Crystal structure and photoreactivity of a halogen-bonded cocrystal based upon 1,2-diiodoperchlorobenzene and 1,2-bis(pyridin-4-yl)ethylene
The formation of a photoreactive cocrystal based upon 1,2-diiodoperchlorobenzene (1,2-C6I2Cl4 ) and trans-1,2-bis(pyridin-4-yl)ethylene (BPE) has been achieved. The resulting cocrystal, 2(1,2-C6I2Cl4 )·(BPE) or C6Cl4I2·0.5C12H10N2, comprises planar sheets of the components held together by the combination of I⋯N halogen bonds and halogen-halogen contacts. Notably, the 1,2-C6I2Cl4 molecules π-stack in a homogeneous and face-to-face orientation that results in an infinite column of the halogen-bond donor. As a consequence of this stacking arrangement and I⋯N halogen bonds, molecules of BPE also stack in this type of pattern. In particular, neighbouring ethylene groups in BPE are found to be parallel and within the accepted distance for a photoreaction. Upon exposure to ultraviolet light, the cocrystal undergoes a solid-state [2+2] cycloaddition reaction that produces rctt-tetrakis(pyridin-4-yl)cyclobutane (TPCB) with an overall yield of 89%. A solvent-free approach utilizing dry vortex grinding of the components also resulted in a photoreactive material with a similar yield.
cocrystal, crystal engineering, halogen bonding, organic solid state, photoreactivity, [2+2] cycloaddition reaction
Bosch, Eric, Jessica D. Battle, and Ryan H. Groeneman. "Crystal structure and photoreactivity of a halogen-bonded cocrystal based upon 1, 2-diiodoperchlorobenzene and 1, 2-bis (pyridin-4-yl) ethylene." Acta Crystallographica Section C: Structural Chemistry 76, no. 6 (2020).
Acta Crystallographica Section C: Structural Chemistry