research communications
X-ray trans-bis(pyridin-3-yl)ethylene: comparing the supramolecular structural features among the symmetrical bis(n-pyridyl)ethylenes (n = 2, 3, or 4) constitutional isomers
ofaDepartment of Chemistry, University of Iowa, 305 Chemistry Building, Iowa City, IA 52242-1290, USA, and bRigaku Oxford Diffraction, 9009 New Trails Dr., The Woodlands, TX 77381, USA
*Correspondence e-mail: len-macgillivray@uiowa.edu
The molecular structure of trans-bis(pyridin-3-yl)ethylene (3,3′-bpe), C12H10N2, as determined by single-crystal X-ray diffraction is reported. The molecule self-assembles into two dimensional arrays by a combination of C—H⋯N hydrogen bonds and edge-to-face C—H⋯π interactions that stack in a herringbone arrangement perpendicular to the crystallographic c-axis. The supramolecular forces that direct the packing of 3,3′-bpe as well as its packing assembly within the crystal are also compared to those observed within the structures of the other symmetrical isomers trans-1,2-bis(n-pyridyl)ethylene (n,n′-bpe, where n = n′ = 2 or 4).
Keywords: crystal structure; bis(pyridin-3-yl)ethylene; olefin.
CCDC reference: 1985201
1. Chemical context
Bis(pyridyl)ethylenes have arisen as somewhat of a natural extension of cinnamic acid as a series of molecules capable of undergoing [2+2] photodimerization in the solid state to generate cyclobutanes. Foundational work by Schmidt and coworkers on trans-cinnamic acids led to the formation of the `Topochemical Postulate', which dictated that within 4.2 Å of one another are capable of undergoing the photodimerization process. Unlike cinnamic acid, which crystallizes in such a way that the are rendered photoactive (olefins within 4.2 Å of one another), the native crystalline forms of bis(pyridyl)ethylenes are photostable (olefins separated by distances > 4.2 Å in the crystal). To achieve photoreactivity of these it often becomes necessary to use a `molecular template' that can interact with the olefin-containing bipyridine via supramolecular interactions such as hydrogen bonding, halogen bonding, argento- and aurophilic interactions, and dative N→B interactions. Analyses of the crystal structures of symmetric bis(pyridyl)ethylenes derivatives such as the trans-bis(n-pyridyl)ethylenes series of isomers (n = 2, 3 or 4) is necessary to understand the forces that govern their crystallization, why they are photostable, and why use templates to achieve photoreactivity (Campillo-Alvarado et al., 2019; Chanthapally et al., 2014; MacGillivray et al., 2008; Pahari et al., 2019; Sezer et al., 2017; Volodin et al., 2018).
2. Structural commentary
The alkene 3,3′-bpe crystallizes in the centrosymmetric monoclinic P21/n (Fig. 1). The consists of one-half molecule of 3,3′-bpe with the C=C bond sitting on a crystallographic center of inversion. The pyridyl rings adopt an anti-conformation with respect to each other (Fig. 1).
3. Supramolecular features
Adjacent 3,3′-bpe molecules interact primarily via edge-to-face C—H⋯π[d(C6⋯pyr) 3.58 Å; Θ(C6—H6⋯pyr) 131.8°] forces between pyridyl rings (Fig. 2). Those rings also participate in C—H⋯N [d(C4⋯N1) 3.59 Å; Θ(C4—H4⋯N1) 139.5°] hydrogen bonds (Fig. 2). The forces generate nearly planar sheets (Fig. 3), which aggregate into a herringbone arrangement of adjacent sheets (Fig. 4). Nearest-neighbor alkene C=C bonds of 3,3′-bpe between adjacent sheets reveals a parallel, but offset orientation of the neighboring relative to one another at a distance of 5.50 Å. The distance exceeds the inter-alkene separation of Schmidt for photodimerizarion and suggests that 3,3′-bpe is photostable (Schmidt, 1971).
4. Database survey
For the n,n′-bpe (where: n = n′ = 2, 3, or 4) series of symmetric all three adopt nearly planar conformations (Table 1), with the pyridyl rings of 3,3′-bpe and 2,2′-bpe adopting anti-conformations with respect to each other. The packings of the symmetric are defined by combinations of C—H⋯π and/or C—H⋯N hydrogen bonds (Table 1) to form either one-dimensional chain (2,2′-bpe, Fig. 5) or two-dimensional sheet (3,3′-bpe and 4,4′-bpe) structures (Fig. 6). Similar to 3,3′-bpe, the alkene C=C bonds of 2,2′-bpe (6.09 Å; Vansant et al., 1980) and 4,4′-bpe (5.72 Å; Tinnemans et al., 2018) (Table 1) are beyond the separation distance of Schmidt (1971).
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5. Synthesis and crystallization
The alkene 3,3′-bpe was prepared as described (Quentin et al., 2020; Gordillo et al., 2007, 2013) via a one-pot, aqueous Pd-catalyzed Hiyama-Heck cross-coupling between 3-bromopyridine and triethoxyvinylsilane (2:1 molar ratio) (Fig. 7). Flash (SiO2, 10% MeOH/CH2Cl2) furnished 3,3′-bpe as yellow crystals: 222.3 mg (23%). A portion of 3,3′-bpe was dissolved in CHCl3 and allowed to slowly evaporate at room temperature. Single crystals in the form of colorless plates suitable for single crystal X-ray diffraction formed within seven days.
6. Refinement
Crystal data, data collection and structure 3,3′-bpe are summarized in Table 2. All non-hydrogen atoms were refined anisotropically. Hydrogen atoms were located in the difference-Fourier map and freely refined with 0.93 < C—H < 0.99 Å. of the hydrogen atoms led to a data-to-parameter ratio of ∼10. The single-crystal data were collected at room temperature to best reflect conditions under which photochemical reactions are typically conducted. Room-temperature data can also lead to fewer reflections and/or scaling anomalies.
details forSupporting information
CCDC reference: 1985201
https://doi.org/10.1107/S2056989020015303/dj2017sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989020015303/dj2017Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S2056989020015303/dj2017Isup3.cml
Data collection: HKL SCALEPACK (Otwinowski & Minor, 1997); cell
COLLECT (Nonius, 1998); data reduction: HKL DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: ShelXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL (Sheldrick, 2015b); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).C12H10N2 | F(000) = 192 |
Mr = 182.22 | Dx = 1.269 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
a = 7.4591 (7) Å | Cell parameters from 1169 reflections |
b = 5.5045 (6) Å | θ = 1.0–26.7° |
c = 11.7803 (12) Å | µ = 0.08 mm−1 |
β = 99.638 (5)° | T = 296 K |
V = 476.86 (8) Å3 | Plate, colourless |
Z = 2 | 0.18 × 0.12 × 0.06 mm |
Bruker Nonius KappaCCD diffractometer | 587 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.034 |
CCD phi and ω scans | θmax = 25.0°, θmin = 3.0° |
Absorption correction: multi-scan (SADABS; Krause et al., 2015) | h = −8→8 |
Tmin = 0.989, Tmax = 0.995 | k = −6→6 |
2410 measured reflections | l = −13→13 |
836 independent reflections |
Refinement on F2 | Primary atom site location: dual |
Least-squares matrix: full | Hydrogen site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.050 | All H-atom parameters refined |
wR(F2) = 0.137 | w = 1/[σ2(Fo2) + (0.0703P)2 + 0.056P] where P = (Fo2 + 2Fc2)/3 |
S = 1.07 | (Δ/σ)max < 0.001 |
836 reflections | Δρmax = 0.13 e Å−3 |
84 parameters | Δρmin = −0.16 e Å−3 |
0 restraints |
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. |
x | y | z | Uiso*/Ueq | ||
N1 | 0.5400 (2) | 0.7577 (3) | 0.63093 (15) | 0.0609 (6) | |
C2 | 0.2479 (2) | 0.5639 (3) | 0.57302 (15) | 0.0459 (5) | |
C3 | 0.3752 (3) | 0.7464 (4) | 0.56601 (17) | 0.0537 (6) | |
C6 | 0.2998 (3) | 0.3821 (4) | 0.65272 (17) | 0.0529 (6) | |
C4 | 0.5835 (3) | 0.5788 (4) | 0.70678 (19) | 0.0564 (6) | |
C1 | 0.0695 (3) | 0.5737 (4) | 0.49890 (16) | 0.0509 (6) | |
C5 | 0.4688 (3) | 0.3894 (4) | 0.71993 (19) | 0.0556 (6) | |
H4 | 0.705 (3) | 0.590 (3) | 0.7528 (19) | 0.062 (6)* | |
H3 | 0.345 (3) | 0.875 (4) | 0.507 (2) | 0.068 (6)* | |
H5 | 0.504 (3) | 0.265 (4) | 0.7803 (18) | 0.063 (6)* | |
H6 | 0.215 (3) | 0.250 (4) | 0.6607 (17) | 0.066 (6)* | |
H1 | 0.051 (3) | 0.706 (4) | 0.4498 (19) | 0.071 (7)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0566 (11) | 0.0569 (11) | 0.0674 (11) | −0.0077 (8) | 0.0048 (9) | 0.0012 (9) |
C2 | 0.0493 (11) | 0.0476 (11) | 0.0416 (10) | −0.0010 (9) | 0.0103 (8) | −0.0024 (8) |
C3 | 0.0562 (13) | 0.0522 (13) | 0.0519 (12) | −0.0045 (9) | 0.0068 (10) | 0.0027 (10) |
C6 | 0.0491 (12) | 0.0522 (13) | 0.0585 (13) | −0.0029 (9) | 0.0120 (10) | 0.0048 (10) |
C4 | 0.0465 (12) | 0.0671 (14) | 0.0551 (12) | 0.0010 (10) | 0.0069 (10) | −0.0019 (11) |
C1 | 0.0553 (12) | 0.0526 (12) | 0.0448 (11) | −0.0034 (8) | 0.0085 (9) | 0.0020 (10) |
C5 | 0.0517 (12) | 0.0591 (13) | 0.0570 (12) | 0.0067 (9) | 0.0117 (10) | 0.0095 (10) |
N1—C3 | 1.336 (3) | C6—H6 | 0.98 (2) |
N1—C4 | 1.333 (3) | C4—C5 | 1.374 (3) |
C2—C3 | 1.395 (3) | C4—H4 | 0.98 (2) |
C2—C6 | 1.382 (3) | C1—C1i | 1.320 (4) |
C2—C1 | 1.465 (3) | C1—H1 | 0.93 (2) |
C3—H3 | 0.99 (2) | C5—H5 | 0.99 (2) |
C6—C5 | 1.372 (3) | ||
C4—N1—C3 | 116.54 (18) | N1—C4—C5 | 123.4 (2) |
C3—C2—C1 | 119.85 (19) | N1—C4—H4 | 115.2 (11) |
C6—C2—C3 | 116.44 (19) | C5—C4—H4 | 121.4 (11) |
C6—C2—C1 | 123.71 (18) | C2—C1—H1 | 115.3 (13) |
N1—C3—C2 | 124.8 (2) | C1i—C1—C2 | 127.1 (3) |
N1—C3—H3 | 116.6 (12) | C1i—C1—H1 | 117.4 (13) |
C2—C3—H3 | 118.6 (12) | C6—C5—C4 | 119.1 (2) |
C2—C6—H6 | 119.4 (12) | C6—C5—H5 | 120.0 (11) |
C5—C6—C2 | 119.80 (19) | C4—C5—H5 | 120.8 (11) |
C5—C6—H6 | 120.8 (12) | ||
N1—C4—C5—C6 | −0.5 (3) | C6—C2—C3—N1 | −0.7 (3) |
C2—C6—C5—C4 | 0.2 (3) | C6—C2—C1—C1i | 4.7 (4) |
C3—N1—C4—C5 | 0.1 (3) | C4—N1—C3—C2 | 0.5 (3) |
C3—C2—C6—C5 | 0.3 (3) | C1—C2—C3—N1 | 178.62 (17) |
C3—C2—C1—C1i | −174.6 (2) | C1—C2—C6—C5 | −178.96 (17) |
Symmetry code: (i) −x, −y+1, −z+1. |
The twist angle is defined as the angle between the plane defined by the four alkene atoms and the plane defined by either pyridine ring. |
Compound | 2,2'-bpe | 3,3'-bpe | 4,4'-bpe |
Twist angle φ (°) | 7.43 | 5.17 | 9.14 |
Solid-state packing assembly | corrugated chains | approximately planar sheets | planar sheets |
Assembly forces | edge-to-face C-H···π | edge-to-face C—H···π, C—H···N | C—H···N, face-to-face π–π |
Nearest-neighbor alkene separation (Å) | 6.09 | 5.50 | 5.72 |
Funding information
Funding for this research was provided by: National Science Foundation (grant No. DMR-1708673 to L. R. MacGillivray).
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