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2,6-Diaminopyridine (26-DAP, C5H7N3) is a common intermediate in the synthesis of aromatic azo chromophores, which are widespread in the dyes and pigments industry. Sublimation of commercial 26-DAP powder yielded a new polymorph, denoted Form II, which grew as colorless orthorhombic needles. Recrystallization from acetone or toluene also yielded Form II as the major phase. Thermal analysis shows that Form II is a less stable polymorph and it converts upon heating at 335 K to the previously reported Form I.
Supporting information
CCDC reference: 1580103
Data collection: APEX2 (Bruker, 2014); cell refinement: SAINT (Bruker, 2014); data reduction: SAINT (Bruker, 2014), XPREP (Bruker, 2014) and SADABS (Bruker,
2014); program(s) used to solve structure: SHELXT2014 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: SHELXTL (Bruker, 2014); software used to prepare material for publication: XCIF (Bruker, 2014).
Crystal data top
C5H7N3 | Dx = 1.313 Mg m−3 |
Mr = 109.14 | Mo Kα radiation, λ = 0.71073 Å |
Orthorhombic, Pbca | Cell parameters from 10034 reflections |
a = 5.1217 (9) Å | θ = 3.7–19.6° |
b = 9.8397 (14) Å | µ = 0.09 mm−1 |
c = 21.914 (4) Å | T = 100 K |
V = 1104.4 (3) Å3 | Needle, colorless |
Z = 8 | 0.44 × 0.05 × 0.02 mm |
F(000) = 464 | |
Data collection top
Bruker APEX DUO/APEXII CCD diffractometer | 948 independent reflections |
Radiation source: fine-focus sealed tube | 559 reflections with I > 2σ(I) |
Multilayer mirrors monochromator | Rint = 0.180 |
profile data from φ and ω scans | θmax = 24.9°, θmin = 1.9° |
Absorption correction: multi-scan (SADABS; Bruker, 2014) | h = −6→6 |
Tmin = 0.518, Tmax = 0.745 | k = −11→11 |
8750 measured reflections | l = −25→25 |
Refinement top
Refinement on F2 | Hydrogen site location: mixed |
Least-squares matrix: full | H atoms treated by a mixture of independent and constrained refinement |
R[F2 > 2σ(F2)] = 0.056 | w = 1/[σ2(Fo2) + (0.0763P)2] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.149 | (Δ/σ)max < 0.001 |
S = 0.98 | Δρmax = 0.32 e Å−3 |
948 reflections | Δρmin = −0.24 e Å−3 |
86 parameters | Extinction correction: SHELXL2014 (Sheldrick, 2015b), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
4 restraints | Extinction coefficient: 0.018 (4) |
Special details top
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell esds are taken
into account individually in the estimation of esds in distances, angles
and torsion angles; correlations between esds in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell esds is used for estimating esds involving l.s. planes. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
N1 | 0.0267 (5) | 0.6215 (2) | 0.18272 (11) | 0.0207 (7) | |
N2 | −0.3151 (5) | 0.4730 (3) | 0.17132 (13) | 0.0272 (8) | |
H2A | −0.460 (5) | 0.456 (4) | 0.1506 (14) | 0.041* | |
H2B | −0.343 (7) | 0.487 (4) | 0.2108 (9) | 0.041* | |
N3 | 0.3660 (6) | 0.7692 (3) | 0.20060 (12) | 0.0237 (7) | |
H3A | 0.399 (7) | 0.730 (3) | 0.2371 (10) | 0.036* | |
H3B | 0.511 (5) | 0.806 (3) | 0.1854 (15) | 0.036* | |
C1 | −0.1445 (6) | 0.5638 (3) | 0.14421 (14) | 0.0231 (8) | |
C2 | −0.1450 (7) | 0.5874 (3) | 0.08154 (14) | 0.0298 (9) | |
H2 | −0.2679 | 0.5442 | 0.0555 | 0.036* | |
C3 | 0.0409 (7) | 0.6765 (4) | 0.05851 (16) | 0.0333 (10) | |
H3 | 0.0474 | 0.6948 | 0.0160 | 0.040* | |
C4 | 0.2160 (6) | 0.7385 (3) | 0.09735 (14) | 0.0257 (8) | |
H4 | 0.3418 | 0.8007 | 0.0820 | 0.031* | |
C5 | 0.2056 (6) | 0.7086 (3) | 0.15879 (13) | 0.0201 (8) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
N1 | 0.0239 (15) | 0.0110 (13) | 0.0272 (15) | 0.0011 (12) | −0.0006 (12) | −0.0004 (11) |
N2 | 0.0247 (17) | 0.0129 (14) | 0.0440 (18) | −0.0037 (13) | −0.0045 (14) | 0.0018 (12) |
N3 | 0.0268 (16) | 0.0154 (15) | 0.0289 (16) | −0.0050 (13) | −0.0012 (14) | 0.0028 (11) |
C1 | 0.0240 (18) | 0.0096 (16) | 0.0358 (18) | 0.0068 (14) | −0.0018 (16) | −0.0022 (13) |
C2 | 0.032 (2) | 0.025 (2) | 0.0318 (19) | 0.0052 (17) | −0.0055 (17) | −0.0057 (13) |
C3 | 0.038 (2) | 0.036 (2) | 0.0258 (19) | 0.0085 (18) | 0.0016 (17) | 0.0043 (15) |
C4 | 0.0289 (19) | 0.0192 (18) | 0.0290 (18) | 0.0016 (16) | −0.0001 (15) | 0.0033 (13) |
C5 | 0.0222 (18) | 0.0103 (16) | 0.0279 (18) | 0.0058 (14) | 0.0010 (14) | −0.0014 (12) |
Geometric parameters (Å, º) top
N1—C1 | 1.343 (4) | C1—C2 | 1.393 (4) |
N1—C5 | 1.360 (4) | C2—C3 | 1.389 (5) |
N2—C1 | 1.384 (4) | C2—H2 | 0.9500 |
N2—H2A | 0.886 (18) | C3—C4 | 1.378 (5) |
N2—H2B | 0.888 (18) | C3—H3 | 0.9500 |
N3—C5 | 1.368 (4) | C4—C5 | 1.379 (4) |
N3—H3A | 0.902 (18) | C4—H4 | 0.9500 |
N3—H3B | 0.891 (18) | | |
| | | |
C1—N1—C5 | 117.6 (3) | C3—C2—H2 | 121.2 |
C1—N2—H2A | 115 (2) | C1—C2—H2 | 121.2 |
C1—N2—H2B | 115 (2) | C4—C3—C2 | 120.0 (3) |
H2A—N2—H2B | 113 (3) | C4—C3—H3 | 120.0 |
C5—N3—H3A | 121 (2) | C2—C3—H3 | 120.0 |
C5—N3—H3B | 115 (2) | C3—C4—C5 | 118.9 (3) |
H3A—N3—H3B | 110 (3) | C3—C4—H4 | 120.5 |
N1—C1—N2 | 114.5 (3) | C5—C4—H4 | 120.5 |
N1—C1—C2 | 123.4 (3) | N1—C5—N3 | 114.9 (3) |
N2—C1—C2 | 122.0 (3) | N1—C5—C4 | 122.5 (3) |
C3—C2—C1 | 117.5 (3) | N3—C5—C4 | 122.6 (3) |
| | | |
C5—N1—C1—N2 | 178.0 (3) | C2—C3—C4—C5 | 1.1 (5) |
C5—N1—C1—C2 | 0.9 (4) | C1—N1—C5—N3 | 176.9 (3) |
N1—C1—C2—C3 | −0.7 (5) | C1—N1—C5—C4 | −0.2 (4) |
N2—C1—C2—C3 | −177.5 (3) | C3—C4—C5—N1 | −0.8 (5) |
C1—C2—C3—C4 | −0.4 (5) | C3—C4—C5—N3 | −177.7 (3) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N3—H3A···N1i | 0.90 (2) | 2.16 (2) | 3.054 (4) | 171 (3) |
N3—H3B···N2ii | 0.89 (2) | 2.29 (2) | 3.118 (4) | 155 (3) |
Symmetry codes: (i) x+1/2, y, −z+1/2; (ii) −x+1/2, y+1/2, z. |
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