The Se ••• Hal halogen bonding: Co-crystals of selenoureas with fluorinated organohalides

Synthesis and structural characterization of binary co-crystals 1-4 is reported in the present paper. Selenourea and 1,1-dimethylselenourea were used as selenium-containing halogen bond (XB) acceptors and iodopentafluorobenzene (IPFB), 1,4-diiodotetrafluorobenzene (1,4-DIFB) and 1,4-dibromotetrafluorobenzene (1,4-DBrFB) as XB donors. A comparative analysis of the similar binary co-crystals of selenourea and thiourea with a halogen donor revealed that Se center dot center dot center dot Hal halogen bonds are up to 13.12% shorter than the sum of vdW radii, while in case of S center dot center dot center dot Hal halogen bonds this value is 11.4%. Therefore, selenium tends to form stronger bonds with halogens than sulfur does. Comparisons of XB interaction energies, Hirschfeld and QTAIM analyses of the Se and S systems supported this observation that selenium based XB acceptor results in slightly stronger Ch center dot center dot center dot Hal halogen bonding.

Automated summary

The synthesis and structural characterization of binary co-crystals 1-4 involving selenourea and halogen donors were reported. It was found that selenium forms stronger halogen bonds with halogens compared to sulfur. The interaction energies, Hirschfeld, and QTAIM analyses supported the observation that selenium-based XB acceptors result in slightly stronger halogen bonding.