C—H...π and π–π interactions in the supramolecular structure of 3-methyl-1,4-diphenyl-1H-pyrazolo[3,4-b]pyridine

The supramolecular structure of the title compound, C₁₉H₁₅N₃, is defined by π–π-stacking and C—H...π interactions. There are no conventional hydrogen bonds in the structure.

S1. Comment

Previously, we have reported different syntheses of biologically active compounds with a pyrazolo[3,4-b]pyridine skeleton. 5-Aminopyrazoles were used as starting materials with α,β-unsaturated ketones (Quiroga, Insuasty, Cruz et al., 1998; Quiroga, Cruz et al., 2001), with benzaldehydes and Meldrum's acid (Quiroga, Hormaza et al., 1998; Quiroga, Insuasty, Hormaza et al., 1998) or with dimedone (Quiroga, Mejía et al., 2001) as reactants. We now report the crystal structure of fully aromatized 3-methyl-1,4-diphenyl-1H-pyrazolo[3,4-b]pyridine, (I), which was prepared to test the synthetic application of 5-(3-aryl-2-propenylidene)-2,2-dimethyl-1,3-dioxane-4,6-diones [the structures of some examples have been reported recently; see, for example, Low et al. (2002)]. Reaction of the phenyl derivative with 5-amino-3-methyl-1-phenylpyrazole yielded (I). In this reaction, the Meldrum's acid fragment was completely eliminated, resulting in a fully aromatized product.

The pyrazole and pyridine rings in (I) are planar within experimental error and have a dihedral angle between them of 5.13 (10)°. The only other compound with a similar pyrazolo–pyridine structure reported in the Cambridge Structural Database (CSD; Version 5.22 of October 2001; Allen & Kennard, 1993) is 6-amino-5-cyano-3-methyl-1,4-diphenylpyrazolo[3,4-b]pyridine (Quiroga et al., 1999), (II), which crystallizes in space group P2₁/n. In (II), the dihedral angle between the pyrazole and pyridine rings is 3.6 (3)°. N·B. the atomic numbering differs for (I) and (II); all values are quoted with respect to the numbering of (I).

The torsion angles for the phenyl groups in (I) are given in Table 1. As can be seen from the examples given below, the conformations of the phenyl rings in compounds (I) and (II) are very similar, for example, in the case of ring 4 (atoms C41–C46) [values for (II) are given in parenthesis], C5—C4—C41—C42 = 112.8 (2)° [118.2 (5)°], but differ by nearly 23° in the case of phenyl ring 1 (atoms C11–C16), where C7A—N1—C11—C12 = 135.2 (2)° [158.0 (5)°].

In (I), the π–π stacking involves the pyridine ring of the pyrazolo–pyridine group. The ring in the molecule at (x,y,z) stacks above the ring at (-x, 2 - y, 1 - z) across the centre of inversion at (0,1.0, 1/2), with a distance of 3.563 (2) Å between the ring centroids, a perpendicular distance between the rings of 3.443 (2) Å and a centroid offset of 0.913 (2) Å, (Fig. 2a). Although compound (II) does contain a conventional N—H···N hydrogen bond, there is similar π–π stacking between the pyridine rings related by the centre of inversion at (0,1,1), with a Cg···Cg distance of 3.701 (3) Å, a perpendicular distance of 3.552 Å and an offset between the centres of 1.04 Å. Fig. 2(b) shows the stacking in (II), labelled in this case with the numbering system used for (I). Figs. 2(a) and 2(b) show the differences in the stacking in the two compounds. These differences result from the different polarizations of the pyridine rings in the the two compounds which result from the presence of the amino and cyano substituents in compound (II).

There are two C—H···π interactions involving each of phenyl rings 3 (atoms C11–C16, centroid Cg3) and 4 (atoms C41–C46, centroid Cg4). The C43—H43···Cg3ⁱⁱ [symmetry code: (ii) 1 - x, 1 - y, 1 - z] interaction (Table 2) links the molecules into centrosymmetrically related dimers via the centre of inversion at (1/2,0.5, 1/2). These dimers are then linked by a C13—H13···Cg4ⁱ [symmetry code: (i) x, y, -1 + z] interaction and the equivalent interaction via the centre at (1/2,0.5,0), so forming chains of dimers running parallel to [001]. These C—H···π and π–π interactions link the molecules into two-dimensional sheets lying parallel to (110) (Fig. 3). In (II), the equivalent ring to ring 3 is involved in a C—H···π interaction. In this case, the atom equivalent to H42 is involved in an interaction with the ring in the molecule at (0.5 - x, 0.5 + y, 1.5 - z), with an H···Cg distance of 2.85 Å, a C···Cg distance of 3.735 (5) Å and an angle at H of 160°.

S2. Experimental

An ethanol solution containing equimolar quantities of 5-(3-phenyl-2-propenylidene)-2,2-dimethyl-[1,3]dioxane-4,6-dione and 5-amino-3-methyl-1-phenylpyrazole in ethanol was heated under reflux for 2 h. The solvent was then removed under vacuum and the resulting crude solid was purified by silica-gel column chromatography using hexane/ethyl acetate (1:1 v/v) as eluant, yielding (I) (55%, m.p. 408 K). Analysis, found: C 79.9, H 5.2, N 14.7%; C₁₉ H₁₅N₃ requires: C 80.0, H 5.3, N 14.7%. Crystals suitable for single-crystal X-ray diffraction analysis were obtained from a chloroform solution.

S3. Refinement

Compound (I) crystallized in the triclinic system; space group P1 was assumed and confirmed by the analysis. H atoms were treated as riding, with C—H distances of 0.95 (aromatic) and 0.98 Å (methyl).

Computing details

Data collection: KappaCCD Server Software (Nonius, 1997); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976) and PLATON (Spek, 2002); software used to prepare material for publication: SHELXL97 and WORDPERFECT macro PRPKAPPA (Ferguson, 1999).

Figures

	Fig. 1. A view of (I) with the atomic numbering scheme. Displacement ellipsoids are plotted at the 30% probability level.
	Fig. 2. View of the π–π-stacking between the molecules in (a) and (b) (II).
	Fig. 3. View of the linked dimer chains and sheet formed by the π–π stacking in (I).

3-methyl-1,4-diphenyl-1H-pyrazolo-(3,4 - b)pyridine

Crystal data

C19H15N3	F(000) = 300
Mr = 285.34	Dx = 1.319 Mg m^−3
Triclinic, P1	Melting point: 408 K
a = 8.1392 (4) Å	Mo Kα radiation, λ = 0.71073 Å
b = 8.4351 (4) Å	Cell parameters from 3135 reflections
c = 11.3852 (6) Å	θ = 3.1–27.4°
α = 77.951 (3)°	µ = 0.08 mm^−1
β = 81.192 (2)°	T = 120 K
γ = 70.681 (2)°	Block, yellow
V = 718.39 (6) Å^3	0.20 × 0.10 × 0.10 mm
Z = 2

Data collection

Nonius KappaCCD diffractometer	3135 independent reflections
Radiation source: fine-focus sealed X-ray tube	1682 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.092
ϕ scans and ω scans with κ offsets	θmax = 27.4°, θmin = 3.1°
Absorption correction: multi-scan (DENZO-SMN; Otwinowski & Minor, 1997)	h = −10→10
Tmin = 0.945, Tmax = 0.994	k = −10→10
9243 measured reflections	l = −14→14

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)] = 0.053	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.123	H-atom parameters constrained
S = 0.94	w = 1/[σ^2(Fo^2) + (0.0455P)^2] where P = (Fo^2 + 2Fc^2)/3
3135 reflections	(Δ/σ)max < 0.001
200 parameters	Δρmax = 0.23 e Å^−3
0 restraints	Δρmin = −0.35 e Å^−3

Special details

Experimental. The program DENZO-SMN (Otwinowski & Minor, 1997) uses a scaling algorithm (Fox & Holmes, 1966) which effectively corrects for absorption effects. High redundancy data were used in the scaling program hence the 'multi-scan' code word was used. No transmission coefficients are available from the program (only scale factors for each frame). The scale factors in the experimental table are calculated from the 'size' command in the SHELXL97 input file.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
N1	0.2099 (2)	0.7124 (2)	0.36276 (14)	0.0209 (4)
C11	0.1372 (2)	0.7024 (2)	0.26026 (17)	0.0206 (5)
C12	0.1878 (3)	0.7803 (3)	0.1474 (2)	0.0251 (5)
C13	0.1172 (3)	0.7719 (3)	0.0469 (2)	0.0275 (5)
C14	−0.0047 (3)	0.6870 (3)	0.0593 (2)	0.0278 (5)
C15	−0.0542 (3)	0.6081 (3)	0.1722 (2)	0.0261 (5)
C16	0.0170 (3)	0.6147 (3)	0.2730 (2)	0.0227 (5)
N2	0.3841 (2)	0.7006 (2)	0.35580 (15)	0.0235 (4)
C3A	0.2566 (2)	0.7526 (2)	0.54031 (17)	0.0202 (5)
C3	0.4136 (3)	0.7226 (3)	0.4612 (2)	0.0216 (5)
C31	0.5912 (3)	0.7175 (3)	0.4816 (2)	0.0269 (5)
C4	0.2026 (3)	0.7966 (2)	0.65522 (17)	0.0203 (5)
C41	0.3267 (3)	0.8092 (3)	0.73378 (17)	0.0213 (5)
C42	0.4536 (3)	0.6646 (3)	0.7850 (2)	0.0264 (5)
C43	0.5646 (3)	0.6793 (3)	0.8599 (2)	0.0306 (5)
C44	0.5525 (3)	0.8376 (3)	0.8827 (2)	0.0311 (6)
C45	0.4285 (3)	0.9822 (3)	0.8311 (2)	0.0289 (5)
C46	0.3154 (3)	0.9669 (3)	0.7580 (2)	0.0249 (5)
C5	0.0263 (3)	0.8325 (3)	0.6900 (2)	0.0234 (5)
C6	−0.0886 (3)	0.8222 (3)	0.6151 (2)	0.0243 (5)
N7	−0.0434 (2)	0.7795 (2)	0.50549 (14)	0.0233 (4)
C7A	0.1285 (2)	0.7469 (2)	0.47302 (17)	0.0196 (5)
H12	0.2712	0.8394	0.1392	0.030*
H13	0.1525	0.8246	−0.0307	0.033*
H14	−0.0548	0.6827	−0.0095	0.033*
H15	−0.1376	0.5490	0.1803	0.031*
H16	−0.0163	0.5596	0.3503	0.027*
H31A	0.6714	0.6908	0.4099	0.040*
H31B	0.6323	0.6297	0.5512	0.040*
H31C	0.5871	0.8288	0.4972	0.040*
H42	0.4636	0.5558	0.7685	0.032*
H43	0.6495	0.5804	0.8957	0.037*
H44	0.6294	0.8473	0.9338	0.037*
H45	0.4211	1.0912	0.8458	0.035*
H46	0.2289	1.0658	0.7239	0.030*
H5	−0.0178	0.8650	0.7666	0.028*
H6	−0.2086	0.8474	0.6443	0.029*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0166 (9)	0.0283 (10)	0.0186 (10)	−0.0062 (7)	−0.0009 (7)	−0.0076 (8)
C11	0.0195 (11)	0.0228 (12)	0.0182 (12)	−0.0025 (9)	−0.0044 (9)	−0.0057 (9)
C12	0.0251 (12)	0.0289 (12)	0.0227 (12)	−0.0089 (10)	−0.0020 (9)	−0.0067 (10)
C13	0.0305 (13)	0.0295 (13)	0.0197 (12)	−0.0059 (10)	−0.0009 (9)	−0.0043 (10)
C14	0.0281 (13)	0.0283 (13)	0.0276 (13)	−0.0036 (10)	−0.0095 (10)	−0.0097 (10)
C15	0.0228 (12)	0.0267 (13)	0.0309 (13)	−0.0066 (9)	−0.0048 (10)	−0.0093 (10)
C16	0.0222 (12)	0.0212 (12)	0.0235 (12)	−0.0049 (9)	−0.0007 (9)	−0.0056 (9)
N2	0.0164 (10)	0.0300 (10)	0.0247 (10)	−0.0075 (8)	−0.0029 (7)	−0.0049 (8)
C3A	0.0195 (11)	0.0198 (12)	0.0213 (11)	−0.0069 (9)	−0.0034 (9)	−0.0011 (9)
C3	0.0229 (12)	0.0214 (11)	0.0213 (12)	−0.0068 (9)	−0.0051 (9)	−0.0033 (9)
C31	0.0206 (12)	0.0316 (13)	0.0289 (12)	−0.0077 (9)	−0.0025 (9)	−0.0065 (10)
C4	0.0242 (12)	0.0181 (11)	0.0170 (11)	−0.0058 (9)	−0.0020 (9)	−0.0007 (9)
C41	0.0201 (11)	0.0281 (13)	0.0164 (11)	−0.0086 (9)	0.0006 (9)	−0.0052 (9)
C42	0.0285 (12)	0.0257 (12)	0.0246 (12)	−0.0042 (10)	−0.0049 (10)	−0.0084 (10)
C43	0.0263 (13)	0.0346 (14)	0.0278 (13)	−0.0014 (10)	−0.0063 (10)	−0.0089 (11)
C44	0.0238 (13)	0.0431 (15)	0.0284 (13)	−0.0086 (11)	−0.0023 (10)	−0.0132 (11)
C45	0.0288 (13)	0.0313 (13)	0.0318 (13)	−0.0119 (10)	−0.0031 (10)	−0.0120 (11)
C46	0.0227 (12)	0.0244 (12)	0.0263 (12)	−0.0048 (9)	−0.0040 (9)	−0.0040 (10)
C5	0.0251 (12)	0.0246 (12)	0.0198 (11)	−0.0057 (9)	−0.0001 (9)	−0.0069 (9)
C6	0.0208 (12)	0.0274 (12)	0.0247 (12)	−0.0086 (9)	0.0023 (9)	−0.0057 (10)
N7	0.0201 (10)	0.0264 (10)	0.0223 (10)	−0.0063 (8)	−0.0008 (7)	−0.0041 (8)
C7A	0.0199 (12)	0.0197 (11)	0.0188 (11)	−0.0058 (9)	−0.0009 (9)	−0.0033 (9)

Geometric parameters (Å, º)

N1—C7A	1.367 (2)	C31—H31B	0.9800
N1—N2	1.380 (2)	C31—H31C	0.9800
N1—C11	1.416 (2)	C4—C5	1.377 (3)
C11—C12	1.384 (3)	C4—C41	1.489 (3)
C11—C16	1.384 (3)	C41—C46	1.384 (3)
C12—C13	1.381 (3)	C41—C42	1.396 (3)
C12—H12	0.9500	C42—C43	1.383 (3)
C13—C14	1.379 (3)	C42—H42	0.9500
C13—H13	0.9500	C43—C44	1.381 (3)
C14—C15	1.385 (3)	C43—H43	0.9500
C14—H14	0.9500	C44—C45	1.386 (3)
C15—C16	1.381 (3)	C44—H44	0.9500
C15—H15	0.9500	C45—C46	1.384 (3)
C16—H16	0.9500	C45—H45	0.9500
N2—C3	1.320 (2)	C46—H46	0.9500
C3A—C4	1.401 (3)	C5—C6	1.393 (3)
C3A—C7A	1.403 (3)	C5—H5	0.9500
C3A—C3	1.427 (3)	C6—N7	1.335 (2)
C3—C31	1.485 (3)	C6—H6	0.9500
C31—H31A	0.9800	N7—C7A	1.342 (2)
C7A—N1—N2	110.45 (15)	H31B—C31—H31C	109.5
C7A—N1—C11	129.27 (16)	C5—C4—C3A	115.83 (18)
N2—N1—C11	120.06 (15)	C5—C4—C41	121.84 (17)
C12—C11—C16	120.38 (18)	C3A—C4—C41	122.31 (18)
C12—C11—N1	119.49 (17)	C46—C41—C42	119.05 (19)
C16—C11—N1	120.12 (18)	C46—C41—C4	119.65 (18)
C13—C12—C11	119.98 (19)	C42—C41—C4	121.30 (18)
C13—C12—H12	120.0	C43—C42—C41	120.1 (2)
C11—C12—H12	120.0	C43—C42—H42	119.9
C14—C13—C12	119.8 (2)	C41—C42—H42	119.9
C14—C13—H13	120.1	C44—C43—C42	120.2 (2)
C12—C13—H13	120.1	C44—C43—H43	119.9
C13—C14—C15	120.1 (2)	C42—C43—H43	119.9
C13—C14—H14	120.0	C43—C44—C45	120.1 (2)
C15—C14—H14	120.0	C43—C44—H44	119.9
C16—C15—C14	120.4 (2)	C45—C44—H44	119.9
C16—C15—H15	119.8	C46—C45—C44	119.6 (2)
C14—C15—H15	119.8	C46—C45—H45	120.2
C15—C16—C11	119.3 (2)	C44—C45—H45	120.2
C15—C16—H16	120.3	C45—C46—C41	120.9 (2)
C11—C16—H16	120.3	C45—C46—H46	119.6
C3—N2—N1	107.08 (15)	C41—C46—H46	119.6
C4—C3A—C7A	117.68 (18)	C4—C5—C6	121.26 (18)
C4—C3A—C3	137.04 (18)	C4—C5—H5	119.4
C7A—C3A—C3	105.02 (17)	C6—C5—H5	119.4
N2—C3—C3A	110.52 (17)	N7—C6—C5	125.14 (18)
N2—C3—C31	119.84 (18)	N7—C6—H6	117.4
C3A—C3—C31	129.63 (18)	C5—C6—H6	117.4
C3—C31—H31A	109.5	C6—N7—C7A	112.52 (16)
C3—C31—H31B	109.5	N7—C7A—N1	125.41 (17)
H31A—C31—H31B	109.5	N7—C7A—C3A	127.56 (18)
C3—C31—H31C	109.5	N1—C7A—C3A	106.90 (17)
H31A—C31—H31C	109.5
C7A—N1—C11—C12	135.2 (2)	C3A—C4—C41—C46	111.6 (2)
N2—N1—C11—C12	−39.0 (3)	C5—C4—C41—C42	112.8 (2)
C7A—N1—C11—C16	−45.1 (3)	C3A—C4—C41—C42	−69.1 (3)
N2—N1—C11—C16	140.78 (18)	C46—C41—C42—C43	0.7 (3)
C16—C11—C12—C13	0.5 (3)	C4—C41—C42—C43	−178.54 (18)
N1—C11—C12—C13	−179.70 (19)	C41—C42—C43—C44	−1.1 (3)
C11—C12—C13—C14	0.5 (3)	C42—C43—C44—C45	0.3 (3)
C12—C13—C14—C15	−1.0 (3)	C43—C44—C45—C46	0.9 (3)
C13—C14—C15—C16	0.5 (3)	C44—C45—C46—C41	−1.3 (3)
C14—C15—C16—C11	0.6 (3)	C42—C41—C46—C45	0.5 (3)
C12—C11—C16—C15	−1.1 (3)	C4—C41—C46—C45	179.71 (18)
N1—C11—C16—C15	179.18 (17)	C3A—C4—C5—C6	1.0 (3)
C7A—N1—N2—C3	1.7 (2)	C41—C4—C5—C6	179.25 (19)
C11—N1—N2—C3	176.87 (18)	C4—C5—C6—N7	−0.5 (3)
N1—N2—C3—C3A	−1.0 (2)	C5—C6—N7—C7A	−0.2 (3)
N1—N2—C3—C31	−179.72 (17)	C6—N7—C7A—N1	−174.98 (19)
C4—C3A—C3—N2	−173.7 (2)	C6—N7—C7A—C3A	0.4 (3)
C7A—C3A—C3—N2	0.0 (2)	N2—N1—C7A—N7	174.47 (18)
C4—C3A—C3—C31	4.9 (4)	C11—N1—C7A—N7	−0.1 (3)
C7A—C3A—C3—C31	178.5 (2)	N2—N1—C7A—C3A	−1.7 (2)
C7A—C3A—C4—C5	−0.8 (3)	C11—N1—C7A—C3A	−176.32 (19)
C3—C3A—C4—C5	172.3 (2)	C4—C3A—C7A—N7	0.1 (3)
C7A—C3A—C4—C41	−179.03 (18)	C3—C3A—C7A—N7	−175.02 (19)
C3—C3A—C4—C41	−5.9 (4)	C4—C3A—C7A—N1	176.20 (18)
C5—C4—C41—C46	−66.5 (3)	C3—C3A—C7A—N1	1.1 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C13—H13···Cg4^i	0.95	2.74	3.543 (3)	142
C43—H43···Cg3^ii	0.95	2.79	3.579 (3)	142

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