Molecular Motion of Tethered Molecules in Bulk and Surface-Functionalized Materials: A Comparative Study of Confinement

Molecular imprinting science and technology: a survey of the literature for the years 2004-2011

Herein, we present a survey of the literature covering the development of molecular imprinting science and technology over the years 2004-2011. In total, 3779 references to the original papers, reviews, edited volumes and monographs from this period are included, along with recently identified uncited materials from prior to 2004, which were omitted in the first instalment of this series covering the years 1930-2003. In the presentation of the assembled references, a section presenting reviews and monographs covering the area is followed by sections describing fundamental aspects of molecular imprinting including the development of novel polymer formats. Thereafter, literature describing efforts to apply these polymeric materials to a range of application areas is presented. Current trends and areas of rapid development are discussed.

Pyrolysis of phenethyl phenyl ether tethered in mesoporous silica. Effects of confinement and surface spacer molecules on product selectivity

There has been expanding interest in exploring porous metal oxides as a confining environment for organic molecules resulting in altered chemical and physical properties including chemical transformations. In this paper, we examine the pyrolysis behavior of phenethyl phenyl ether (PPE) confined in mesoporous silica by covalent tethers to the pore walls as a function of tether density and the presence of cotethered surface spacer molecules of varying structure (biphenyl, naphthyl, octyl, and hexadecyl). The PPE pyrolysis product selectivity, which is determined by two competitive free-radical pathways cycling through the two aliphatic radical intermediates (PhCH·CH(2)OPh and PhCH(2)CH·OPh), is shown to be significantly different from that measured in the liquid phase as well as for PPE tethered to the exterior surface of nonporous silica nanoparticles. Tailoring the pore surface with spacer molecules further alters the selectivity such that the PPE reaction channel involving a molecular rearrangement (O-C phenyl shift in PhCH(2)CH·OPh), which accounts for 25% of the products in the liquid phase, can be virtually eliminated under pore confinement conditions. The origin of this change in selectivity is discussed in the context of steric constraints on the rearrangement path inside the pores, surface and pore confinement effects, pore surface curvature, and hydrogen bonding of PPE with residual surface silanols supplemented by nitrogen physisorption data and molecular dynamics simulations.

Investigation of the hydrophobization efficiency of terbium-exchanged BEA zeolites by means of FT-IR, TGA, physical adsorption, and time-resolved photoluminescence

Terbium-exchanged BEA zeolites were hydrophobized with phenyl-, vinyl-, and hexadecyltrimethoxysilanes by means of postsynthesis grafting. These materials were investigated using XRD, FT-IR, TGA, physical adsorption, and photoluminescence. Different methods for the analysis of the non-exponential decay of terbium photoluminescence in BEA zeolites were used ranging from discrete exponential to more complex approaches based on maximum entropy and global analysis. Two groups of decay times varying between 480 and 580 micros and 1-1.3 ms were assigned to the lifetimes of terbium exposed to water (unprotected) and protected by the organic groups, respectively. Our results showed that the preservation of terbium PL properties against detrimental effects of moisture adsorption could be ordered in the following sequence: hexadecyl > phenyl approximately vinyl. The photoluminescence results were in good agreement with the FT-IR, TGA, and physical adsorption data.