Abstract
Molecular organic cage compounds have attracted considerable attention due to their potential applications in gas storage, catalysis, chemical sensing, molecular separations, etc. In this study, a homochiral pentyl cage compound was synthesized from a condensation reaction of (S,S)-1,2-pentyl-1,2-diaminoethane and 1,3,5-triformylbenzene. The imine-linked pentyl cage diluted with a polysiloxane (OV-1701) was explored as a novel stationary phase for high-resolution gas chromatographic separation of organic compounds. Some positional isomers were baseline separated on the pentyl cage-coated capillary column. In particular, various types of enantiomers including chiral alcohols, esters, ethers and epoxides can be resolved without derivatization on the pentyl cage-coated capillary column. The reproducibility of the pentyl cage-coated capillary column for separation was investigated using nitrochlorobenzene and styrene oxide as analytes. The results indicate that the column has good stability and separation reproducibility after being repeatedly used. This work demonstrates that molecular organic cage compounds could become a novel class of chiral separation media in the near future.
Highlights
The separation of chiral compounds is one of the most interesting and challenging tasks in the field of separation science [1], because enantiomers show identical chemical and physical properties in an achiral environment
The corresponding Thermogravimetric analysis (TGA) curve reveals that the pentyl cage is at least stable up to 290 ◦ C, indicating its suitability for use in gas chromatography (GC) (Figure 1a)
The inner surface of the pentyl cage-coated capillary column was characterized by SEM
Summary
The separation of chiral compounds is one of the most interesting and challenging tasks in the field of separation science [1], because enantiomers show identical chemical and physical properties in an achiral environment. Cooper and co-workers reported a series of new POCs obtained through the condensation of 1,3,5-triformylbenzene or tris(4-formylphenyl)amine with various diamines [26,27,28,29] These cage molecules can self-assemble into crystalline materials with permanent porosity through weak intermolecular forces and separate rare gases and some organic molecules [30,31]. Several homochiral POCs (e.g., CC3-R [33,34], CC9 [35] and CC10 [36]) useful as capillary GC stationary phases for enantioselective separation of enantiomers have been reported by the Cooper group and our group These POCs-based stationary phases exhibited excellent chiral recognition ability toward a wide range of chiral compounds. The pentyl cage-based capillary column offers good performance for the separation of positional isomers
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