Self-assembly of chiral (1R,2S)-ephedrine and (1S,2S)-pseudoephedrine into low-dimensional aluminophosphate materials driven by their amphiphilic nature

Abstract

In an attempt to promote the crystallization of chiral inorganic frameworks, we explore the ability of chiral (1R,2S)-ephedrine and its diastereoisomer (1S,2S)-pseudoephedrine to act as organic building blocks for the crystallization of hybrid organo-inorganic aluminophosphate frameworks in the presence of fluoride. These molecules were selected because of their particular molecular asymmetric structure, which enables a rich supramolecular chemistry and a potential chiral recognition phenomenon during crystallization. Up to four new low-dimensional materials have been produced, wherein the organic molecules form an organic bilayer in-between the inorganic networks. We analyze by molecular simulations the trend of these chiral molecules to form these types of framework, which is directly related to their amphiphilic nature that triggers a strong self-assembly through hydrophobic interactions between aromatic rings and hydrophilic interactions with the fluoro-aluminophosphate inorganic units. Such a self-assembly process is strongly dependent on the concentration of the organic molecules.

Driving the Active Site Incorporation in Zeolitic Materials via the Organic Structure‐Directing Agent Through Development of H‐Bonds with Hydroxyl Groups

“…360, 440 and 470 nm, which must correspond to some minor MPS molecules arranged as dimers; though clearly minority, these species are slightly more abundant in the sample obtained at high temperature, in good agreement with our previous observations in materials obtained with ephedrine and pseudoephedrine (these results are confirmed by UV‐Vis diffuse reflectance spectroscopy by the presence of shoulders between 300 and 400 nm for the sample obtained at 180 °C, see Figure S5 in the Supporting Information). We also note that a red‐shift of the fluorescence monomer band to 320 nm, keeping the vibronic structure, which we previously assigned to monomers developing co‐planar (rather than π‐π‐stacked) interactions, [36] was not observed in this case. These results suggest that MPS protonated species pack within the AFI channels as monomers in a head‐to‐tail configuration (see inset in Figure 2), with the aromatic rings of consecutive molecules at opposite sides, preventing aromatic interactions.…”

Conformational sieving effect of organic structure-directing agents during the synthesis of zeolitic materials

“…In order to properly understand the structure-directing behavior of chiral SDAs, in our group we have been working for some time with derivatives of chiral alkaloids (1R,2S)ephedrine and (1S,2S)-pseudoephedrine during the synthesis of zeolitic nanoporous materials, especially in AlPO4 composition using secondary or tertiary amines [31][32][33][34][35][36][37][38].…”