A second monoclinic polymorph of 5,6-diphenyl-3-(2-pyrid­yl)-1,2,4-triazine

A second monoclinic polymorph of 5,6-diphenyl-3-(2-pyrid­yl)-1,2,4-triazine, C₂₀H₁₄N₄, is reported. The unit-cell dimensions and the orientation of the pyridine ring with respect to the triazine ring are different from those of the previously reported monoclinic form [Eltayeb, Teoh, Ng, Fun & Ibrahim (2007). Acta Cryst. E63, o1041–o1042]. In the crystal structure, inter­molecular C—H...N inter­actions connect the mol­ecules into chains along the c axis. The crystal packing is also stabilized by C—H...π and π–π [centroid–centroid distance 3.5917 (9) Å] inter­actions. The crystal used was twinned and the ratio of the twin components refined to 0.726 (1)/0.274 (1).

Key indicators

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.045
• wR factor = 0.117
• Data-to-parameter ratio = 20.5

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT230_ALERT_2_B Hirshfeld Test Diff for    C4     -   C8      ..       7.28 su
PLAT411_ALERT_2_B Short Inter H...H Contact  H8     ..  H8      ..       1.97 Ang.

Alert level C
PLAT066_ALERT_1_C Predicted and Reported Transmissions Identical .          ?
PLAT127_ALERT_1_C Implicit Hall Symbol  Inconsistent with Explicit     -P 2yb
PLAT230_ALERT_2_C Hirshfeld Test Diff for    C7     -   C8      ..       6.29 su
PLAT432_ALERT_2_C Short Inter X...Y Contact  C1     ..  C10     ..       3.15 Ang.

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

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   4 ALERT type 2 Indicator that the structure model may be wrong or deficient
   0 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

The 1,2,4-triazine compounds are well known natural products and show interesting biological, pharmacological and medicinal properties. The 3,5,6-trisubstituted-1,2,4-triazines are a principal class of N-donor heterocyclic ligands. Some can be active as blood platelet aggregation inhibitors and others exhibit antiviral activity, significant activity towards leukemia and ovarian cancer, and anti-HIV activity (Soudi et al., 2005; Mashly et al., 1999). Also 1,2,4-triazines have been used in analytical chemistry to determine the concentration of some trace metal ions (Almog et al., 1996; Croot & Hunter 2000).

The crystal structure of the title compound was previously reported by Eltayeb et al. (2007) in the monoclinic space group P2₁/c, with with a = 11.5830 (3), b = 11.0381 (2), c = 11.9550 (3) Å, β = 94.127 (1)°, V = 1524.53 (6) ų and Z = 4. In the present work, the compound crystallized again in the monoclinic space group P2₁/c, but with different cell parameters. The crystal used is found be twinned.

Bond lengths and angles in the title compound show normal values (Allen et al., 1987), and are comparable to those observed in the other monoclinic polymorph (Eltayeb et al., 2007) and related structures (Eltayeb, Teoh, Teh et al., 2006; Eltayeb, Guan & Yamin, 2006). The C9–C14 and C15—C20 phenyl rings are attached to the triazine ring at atoms C2 and C3, with torsion angles C3—C2—C9—C14 = 35.9 (2)° [33.36 (14)° in the other polymorph (Eltayeb et al., 2007)] and N3—C3—C15—C20 = 56.18 (18)° [51.09 (12)° in Eltayeb et al., 2007]. The triazine ring in the present structure is essentially planar, the maximum deviation from planarity is 0.035 (1) Å for atom C3. The pyridine, C9–C14 and C15–C20 rings form dihedral angles of 7.69 (7)°, 34.41 (7)° and 57.39 (7)°, respectively, with the triazine ring. In the present structure atom N4 of the pyridine ring and N1 of the triazine ring are cis with respect to the C1—C4 bond [N1—C1—C4—N4 = 9.06 (19)°] while in the other monoclinic polymorph (Eltayeb et al., 2007), the N4 and N3 atoms are cis with respect to the C1—C4 bond [N3—C1—C4—N4 = -1.04 (13)°].

In the crystal, the molecules are linked into chains along the c axis by C18—H18A···N1 hydrogen bonds (Fig. 2 and Table 1). In addition, C—H···π interactions (Table 1) involving the C9–C14 phenyl ring (centroid Cg1), and π-π stacking interactions involving the triazine ring (centroid Cg2) at (x, y, z) and the pyridine ring (centroid Cg3) at (x + 1, y,z) [Cg2···Cg3 =3.5917 (9) Å] are observed.

Related literature

For bond-length data, see: Allen et al. (1987). For biological activities and applications of triazines, see: Almog et al. (1996); Croot & Hunter (2000); Mashly et al. (1999); Soudi et al. (2005). For related structures, see: Eltayeb, Guan & Yamin (2006); Eltayeb et al. (2007); Eltayeb, Teoh, Teh et al. (2006). Cg1 is the centroid of the C9–C14 phenyl ring.

S2. Experimental

The title compound was obtained unexpectedly during our attempt to prepare a Ir^III complex with 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine. A mixture of 5,6-diphenyl-3-(2-pyridyl)- 1,2,4-triazine (0.310 g, 1.0 mmol) and IrCl₃ (0.298 g, 1.0 mmol) in acetonitrile (20 ml) was refluxed for 2 h. The resulting dark-red solution was filtered and left to evaporate slowly at room temperature. Orange crystals suitable for X-ray diffraction were obtained after a few days.

S3. Refinement

All H atoms were positioned geometrically and allowed to ride on their parent atoms, with C—H = 0.93 Å and U_iso(H) = 1.2U_eq(C). The crystal was twinned and for a successful refinement the twin law (1 0 0/0 - 1 0/-2 0 - 1) was applied. The ratio of the twin components refined to 0.726 (1)/0.274 (1).

Computing details

Data collection: APEX2 (Bruker, 2005); cell refinement: APEX2; data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 1998); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2003).

Figures

	Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids and the atomic numbering.
	Fig. 2. The crystal packing of the title compound, viewed approximately along the a axis. Hydrogen bonds are shown as dashed lines.

5,6-Diphenyl-3-(2-pyridyl)-1,2,4-triazine

Crystal data

C20H14N4	F(000) = 648
Mr = 310.35	Dx = 1.342 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yb	Cell parameters from 4476 reflections
a = 5.9729 (2) Å	θ = 1.1–30.0°
b = 13.5580 (4) Å	µ = 0.08 mm^−1
c = 19.8855 (6) Å	T = 100 K
β = 107.438 (1)°	Block, orange
V = 1536.33 (8) Å^3	0.57 × 0.16 × 0.16 mm
Z = 4

Data collection

Bruker SMART APEX II CCD area-detector diffractometer	4476 independent reflections
Radiation source: fine-focus sealed tube	4101 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.040
Detector resolution: 8.33 pixels mm^-1	θmax = 30.0°, θmin = 1.1°
ω scans	h = −8→8
Absorption correction: multi-scan (SADABS; Bruker, 2005)	k = −19→19
Tmin = 0.954, Tmax = 0.987	l = −27→27
38187 measured reflections

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)] = 0.045	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.117	H-atom parameters constrained
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0596P)^2 + 0.4643P] where P = (Fo^2 + 2Fc^2)/3
4476 reflections	(Δ/σ)max = 0.001
218 parameters	Δρmax = 0.34 e Å^−3
0 restraints	Δρmin = −0.38 e Å^−3

Special details

Experimental. The low-temparture data was collected with the Oxford Cyrosystem Cobra low-temperature attachment.

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	0.0885 (2)	0.63510 (9)	0.19330 (6)	0.0209 (2)
N2	0.2552 (2)	0.69821 (9)	0.18859 (6)	0.0196 (2)
N3	−0.1071 (2)	0.65178 (9)	0.07043 (6)	0.0200 (2)
N4	−0.2802 (3)	0.52978 (13)	0.21111 (8)	0.0375 (4)
C1	−0.0899 (2)	0.61748 (10)	0.13517 (8)	0.0190 (3)
C2	0.2460 (2)	0.73841 (9)	0.12619 (7)	0.0170 (3)
C3	0.0653 (2)	0.71036 (10)	0.06486 (7)	0.0174 (3)
C4	−0.2826 (2)	0.55369 (10)	0.14390 (8)	0.0195 (3)
C5	−0.4601 (3)	0.47228 (15)	0.21788 (10)	0.0378 (4)
H5	−0.4614	0.4535	0.2628	0.045*
C6	−0.6398 (3)	0.44113 (11)	0.16042 (10)	0.0304 (4)
H6	−0.7617	0.4026	0.1661	0.036*
C7	−0.6335 (3)	0.46882 (15)	0.09450 (10)	0.0373 (4)
H7	−0.7528	0.4481	0.0551	0.045*
C8	−0.4566 (3)	0.52592 (13)	0.08537 (8)	0.0287 (3)
H8	−0.4550	0.5452	0.0406	0.034*
C9	0.4333 (3)	0.81146 (10)	0.12891 (7)	0.0183 (3)
C10	0.6530 (3)	0.79836 (10)	0.17869 (8)	0.0197 (3)
H10	0.6800	0.7434	0.2080	0.024*
C11	0.8312 (3)	0.86651 (11)	0.18478 (9)	0.0262 (3)
H11	0.9775	0.8565	0.2175	0.031*
C12	0.7913 (3)	0.94958 (12)	0.14202 (10)	0.0314 (3)
H12	0.9112	0.9949	0.1457	0.038*
C13	0.5719 (3)	0.96479 (11)	0.09374 (9)	0.0291 (3)
H13	0.5441	1.0213	0.0659	0.035*
C14	0.3935 (3)	0.89615 (11)	0.08669 (8)	0.0231 (3)
H14	0.2475	0.9065	0.0539	0.028*
C15	0.0542 (2)	0.74154 (10)	−0.00777 (7)	0.0177 (3)
C16	0.2385 (3)	0.72039 (11)	−0.03508 (8)	0.0217 (3)
H16	0.3721	0.6883	−0.0075	0.026*
C17	0.2210 (3)	0.74768 (11)	−0.10402 (8)	0.0238 (3)
H17	0.3423	0.7328	−0.1227	0.029*
C18	0.0233 (3)	0.79704 (11)	−0.14501 (8)	0.0239 (3)
H18	0.0135	0.8160	−0.1908	0.029*
C19	−0.1599 (3)	0.81814 (12)	−0.11768 (8)	0.0257 (3)
H19	−0.2919	0.8515	−0.1450	0.031*
C20	−0.1459 (3)	0.78941 (11)	−0.04947 (8)	0.0225 (3)
H20	−0.2701	0.8021	−0.0316	0.027*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0226 (6)	0.0209 (5)	0.0229 (6)	0.0003 (5)	0.0121 (5)	0.0018 (5)
N2	0.0201 (6)	0.0209 (5)	0.0195 (5)	0.0005 (5)	0.0084 (5)	0.0008 (4)
N3	0.0193 (6)	0.0187 (5)	0.0230 (6)	−0.0011 (5)	0.0082 (5)	−0.0008 (4)
N4	0.0257 (7)	0.0520 (9)	0.0347 (8)	0.0001 (7)	0.0088 (6)	0.0220 (7)
C1	0.0205 (6)	0.0157 (6)	0.0245 (7)	0.0009 (5)	0.0124 (5)	−0.0002 (5)
C2	0.0183 (6)	0.0168 (6)	0.0178 (6)	0.0014 (5)	0.0084 (5)	−0.0014 (5)
C3	0.0183 (6)	0.0171 (6)	0.0181 (6)	0.0007 (5)	0.0078 (5)	−0.0006 (5)
C4	0.0198 (6)	0.0158 (6)	0.0262 (7)	0.0006 (5)	0.0116 (6)	0.0006 (5)
C5	0.0262 (8)	0.0565 (11)	0.0338 (9)	0.0057 (8)	0.0136 (7)	0.0265 (8)
C6	0.0296 (8)	0.0179 (7)	0.0505 (10)	−0.0031 (6)	0.0226 (8)	0.0000 (6)
C7	0.0288 (8)	0.0528 (11)	0.0334 (9)	−0.0189 (8)	0.0142 (7)	−0.0218 (8)
C8	0.0295 (8)	0.0419 (9)	0.0192 (6)	−0.0180 (7)	0.0142 (6)	−0.0141 (6)
C9	0.0216 (7)	0.0177 (6)	0.0175 (6)	−0.0016 (5)	0.0091 (5)	−0.0033 (5)
C10	0.0207 (6)	0.0173 (6)	0.0226 (7)	0.0006 (5)	0.0086 (5)	−0.0031 (5)
C11	0.0196 (7)	0.0234 (7)	0.0358 (8)	−0.0018 (5)	0.0085 (6)	−0.0058 (6)
C12	0.0282 (8)	0.0223 (7)	0.0465 (10)	−0.0077 (6)	0.0157 (8)	−0.0033 (6)
C13	0.0396 (9)	0.0193 (7)	0.0306 (8)	−0.0047 (6)	0.0137 (7)	0.0009 (6)
C14	0.0279 (7)	0.0212 (6)	0.0197 (6)	−0.0018 (6)	0.0064 (6)	−0.0006 (5)
C15	0.0190 (6)	0.0182 (6)	0.0161 (6)	−0.0030 (5)	0.0056 (5)	−0.0008 (5)
C16	0.0205 (7)	0.0254 (7)	0.0194 (6)	0.0009 (5)	0.0066 (5)	0.0004 (5)
C17	0.0252 (7)	0.0284 (7)	0.0198 (7)	−0.0034 (6)	0.0100 (6)	−0.0019 (5)
C18	0.0283 (8)	0.0254 (7)	0.0171 (6)	−0.0071 (6)	0.0057 (6)	0.0009 (5)
C19	0.0221 (7)	0.0281 (7)	0.0237 (7)	−0.0015 (6)	0.0020 (6)	0.0050 (6)
C20	0.0184 (6)	0.0263 (7)	0.0231 (7)	−0.0006 (5)	0.0067 (5)	0.0021 (5)

Geometric parameters (Å, º)

N1—N2	1.3376 (17)	C10—C11	1.387 (2)
N1—C1	1.3381 (19)	C10—H10	0.93
N2—C2	1.3413 (18)	C11—C12	1.388 (2)
N3—C3	1.3311 (18)	C11—H11	0.93
N3—C1	1.3434 (18)	C12—C13	1.388 (3)
N4—C5	1.367 (2)	C12—H12	0.93
N4—C4	1.3711 (19)	C13—C14	1.390 (2)
C1—C4	1.4909 (19)	C13—H13	0.93
C2—C3	1.4169 (19)	C14—H14	0.93
C2—C9	1.4828 (19)	C15—C20	1.394 (2)
C3—C15	1.4872 (18)	C15—C16	1.396 (2)
C4—C8	1.361 (2)	C16—C17	1.393 (2)
C5—C6	1.379 (3)	C16—H16	0.93
C5—H5	0.93	C17—C18	1.389 (2)
C6—C7	1.375 (3)	C17—H17	0.93
C6—H6	0.93	C18—C19	1.390 (2)
C7—C8	1.365 (2)	C18—H18	0.93
C7—H7	0.93	C19—C20	1.389 (2)
C8—H8	0.93	C19—H19	0.93
C9—C10	1.398 (2)	C20—H20	0.93
C9—C14	1.4001 (19)
N2—N1—C1	118.07 (12)	C11—C10—H10	119.7
N1—N2—C2	119.98 (12)	C9—C10—H10	119.7
C3—N3—C1	116.59 (12)	C10—C11—C12	120.03 (15)
C5—N4—C4	116.87 (15)	C10—C11—H11	120.0
N1—C1—N3	125.34 (13)	C12—C11—H11	120.0
N1—C1—C4	116.46 (12)	C11—C12—C13	119.83 (15)
N3—C1—C4	118.20 (13)	C11—C12—H12	120.1
N2—C2—C3	119.79 (12)	C13—C12—H12	120.1
N2—C2—C9	114.59 (12)	C12—C13—C14	120.44 (15)
C3—C2—C9	125.62 (12)	C12—C13—H13	119.8
N3—C3—C2	119.81 (12)	C14—C13—H13	119.8
N3—C3—C15	116.10 (12)	C13—C14—C9	120.09 (15)
C2—C3—C15	124.09 (12)	C13—C14—H14	120.0
C8—C4—N4	123.42 (14)	C9—C14—H14	120.0
C8—C4—C1	118.63 (13)	C20—C15—C16	120.00 (13)
N4—C4—C1	117.88 (14)	C20—C15—C3	119.41 (13)
N4—C5—C6	122.22 (15)	C16—C15—C3	120.56 (13)
N4—C5—H5	118.9	C17—C16—C15	119.53 (14)
C6—C5—H5	118.9	C17—C16—H16	120.2
C7—C6—C5	117.99 (15)	C15—C16—H16	120.2
C7—C6—H6	121.0	C18—C17—C16	120.34 (14)
C5—C6—H6	121.0	C18—C17—H17	119.8
C8—C7—C6	121.68 (16)	C16—C17—H17	119.8
C8—C7—H7	119.2	C17—C18—C19	120.02 (14)
C6—C7—H7	119.2	C17—C18—H18	120.0
C4—C8—C7	117.79 (15)	C19—C18—H18	120.0
C4—C8—H8	121.1	C20—C19—C18	119.99 (15)
C7—C8—H8	121.1	C20—C19—H19	120.0
C10—C9—C14	118.90 (13)	C18—C19—H19	120.0
C10—C9—C2	118.61 (12)	C19—C20—C15	120.10 (14)
C14—C9—C2	122.36 (13)	C19—C20—H20	119.9
C11—C10—C9	120.68 (13)	C15—C20—H20	119.9
C1—N1—N2—C2	−2.93 (19)	N2—C2—C9—C10	32.21 (17)
N2—N1—C1—N3	5.8 (2)	C3—C2—C9—C10	−148.35 (14)
N2—N1—C1—C4	−174.83 (11)	N2—C2—C9—C14	−143.56 (14)
C3—N3—C1—N1	−2.1 (2)	C3—C2—C9—C14	35.9 (2)
C3—N3—C1—C4	178.48 (11)	C14—C9—C10—C11	−1.9 (2)
N1—N2—C2—C3	−2.89 (19)	C2—C9—C10—C11	−177.85 (13)
N1—N2—C2—C9	176.59 (11)	C9—C10—C11—C12	1.1 (2)
C1—N3—C3—C2	−4.02 (19)	C10—C11—C12—C13	0.7 (2)
C1—N3—C3—C15	175.40 (12)	C11—C12—C13—C14	−1.6 (3)
N2—C2—C3—N3	6.56 (19)	C12—C13—C14—C9	0.7 (2)
C9—C2—C3—N3	−172.86 (12)	C10—C9—C14—C13	1.1 (2)
N2—C2—C3—C15	−172.81 (13)	C2—C9—C14—C13	176.81 (13)
C9—C2—C3—C15	7.8 (2)	N3—C3—C15—C20	56.18 (18)
C5—N4—C4—C8	2.2 (2)	C2—C3—C15—C20	−124.42 (15)
C5—N4—C4—C1	179.20 (14)	N3—C3—C15—C16	−121.70 (14)
N1—C1—C4—C8	−173.80 (14)	C2—C3—C15—C16	57.69 (19)
N3—C1—C4—C8	5.7 (2)	C20—C15—C16—C17	0.2 (2)
N1—C1—C4—N4	9.06 (19)	C3—C15—C16—C17	178.04 (14)
N3—C1—C4—N4	−171.47 (14)	C15—C16—C17—C18	1.1 (2)
C4—N4—C5—C6	−1.5 (3)	C16—C17—C18—C19	−1.0 (2)
N4—C5—C6—C7	0.6 (3)	C17—C18—C19—C20	−0.3 (2)
C5—C6—C7—C8	−0.4 (3)	C18—C19—C20—C15	1.6 (2)
N4—C4—C8—C7	−2.0 (3)	C16—C15—C20—C19	−1.5 (2)
C1—C4—C8—C7	−178.98 (15)	C3—C15—C20—C19	−179.37 (13)
C6—C7—C8—C4	1.1 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C18—H18···N1^i	0.93	2.56	3.477 (2)	167
C5—H5···Cg1^ii	0.93	2.63	3.522 (2)	160

Symmetry codes: (i) x, −y+3/2, z−1/2; (ii) −x, y−1/2, −z+1/2.