General Method for Chiral Imprinting of Sol−Gel Thin Films Exhibiting Enantioselectivity

Abstract

Chirally imprinted sol-gel thin films were fabricated through the molecular imprinting technique. The films were spin coated on glass plate substrates. Enantioselective discrimination of these films was observed toward three different templates. In each case a different enantiomer pair was selected as a template and a sol mixture was tailored accordingly. By extracting the template molecule a defined chiral cavity was created. The enantiomer pairs were (R)-and (S)-propranolol, (R)-and (S)-2,2,2-trifluoro-1-(9-anthryl) ethanol, and D-and L-3,4-dihydroxyphenylalanine (D-and L-dopa). Selective adsorption properties of the resulted films toward the imprinted molecules were measured by radioactive and fluorescence analysis. In all cases, preferred adsorption of one enantiomer was revealed. This preference was due to configuration match between the cavity and the adsorbed molecule. Nonspecific adsorption was remarkably low and was measured for reference nonimprinted films.

Recent Applications of Ionic Liquids in the Sol-Gel Process for Polymer–Silica Nanocomposites with Ionic Interfaces

“…A very illustrative example can be given by the entrapment of chiral molecules. Depending on how a chiral template is applied to the sol-gel process it can lead to the formation of quiral pores [74] that after the template removal will be selective for that enantiomer used [75], or even the whole gel structure can self-assemble to a helical structure obeying the template's chirality (Figure 3c) [76]. In the sol-gel process, ILs not only act as templates, but have ability to stabilize the structures formed, working as efficient templates/solvents [67] and, in some cases templates/solvents/reactants [77].…”

Biomimetic Polymers for Chiral Resolution and Antifreeze Applications

“…110 Chiral imprinting of sol-gel thin films exhibiting enantioselectivity has been developed by David Avnir's group. In a series of articles, Avnir et al [111][112] showed that template molecules such as propranolol, 2,2,2-trifluoro-1-(9-anthryl) ethanol, DOPA, and tyrosine can be used to prepare a chiral imprint sol-gel matrix. The shape of the chiral matrix is maintained when the template molecule is extracted.…”

Nano/Micro Patterning of Inorganic Thin Films

“…These techniques fall into at least two categories: vacuum-based methods such as chemical vapor deposition (CVD), 19 sputtering, 20 metal organic chemical vapor deposition (MOCVD), 21 atomic layer deposition (ALD), 22 and chemical solution methods including sol-gel, electrochemical deposition, and hydrothermal synthesis. 23,24 Vacuum-based techniques are an expensive investment, are limited to line-of-sight production, and usually require highvapor-pressure chemicals or high-purity targets as starting materials. For conventional CVD methods, precursors exhibiting volatility are needed, which requires that the precursor is liquid or solid with a low melting point.…”