Janus POSS Based on Mixed [2:6] Octakis-Adduct Regioisomers.

A series of regioisomeric Janus-type polyhedral oligomeric silsesquioxanes (POSS) with multiple, mixed surface functional groups has been successfully synthesized based on the cubic T8 -POSS framework in two consecutive thiol-ene reactions. The first thiol-ene addition of β-mercaptoethanol leads to a statistical mixture of multi-adducts where the regioisomers of bis-adducts (ortho, meta, and para isomers) can be isolated at synthetically useful quantities by flash column chromatography. Then, the second thiol-ene reaction readily installs a variety of functional groups onto the remaining vinyl groups of each regioisomer, providing an easy access to precisely defined, hetero-bifunctional Janus POSS nano-building blocks. The configurations and structures of the products have been unambiguously proven by using (1) H, (13) C, and (29) Si NMR spectroscopy as well as MALDI-TOF mass spectrometry.