed red and yellow lines represent N—H···N and C—H···O hydrogen bonds, respectively.

1,2,3-trihydroxybenzene:1,3,5-triazine (1/1)

Crystal data

C6H6O3·C3H3N3	F(000) = 432
Mr = 207.19	Dx = 1.498 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P2yn	Cell parameters from 2011 reflections
a = 8.7299 (8) Å	θ = 2.8–27.1°
b = 10.8999 (10) Å	µ = 0.12 mm^−1
c = 9.7586 (8) Å	T = 100 K
β = 98.363 (2)°	Block, colourless
V = 918.71 (14) Å^3	0.27 × 0.25 × 0.20 mm
Z = 4

Data collection

Bruker APEX CCD area-detector diffractometer	2011 independent reflections
Radiation source: fine-focus sealed tube	1049 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.062
ω scans	θmax = 27.1°, θmin = 2.8°
Absorption correction: multi-scan (SADABS; Sheldrick, 1997)	h = −8→11
Tmin = 0.666, Tmax = 0.977	k = −13→11
5630 measured reflections	l = −11→12

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)] = 0.050	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.107	H-atom parameters constrained
S = 0.89	w = 1/[σ^2(Fo^2) + (0.0395P)^2] where P = (Fo^2 + 2Fc^2)/3
2011 reflections	(Δ/σ)max < 0.001
139 parameters	Δρmax = 0.20 e Å^−3
0 restraints	Δρmin = −0.20 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
O3	0.25207 (18)	0.89079 (14)	0.59666 (18)	0.0346 (5)
H3	0.2643	0.9670	0.5919	0.042*
O1	0.52346 (19)	0.52246 (13)	0.72620 (18)	0.0355 (5)
H1	0.4440	0.4936	0.6781	0.043*
C2	0.3880 (3)	0.7098 (2)	0.6593 (2)	0.0237 (6)
O2	0.25916 (18)	0.64060 (14)	0.61386 (18)	0.0312 (5)
H2	0.1837	0.6872	0.5885	0.037*
C4	0.5210 (3)	0.9022 (2)	0.7044 (2)	0.0303 (6)
H4	0.5213	0.9892	0.7004	0.036*
C6	0.6534 (3)	0.7129 (2)	0.7686 (2)	0.0277 (6)
H6	0.7439	0.6705	0.8090	0.033*
C3	0.3890 (3)	0.8371 (2)	0.6531 (2)	0.0247 (6)
C1	0.5214 (3)	0.6477 (2)	0.7165 (2)	0.0251 (6)
C5	0.6533 (3)	0.8389 (2)	0.7619 (2)	0.0286 (6)
H5	0.7444	0.8831	0.7968	0.034*
N2	0.2491 (2)	0.14320 (17)	0.5545 (2)	0.0266 (5)
N3	0.0615 (2)	0.28987 (17)	0.4636 (2)	0.0275 (5)
N1	0.3066 (2)	0.35516 (17)	0.5783 (2)	0.0280 (5)
C8	0.1115 (3)	0.1755 (2)	0.4894 (2)	0.0285 (6)
H8	0.0417	0.1112	0.4580	0.034*
C9	0.1645 (3)	0.3751 (2)	0.5111 (2)	0.0283 (6)
H9	0.1340	0.4582	0.4958	0.034*
C7	0.3420 (3)	0.2374 (2)	0.5965 (2)	0.0286 (6)
H7	0.4422	0.2184	0.6436	0.034*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O3	0.0300 (11)	0.0200 (9)	0.0497 (12)	0.0034 (8)	−0.0085 (9)	−0.0004 (9)
O1	0.0262 (11)	0.0250 (10)	0.0513 (12)	0.0017 (8)	−0.0079 (9)	0.0032 (9)
C2	0.0207 (14)	0.0248 (14)	0.0246 (14)	−0.0012 (11)	0.0001 (11)	−0.0012 (11)
O2	0.0232 (10)	0.0207 (9)	0.0455 (11)	0.0031 (7)	−0.0090 (9)	−0.0012 (8)
C4	0.0313 (16)	0.0233 (14)	0.0360 (16)	−0.0035 (12)	0.0036 (13)	−0.0012 (12)
C6	0.0178 (14)	0.0346 (16)	0.0297 (15)	0.0028 (12)	0.0002 (12)	0.0031 (12)
C3	0.0224 (14)	0.0248 (14)	0.0255 (14)	0.0021 (11)	−0.0008 (11)	−0.0002 (12)
C1	0.0237 (15)	0.0224 (14)	0.0294 (14)	0.0027 (11)	0.0048 (12)	−0.0004 (12)
C5	0.0209 (14)	0.0339 (16)	0.0308 (16)	−0.0072 (11)	0.0025 (12)	−0.0022 (12)
N2	0.0248 (12)	0.0242 (12)	0.0301 (12)	0.0040 (9)	0.0016 (10)	0.0012 (10)
N3	0.0279 (13)	0.0210 (11)	0.0316 (12)	0.0040 (9)	−0.0028 (10)	0.0003 (10)
N1	0.0239 (12)	0.0258 (12)	0.0330 (13)	0.0033 (9)	0.0000 (10)	0.0001 (10)
C8	0.0261 (15)	0.0270 (14)	0.0324 (16)	−0.0015 (11)	0.0037 (12)	−0.0026 (12)
C9	0.0282 (15)	0.0223 (14)	0.0343 (15)	0.0027 (12)	0.0042 (12)	−0.0006 (12)
C7	0.0205 (15)	0.0313 (16)	0.0339 (15)	0.0031 (11)	0.0033 (12)	0.0000 (12)

Geometric parameters (Å, º)

O3—C3	1.373 (3)	C6—C1	1.386 (3)
O3—H3	0.8400	C6—H6	0.9500
O1—C1	1.369 (2)	C5—H5	0.9500
O1—H1	0.8400	N2—C8	1.322 (3)
C2—O2	1.373 (3)	N2—C7	1.335 (3)
C2—C3	1.389 (3)	N3—C9	1.329 (3)
C2—C1	1.391 (3)	N3—C8	1.332 (3)
O2—H2	0.8400	N1—C7	1.326 (3)
C4—C3	1.383 (3)	N1—C9	1.334 (3)
C4—C5	1.392 (3)	C8—H8	0.9500
C4—H4	0.9500	C9—H9	0.9500
C6—C5	1.375 (3)	C7—H7	0.9500
C3—O3—H3	109.5	C6—C1—C2	120.1 (2)
C1—O1—H1	109.5	C6—C5—C4	120.6 (2)
O2—C2—C3	123.0 (2)	C6—C5—H5	119.7
O2—C2—C1	117.5 (2)	C4—C5—H5	119.7
C3—C2—C1	119.5 (2)	C8—N2—C7	114.3 (2)
C2—O2—H2	109.5	C9—N3—C8	113.7 (2)
C3—C4—C5	119.4 (2)	C7—N1—C9	113.9 (2)
C3—C4—H4	120.3	N2—C8—N3	126.2 (2)
C5—C4—H4	120.3	N2—C8—H8	116.9
C5—C6—C1	120.0 (2)	N3—C8—H8	116.9
C5—C6—H6	120.0	N3—C9—N1	126.3 (2)
C1—C6—H6	120.0	N3—C9—H9	116.9
O3—C3—C4	123.9 (2)	N1—C9—H9	116.9
O3—C3—C2	115.6 (2)	N1—C7—N2	125.7 (2)
C4—C3—C2	120.5 (2)	N1—C7—H7	117.2
O1—C1—C6	118.9 (2)	N2—C7—H7	117.2
O1—C1—C2	120.9 (2)
C5—C4—C3—O3	178.8 (2)	O2—C2—C1—C6	−177.7 (2)
C5—C4—C3—C2	0.3 (4)	C3—C2—C1—C6	0.9 (4)
O2—C2—C3—O3	−0.7 (4)	C1—C6—C5—C4	0.7 (4)
C1—C2—C3—O3	−179.2 (2)	C3—C4—C5—C6	−0.3 (4)
O2—C2—C3—C4	178.0 (2)	C7—N2—C8—N3	0.2 (4)
C1—C2—C3—C4	−0.6 (4)	C9—N3—C8—N2	−0.4 (4)
C5—C6—C1—O1	−179.0 (2)	C8—N3—C9—N1	0.4 (4)
C5—C6—C1—C2	−1.0 (4)	C7—N1—C9—N3	−0.1 (4)
O2—C2—C1—O1	0.3 (3)	C9—N1—C7—N2	−0.2 (3)
C3—C2—C1—O1	178.9 (2)	C8—N2—C7—N1	0.2 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···N1	0.84	2.08	2.863 (2)	155
O2—H2···N3^i	0.84	2.14	2.892 (2)	149
O3—H3···N2^ii	0.84	1.96	2.781 (2)	167

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