Abstract
The mol-ecular structure of trans-bis-(pyridin-3-yl)ethyl-ene (3,3'-bpe), C12H10N2, as determined by single-crystal X-ray diffraction is reported. The mol-ecule self-assembles into two dimensional arrays by a combination of C-H⋯N hydrogen bonds and edge-to-face C-H⋯π inter-actions that stack in a herringbone arrangement perpendicular to the crystallographic c-axis. The supra-molecular 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-pyrid-yl)ethyl-ene ( n , n '-bpe, where n = n' = 2 or 4).
Highlights
The molecular structure of trans-bis(pyridin-3-yl)ethylene (3,30-bpe), C12H10N2, as determined by single-crystal X-ray diffraction is reported
The molecule selfassembles into two dimensional arrays by a combination of C—HÁ Á ÁN hydrogen bonds and edge-to-face C—HÁ Á Á interactions that stack in a herringbone arrangement perpendicular to the crystallographic c-axis
Foundational work by Schmidt and coworkers on trans-cinnamic acids led to the formation of the ‘Topochemical Postulate’, which dictated that olefins within 4.2 Aof one another are capable of undergoing the photodimerization process
Summary
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. Unlike cinnamic acid, which crystallizes in such a way that the olefins are rendered photoactive (olefins within 4.2 Aof one another), the native crystalline forms of bis(pyridyl)ethylenes are photostable (olefins separated by distances > 4.2 Ain the crystal). 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). 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
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