29Si Solid-state NMR Research Articles

Synergic Effects of Ordered Mesoporous Bifunctional Ionic Liquid: A Recyclable Catalyst to Access Chemoselective N-Protected Indoline-2,3-dione Analogous

SBA-15 and organic ionic liquid were incorporated in a post-grafting technique for generating a bifunctional ionic liquid embedded mesoporous SBA-15. The prepared heterogeneous catalyst was employed for the first time to synthesize N-alkylated indoline-2,3-dione at mild conditions to afford excellent yields in a short reaction time. The synthesized DABCOIL@SBA-15 catalyst was meticulously characterized by various techniques, such as FT-IR, solid-state 13C NMR, solid-state 29Si NMR, small-angle X-ray diffraction (XRD), and N2 adsorption–desorption. Further, the morphological behavior of the catalyst was studied by SEM and TEM. The thermal stability and number of active sites were determined by thermogravimetric analysis (TGA). The Hammett equation was used to analyze the synergetic effect of the catalyst and substituent effects on the N-alkylated products of 5-substituted isatin derivatives, which resulted in a negative slope. This negative slope indicates a positive charge in the transition state. Notably, the DABCOIL@SBA-15 catalyst demonstrated its practicality by being reused for seven cycles with consistently high catalytic activity.

Tris-Silanide f-Block Complexes: Insights into Paramagnetic Influence on NMR Chemical Shifts.

The paramagnetism of f-block ions has been exploited in chiral shift reagents and magnetic resonance imaging, but these applications tend to focus on 1H NMR shifts as paramagnetic broadening makes less sensitive nuclei more difficult to study. Here we report a solution and solid-state (ss) 29Si NMR study of an isostructural series of locally D 3h -symmetric early f-block metal(III) tris-hypersilanide complexes, [M{Si(SiMe3)3}3(THF)2] (1-M; M = La, Ce, Pr, Nd, U); 1-M were also characterized by single crystal and powder X-ray diffraction, EPR, ATR-IR, and UV-vis-NIR spectroscopies, SQUID magnetometry, and elemental analysis. Only one SiMe3 signal was observed in the 29Si ssNMR spectra of 1-M, while two SiMe3 signals were seen in solution 29Si NMR spectra of 1-La and 1-Ce. This is attributed to dynamic averaging of the SiMe3 groups in 1-M in the solid state due to free rotation of the M-Si bonds and dissociation of THF from 1-M in solution to give the locally C 3v -symmetric complexes [M{Si(SiMe3)3}3(THF) n ] (n = 0 or 1), which show restricted rotation of M-Si bonds on the NMR time scale. Density functional theory and complete active space self-consistent field spin-orbit calculations were performed on 1-M and desolvated solution species to model paramagnetic NMR shifts. We find excellent agreement of experimental 29Si NMR data for diamagnetic 1-La, suggesting n = 1 in solution and reasonable agreement of calculated paramagnetic shifts of SiMe3 groups for 1-M (M = Pr and Nd); the NMR shifts for metal-bound 29Si nuclei could only be reproduced for diamagnetic 1-La, showing the current limitations of pNMR calculations for larger nuclei.

The Phosphidosilicates AE2 Li4 SiP4 (AE=Ca, Sr, Eu) Ba4 Li16 Si3 P12.

The quaternary phosphidosilicates AE2 Li4 SiP4 (AE=Ca, Sr, Eu) and Ba4 Li16 Si3 P12 were synthesized by heating the elements and Li3 P under argon atmosphere. Their crystal structures were determined by single crystal X-ray diffraction. AE2 Li4 SiP4 crystallize in a new layered structure type (P21 /m, Z=2) with CdI2 -analoguos layers. Edge sharing CaP6 octahedra are separated by layers of vertex-sharing SiP4 and LiP4 tetrahedra, which contain additional chains of LiP6 octahedra. Ba4 Li16 Si3 P12 forms likewise a new structure type (P21 /c, Z=16) with a three-dimensional network of SiP4 , Si2 P6 and LiP4 entities as well as one phosphorus site not bonded to silicon. Barium is located in capped trigonal prisms of phosphorus which form strongly corrugated layers. 31 P and 29 Si solid-state NMR spectra confirm the crystal structures of the compounds AE2 Li4 SiP4 . 7 Li spectra show only one signal in spite of quite different crystallographic positions, which indicate possible Li+ mobility. However, this signal is much broader compared to the known Li+ conducting phosphidosilicates. Accordingly, electrochemical impedance measurements show low Li+ conductivities.

Effect of SH/SBA‐15 Molar Ratio on Pb(II) and Cd(II) Ions Adsorption from Aqueous Solution by Mercaptopropyl‐grafted SBA‐15 Mesoporous Material as Adsorbent

AbstractThe purposes of the current study were to investigate the adsorption of Pb(II) and Cd(II) from aqueous solution by thiol‐functionalized SBA‐15 materials designed by SBA‐15‐SH (x) where x is the SH/SBA‐15 molar ratio, which corresponds to the introduced moles number of Mercapto moieties to that of siliceous of the SBA‐15 materials. Furthermore, these materials were synthesized using 3‐Mercaptopropyltrimethoxysilane (MPTMS) via post‐grafting approach. SBA‐15‐SH(x) materials were characterized by XRD, N2 adsorption‐desorption and FT‐IR. The incorporation of SH fragments was proved by FT‐IR Spectroscopy, thermogravimetric analysis (TGA) and solid state 13C and 29Si NMR Spectroscopy.The removal of lead ions is more important than that of cadmium ions. Furthermore, the lead removal on SBA‐15‐SH(x) increased with the increase of SH/SBA‐15 molar ratio (removal rate of 28.5, 71.3, and 96.8 % for SH/SBA‐15 molar ratio=0.35, 0.7 and 1.4, respectively) while the removal of cadmium was not affected (around 57 % removal rate for all molar ratios).

Thioxanthone-Based Siloxane Photosensitizer for Cationic/Radical Photopolymerization and Photoinduced Sol-Gel Reactions.

In this investigation, a multifunctional visible-light TX-based photosensitizer containing a siloxane moiety (TXS) was designed with a good overall yield of 54%. The addition of a siloxane moiety enabled the incorporation of a TX photosensitizer into a siloxane network by photoinduced sol-gel chemistry, thus avoiding its release. Both liquid 1H and solid-state 29Si NMR measurements undeniably confirmed the formation of photoacids resulting from the photolysis of the TXS/electron acceptor molecule (Iodonium salt), which promoted the photoinduced hydrolysis/condensation of the trimethoxysilane groups of TXS, with a high degree of condensation of its inorganic network. Notably, the laser flash photolysis, fluorescence, and electron paramagnetic resonance spin-trapping (EPR ST) experiments demonstrated that TXS could react with Iod through an electron transfer reaction through its excited states, leading to the formation of radical initiating species. Interestingly, the TXS/Iod was demonstrated to be an efficient photoinitiating system for free-radical (FRP) and cationic (CP) polymerization under LEDs@385, 405, and 455 nm. In particular, whatever the epoxy monomer mixtures used, remarkable final epoxy conversions were achieved up to 100% under air. In this latter case, we demonstrated that both the photoinduced sol-gel process (hydrolysis of trimethoxysilane groups) and the cationic photopolymerization occurred simultaneously.

Preparations of spherical nanoparticles of chiral Cinchona alkaloid-based bridged silsesquioxanes and their use in heterogeneous catalysis of enantioselective reactions.

Two spherical nanoparticulate materials were prepared by base-catalyzed sol-gel hydrolysis/self-condensation of the bis-Cinchona alkaloid-phthalazine-based bridged bis(triethoxysilanes). For the purpose of comparing the catalytic properties, two compact materials were also prepared from the same precursors using a fluoride-catalyzed sol-gel process. All materials were characterized by SEM, TEM, solid-state 29Si NMR and 13C NMR, TGA, and FTIR. The prepared silsesquioxane-based materials were studied as potential heterogeneous catalysts for selected enantioselective reactions. The spherical material with regularly incorporated bis-quinine-phthalazine chiral units exhibited good to excellent enantioselectivities in osmium-catalyzed dihydroxylations of alkenes. Enantioselectivities observed in dihydroxylations of aromatic trans-alkenes were as excellent as those observed with the homogeneous catalyst (DHQ)2-PHAL. One compact and one nanoparticulate material was successfully recycled and reused five times without loss of enantioselectivity. Furthermore, both quinine-based and cinchonine-based materials were tested as heterogeneous organocatalysts for chlorolactonization of 4-arylpent-4-enoic acids. The materials showed only moderate enantioselectivities; however, these are the first heterogeneous catalysts for enantioselective chlorolactonization published so far.

Densification of sodium and magnesium aluminosilicate glasses at ambient temperature: structural investigations by solid-state nuclear magnetic resonance and molecular dynamics simulations.

Sodium and magnesium aluminosilicate glasses with compositions 20Na2O-20Al2O3-60SiO2 (NAS) and 20MgO-20Al2O3-60SiO2 (MAS) were subjected to a 12 and 25 GPa compression and decompression at room temperature, resulting in density increases from 3.7% to 5.3% (NAS) and from 8.2 to 8.4% (MAS), respectively. The pressurization at 25 GPa was done on 17O-enriched glasses, to facilitate characterization by 17O NMR. The structural changes associated with this process have been investigated by solid state 29Si, 27Al, 23Na, 25Mg, and 17O magic-angle spinning NMR and compared with the situation in thermally relaxed glasses and/or glasses prepared at ambient pressure. While in the Na aluminosilicate glass only subtle structural changes were observed in a sample densified at 12 GPa, the average coordination number of Al 〈CN(Al)〉 increases moderately from 4.00 to 4.26 by pressurization at 25 GPa. In the Mg-based system, 〈CN(Al)〉 increases from 4.34 to 4.57 to 4.83 in the sequence 10-4 GPa → 12 GPa → 25 GPa. The experimental result at 25 GPa was qualitatively confirmed by molecular dynamics (MD) simulations. Overall, pressurization results in more positive 29Si and 17O chemical shifts, most likely reflecting a reduction in the Si-O-Si and Si-O-Al bonding angles in the pressurized glasses. Furthermore, the results are also consistent with either an increased number of non-bridging O-atoms upon pressurization, or a larger number of Si-O-Al or Al-O-Al linkages. The significantly higher sensitivity of MAS, compared to NAS glass, to an increase in 〈CN(Al)〉 upon pressurization, provides a good structural rationale for its significantly higher crack initiation resistance.

Structural and sorption characteristics of an aerogel composite material loaded with flufenamic acid: insights from MAS NMR and high-pressure NOESY studies.

The structural and sorption characteristics of a composite material consisting of a silica aerogel loaded with flufenamic acid were investigated using a variety of nuclear magnetic resonance techniques. The composite structure was analyzed using magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, which revealed significant interactions between the aerogel matrix and the FFA molecules. Solid-state 29Si NMR provided insights into the aerogel's stability, while 1H and 13C NMR confirmed the presence of FFA in the matrix, with signals from FFA molecules observed alongside tetraethoxysilane (TEOS) groups. Ethanol-induced desorption of FFA led to narrowed spectral lines, suggesting the breaking of intermolecular hydrogen bonds. 19F MAS NMR spectra indicated changes in FFA local environments upon loading into AG pores. Evaluation of CO2 sorption characteristics using 13C NMR demonstrated a slower sorption rate for AG + FFA than that for pure AG, attributed to decreased pore volume. Furthermore, nuclear Overhauser effect spectroscopy (NOESY) was employed to explore the conformational behavior of FFA within the aerogel matrix. The results indicated a shift in conformer populations, particularly those related to the rotation of one cyclic fragment relative to the other. These findings provide insights into the structural and sorption characteristics of the AG + FFA composite, which are valuable for developing novel drug solid forms.

Preparation of a thin silica nonwoven fabric composed of nanofibers and micropores by electrospinning after controlled hydrolysis in a sol-gel reaction

Ceramics are recognized as highly suitable materials for creating guided bone regeneration (GBR) barrier membranes due to their bioresorbable and osteoconductive properties. However, techniques have not been fully developed for the production of ceramic membranes with the appropriate fiber thickness and pore size. In this study, a thin silica nonwoven fabric with pores smaller than cells, achieved by nanofiber technology, was prepared by electrospinning, and its potential as a GBR barrier membrane was explored. In addition, efforts were made to elucidate the nanoscale fiber formation mechanism through molecular dynamics-based geometric optimization using solid-state 29Si-NMR data. As a result, a thin silica nonwoven fabric composed of nanofibers and micropores was prepared by electrospinning a silica gel prepared by lowering the TEOS-to-water ratio during the sol-gel reaction. Insufficient water addition during the sol-gel reaction caused a decrease in the number of siloxane bonds, resulting in a linear growth behavior of the silica molecules instead of the original network growth behavior. This led to a decrease in fiber thickness, which in turn caused a decrease in pore size. The thin silica nonwoven fabric showed exceptional performance in the cell occlusion ability test, suggesting its strong potential as a GBR barrier membrane.

Unravelling the dynamic crosslinking mechanism in polyborosiloxane

This study offers a comprehensive investigation into the mechanism behind the dynamic crosslinking of polyborosiloxane (PBS). Despite this material being well known for over 70 years, the origin of PBS's unique viscoelastic properties has been a topic of debate in the literature. Through combined FTIR and solid-state 29Si and 11B MAS NMR analyses, this study provides evidence that the formation of Si–O–B dynamic covalent bonds, along with their associative exchange with neighboring hydroxyl-bearing species (free silanol, water, alcohol, etc.), drives the gelation and viscoelastic behavior of PBS. Results show no indication of hydrogen or dative bonding, instead the low energy barrier for formation and breakage of Si–O–B bonds allows for easy exchange at room temperature. Moreover, the study finds that the viscoelastic properties of PBS can be adjusted by the choice of boron B–O functionality, leading to n-functional dynamic crosslinking through Si–O–B bonds. This research provides a clear understanding of the mechanism of dynamic crosslinking in PBS, resolving long-standing controversies in the field.

SiCO Ceramics as Storage Materials for Alkali Metals/Ions: Insights on Structure Moieties from Solid-State NMR and DFT Calculations.

Polymer-derived silicon oxycarbide ceramics (SiCO) have been considered as potential anode materials for lithium- and sodium-ion batteries. To understand their electrochemical storage behavior, detailed insights into structural sites present in SiCO are required. In this work, the study of local structures in SiCO ceramics containing different amounts of carbon is presented. 13 C and 29 Si solid-state MAS NMR spectroscopy combined with DFT calculations, atomistic modeling, and EPR investigations, suggest significant changes in the local structures of SiCO ceramics even by small changes in the material composition. The provided findings on SiCO structures will contribute to the research field of polymer-derived ceramics, especially to understand electrochemical storage processes of alkali metal/ions such as Na/Na+ inside such networks in the future.

Near-infrared-emitting silsesquioxane-based porous polymer containing thiophene for highly efficient adsorption and detection of iodine vapor and solution phase

The powerful gathering and potent detection of radioactive iodine, which may be created during the production of nuclear energy or the management of nuclear waste, are essential. Herein, near-infrared-emitting (NIR) porous polymeric materials with thiophene (PCS-DPBS) were employed for the first time to capture iodine vapor effectively and reversibly. The fluorophore monomer (CN-DPBS) with a donor–acceptor-donor (D-A-D) typed electronic configuration exhibiting near-infrared fluorescence emission was successfully produced by the Knoevenagel reaction. Then, CN-DPBS reacted with octavinylsilsesquioxane (OVS) via the Friedel-Crafts reaction, resulting in a series of porous polymers based on silsesquioxane (PCS-DPBS). The polymer was effectively synthesized, as evidenced by elemental analysis, FT-IR, solid-state 29Si NMR, and solid-state 13C NMR spectra. The morphology of PCS-DPBS was also demonstrated by XRD and SEM results. Interestingly, the resulting polymer has distinct properties and characteristics such as NIR emission (663 nm), adjustable porosity (specific surface area of 245 m2 g−1 and total pore volumes of 0.150 cm3 g−1), and thermal stability with Td5% and Td10% of 202 and 414 °C, respectively, in N2 atmosphere. With a large micropore volume and a high thiophene content in its polymer structure, this results in high iodine vapor adsorption capacities, with uptake capacities up to 2.81 g g−1 at 70 °C. The recycling ability is at least five times and the iodine uptake capacity is still >50%. The CN-DPBSunit provides PCS-DPBS with unique luminescence, allowing it to function as a probe to detect iodine solution with great sensitivity with KSV values of 1622.4 M−1. This study on a thiophene-containing adsorbent brings up new possibilities for the effective capture and detection of iodine in environment.

Role of Ordered Mesoporous Silica Loaded with Cerium and with an Amine‐Modified Surface as an Effective Binder and Nano‐container in Corrosion Resistant Hybrid Coating

AbstractOrdered mesoporous silica was synthesized through sol‐gel technique under hydrothermal conditions by using tetraethylorthosilicate. The template free material was obtained by calcination and the channels of ordered mesoporous silica (OMS) were successfully loaded with cerium (corrosion inhibitor). This cerium loaded material was modified with N1‐(3‐Trimethoxysilylpropyl)diethylenetriamine through grafting with surface hydroxyl group. Subsequently, the surface‐modified material was actively used as a curing agent, host for corrosion inhibitors and filler as well in epoxy‐based coatings for mild steel. The mesoporous silica material was characterized by using a combination of various analytic and spectroscopic techniques like FT‐IR, powder‐XRD, N2 sorption, solid state 29Si and 13C MAS NMR studies. The physicochemical, physicomechanical, and thermal properties of the hybrid film were analyzed through standard techniques like FT‐IR, TGA‐DTA, DMTA and FE‐SEM. The coated hybrid film on mild steel was tested for corrosion inhibition by using potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) studies. The aforementioned studies revealed the developed coating system exhibited promising corrosion protection performance which was evident from icorr (6.65 nA), Ecorr (−502.850 mV), impedance (1.2×106 Ω) and phase angle (>80°). The observed water contact angle (WCA)>90° suggesting the hydrophobic nature of the coated surface.

A Non-Hydrolytic Sol–Gel Route to Organic-Inorganic Hybrid Polymers: Linearly Expanded Silica and Silsesquioxanes

Condensation reactions of chlorosilanes (SiCl4 and CH3SiCl3) and bis(trimethylsilyl)ethers of rigid, quasi-linear diols (CH3)3SiO-AR-OSi(CH3)3 (AR = 4,4'-biphenylene (1) and 2,6-naphthylene (2)), with release of (CH3)3SiCl as a volatile byproduct, afforded novel hybrid materials that feature Si-O-C bridges. The precursors 1 and 2 were characterized using FTIR and multinuclear (1H, 13C, 29Si) NMR spectroscopy as well as single-crystal X-ray diffraction analysis in case of 2. Pyridine-catalyzed and non-catalyzed transformations were performed in THF at room temperature and at 60 °C. In most cases, soluble oligomers were obtained. The progress of these transsilylations was monitored in solution with 29Si NMR spectroscopy. Pyridine-catalyzed reactions with CH3SiCl3 proceeded until complete substitution of all chlorine atoms; however, no gelation or precipitation was found. In case of pyridine-catalyzed reactions of 1 and 2 with SiCl4, a Sol-Gel transition was observed. Ageing and syneresis yielded xerogels 1A and 2A, which exhibited large linear shrinkage of 57-59% and consequently low BET surface area of 10 m2⋅g-1. The xerogels were analyzed using powder-XRD, solid state 29Si NMR and FTIR spectroscopy, SEM/EDX, elemental analysis, and thermal gravimetric analysis. The SiCl4-derived amorphous xerogels consist of hydrolytically sensitive three-dimensional networks of SiO4-units linked by the arylene groups. The non-hydrolytic approach to hybrid materials may be applied to other silylated precursors, if the reactivity of the corresponding chlorine compound is sufficient.

Revisiting Alkoxysilane Assembly on Silica Surfaces: Grafting versus Homo-Condensation in Solution

Silica surface functionalization is often done through the condensation of functional silanes on silanols, silica surfaces' terminal groups. APTES, aminopropyltriethoxysilane, is widely used due to its assumed high reactivity with silanols, kinetically promoted by the catalytic action of the terminal amine function. Here, we revisit, based on a quantitative analysis by solid-state 29Si NMR, the assembly of this silane on silica surfaces to investigate whether its presence results from grafting, i.e., hetero-condensation with silanol groups or from homo-condensation of silane molecules in solution leading to polycondensates physisorbed on silica. We investigate the interaction of APTES with a crystalline layered silicate, ilerite, and with amorphous nonporous silica. We also studied a second silane, cyanopropyltrichlorosilane (CPTCS), terminated with a nitrile group. Our results undoubtedly prove that while CPTCS is grafted on the silica surface, the presence of APTES on silica and silicate materials is only marginally associated with silanol consumption. The analysis of the signal related to silicon atoms from silanes (Tn species) and those from silica (Qn species) allowed for the accurate estimation of the extent of homo-condensation vs grafting based on the ratio of T-O-T/Q-O-T siloxane bridges. These findings deeply question the well-established certainties on APTES assembly on silica that should no longer be seen as grafting of alkoxysilane by hetero-condensation with silanol groups but more accurately as a homo-condensed network of silanes, predominantly physisorbed on the surface but including some sparse anchoring points to the surface involving less than 6% of the overall silanol groups.

Design Hybrid Porous Organic/Inorganic Polymers Containing Polyhedral Oligomeric Silsesquioxane/Pyrene/Anthracene Moieties as a High-Performance Electrode for Supercapacitor.

We synthesized two hybrid organic-inorganic porous polymers (HPP) through the Heck reaction of 9,10 dibromoanthracene (A-Br2) or 1,3,6,8-tetrabromopyrene (P-Br4)/A-Br2 as co-monomers with octavinylsilsesquioxane (OVS), in order to afford OVS-A HPP and OVS-P-A HPP, respectively. The chemical structures of these two hybrid porous polymers were validated through FTIR and solid-state 13C and 29Si NMR spectroscopy. The thermal stability and porosity of these materials were measured by TGA and N2 adsorption/desorption analyses, demonstrating that OVS-A HPP has higher thermal stability (Td10: 579 °C) and surface area (433 m2 g-1) than OVS-P-A HPP (Td10: 377 °C and 98 m2 g-1) due to its higher cross-linking density. Furthermore, the electrochemical analysis showed that OVS-P-A HPP has a higher specific capacitance (177 F g -1 at 0.5 A F g-1) when compared to OVS-A HPP (120 F g -1 at 0.5 A F g-1). The electron-rich phenyl rings and Faradaic reaction between the π-conjugated network and anthracene moiety may be attributed to their excellent electrochemical performance of OVS-P-A HPP.

Designing Fe-containing polyhedral oligomeric silsesquioxane to endow superior mechanical and flame-retardant performances of polyamide 1010

With increasing attention to environmental safety and health, long-chain biologically-based polyamides (PA) are considered to be promising materials owing to their biocompatibility and combining the dual advantages of polyolefins and short-chain petroleum-based polyamides. However, poor flame retardancy severely impedes long-chain biologically-based polyamides’ application in versatile high-standard fields. Herein, we introduced Fe element into the polyhedral oligomeric silsesquioxane (POSS) cage to obtain iron-containing hepta-phenyl POSS (Fe-Ph-POSS), deriving from the chemical reaction between Li-Ph-POSS and FeCl3. The chemical structure of Fe-Ph-POSS was fully characterized and confirmed by FTIR, 1H NMR, 13C NMR, Solid state 29Si NMR, XPS and MALDI-TOF MS. Thereafter, Li-Ph-POSS and Fe-Ph-POSS were adopted to flame retarded biologically-based PA1010. The addition of 10 wt% Fe-Ph-POSS distinctly enhanced the thermal stability without affecting the melting and crystallization temperature of PA1010 composites. Additionally, the introduction of Fe-Ph-POSS did not cause embrittlement for PA1010 and almost completely maintained its excellent mechanical properties (elongation at break, tensile and impact strength were reached 473.8%, 46.87 MPa and 4.52 kJ/m2, respectively). The burning tests results suggested that 10 wt% Fe-Ph-POSS increased the LOI value of PA1010 from 22.6 to 28.4%, and the generation of red-brown char layers rich in iron-containing silicates and carbonates, which effectively hindered the release of heat, smoke and toxic volatiles. Thereby imparting the resultant PA1010 composites to superior flame-retardant performances. Therefore, our work offers an exceptional thought for construction of high-performance biologically-based polyamide composites based on environmentally friendly organic-inorganic hybrid nanomaterials.

Copper Complexes of Silicon Pyridine-2-olates RSi(pyO)3 (R = Me, Ph, Bn, Allyl) and Ph2Si(pyO)2

The organosilicon pyridine-2-olates 1a–1d (RSi(pyO)3, R = Me (a), Ph (b), Bn (c), Allyl (d); pyO = pyridine-2-olate) may serve as tripodal ligands toward CuCl with formation of complexes of the type RSi(μ2-pyO)3CuCl (2a–2d). In addition, for R = Allyl, formation of the more stable isomer 2d′ (κO-pyO)Si(μ2-pyO)2(μ2-Allyl)CuCl was observed. In the presence of dry air (as a source of oxygen), reactions of 1a–1d and CuCl afforded Cu(II) complexes RSi(μ2-pyO)4CuCl (3a–3d); 3a–3c in good yield, and 3d only as a side product. Reaction of Ph2Si(pyO)2 (4) and CuCl in equimolar ratio afforded, depending on reaction conditions, a series of (CuCl)n-ladder-type oligonuclear Cu(I) complexes Ph2Si(μ2-pyO)2(CuCl)n(μ2-pyO)2SiPh2 (n = 2 (52), 3 (53), 4 (54)). In all of the above compounds, the pyO group is Si–O bound and, in the case of μ2 coordination, Cu–N bound. All new compounds (1c, 1d, 2b, 2c, 2d, 2d′, 3b, 3c, 3d, 52, 53, 54) were characterized by single-crystal X-ray diffraction, and further characterization includes solution 1H, 13C, 29Si NMR spectroscopy (1c, 1d, 2b, 2c, 2d’, 53, 54), solid-state 29Si (2b, 2c, 2d′, 53, 54) and 63Cu NMR spectroscopy (2c, 2d′) as well as computational analyses of the isomerization of the couple 2d, 2d′.

A Three-Dimensional Silicon-Diacetylene Porous Organic Radical Polymer

A Three-Dimensional Silicon-Diacetylene Porous Organic Radical Polymer

The preparation of CaCO3-polyalkoxysilane porous nanocomposites as effective sorbent for oil spill removal.

The novel porous nanocomposite sorbent was synthesized by the condensation of the diol monomer with the alkoxysilane cross-linker at moderately high temperatures in the presence of nano-CaCO3 particles. The structural, thermal, and morphological properties of the nanocomposite sorbents were determined by using Fourier transform infrared spectroscopy (FTIR), solid-state CPMAS 13C and 29Si NMR,scanning electron microscope (SEM), and thermal gravimetric analysis (TGA). Adding nano-CaCO3 to the network structure of the polymer not only provided pores to the sorbent but also enhanced its sorption capacity towards various oils and toxic organic solvents. The nanocomposite sorbent exhibited excellent absorption capacity for different toxic organic solvents and oils and great reusability for ten cycles. Moreover, the obtained sorbent material selectively absorbed organic liquids from the surface and bottom of the water without any capacity change owing to their hydrophobicity and oleophilicity. These features of the nanocomposite make it a potential sorbent for the cleaning of oils and oil derivative organic contaminants from the environment.