Chalcogen Bonding in Co-Crystals: Activation through 1,4-Perfluorophenylene vs. 4,4'-Perfluorobiphenylene Cores.

The ability of alkylseleno/alkyltelluroacetylenes such as bis(selenomethylethynyl)-perfluorobenzene (4F-Se) to act as a ditopic chalcogen bond (ChB) donor in co-crystals with ditopic Lewis bases such as 4,4'-bipyridine is extended here to the octafluorobiphenylene analog, 4,4'-bis(selenomethylethynyl)-perfluorobiphenyl (8F-Se), with the more electron-rich 4,4'-bipyridylethane (bpe), showing in the 1:1 (8F-Se)•(bpe) co-crystal a shorter and more linear C-Se•••N ChB interaction than in (4F-Se)•(bpe), with Se•••N distances down to 2.958(2) Å at 150 K, i.e., a reduction ratio of 0.85 vs. the van der Waals contact distance.