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A 9,10-diarylanthracene derivative having two terminal trimethoxysilyl groups has been synthesized and used in combination with tetraethyl orthosilicate as a silicon source for the preparation of two periodic mesoporous silicas with MCM-41 and SBA-15 structures having about 15 wt % of the organic component. The resulting solids exhibit electrochemiluminescence arising from the organic moieties. The benefit for the electrochemiluminescence activity of having a large surface area solid with periodic porous structure is revealed by the fact that an analogous amorphous material prepared with the same precursor does not exhibit any measurable electrochemiluminescence activity under the same conditions.

A tris(bipyridine)ruthenium derivative with two terminal triethoxysilyl groups attached to one of the bipyridine ligands has been synthesized and used in combination with TEOS for the preparation of a tris(bipyridine)ruthenium-containing mesoporous silica, using CTABr as a structure-directing agent, under basic conditions at 100 °C. The resulting solids exhibited XRD patterns, isothermal gas adsorption and electron-microscopy images characteristic of hexagonal mesoporous silica, while the presence of tris(bipyridine)ruthenium complexes at the walls is manifested by the orange coloration of the solids and the optical spectra of the material corresponding to tris(bipyridine)ruthenium(II). The removal of the structure-directing agent without damaging the complex or the mesoporous structure of the pores was done by exhaustive solid–liquid extraction. As-synthesized mpRu exhibits photovoltaic (VOC = 140 mV, ISC = 2.6 µA) and electrochemiluminescence activity (λmax = 610 nm), the presence of CTABr plays a positive role in the activity by promoting intraparticle charge migration. In contrast, for an analogous material prepared under the same conditions but in the absence of the structure-directing agent and having a low surface area, the amorphous structure did not exhibit significant a photovoltaic or electrochemiluminescence response. This result exemplifies the benefits of having porosity and accessibility to the photoactive metallic complexes.

A periodic mesoporous SBA-15 silica containing 4,4-(N,N′- diallylaminophenyl)-2,6-diphenylpyrylium ion (BET surface area of 578 m 2 g-1, pore size 5.2 nm) exhibits upon excitation at 1064 nm activity for second harmonic generation that is the double than that of an analogous MCM-41 material synthesized under basic conditions using cetyltrimethylammonium bromide. This fact has been explained as arising from the instability of pyrylium to basic pHs.

Two differently substituted azobenzenes having terminal trimethoxysilyl groups attached to the para position of the phenyl rings by means of different linkers have been used in combination with tetraethyl orthosilicate to prepare two periodic mesoporous organosilicas. As the corresponding precursors in solution, these solids exhibit a photochemical trans-to-cis isomerization of the azo group upon irradiation at 358 nm. The cis-configured isomer reverts to the trans isomer either photochemically upon irradiation at 450 nm or thermally at room temperature within days. As a consequence of the dramatic changes in the molecular dimension of azobenzene upon trans/cis isomerization, the adsorption of gold nanoparticles (1−10 nm) into the mesoporous silica depends reversibly on the trans or cis configuration of the azo groups grafted on the walls, the adsorption capacity of the trans-configured azobenzene being larger.

A series of periodic mesoporous silicas of MCM-41 type containing varying amounts (5−50%) of chiral binaphthyl and cyclohexadiyl moieties occupying framework positions have been synthesized, and their characteristic MCM-41 features were observed by powder XRD and porosity measurements. The covalent bonding of the organics to the silicate framework was confirmed by 1H and 29Si MAS NMR experiments. Direct measurement of the optical activity demonstrates that the solids are able to rotate the angle of plane-polarized light. Also, a certain degree of chiral discrimination has been observed for the asymmetric enhancement of the binaphthyl fluorescence by adding enantiomerically pure 1,2-cyclohexadiamine.

Starting from colloidal TiO2 nanoparticles in combination with tetraethyl orthosilicate using neutral Pluronic or cationic cetyltrimethylammonium as templates, a series of structured mesoporous silicas has been obtained. The structure of the mesoporous titania was confirmed by isothermal gas adsorption, transmission electron microscopy, and X-ray diffraction. The pore diameter ranged between 3.8 and 10.9 nm, and the BET surface area varied from 99 to 584 m2 g-1. The photocatalytic activity of these samples for the degradation of phenol in aqueous solution has been compared with that of standard P-25 TiO2. Even though the activity of these new mesostructured materials is lower that those found for P-25 TiO2, the turnover frequency of the photocatalytic activity (moles of phenol degraded per Ti atom present at initial reaction time) is much higher for the mesoporous titania, particularly with low titanium contents for those materials (mpTiO2-5 and TiO 2-SBA15-5).

[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.