4,4′-Di-tert-butyl-2,2′-bipyridine

Tatiana R Amarante; Sónia Figueiredo; André D Lopes; Isabel S Gonçalves; Filipe A Almeida Paz

doi:10.1107/S1600536809029109

. 2009 Jul 31;65(Pt 8):o2047. doi: 10.1107/S1600536809029109

4,4′-Di-tert-butyl-2,2′-bipyridine

Tatiana R Amarante ^a, Sónia Figueiredo ^b, André D Lopes ^b, Isabel S Gonçalves ^a, Filipe A Almeida Paz ^a,^*

PMCID: PMC2977408 PMID: 21583710

Abstract

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

C₁₈H₂₄N₂
M _r = 268.39
Monoclinic,
a = 10.241 (5) Å
b = 6.228 (3) Å
c = 24.559 (10) Å
β = 99.75 (3)°
V = 1543.7 (12) Å³
Z = 4
Mo Kα radiation
μ = 0.07 mm⁻¹
T = 296 K
0.20 × 0.16 × 0.14 mm

Data collection

Bruker X8 Kappa CCD APEXII diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1997 ▶) T _min = 0.98, T _max = 0.99
15295 measured reflections
2722 independent reflections
1805 reflections with I > 2σ(I)
R _int = 0.044

Refinement

R[F ² > 2σ(F ²)] = 0.080
wR(F ²) = 0.217
S = 1.12
2722 reflections
187 parameters
H-atom parameters constrained
Δρ_max = 0.29 e Å⁻³
Δρ_min = −0.44 e Å⁻³

Data collection: APEX2 (Bruker, 2006 ▶); cell refinement: 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.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809029109/bg2282sup1.cif

e-65-o2047-sup1.cif^{(19.2KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809029109/bg2282Isup2.hkl

e-65-o2047-Isup2.hkl^{(133.7KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Enhanced figure: interactive version of Fig. 3

Enhanced figure: interactive version of Fig. 4

Table 1. Hydrogen-bond geometry (Å, °).

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

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Symmetry codes: (i) Inline graphic ; (ii) . Cg1 and Cg2 are the centroids of the N1,C1–C5 and N2,C6–C10 rings, respectively.

Acknowledgments

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.

supplementary crystallographic information

Comment

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 (d_D···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; d_C···_π = ca 3.78 Å; <(C12—H12A···π) = ca 140°]. A similar contact connects two adjacent aromatic rings [not shown; d_C1···_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.

Experimental

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%).