organic compounds
4,4′-Di-tert-butyl-2,2′-bipyridine
aDepartment of Chemistry, University of Aveiro, CICECO, 3810-193 Aveiro, Portugal, and bFaculty of Science and Technology, CIQA, University of the Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
*Correspondence e-mail: filipe.paz@ua.pt
In the title compound, C18H24N2, the molecular unit adopts a trans conformation around the central C—C bond [N—C—C—N torsion angle of 179.2 (3)°], with the two aromatic rings almost coplanar [dihedral angle of only 0.70 (4)°]. The crystal packing is driven by co-operative contacts involving weak C—H⋯N and C—H⋯π interactions, and also the need to fill effectively the available space.
Related literature
For related structures, see: Batsanov et al. (2007); Coelho et al. (2007); Paz & Klinowski (2003); Paz et al. (2002). For a description of the Cambridge Structural Database, see: Allen (2002).
Experimental
Crystal data
|
Refinement
|
Data collection: APEX2 (Bruker, 2006); cell SAINT-Plus (Bruker, 2005); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: DIAMOND (Brandenburg, 2009); software used to prepare material for publication: SHELXTL.
Supporting information
10.1107/S1600536809029109/bg2282sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536809029109/bg2282Isup2.hkl
4,4'-Di-tert-butyl-2,2'-dipyridyl was purchased from Sigma-Aldrich (98% purity) and used as received without further purification. Single crystals were isolated from the slow evaporation (at ambient temperature) over the period of one month from a solution of the title compound in toluene (Sigma-Aldrich, ACS reagent, >99.5%).
Hydrogen atoms bound to carbon were located at their idealized positions and were included in the final structural model in riding-motion approximation with C—H = 0.93 (aromatic C—H) or 0.96 Å (for the —CH3 moieties). The isotropic thermal displacement parameters for these atoms were fixed at 1.2 or 1.5 for the aromatic C—H or the —CH3 moieties, respectively, times Ueq(C).
Data collection: APEX2 (Bruker, 2006); cell
SAINT-Plus (Bruker,2005); data reduction: SAINT-Plus (Bruker,2005); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2009); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).C18H24N2 | F(000) = 584 |
Mr = 268.39 | Dx = 1.155 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 5252 reflections |
a = 10.241 (5) Å | θ = 3.4–25.3° |
b = 6.228 (3) Å | µ = 0.07 mm−1 |
c = 24.559 (10) Å | T = 296 K |
β = 99.75 (3)° | Plate, colourless |
V = 1543.7 (12) Å3 | 0.20 × 0.16 × 0.14 mm |
Z = 4 |
Bruker X8 Kappa CCD APEXII diffractometer | 2722 independent reflections |
Radiation source: fine-focus sealed tube | 1805 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.044 |
ω and ϕ scans | θmax = 25.3°, θmin = 3.6° |
Absorption correction: multi-scan (SADABS; Sheldrick, 1997) | h = −12→11 |
Tmin = 0.98, Tmax = 0.99 | k = −7→5 |
15295 measured reflections | l = −29→29 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.080 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.217 | H-atom parameters constrained |
S = 1.12 | w = 1/[σ2(Fo2) + (0.0449P)2 + 4.7425P] where P = (Fo2 + 2Fc2)/3 |
2722 reflections | (Δ/σ)max < 0.001 |
187 parameters | Δρmax = 0.29 e Å−3 |
0 restraints | Δρmin = −0.44 e Å−3 |
C18H24N2 | V = 1543.7 (12) Å3 |
Mr = 268.39 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 10.241 (5) Å | µ = 0.07 mm−1 |
b = 6.228 (3) Å | T = 296 K |
c = 24.559 (10) Å | 0.20 × 0.16 × 0.14 mm |
β = 99.75 (3)° |
Bruker X8 Kappa CCD APEXII diffractometer | 2722 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1997) | 1805 reflections with I > 2σ(I) |
Tmin = 0.98, Tmax = 0.99 | Rint = 0.044 |
15295 measured reflections |
R[F2 > 2σ(F2)] = 0.080 | 0 restraints |
wR(F2) = 0.217 | H-atom parameters constrained |
S = 1.12 | Δρmax = 0.29 e Å−3 |
2722 reflections | Δρmin = −0.44 e Å−3 |
187 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
N1 | 0.3249 (3) | 0.3001 (5) | 0.25918 (12) | 0.0246 (7) | |
N2 | 0.1719 (3) | 0.8151 (5) | 0.24419 (12) | 0.0243 (7) | |
C1 | 0.3931 (3) | 0.1715 (6) | 0.23049 (14) | 0.0252 (8) | |
H1 | 0.4201 | 0.0386 | 0.2456 | 0.030* | |
C2 | 0.4260 (3) | 0.2236 (6) | 0.17986 (14) | 0.0256 (9) | |
H2 | 0.4757 | 0.1284 | 0.1625 | 0.031* | |
C3 | 0.3852 (3) | 0.4166 (6) | 0.15491 (13) | 0.0227 (8) | |
C4 | 0.3118 (3) | 0.5477 (6) | 0.18389 (14) | 0.0240 (8) | |
H4 | 0.2801 | 0.6786 | 0.1689 | 0.029* | |
C5 | 0.2852 (3) | 0.4848 (6) | 0.23540 (14) | 0.0218 (8) | |
C6 | 0.2103 (3) | 0.6285 (6) | 0.26780 (14) | 0.0213 (8) | |
C7 | 0.1830 (3) | 0.5671 (6) | 0.31914 (14) | 0.0226 (8) | |
H7 | 0.2130 | 0.4351 | 0.3340 | 0.027* | |
C8 | 0.1115 (3) | 0.7010 (6) | 0.34851 (14) | 0.0233 (8) | |
C9 | 0.0721 (3) | 0.8944 (6) | 0.32347 (14) | 0.0259 (9) | |
H9 | 0.0241 | 0.9917 | 0.3409 | 0.031* | |
C10 | 0.1041 (3) | 0.9434 (6) | 0.27250 (15) | 0.0258 (9) | |
H10 | 0.0763 | 1.0752 | 0.2569 | 0.031* | |
C11 | 0.4250 (4) | 0.4806 (7) | 0.10003 (14) | 0.0272 (9) | |
C12 | 0.5727 (4) | 0.5224 (11) | 0.11030 (19) | 0.0645 (17) | |
H12A | 0.6188 | 0.3938 | 0.1238 | 0.097* | |
H12B | 0.5929 | 0.6345 | 0.1372 | 0.097* | |
H12C | 0.6000 | 0.5655 | 0.0764 | 0.097* | |
C13 | 0.3929 (6) | 0.3050 (10) | 0.05788 (19) | 0.0722 (19) | |
H13A | 0.4108 | 0.3540 | 0.0228 | 0.108* | |
H13B | 0.3009 | 0.2675 | 0.0545 | 0.108* | |
H13C | 0.4464 | 0.1813 | 0.0694 | 0.108* | |
C14 | 0.3543 (6) | 0.6789 (11) | 0.0762 (2) | 0.075 (2) | |
H14A | 0.3818 | 0.7133 | 0.0417 | 0.112* | |
H14B | 0.3754 | 0.7963 | 0.1015 | 0.112* | |
H14C | 0.2604 | 0.6542 | 0.0701 | 0.112* | |
C15 | 0.0734 (4) | 0.6350 (7) | 0.40367 (14) | 0.0277 (9) | |
C16 | 0.1739 (5) | 0.4837 (10) | 0.43529 (18) | 0.0592 (16) | |
H16A | 0.1497 | 0.4522 | 0.4705 | 0.089* | |
H16B | 0.2599 | 0.5496 | 0.4407 | 0.089* | |
H16C | 0.1761 | 0.3530 | 0.4147 | 0.089* | |
C17 | −0.0606 (5) | 0.5247 (10) | 0.39153 (18) | 0.0558 (15) | |
H17A | −0.1247 | 0.6214 | 0.3717 | 0.084* | |
H17B | −0.0877 | 0.4840 | 0.4256 | 0.084* | |
H17C | −0.0541 | 0.3989 | 0.3695 | 0.084* | |
C18 | 0.0621 (6) | 0.8287 (9) | 0.44040 (18) | 0.0594 (15) | |
H18A | −0.0077 | 0.9208 | 0.4229 | 0.089* | |
H18B | 0.1443 | 0.9062 | 0.4462 | 0.089* | |
H18C | 0.0426 | 0.7812 | 0.4753 | 0.089* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0221 (16) | 0.0236 (19) | 0.0285 (16) | −0.0027 (14) | 0.0056 (12) | −0.0015 (13) |
N2 | 0.0191 (15) | 0.0244 (19) | 0.0306 (16) | 0.0026 (14) | 0.0073 (12) | 0.0036 (14) |
C1 | 0.0225 (19) | 0.021 (2) | 0.0313 (19) | 0.0014 (16) | 0.0021 (15) | 0.0012 (16) |
C2 | 0.0210 (19) | 0.029 (2) | 0.0274 (18) | −0.0026 (17) | 0.0044 (15) | −0.0060 (16) |
C3 | 0.0175 (18) | 0.027 (2) | 0.0240 (18) | −0.0001 (16) | 0.0029 (14) | −0.0027 (16) |
C4 | 0.0197 (18) | 0.026 (2) | 0.0256 (18) | 0.0016 (16) | 0.0027 (14) | 0.0020 (16) |
C5 | 0.0166 (17) | 0.023 (2) | 0.0249 (17) | 0.0002 (16) | 0.0023 (14) | −0.0001 (15) |
C6 | 0.0165 (17) | 0.021 (2) | 0.0256 (18) | −0.0033 (15) | 0.0013 (14) | −0.0043 (15) |
C7 | 0.0215 (18) | 0.019 (2) | 0.0260 (18) | 0.0003 (16) | 0.0015 (14) | 0.0009 (15) |
C8 | 0.0178 (18) | 0.026 (2) | 0.0263 (18) | −0.0042 (16) | 0.0031 (14) | −0.0051 (16) |
C9 | 0.0205 (19) | 0.026 (2) | 0.0320 (19) | 0.0022 (16) | 0.0064 (15) | −0.0027 (16) |
C10 | 0.0198 (18) | 0.024 (2) | 0.0336 (19) | 0.0025 (16) | 0.0055 (15) | 0.0023 (17) |
C11 | 0.026 (2) | 0.033 (2) | 0.0240 (18) | −0.0017 (17) | 0.0078 (15) | 0.0013 (16) |
C12 | 0.041 (3) | 0.112 (5) | 0.043 (3) | −0.022 (3) | 0.012 (2) | 0.017 (3) |
C13 | 0.118 (5) | 0.071 (4) | 0.034 (3) | −0.030 (4) | 0.031 (3) | −0.013 (3) |
C14 | 0.102 (5) | 0.085 (5) | 0.049 (3) | 0.046 (4) | 0.045 (3) | 0.034 (3) |
C15 | 0.028 (2) | 0.033 (2) | 0.0227 (18) | 0.0033 (18) | 0.0056 (15) | −0.0009 (16) |
C16 | 0.061 (3) | 0.085 (4) | 0.036 (2) | 0.028 (3) | 0.021 (2) | 0.025 (3) |
C17 | 0.050 (3) | 0.084 (4) | 0.037 (2) | −0.031 (3) | 0.018 (2) | −0.003 (3) |
C18 | 0.100 (4) | 0.048 (3) | 0.036 (2) | 0.001 (3) | 0.028 (3) | −0.002 (2) |
N1—C5 | 1.323 (5) | C11—C12 | 1.513 (6) |
N1—C1 | 1.338 (5) | C12—H12A | 0.9600 |
N2—C6 | 1.328 (5) | C12—H12B | 0.9600 |
N2—C10 | 1.329 (5) | C12—H12C | 0.9600 |
C1—C2 | 1.381 (5) | C13—H13A | 0.9600 |
C1—H1 | 0.9300 | C13—H13B | 0.9600 |
C2—C3 | 1.382 (5) | C13—H13C | 0.9600 |
C2—H2 | 0.9300 | C14—H14A | 0.9600 |
C3—C4 | 1.385 (5) | C14—H14B | 0.9600 |
C3—C11 | 1.526 (5) | C14—H14C | 0.9600 |
C4—C5 | 1.395 (5) | C15—C16 | 1.510 (6) |
C4—H4 | 0.9300 | C15—C17 | 1.518 (6) |
C5—C6 | 1.493 (5) | C15—C18 | 1.522 (6) |
C6—C7 | 1.390 (5) | C16—H16A | 0.9600 |
C7—C8 | 1.389 (5) | C16—H16B | 0.9600 |
C7—H7 | 0.9300 | C16—H16C | 0.9600 |
C8—C9 | 1.382 (5) | C17—H17A | 0.9600 |
C8—C15 | 1.529 (5) | C17—H17B | 0.9600 |
C9—C10 | 1.381 (5) | C17—H17C | 0.9600 |
C9—H9 | 0.9300 | C18—H18A | 0.9600 |
C10—H10 | 0.9300 | C18—H18B | 0.9600 |
C11—C14 | 1.500 (6) | C18—H18C | 0.9600 |
C11—C13 | 1.503 (6) | ||
C5—N1—C1 | 115.9 (3) | H12A—C12—H12B | 109.5 |
C6—N2—C10 | 116.1 (3) | C11—C12—H12C | 109.5 |
N1—C1—C2 | 124.2 (4) | H12A—C12—H12C | 109.5 |
N1—C1—H1 | 117.9 | H12B—C12—H12C | 109.5 |
C2—C1—H1 | 117.9 | C11—C13—H13A | 109.5 |
C1—C2—C3 | 120.1 (3) | C11—C13—H13B | 109.5 |
C1—C2—H2 | 119.9 | H13A—C13—H13B | 109.5 |
C3—C2—H2 | 119.9 | C11—C13—H13C | 109.5 |
C2—C3—C4 | 115.8 (3) | H13A—C13—H13C | 109.5 |
C2—C3—C11 | 120.9 (3) | H13B—C13—H13C | 109.5 |
C4—C3—C11 | 123.3 (3) | C11—C14—H14A | 109.5 |
C3—C4—C5 | 120.4 (4) | C11—C14—H14B | 109.5 |
C3—C4—H4 | 119.8 | H14A—C14—H14B | 109.5 |
C5—C4—H4 | 119.8 | C11—C14—H14C | 109.5 |
N1—C5—C4 | 123.5 (3) | H14A—C14—H14C | 109.5 |
N1—C5—C6 | 115.7 (3) | H14B—C14—H14C | 109.5 |
C4—C5—C6 | 120.8 (3) | C16—C15—C17 | 109.5 (4) |
N2—C6—C7 | 123.1 (3) | C16—C15—C18 | 107.7 (4) |
N2—C6—C5 | 115.6 (3) | C17—C15—C18 | 108.6 (4) |
C7—C6—C5 | 121.3 (3) | C16—C15—C8 | 111.7 (3) |
C8—C7—C6 | 120.7 (4) | C17—C15—C8 | 107.8 (3) |
C8—C7—H7 | 119.7 | C18—C15—C8 | 111.6 (4) |
C6—C7—H7 | 119.7 | C15—C16—H16A | 109.5 |
C9—C8—C7 | 115.6 (3) | C15—C16—H16B | 109.5 |
C9—C8—C15 | 122.0 (3) | H16A—C16—H16B | 109.5 |
C7—C8—C15 | 122.4 (3) | C15—C16—H16C | 109.5 |
C10—C9—C8 | 120.0 (3) | H16A—C16—H16C | 109.5 |
C10—C9—H9 | 120.0 | H16B—C16—H16C | 109.5 |
C8—C9—H9 | 120.0 | C15—C17—H17A | 109.5 |
N2—C10—C9 | 124.5 (4) | C15—C17—H17B | 109.5 |
N2—C10—H10 | 117.7 | H17A—C17—H17B | 109.5 |
C9—C10—H10 | 117.7 | C15—C17—H17C | 109.5 |
C14—C11—C13 | 107.2 (4) | H17A—C17—H17C | 109.5 |
C14—C11—C12 | 109.0 (4) | H17B—C17—H17C | 109.5 |
C13—C11—C12 | 109.6 (4) | C15—C18—H18A | 109.5 |
C14—C11—C3 | 112.1 (3) | C15—C18—H18B | 109.5 |
C13—C11—C3 | 111.0 (3) | H18A—C18—H18B | 109.5 |
C12—C11—C3 | 107.9 (3) | C15—C18—H18C | 109.5 |
C11—C12—H12A | 109.5 | H18A—C18—H18C | 109.5 |
C11—C12—H12B | 109.5 | H18B—C18—H18C | 109.5 |
C5—N1—C1—C2 | 1.9 (5) | C6—C7—C8—C9 | −0.5 (5) |
N1—C1—C2—C3 | −1.7 (6) | C6—C7—C8—C15 | 176.8 (3) |
C1—C2—C3—C4 | 0.1 (5) | C7—C8—C9—C10 | 0.1 (5) |
C1—C2—C3—C11 | 177.7 (3) | C15—C8—C9—C10 | −177.2 (3) |
C2—C3—C4—C5 | 1.2 (5) | C6—N2—C10—C9 | −0.2 (5) |
C11—C3—C4—C5 | −176.3 (3) | C8—C9—C10—N2 | 0.2 (6) |
C1—N1—C5—C4 | −0.5 (5) | C2—C3—C11—C14 | 171.5 (4) |
C1—N1—C5—C6 | −179.4 (3) | C4—C3—C11—C14 | −11.1 (6) |
C3—C4—C5—N1 | −1.1 (5) | C2—C3—C11—C13 | 51.7 (5) |
C3—C4—C5—C6 | 177.8 (3) | C4—C3—C11—C13 | −131.0 (4) |
C10—N2—C6—C7 | −0.3 (5) | C2—C3—C11—C12 | −68.5 (5) |
C10—N2—C6—C5 | 179.4 (3) | C4—C3—C11—C12 | 108.9 (5) |
N1—C5—C6—N2 | 179.2 (3) | C9—C8—C15—C16 | −152.6 (4) |
C4—C5—C6—N2 | 0.2 (5) | C7—C8—C15—C16 | 30.2 (5) |
N1—C5—C6—C7 | −1.1 (5) | C9—C8—C15—C17 | 87.1 (5) |
C4—C5—C6—C7 | 179.9 (3) | C7—C8—C15—C17 | −90.1 (4) |
N2—C6—C7—C8 | 0.6 (5) | C9—C8—C15—C18 | −32.0 (5) |
C5—C6—C7—C8 | −179.0 (3) | C7—C8—C15—C18 | 150.8 (4) |
D—H···A | H···A | D···A | D—H···A |
C12—H12B···N1i | 2.74 | 3.637 (4) | 155 |
C12—H12A···Cg2ii | 3.78 | 140 | |
C1—H1···Cg1ii | 3.40 | 137 |
Symmetry codes: (i) −x+1, y+1/2, −z+1/2; (ii) −x+1, y−1/2, −z+1/2. |
Experimental details
Crystal data | |
Chemical formula | C18H24N2 |
Mr | 268.39 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 296 |
a, b, c (Å) | 10.241 (5), 6.228 (3), 24.559 (10) |
β (°) | 99.75 (3) |
V (Å3) | 1543.7 (12) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.07 |
Crystal size (mm) | 0.20 × 0.16 × 0.14 |
Data collection | |
Diffractometer | Bruker X8 Kappa CCD APEXII diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1997) |
Tmin, Tmax | 0.98, 0.99 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 15295, 2722, 1805 |
Rint | 0.044 |
(sin θ/λ)max (Å−1) | 0.602 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.080, 0.217, 1.12 |
No. of reflections | 2722 |
No. of parameters | 187 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.29, −0.44 |
Computer programs: APEX2 (Bruker, 2006), SAINT-Plus (Bruker,2005), SHELXTL (Sheldrick, 2008), DIAMOND (Brandenburg, 2009).
D—H···A | H···A | D···A | D—H···A |
C12—H12B···N1i | 2.742 | 3.637 (4) | 155 |
C12—H12A···Cg2ii | . | 3.78 | 140 |
C1—H1···Cg1ii | . | 3.40 | 137 |
Symmetry codes: (i) −x+1, y+1/2, −z+1/2; (ii) −x+1, y−1/2, −z+1/2. |
Acknowledgements
We are grateful to Fundação para a Ciência e a Tecnologia (FCT, Portugal) for their general financial support (project PTDC/QUI/71198/2006) and also for specific funding towards the purchase of the single-crystal diffractometer.
References
Allen, F. H. (2002). Acta Cryst. B58, 380–388. Web of Science CrossRef CAS IUCr Journals Google Scholar
Batsanov, A. S., Mkhalid, I. A. I. & Marder, T. B. (2007). Acta Cryst. E63, o1196–o1198. Web of Science CSD CrossRef IUCr Journals Google Scholar
Brandenburg, K. (2009). DIAMOND. Crystal Impact GbR, Bonn, Germany. Google Scholar
Bruker (2005). SAINT-Plus. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Bruker (2006). APEX2. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Coelho, A. C., Gonçalves, I. S. & Almeida Paz, F. A. (2007). Acta Cryst. E63, o1380–o1382. Web of Science CSD CrossRef IUCr Journals Google Scholar
Paz, F. A. A., Bond, A. D., Khimyak, Y. Z. & Klinowski, J. (2002). New J. Chem. 26, 381–383. Google Scholar
Paz, F. A. A. & Klinowski, J. (2003). CrystEngComm, 5, 238–244. Web of Science CSD CrossRef CAS Google Scholar
Sheldrick, G. M. (1997). SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
Organic derivatives of 2,2'-bipyridine find innumerous applications in the field of synthetic chemistry, in particular as N,N-chelating agents which are able to coordinate to a myriad of metal centres. A search in the literature and in the Cambridge Structural Database (CSD, Version of November 2008 with three updates; Allen, 2002) reveals that the title compound has been predominantely employed in the coordination chemistry field with only the structure by Batsanov et al. (2007) being of an organic crystal in which the title compound co-crystallizes with hexafluorobenzene: C18H24N2.C6F6. Following our interest on organic crystals with pyridine derivatives (Coelho et al., 2007; Paz & Klinowski, 2003; Paz et al., 2002) we wish to report the structure of the title compound (I) at 150K.
The asymmetric unit is composed of an entire molecular unit as depicted in Fig. 1. The molecule adopts in the crystal structure a trans conformation around the central C—C bond, a feature also reported by Batsanov et al. for the co-crystal with hexafluorobenzene. This conformation seems to minimize steric repulsion between the substituent tert-butyl groups and the heteroatoms from the aromatic rings. While in the structure of Batsanov et al. the 4,4'-di-tert-butyl-2,2'-dipyridyl residue is structurally located on a mirror plane, which ensures coplanarity for the two aromatic rings, in the standalone crystal here reported the atoms are located on generic positions. Nevertheless, the average planes containing the two aromatic rings subtend a dihedral angle of only ca 0.70°, with the corresponding <(N1—C5—C6—N2) torsion angle around the central bond being of 179.2 (3)°.
Individual molecules close pack in the solid state forming layers placed in the (001) plane of the unit cell (Fig. 2). The presence of the large tert-butyl groups seems to prevent the presence of π-π stacking interactions as it can be easily observed by manipulating Enhanced Fig. 4. We note the existence of a terminal —CH3 group engaged in a C—H···N hydrogen bonding interaction: even though this contact is considered as weak (dD···A being ca 3.64 Å) it is directional with <(DHA) being above 150° (Table 1). In addition, the same —CH3 group is involved in a C—H···π contact with the aromatic ring of an adjacent molecular unit [not shown; dC···π = ca 3.78 Å; <(C12—H12A···π) = ca 140°]. A similar contact connects two adjacent aromatic rings [not shown; dC1···π = ca 3.40 Å; <(C1—H1···π) = ca 137°]. Besides these weak cooperative interactions, close packing in (I) is further mediated by van der Waals interactions so to promote an effective filling of the available space. Noteworthy, in the C18H24N2.C6F6 organic crystal π-π contacts mediate the close packing because the auxiliary C6F6 molecule is small and can easily be accommodated on top of the 2,2'-dipyridyl residue.