Chiral Mesoporous Research Articles

Enlarged Pore Size Chiral Mesoporous Silica Nanoparticles Loaded Poorly Water-Soluble Drug Perform Superior Delivery Effect.

Large mesopores of chiral silica nanoparticles applied as drug carrier are worth studying. In this study, chiral mesoporous silica nanoparticles (CMSN) and enlarged chiral mesoporous silica nanoparticles (E-CMSN) with a particle size from 200 to 300 nm were synthesized. Fourier transform infrared spectrometer (FTIR), circular dichroism spectrum, scanning electron microscopy (SEM), transmission electron microscope (TEM), and nitrogen adsorption/desorption measurement were adopted to explore their characteristics. The results showed that the surface area, pore volume, and pore diameter of E-CMSN were higher than those of CMSN due to enlarged mesopores. Poorly water-soluble drug nimesulide (NMS) was taken as the model drug and loaded into carriers using adsorption method. After NMS was loaded into CMSN and E-CMSN, most crystalline NMS converted to amorphous phase and E-CMSN was superior. The anti-inflammatory pharmacodynamics and in vivo pharmacokinetics results were consistent with the wetting property and in vitro drug dissolution results, verifying that NMS/E-CMSN exhibited superior NMS delivery system based on its higher oral relative bioavailability and anti-inflammatory effect because its enlarge mesopores contributed to load and release more amorphous NMS. The minor variations in the synthesis process contributed to optimize the chiral nano-silica drug delivery system.

Electron Transition‐Based Optical Activity (ETOA) of Achiral Metal Oxides Derived from Chiral Mesoporous Silica

Electron Transition‐Based Optical Activity (ETOA) of Achiral Metal Oxides Derived from Chiral Mesoporous Silica

Chiral Inorganic Solid Material Development

After the invention of mesoporous, the chiral mesoporous materials had been regarded a hot research issue. Inspired by the chiral phenomenon, in this investigation, we presented several aspect of chiral mesoporous from its first appearance, especially stated the template that could be used to prepare chiral mesoporous, including chiral template and achiral template, besides, the different mechanism of some distinguished scientists’ works were introduced, and some application of these material were introduced such as catalyst, HPLC stationary phases and many other fields.

ChemInform Abstract: Chiral Mesoporous Silica: Chiral Construction and Imprinting via Cooperative Self‐Assembly of Amphiphiles and Silica Precursors

AbstractReview: 53 refs.

Chiral Mesoporous Organosilica Nanospheres: Effect of Pore Structure on the Performance in Asymmetric Catalysis

(R)-(+)-1,1'-Bi-2-naphthol ((R)-(+)-Binol)-functionalized (Binol=2,2'-dihydroxy-1,1'-binaphthyl) chiral mesoporous organosilica nanospheres with uniform particle size (100 to 300 nm) have been synthesized by co-condensation of tetraethoxysilane and (R)-2,2'-di(methoxymethyl)oxy-6,6'-di(1-propyl trimethoxysilyl)-1,1'-binaphthyl in a basic medium with cetyltrimethylammonium bromide as the template. Nanospheres with a radiative 2D hexagonal channel arrangement exhibit higher enantioselectivity and turnover frequency than those with a penetrating 2D hexagonal channel arrangement (94 versus 88 % and 43 versus 15 h(-1), respectively) in the asymmetric addition of diethylzinc to aldehydes. In addition, under similar conditions, the enantioselectivity of the nanospheres can be greatly improved as the structural order of the framework increases. These results clearly show that the structural order of nanospheres affects enantioselective reactions. The enantioselectivity of the nanospheres synthesized by the co-condensation method is higher than that of nanospheres prepared by a grafting method and even higher than that of their homogeneous counterpart. These results indicate that the bite angle of (R)-(+)-Binol bridging in a more rigid porous network is in a more favorable position for achieving higher enantioselectivity. The efficiency of a co-condensation method for the synthesis of high-performance heterogeneous asymmetric catalysts is also reported.

Chiral-mesoporous-polypyrrole nanoparticles: Its chiral recognition abilities and use in enantioselective separation

Chiral-mesoporous-polypyrrole (CMPPy) nanoparticles are synthesized by templating chiral block copolymers (CBCs) of poly(ethylene oxide), (PEO) and chiral L-/D- glutamic acid [PEO-b-(L-/D-GluA)10] and blocks of chiral L-/D-phenylalanine [PEO-b-(L-/D-Phe)10]. The well ordered chiral mesopores of nanoparticles are characterized by HRTEM and BET. The CMPPy nanoparticles have well organized pores with sizes ca. 3.5–3.7 nm in diameter and with a high surface area. These CMPPy nanoparticles are able to recognize chiral molecules. Using the selective chiral recognition abilities, the chiral resolution of the copolymer-extracted CMPPy nanoparticles and the chiral separation kinetics using a racemic mixture of valine are probed by circular dichroism (CD) and optical polarimetry. Further, the chiral resolution of the CMPPy is confirmed with a racemic mixture of alanine. The chiral selectivity factor is 5.05 for a specific enantiomer which is adsorbed preferably by the CMPPy. These results allow a new approach towards the enantiomeric separation and other enantiomeric applications of novel CMPPy.

Chiral separation abilities: Aspartic acid block copolymer-imprinted mesoporous silica

Herein we report on the synthesis of chiral mesoporous silica (CMS) that can be used for chiral separation from a racemic mixture of two enantiomers. The CMS with a pore size of 3–5 nm and a high surface area of 725 m 2 g −1 was synthesized by templating chiral block copolymers (CBCs) of polyethylene oxide (PEG) and D/L-aspartic acid (D/L-AspA), [PEO 45-b-(D/L-AspA) 10]. The chiral mesopores were characterized by HRTEM, small angle XRD and BET. The chiral resolution abilities and the chiral separation kinetics of the copolymer-extracted CMS were investigated using a racemic mixture of valine by circular dichroism (CD) and optical polarimetry. The chiral resolution of the CMS was further verified with a racemic mixture of alanine. A chiral selectivity factor of 7.52 was found for the specific enantiomer which is adsorbed preferably. These results allow a new approach towards enantiomeric separation and other enantiomeric applications of novel CMS.

Enantioselective Separation Using Chiral Mesoporous Spherical Silica Prepared by Templating of Chiral Block Copolymers

In this work, we synthesized chiral mesoporous silica (CMS) spheres, which can be used as a potential candidate for chiral separation. The CMS spheres with controllable pore sizes (of 2-3 nm) and high surface areas of ca. 614 m(2) g(-1) were synthesized by chiral templating with chiral block copolymers based on poly(ethylene oxide) and dl-glutamic acid [PEO(113)-b-(GluA)(10)]. The ordered structure of the chiral mesopores was characterized by high-resolution transmission electron microscopy, and the average pore diameters of chiral mesopores were estimated from the nitrogen adsorption-desorption measurements. The enantioselectivity properties and chiral resolution kinetics of the mesopores of silica spheres, after extraction of chiral polymers of PEO(113)-b-(l/d-GluA)(10), were scrutinized using a racemic solution of valine and measuring the circular dichroism and optical polarimetery. A chiral selectivity factor of 5.22 was found with a specific enantiomer of valine adsorbed preferably. These results raise the new possibilities of CMS spheres for enantiomeric separation and other enantioselective applications.

Formation of Chiral Mesopores in Conducting Polymers by Chiral‐Lipid‐Ribbon Templating and “Seeding” Route

AbstractConducting polymer nanofibers with controllable chiral mesopores in the size, the shape, and handedness have been synthesized by chiral lipid ribbon templating and “seeding” route. Chiral mesoporous conducting poly(pyrrole) (CMPP) synthesized with very small amount of chiral amphiphilic molecules (usually < 3%) has helically twisted channels with well‐defined controllable pore size of 5–20 nm in central axis of the twisted fibers. The structure and chirality of helical mesopores have been characterized by high‐resolution transmission electron microscope (HRTEM), scanning electron microscope (SEM) and electron tomography. The average pore diameters of chiral mesopores were approximately estimated from the N2 adsorption–desorption data and calculated by the conversion calculation from helical ribbons to a rectangular straight tape. The pore size of CMPP has been controlled by choosing different alkyl chain lengths of chiral lipid molecules or precisely adjusting the H2O/EtOH volume ratio.

Chiral Mesoporous Materials Based on the Self-Assembly

Ordered mesoporous materials with various structures are synthesized based on the self-assembly of surfactant and inorganic precursors and covered by several excellent reviews. However, less work has been directed to chiral structured mesoporous materials, although these could have wide-ranging applications on the manufacturing of enantio-pure chemicals and pharmaceuticals as catalysts and separation media with both shape selectivity and enantioselectivity. This short review will address the synthesis of chiral mesoporous materials by chiral organic compounds templating route, covering single and 2-dimensional ordered chiral channel mesoporous materials. Non-porous helical fiber, atomic-scale enantio-morphism and zeolite-like materials with three-dimensional helical pores are beyond the scope of this paper.

Structure Elucidation of the Highly Active Titanosilicate Catalyst Ti‐YNU‐1

Three novel zeolites (M-IEZ-MWW, IEZ-FER and IEZ-CDO) have been successfully synthesised from the corresponding precursors. Structure characterisation of those materials was conducted by TEM. Our studies show that the structure of the new zeolites keeps identical layer to the corresponding known 3D zeolite, except for the distinct expansion of the layer spacing. Combining with results from XRD, N2 adsorption, IR and NMR, the expansion can be explained by the pillaring of T sites between the layers. Meanwhile, the intergrowth of 3D MWW and IEZ-MWW was observed in the Al-IEZ-MWW and Si-IEZ-MWW crystals, IEZ-CDO structure was found in the IEZ-FER crystals, and the intergrowth of CDO and new polymorph was observed in the CDS-1 crystal. Moreover, two new zeolites IM-5 and SSZ-57 were also studied by TEM. We found that the space group of IM-5 is non-centrosymmetrical, and in SSZ-57 the new structure with slightly larger c parameter was observed compared to MEL. Chiral mesoporous silica nanotube and chiral mesoporous carbon nanotube were aslo investigated by TEM. We found that the former was synthesised by hollowing out process and it possesses chiral mesopores in the wall, the latter was synthesised by templating and seeding method. Electron tomography was first applied to study the handedness of the chiral mesoporous nanotube. Furthermore, TEM studies verified that bifunctional mesoporous silica has a Fm-3m structure, and mesoporous carbon FDU-16 has a Im-3m structure.

Design of a Chiral Mesoporous Silica and Its Application as a Host for Stereoselective Di-π-methane Rearrangements.

Design of a Chiral Mesoporous Silica and Its Application as a Host for Stereoselective Di-π-methane Rearrangements.

Design of a Chiral Mesoporous Silica and Its Application as a Host for Stereoselective Di-π-methane Rearrangements

[reaction: see text] A chiral periodic mesoporous organosilica (ChiMO) was prepared, in which a 1,2-bis-(ureido)cyclohexyl linker (38 wt %) is introduced into the walls of the hybrid organic-inorganic material. This silica was used as a host for 11-formyl-12-methyldibenzobarrelene (2), and the stereoselectivity of the di-pi-methane rearrangement of 2 within this host-guest complex was studied. At low conversions, the only product was the corresponding dibenzosemibullvalene. An enantiomeric excess of 24% at 11% conversion was obtained using the ChiMO as host. These values compare well with those achieved using a system based on conventional faujasites (LiY and NaY) as hosts incorporating a chiral auxiliary. We tested S-phenylglycine, S-proline, S-camphanic acid, and S-mandelic acid as chiral auxiliaries. In contrast to the behavior of the ChiMO material, adsorption of dibenzobarrelene in purely siliceous mesoporous MCM-41 silica (3.2 nm pore size) containing ephedrine failed, a failure that can be explained as arising from the large internal silanol population and high hydrophilicity of the siliceous MCM-41 sample.

Composite mesostructures by nano-confinement

In a physically confined environment, interfacial interactions, symmetry breaking, structural frustration and confinement-induced entropy loss can play dominant roles in determining molecular organization. Here we present a systematic study of the confined assembly of silica-surfactant composite mesostructures within cylindrical nanochannels of varying diameters. Using exactly the same precursors and reaction conditions that form the two-dimensional hexagonal SBA-15 mesostructured thin film, unprecedented silica mesostructures with chiral mesopores such as single- and double-helical geometries spontaneously form inside individual alumina nanochannels. On tightening the degree of confinement, a transition is observed in the mesopore morphology from a coiled cylindrical to a spherical cage-like geometry. Self-consistent field calculations carried out to account for the observed mesostructures accord well with experiment. The mesostructures produced by confined syntheses are useful as templates for fabricating highly ordered mesostructured nanowires and nanowire arrays.