Logo image
Probing the Landscape of Photoactive Mixed Cocrystals: Unexpected Photostability Involving a Br/I Halogen Exchange
Journal article   Peer reviewed

Probing the Landscape of Photoactive Mixed Cocrystals: Unexpected Photostability Involving a Br/I Halogen Exchange

Tyler L. H. Ramstack, Daniel K. Unruh, Leonard R. MacGillivray and Ryan H. Groeneman
ChemPlusChem (Weinheim, Germany), Vol.91(7), e70193
07/2026
DOI: 10.1002/cplu.70193
PMID: 42402219

View Online

Abstract

The formation, structural diversity, and photoreactivity of members of a series of hydrogen‐bonded mixed cocrystals were achieved by changing the halogen atoms of trihalophenols; namely, 2,4,6‐trichlorophenol, 2,4,6‐tribromophenol, and 2,4,6‐triiodophenol. The inclusion of two isosteric hydrogen‐bond donors led to structural diversity and different photochemical behavior when combined with trans ‐1,2‐bis(4‐pyridyl)ethylene. The realization of a three‐component mixed cocrystal was achieved when combining neighboring halogen atoms such as Cl/Br and Br/I pairs. The mixed cocrystal based upon 2,4,6‐trichlorophenol and 2,4,6‐tribromophenol was the only mixed solid to undergo a [2 + 2] photocycloaddition reaction. The overall yield for the equal molar‐mixed cocrystal lies at the midpoint between the two binary cocrystals, which demonstrates that the extent of a solid‐state photoreaction can be affected using halogen exchange. The mixed cocrystal containing 2,4,6‐tribromophenol and 2,4,6‐triiodophenol yielded a different face‐to‐face π – π stacking pattern, which illustrates that the type of halogen atom can influence crystal packing. The mixed cocrystal was determined to be photostable owing to improper positioning of the carbon─carbon double bond. To test structural reliability, an additional isostructural mixed cocrystal for each system was also realized by using 1,2‐bis(4‐pyridyl)acetylene as a hydrogen‐bond acceptor.
[2+2] photocycloaddition reaction halogen exchange hydrogen bonding mixed cocrystals organic solid state

Details

Logo image