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In this study, a high‐performance inorganic‐organic hybrid hole transporting layer (HTL) was developed using ethanol‐soluble alkoxide precursors and a self‐assembled monolayer (SAM). Three metal oxides‐vanadium oxide (VOx), niobium oxide (Nb2O5), and tantalum oxide (Ta2O5)‐were synthesized through successive low‐temperature (100 °C) thermal annealing (TA) and UV‐ozone (UVO) treatments of their respective precursors: vanadium oxytriethoxide (EtO−V), niobium ethoxide (EtO−Nb), and tantalum ethoxide (EtO−Ta). Among these, the Nb2O5 film exhibited excellent transmittance, a high work function, and good conductivity, along with a more compact and uniform structure featuring fewer interfacial defects, which facilitated efficient charge extraction and transport. Furthermore, the deposition of a SAM of (2‐(9H‐carbazol‐9‐yl)ethyl)phosphonic acid (2PACz) on top of Nb2O5 further passivated defects, enhancing interfacial contact with the photoactive layer. The resulting inorganic‐organic hybrid HTL of Nb2O5/2PACz demonstrated excellent compatibility with various photoactive blends, achieving impressive power conversion efficiencies of 19.44 %, 19.18 %, and 20.12 % for the PM6:L8‐BO, PM6:BTP‐eC9, and D18:BTP‐eC9 based organic solar cells, respectively. 20.12 % is the best performance for bulk heterojunction organic solar cells with binary components as the photoactive layer. [ABSTRACT FROM AUTHOR]

Entropy stabilized multi-cation oxides are of significant interest in heterogeneous catalysis due to higher number of active sites, when compared to simple binary oxides, which reduces the overpotential for catalytic transformations. To control the enthalpy of mixing and suppress potential phase segregation, the use of molecular metal alkoxides for chemical cross-linking of different metal centers shows promise in creating homogenous high entropy chemical preceramic networks. Herein, we report on a high-entropy MO 2 phase (M = V, Sn, Ti, Zr, Hf), synthesized by cross-linking partially hydrolyzed metal iso-propoxides [M(OH) n (O i Pr) 4-n ] x. The amorphous xerogels calcined at 700 °C, 900 °C and 1250 °C revealed the formation of a single crystalline phase [(V, Sn, Ti, Zr, Hf)O 2 ] that was verified by powder X-ray diffraction analysis, whereas the chemical composition was investigated by X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. The HEO exhibited superior catalytic activity in oxygen evolution reaction with an overpotential of 312.7 mV and an electrochemically active surface area of 0.625 F cm−2. Furthermore, the chronopotentiometry measurements confirmed a high stability (> 90 h) for the HEO samples. [ABSTRACT FROM AUTHOR]

A series of metal alkoxides with different transition metal centers and alkoxide anions were prepared for lithium-ion battery anode. Among them, the Co-EG/rGO presents a stable structure, small molecular weight, high electron transportation ability, and fast Li+ diffusion, leading to the best Li-storage performance in terms of high specific capacity (975 mAh g−1 at 0.2 A g−1), excellent rate capability (400.8 mAh g−1 at 10 A g−1), and stable cycling performance (86.8 % capacity retention after 600 cycles). [Display omitted] Metal-organic compounds have attracted significant attention for lithium-ion battery (LIB) anodes. However, their practical application is severely hindered by the poor structural stability and sluggish Li+ reaction kinetics. Herein, we proposed a new type of metal–organic compound, metal alkoxides, for high-performance LIBs. A series of metal-alkoxide/graphene composites with different transition metal centers and alkoxide anions are prepared to investigate the structural stability, Li-storage ability, and Li+ diffusion kinetics. The results reveal that the metal centers and alkoxide anions have significant influence on the structural stability, molar mass, and electronic structures, which are highly related to the Li-storage performance. Among them, Co-EG/rGO (EG represents the ethylene glycol anion) delivers the best performance involving high specific capacity (975 mAh g−1 at 0.2 A g−1), excellent rate capability (400.8 mAh g−1 at 10 A g−1), and stable cycling performance (86.8 % capacity retention after 600 cycles) due to its stable structure, smaller molar mass, and favorable electronic structure. Moreover, the Li-storage mechanism and solid electrolyte interphase (SEI) evolution of the Co-EG/rGO electrode are studied in detail through multiple ex-situ/in-situ characterizations. This work provides a new type of metal alkoxide anode material for high-rate and long-life LIBs toward practical energy applications. [ABSTRACT FROM AUTHOR]

Thermal stabilizers are essential for polyvinyl chloride (PVC) processing. It is the emergence of thermal stabilizers that made PVC's applications migrate from laboratory to large‐scale industrial use. Herein we overview the development status of some traditional thermal stabilizers including lead salt, metal soaps, and organotin along with relatively newer thermal stabilizers such as organic thermal stabilizers and metal alkoxides. Taking into consideration the high market demand, opportunities for cost‐effective additives for thermal stabilizers are also briefly discussed. Finally, with the recent shift in focus on thermal stabilizer synthesis and their performance characterization but neglecting mechanical property testing and verification, we put forward application prospect of quantum chemical calculation for the development of PVC thermal stabilizers. [ABSTRACT FROM AUTHOR]

Metal alkoxides are easily available and versatile precursors for functional materials, such as solid catalysts. However, the poor solubility of metal alkoxides in organic solvents usually hinders their facile application in sol–gel processes and complicates access to complex carbonate or oxidic compounds after hydrolysis of the precursors. In our contribution we have therefore shown three different solubilization strategies for metal alkoxides, namely the derivatization, the hetero-metallization and CO2 insertion. The latter strategy leads to a stoichiometric insertion of CO2 into the metal–oxygen bond of the alkoxide and the subsequent formation of metal alkyl carbonates. These precursors can then be employed advantageously in sol–gel chemistry and, after controlled hydrolysis, result in chemically defined crystalline carbonates and hydroxycarbonates. Cu- and Zn-containing carbonates and hydroxycarbonates were used in an exemplary study for the synthesis of Cu/Zn-based bulk catalysts for methanol synthesis with a final comparable catalytic activity to commercial standard reference catalysts. [ABSTRACT FROM AUTHOR]

• Metal alkoxides were prepared using alcohol splitting in bipolar membranes. • Neosepta BP-1E has a threshold voltage of 6.02 V for alcohol splitting. • Diffusion boundary layer is the predominant impedance for water splitting. • Swelling of bipolar membrane in alcohol affect the metal alkoxides production. In this study, an electrochemical route was proposed for metal alkoxides preparation by taking advantage of alcohol dissociation (ROH → RO− + H+) in a bipolar membrane. A current density of 25 mA cm−2 was optimized for lithium methoxide and magnesium methoxide production with energy consumption of 28.84 kWh∙kg−1 and 27.98 kWh∙kg−1, respectively. Electrochemical impedance spectroscopy (EIS) characterization indicated that the threshold voltage for alcohol dissociation for the Neosepta BP-1E bipolar membrane is 6.02 V, which is much higher than that for water splitting of 0.72 V. For a bipolar membrane, the resistance of the alcohol dissociation (R AD) and the resistance of the diffusion boundary layer (R DBL) are the major contributors to the impedance for methanol splitting, while only the latter is the predominant contributor to the impedance for water splitting. Overall, alcohol splitting in bipolar membrane provides a versatile platform for green preparation of metal alkoxides. [ABSTRACT FROM AUTHOR]

Metal alkoxides are easily available and versatile precursors for functional materials, such as solid catalysts. However, the poor solubility of metal alkoxides in organic solvents usually hinders their facile application in sol–gel processes and complicates access to complex carbonate or oxidic compounds after hydrolysis of the precursors. In our contribution we have therefore shown three different solubilization strategies for metal alkoxides, namely the derivatization, the hetero-metallization and CO2 insertion. The latter strategy leads to a stoichiometric insertion of CO2 into the metal–oxygen bond of the alkoxide and the subsequent formation of metal alkyl carbonates. These precursors can then be employed advantageously in sol–gel chemistry and, after controlled hydrolysis, result in chemically defined crystalline carbonates and hydroxycarbonates. Cu- and Zn-containing carbonates and hydroxycarbonates were used in an exemplary study for the synthesis of Cu/Zn-based bulk catalysts for methanol synthesis with a final comparable catalytic activity to commercial standard reference catalysts.

In this paper, reaction control of metal alkoxides has been tried to obtain oxide nano-particles with controlled properties. As a result, the principle to design the molecular structure of the precursors consisted of metal-oxygen-metal bonds was proposed based on the Zachariasen and Warren’s network theory or single bond strength proposed by K. H. Sun. Some examples of the molecular design were presented and discussed, such as the stoichiometric mullite nano-particles, non-silicates of zirconia and VO2/SiO2 nanocomposite particles. In the case of mullite nano-particles, importance of the aggregation control was discussed for the control of the nanostructure of the resulting nanoparticles. Zirconium alkoxide was the model case of the reaction control for the metal alkoxides with lower electronegativity using controlled chemical modification (CCM) method for the partial hydrolysis and following polycondensation to obtain the bulk gel. Nanocoating on the nanoparticles was also realized by CCM method. A few nanometers thick of VO2 nanolayer was successfully deposited on a monodispersed silica particles of 50 nm, and their thermochromic property was confirmed at around room temperatures. All these results exhibits that the molecular design using metal alkoxides is the powerful tool to obtain the high performance oxide nano-particles. [ABSTRACT FROM AUTHOR]

The coordination behavior of the tridentate alkoxy ligand 6,6'-(((2-hydroxyethyl)azanediyl)bis(methylene)) bis(2,4-di-tert-butylphenol) (termed H3-AM-DBP2) with group 4 metal alkoxides ([M(OR)4]) in a 1:1 ratio was previously found to generate [(ONep)Ti(κ 4 (O,O',O",N)-AM-DBP2)] and [(OR)Zr(κ4 (μ-O,O',O",N)-AM-DBP2)]2 (M = Zr, Hf). Additional studies revealed that increasing the stoichiometric ratio to 1:2 H3-AM-DBP2:[M(OR)4] led to the isolation of [(ONep)Ti(κ4 (μ-O,O',O",N)-AM-DBP2)(μ-ONep)Ti(ONep)3] (1)•tol, [(OBu t)Zr(κ4 (μ-O,O',O",N)-AM-DBP2)(μ-OBu t)Zr(OBu t)3] (2) and [(OBu t)Hf(κ4 (μ-O,O',O",N)-AM-DBP2)(μ-OBu t)Hf(OBu t)3] (3). The asymmetric dinuclear complexes of 1-3 resemble the chelation of a [M(OR)4] moiety to a "(OR)M(κ4 (O,O',O",N)-AM-DBP2)" fragment. The metal complexed by the AM-DBP2 ligand has a pseudo octahedral geometry while the other metal adopts an intermediate trigonal bipyramidal (TBP-5)/square base pyramidal (SBP-5) geometry for 1 but a distorted SBP-5 for both 2 and 3. The structure and properties of 1-3 were analyzed by computational modeling and fully characterized by standard analytical methods. [ABSTRACT FROM AUTHOR]

A comprehensive investigation of the formation of tin and lead alkoxides with the polyalcohols ethylene glycol (C2H6O2, EG) and glycerol (C3H8O3) was conducted. Starting from tin(II) and lead(II) precursors, five alkoxides with either double‐ or triple‐deprotonated alcohol ligands were obtained. Four of them were structurally characterized by single‐crystal and one by powder X‐ray diffraction. The ethylene glycolates of tin(II) and lead(II), Sn(C2H4O2) and Pb(C2H4O2), show polymorphism. α‐ and β‐Sn(C2H4O2) can be synthesized selectively by applying different reaction times. α‐ and β‐Pb(C2H4O2), as well as Pb4(C2H4O2)4(C2H6O2), were obtained by altering the amount of NaOH and/or water used in the synthesis. With glycerol, mixed‐valent tin(II,IV) glycerolate Sn5(C3H5O3)4 and lead(II) glycerolate Pb(C3H6O3) crystallized. Except for Pb(C2H4O2), the obtained alkoxides are stable at ambient conditions for at least several months. The tin alkoxides were thermally decomposed in air to SnO2. A small amount of tin(II) in a SnO2 sample obtained at a low decomposition temperature was revealed by 119Sn Mössbauer spectroscopy. At the highest decomposition temperature of 800 °C, only tin(IV) could be detected. The morphology of the alkoxide material is retained upon decomposition; however, the produced SnO2 consists of nanosized crystalline domains. The thermal decomposition of the lead(II) alkoxides in air yielded PbO particles with a significantly changed morphology. [ABSTRACT FROM AUTHOR]

A facile, sol-gel method was developed to obtain Al-containing layered double hydroxides (LDHs) with Ca or Mg divalent cations. Ca- and Al-alkoxide were added to aqueous NaNO3 solution, and, after rapid gelation, a solid product, phase-pure, highly crystalline CaAl-LDH was formed with exceptionally regular morphology without impurities for the first time with sol-gel method. The lack of salt in the solution used for the hydrolysis resulted in a non-desirable by-product (katoite). For the sol-gel synthesis of MgAl-LDH, it was found that its formation was less sensitive to the presence of nitrate ions, and pure water or aqueous NaOH worked equally well. The product was also a highly crystalline material with thin, plate-like morphology as revealed by X-ray diffractometry and scanning electron microscopy. IR measurements indicate the lack of organic substance in the interlamellar space for both materials. A novel version of sol-gel synthesis was utilized to prepare two types of layered double hydroxides.The platelets have well-defined hexagonal morphology.The products have thin crystals with high aspect ratio. [ABSTRACT FROM AUTHOR]

The investigation of the reactivity of six membered N-heterocyclic carbene 1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-1-ylidene (6-Mes) towards dialkylgallium and dialkylindium alkoxides/aryloxides has shown that both steric hindrances and donor properties of 6-Mes significantly influence the strength of M-C6-Mes bond, as well as the formation, structure and reactivity of Me2MOR(6-Mes) (M=Ga, In) complexes. While the reactions of simple dimethylgallium alkoxides with 6-Mes lead to the formation of stable monomeric Me2Ga(OCH2CH2OMe)(6-Mes) (1) andMe2GaOMe(6-Mes) complexes, the analogous Me2InOR(6-Mes) are unstable and disproportionate to methylindium alkoxides and Me3In(6-Mes) (2). The use of bulky alkoxide ligand--OCPh2Me or aryloxide ligand--OC6H4OMe allowed for the synthesis of stableMe2M(OCPh2Me)(6-Mes) (M= Ga (3) and In (4)) as well as Me2M(OC6H4OMe)(6-Mes) (M = Ga (5) and In (6)). The structures of 1-6 have been determined using both spectroscopic methods in solution and X-ray diffraction studies, which confirmed the effect of both steric hindrances and donor properties of 6-Mes on their structure and catalytic properties in the ring-opening polymerization (ROP) of rac-lactide. [ABSTRACT FROM AUTHOR]

Metal alkoxides are metal-organic compounds characterized by the presence of MOC bonds (M = metal). Their chemistry seems to be, in principle, relatively simple but the number of possible reactant species arising as a consequence of their behavior is very remarkable. The physico-chemical properties of metal alkoxides are determined by many different parameters, the most important ones being the electronegativity of the metal, the ramification of the ligand, and the acidity of the corresponding alcohol. Their reactivity makes them suitable and versatile candidates for many applications, including homogeneous catalysis, synthesis of new ceramic materials through the sol-gel process and, recently, also for Cultural Heritage. Metal alkoxides are characterized by a strong tendency to give clusters and/or oligomers through oxo-bridges. Mass spectrometry has been successfully employed for the characterization of metal alkoxides in the gas-phase. Electron ionization (EI) allowed the assessment of the molecular weight and of the most relevant decomposition pathways giving information on the relative bond strength of differently substituted molecules. On the other hand, information on the reactivity in solution of these molecules have been obtained by electrospray ionization (ESI)-matrix assisted laser desorption ionization (MALDI) experiments performed on their reaction products. These data were relevant to investigate the sol-gel process. In this review, these aspects are described and the results obtained are critically evaluated. © 2016 Wiley Periodicals, Inc. Mass Spec Rev [ABSTRACT FROM AUTHOR]

The preparation of (E)-4-methylhexa-3,5-dien-1-ol has been achieved in a single step from 3-methylpenta-1,4-diene through deprotonation with BuLi, alkylation with paraformaldehyde and metal-counterion exchange in situ to promote oxy-anion-accelerated [1,3]-sigmatropic shift. This alcohol is shown to undergo intermolecular Diels-Alder reaction with 3-isopropyl acrylate thioesters; the so-formed exclusive endoadduct may then be closed to the bicyclic lactone, the product of formal intramolecular Diels-Alder reaction (a much more difficult process). Use of chiral thioesters results in an enantioselective synthesis of this bicyclic lactone, an intermediate with application to eunicellane (cladiellane) diterpene synthesis. [ABSTRACT FROM AUTHOR]

Here we describe and discuss an approach to the synthesis of alkylgallium alkoxide and aryloxide cations stabilized with N -heterocyclic carbenes (NHCs). The reaction of methyl abstracting agent B(C 6 F 5 ) 3 with Me 2 Ga(O Ar ,C NHC ) complexes stabilized by aryloxide ligands with N -heterocyclic carbene functionalities ( 1 and 2 ) has led to the formation of cationic complexes [MeGa(O Ar ,C NHC )] 2 2+ ( 3 2+ and 4 2+ ). [ 3 ][MeB(C 6 F 5 ) 3 ] 2 and [ 4 ][MeB(C 6 F 5 ) 3 ] 2 , which are the first examples of alkylgallium aryloxide cationic complexes, have been isolated and characterized by both spectroscopic and X-ray techniques. In contrast, the reaction of alkoxide derivative Me 2 Ga(O,C NHC ) ( 5 ) with B(C 6 F 5 ) 3 and [Ph 3 C][B(C 6 F 5 ) 4 ] has led to the formation of adducts Me 2 Ga(O,C NHC )·B(C 6 F 5 ) 3 ( 6 ) and [Me 2 Ga(O,C NHC )·Ph 3 C] + . Although, the reactions of B(C 6 F 5 ) 3 with Me 2 Ga(OC 6 H 4 OMe)(SIMes) ( 7 ) or Me 2 GaOMe(SIMes) ( 8 ) (SIMes = 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene) have resulted in the formation of cationic species [MeGaOR(SIMes)] + , as evidenced by spectroscopic techniques, the side reactions resulting in the formation of (SIMes)B(C 6 F 5 ) 3 and boron alkoxide species have also been observed. Cationic complexes [ 3 ][MeB(C 6 F 5 ) 3 ] 2 and [ 4 ][MeB(C 6 F 5 ) 3 ] 2 are poor catalysts for the ring-opening polymerization of cyclic esters and are essentially not active in the low pressure polymerization of ethylene. [ABSTRACT FROM AUTHOR]

The investigation of the reactivity of six membered N-heterocyclic carbene 1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-1-ylidene (6-Mes) towards dialkylgallium and dialkylindium alkoxides/aryloxides has shown that both steric hindrances and donor properties of 6-Mes significantly influence the strength of M–C6-Mes bond, as well as the formation, structure and reactivity of Me2MOR(6-Mes) (M = Ga, In) complexes. While the reactions of simple dimethylgallium alkoxides with 6-Mes lead to the formation of stable monomeric Me2Ga(OCH2CH2OMe)(6-Mes) (1) and Me2GaOMe(6-Mes) complexes, the analogous Me2InOR(6-Mes) are unstable and disproportionate to methylindium alkoxides and Me3In(6-Mes) (2). The use of bulky alkoxide ligand—OCPh2Me or aryloxide ligand—OC6H4OMe allowed for the synthesis of stable Me2M(OCPh2Me)(6-Mes) (M = Ga (3) and In (4)) as well as Me2M(OC6H4OMe)(6-Mes) (M = Ga (5) and In (6)). The structures of 1–6 have been determined using both spectroscopic methods in solution and X-ray diffraction studies, which confirmed the effect of both steric hindrances and donor properties of 6-Mes on their structure and catalytic properties in the ring-opening polymerization (ROP) of rac-lactide.

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This paper presents a few methods of sol-gel synthesis: alkoxide, non-hydrolytic and colloidal. Sol-gel technology of nanocomposites based on the use of soluble silicates as precursors is discussed. Availability of nanocomposites based on silica aerogels and analysis of mixing technologies of the nanocomposites preparation are considered. Different types of nano-phase used for producing of the nanocomposites are examined. The authors have studied the various models of packaging of nanoparticles (spherical, fibrous and layered) introduced into the nanocomposite structure during its preparation. [ABSTRACT FROM AUTHOR]

In the focus was the question whether metal alkoxide coupling agents - titanium, silane, and zirconium - form covalent bonds to wood and how they improve coating adhesion. In a previous work, a downshift of the lignin infrared (IR) band ∼1600 cm-1 was shown to be consistent with the formation of ether linkages between lignin and titanium coupling agent. In the present work, changes were found in the attenuated total reflectance-Fourier transform IR (ATR-FTIR) spectra of lignin and wood mixed with silane, and titanium coupling agents, and to a lesser extent for a zirconium coupling agent. This was seen as evidence for covalent bonds between lignin phenolics and the coupling agents. No spectral changes were observed when the coupling agents were mixed with the wood constituents cellulose and hemicellulose. For verification of the results, a modified EN 311 wet adhesion pull strength test was performed with softwood panels painted with a solvent-borne alkyd/acrylic coating. The results revealed an improved adhesion for all tested coupling agents compared to the untreated reference. The spectroscopic and pull test results underline that the presence of the lignin moiety in wood is of central importance for improved wood coating adhesion. [ABSTRACT FROM AUTHOR]

The synthesis and structural characterization of two new homo- and heteroleptic tetravalent cerium complexes with tert-butoxo and heteroarylalkenolate ligands of the general formula [Ce(O tBu)2- xLx+2] [ x = 2 ( 1), x = 0 ( 2)] [ L = Dmox-CHC(CF3)O] is described. Their thermal decomposition behavior as well as their potential as single-source precursor for the fabrication of nanostructured ceria was evaluated. By using the heteroleptic alkoxide complex 2 as metal organic precursor, an efficient synthesis of highly crystalline CeO2 QDs with a narrow size distribution was achieved by microwave assisted solvothermal synthesis in NMP. It was found that an expedient choice of precursor enabled the replacement of additives like bases or other mineralizer and opens an efficient pathway for controlled nucleation of metal oxide nanoparticles. [ABSTRACT FROM AUTHOR]

Highlights: [•] TiO2 based nanomaterials were prepared using sol–gel process. [•] Nucleophilic addition is possible giving rise to the intermediate: Ti(OBun)4(PrOH). [•] The samples were characterized using thermal (DTA–TG–DTG) analysis. [•] Optical spectroscopy, XRD and SEM were employed for material characterization. [•] Materials have uniformly distribution even at low temperatures. [ABSTRACT FROM AUTHOR]

Stereoselective polymerization of rac-lactide is one of the most important issues as the properties of polylactide (PLA) depend strongly on its tacticity. There is, however, a paucity of catalysts that allow for easy switching between heteroselectivity and isoselectivity, which limits the synthesis of stereo copolymers of PLA and modification of polylactide properties. Dialkylgallium alkoxides activated by organosuperbases have been used as catalysts in the ring-opening polymerization of racemic lactide ( rac-LA). The reaction of ( S, S)-[Me2Ga(μ-OCH(Me)CO2Me)]2 ( 1) with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) or 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) resulted in the formation of isoselective gallium species, highly active in the polymerization of rac-LA. DOSY (diffusion-ordered spectroscopy) NMR was indicative for the presence of dimeric gallium species. However, the structure of model monomeric gallium alkoxide Me2Ga( ON) (where ON is monoanionic bidentate ligand possessing organosuperbase functionality) shows that the presence of an organosuperbase may substantially weaken Ga−Oalkoxide−Ga bridges. The facile switch of stereoselectivity upon addition of organosuperbase to nonselective/heteroselective 1 allowed for the first time the synthesis of diblock polylactide comprised of isotactically and heterotactically enriched blocks. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Long term storage of the pure commercial Zr(O t Bu)4 in a sealed ampoule results in crystallization of a new high symmetry phase of Zr3O(O t Bu)10 (1). Modification of Zr(O t Bu)4 and Hf(O t Bu)4 with 2,2,6,6,-tetramethyl-3,5-heptanedione (Hthd) produces dependent on the stoichiometry two types of derivatives, M(O t Bu)2(thd)2 (2, 3) and M(O t Bu)(thd)3 (4, 5) M=Zr(2, 4), Hf(3, 5), which have all been characterized by NMR and mass-spectral studies and for 4 and 5 also by complete X-ray single crystal studies. The latter failed for 2 and 3 in the view of their poor X-ray reflectivity. Addition of minor amounts of n-C5H11OH to 3 resulted in isolation of an unusual heteroleptic complex Hf2(OH)(O n C5H11)(O t Bu)2(thd)4 (6). Thermal decomposition of compounds 1 and 3 in nitrogen atmosphere was studied for different thermal regimes by TGA-FTIR approach, revealing in all cases the formation of tetragonal ZrO2 and monoclinic HfO2 respectively, along with iso-butene, butanol and water for 1 and the same mixture including also Hthd for 3. Decomposition of 3 occurred always through intermediate melting, while higher heating rate for 1 permitted to achieve decomposition on in situ evaporation resulting in 3D hedgehog nanostructures according to SEM. [Copyright &y& Elsevier]

Abstract: Mesoporous TiO2 with a hierarchically 3D dendrimeric nanostructure comprised of nanoribbon building units has been synthesized via a spontaneous self-formation process from various titanium alkoxides. These hierarchically 3D dendrimeric architectures can be obtained by a very facile, template-free method, by simply dropping a titanium butoxide precursor into methanol solution. The novel configuration of the mesoporous TiO2 nanostructure in nanoribbon building units yields a high surface area. The calcined samples show significantly enhanced photocatalytic activity and degradation rates owing to the mesoporosity and their improved crystallinity after calcination. Furthermore, the 3D dendrimeric architectures can be preserved after phase transformation from amorphous TiO2 to anatase or rutile, which occurs during calcination. In addition, the spontaneous self-formation process of mesoporous TiO2 with hierarchically 3D dendrimeric architectures from the hydrolysis and condensation reaction of titanium butoxide in methanol has been followed by in situ optical microscopy (OM), revealing the secret on the formation of hierarchically 3D dendrimeric nanostructures. Moreover, mesoporous TiO2 nanostructures with similar hierarchically 3D dendrimeric architectures can also be obtained using other titanium alkoxides. The porosities and nanostructures of the resultant products were characterized by SEM, TEM, XRD, and N2 adsorption–desorption measurements. The present work provides a facile and reproducible method for the synthesis of novel mesoporous TiO2 nanoarchitectures, which in turn could herald the fabrication of more efficient photocatalysts. [Copyright &y& Elsevier]

A technique of preparing microtube shape oxide structures by metal alkoxide gel sheet rolling is presented and discussed. Zr(OBu)4 and Hf(OBu)4 precursors have been used for self-formation of ZrO2 and HfO2 microrolls. The technique involves gelling the surface of concentrated sol, partition of gel film into segments by gel cracking and spontaneous rolling of obtained gel film segments. A phenomenological study of crack evolution in gel films has been conducted. The dependence of the thickness of formed gel film and rolling diameter on hydrolysis extent of metal alkoxide precursor and reaction time is reported. [ABSTRACT FROM AUTHOR]

Reaction of spermine with M(O iPr) (M = Ti, Zr) in toluene solution results in the formation of crystalline coordination polymers [M(O iPr)(CHN)]. In these compounds, only the terminal primary amino groups are coordinated to the metal centers. The adducts are stabilized by intramolecular hydrogen bonds. NMR spectroscopy indicates that only the adduct with Zr(O iPr) is stable in benzene solution, whereas it dissociates in the case of Ti(O iPr). When dichloromethane was used as the solvent, spermine dihydrochloride crystallized from the solution. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: Using the molecular compound Zr(OBut)4 in a liquid-injection chemical vapor deposition process, microporous zirconia membranes were deposited on porous multi-layered alumina substrates consisting of a macroporous α-alumina base covered with a mesoporous γ-alumina layer. The structure of nanocrystalline zirconia (ZrO2), membranes formed by the thermal decomposition of the precursor varied depending on the decomposition temperature and the injection frequency. The deposited zirconia membranes were characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and atomic force microscopy (AFM). X-ray diffraction analysis patterns of the deposits obtained at 500 and 600°C indicated a mixture of tetragonal and monoclinic ZrO2 phases, whereas the fraction of the monoclinic phase increased at higher substrate temperature and injection frequency. Morphology and surface roughness are strongly dependent on the process parameters. ZrO2 membranes prepared by the liquid-injection chemical vapor deposition had a microporous structure with less than 1nm Kelvin diameter. The liquid-injection chemical vapor deposition is a unique method to prepare microporous membranes in one step without any post-treatment. [Copyright &y& Elsevier]

Abstract: A comprehensive computational study of the initiation stage of the ring-opening polymerization (ROP) of meso-lactide catalyzed by various metal alkoxides MOR (M=Li, Mg, Zn, OR=OiPr, OtBu) is presented. Density functional theory at B3LYP/6-31G(d,p) level is applied in examining the coordination-insertion mechanism and reactivity. The influence of tetrahydrofuran medium is simulated both as an explicit coordination and as a bulk solvent. The theoretical computations characterized energetically two possible channels for initiation of the ROP of m-lactide. These channels are associated with the possible attack of the catalyst at two enantiotopic O-acyl bonds of the lactide. The attack at the least staggered plane of the lactide molecule is energetically favored. The theoretical results reveal that the energy pathway for the initiation of ROP catalyzed by alkoxides proceeds via 3 major steps: (1) coordination-addition of the alkoxide MOR to the lactide carbonyl bond; (2) shift of the metal (one step) or rotation of the metal and alkyl (from the alkoxide) grouping in two steps; (3) acyl-oxygen cleavage that leads to ring opening of the lactide. The results reveal that the activity of the initiators follows the trend Li>Mg>Zn. Depending on the ligand, the catalytic activity of the alkoxides decreases in the order OiPr>OtBu. The relative reactivity of the alkoxides is rationalized in terms of theoretical electronic structure indices: NBO charges on the carbonyl oxygen atom and the energy of the LUMO orbital of the alkoxide catalyst. [Copyright &y& Elsevier]

Abstract: Zirconium, titanium and aluminum phthalate (PH, C8H4O4) and pyridine-2-carboxylate (Pyca, C6H4NO2) compounds were prepared by reaction of Zr, Ti and Al-alkoxides with phthalic acid (PHA) and pyridine-2-carboxylic acid (PycaH) in alcohol. All new complexes were characterized by a combination of elemental analysis, NMR and FTIR spectroscopy and used in polymerization of 3-glycidyloxypropyltrimethoxysilane (GPTS) in order to see their catalytic activity over epoxides. Especially, Al, Ti and Zr-phthalate catalysts were more effective in ring opening of GPTS when compared to Al, Ti and Zr-pyridine-2-carboxylate catalysts. Poly-GPTS were characterized by 1H, 13C NMR and gel permeation chromatography (GPC). [Copyright &y& Elsevier]

The syntheses, structural characterization, and thermal degradation of a series of the new indium and gallium siloxide dimers [{Me2In(OSiEt3)}2] ( 1), [{Me2Ga(OSiEt3)}2] ( 2), [{Me2In(OSi(O tBu)3)}2] ( 3), [{Me2Ga(OSi(O tBu)3)}2] ( 4), and In[OSi(O tBu)3)] ( 5) is reported. Compounds 1- 4 are readily accessible by facile Brönsted reaction of InMe3 or GaMe3 with the corresponding silanols Et3SiOH and ( tBuO)3SiOH, respectively. Compound 5 could be obtained by analogous protolysis of [In{N(SiMe3)2}3] with an excess amount of ( tBuO)3SiOH. The suitability of 1- 5 to serve as molecular precursors for low-temperature synthesis of amorphous indium and gallium oxide for electronic applications was probed. Thus their thermal degradation was studied by Thermogravimetric/differential thermogravimetry analysis (TGA/DTG). Compounds 1- 4 were decomposed under dry synthetic air (20 % O2, 80 % N2) at low temperature to yield amorphous indium oxide and gallium oxide particles, respectively. In contrast, thermal degradation of 5 affords amorphous indium silicate. All of these products were analyzed by multiple techniques including powder X-ray diffraction analysis (PXRD), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). Thin-film field-effect transistors (FETs) could be fabricated through spin-coating of silicon-wafers with solutions of 1 in toluene and subsequent calcination under dry synthetic air at 350 °C. These films exhibit very good FET performance with a field-effect mobility of 3.0×10−1 cm2 V−1 s and an on/off current ratio of 108. [ABSTRACT FROM AUTHOR]

The syntheses and structural elucidation of dimeric [Sn(OCyHex)2] ( 1), its corresponding (cyclohexoxy)alkalistannates(II) [{M(OCyHex)3Sn}2] (M=Li ( 2), Na ( 3), K ( 4)), and of the first heteroleptic heterotermetallic Li/In/Sn-haloalkoxide clusters [X2In{LiSn2(OCyHex)6}] (X=Br ( 5), Cl ( 6)) with a double seco-norcubane core are reported. They represent suitable precursors for new amorphous indium tin oxide (ITO) materials as transparent conducting oxides with drastically reduced concentrations of expensive indium, while maintaining their high electrical performance. In fact, compounds 5 and 6 were successfully degraded under dry synthetic air at relatively low temperature, resulting in new semiconducting tin-rich ITOs homogeneously dispersed in a tin oxide/lithium oxide matrix. The obtained particles were investigated and characterised by different analytical techniques, such as powder XRD, IR spectroscopy, SEM, TEM and energy-dispersive X-ray spectroscopy (EDX). The analytical data confirm that the final materials consist of tin-containing indium oxide embedded in an amorphous tin oxide matrix. The typical broadening and shift of the observed indium oxide reflections to higher 2 θ values in the powder XRD pattern clearly indicated that tin centres were successfully incorporated into the In2O3 lattice and partially occupied In3+ sites. Investigations by EDX mapping proved that Sn was homogeneously distributed in the final materials. Thin-film field-effect transistors (FETs) were fabricated by spin-coating of silicon wafers with solutions of 5 in toluene and subsequent calcination under dry air (25-700 °C). The FETs prepared with precursor 5 exhibited excellent performances, as shown by a charge-carrier mobility of 6.36×10−1 cm2 V−1 s (calcination at 250 °C) and an on/off current ratio of 106. [ABSTRACT FROM AUTHOR]

Abstract: Aluminum, titanium and zirconium perfluoroheptanoate (PFH) were prepared by reaction of Al, Ti and Zr-alkoxides with perfluoroheptanoic acid (PFHA) in alcohol. All compounds were characterized by NMR spectroscopy, FTIR, MS and elemental analysis and used in polymerization of 3-glycidyloxypropyltrimethoxysilane (GPTS) in order to see their catalytic activity over epoxides. These catalysts were effective in ring opening of epoxide. Poly-GPTS was characterized by 1H, 13C NMR and gel permeation chromatography (GPC). [Copyright &y& Elsevier]

Abstract: A novel strategy that tailors porous zirconia structures via a control of zirconium alkoxide reactivities has been developed. This control was achieved by limiting the amount of water present in the system through the use of an acetonitrile medium. Varying the amount of water present during the reaction has led to a better understanding of the self-formation phenomenon of hierarchical porosity. The choice of zirconium alkoxide precursor has also been studied. The porosity of the zirconia can be altered simply by tuning the water:acetonitrile ratio. A significant change in the porous structure has been observed with increasing water content. This revelation has led to a better understanding of the formation of hierarchically porous structures and the development of a very efficient and simple method to tailor hierarchical porosity over different length scales. The synthesized zirconia products, with differing porous structures, showed a very high adsorption capacity for dye molecules in aqueous solution. A relationship between the porous structure and the adsorption capacity of dye molecules has been evidenced, suggesting their potential application in water treatment as decontamination materials. [Copyright &y& Elsevier]

A bipolar membrane (BPM) was prepared by the layer-by-layer solution casting method (in the same solvent to achieve good adhesion between the layers). Thin films of different metal alkoxides (M(OR)n, where M is Si, Ti or Zr, and R is ⚊ (CH2)n⚊CH3) were used as interfacial layers (ILs), which were sandwiched between heterogeneous anion-exchange layers (AELs) and homogeneous cation-exchange layers (CELs) of sulfonated poly (ether sulfone) (SPS). The CELs and the AELs were separately evaluated for their physicochemical and electrochemical properties. BPMs prepared with ILs (containing different metal alkoxides) showed good stability and low resistance. Current–voltage (i–V) curves were explained in terms of the first limiting current density (ilim1), the second limiting current density (ilim2), the water dissociation potential (Vdiss), the water dissociation resistance (Rdiss) and the operational area resistance (Rop). The catalytic activity of the metal alkoxides improved the water dissociation performance of the BPMs. The BPM–SiOH performed better than the commercially available BPMs. Furthermore, electrodialysis with a bipolar membrane (EDBPM) experiments confirmed that water dissociation occurred at the BPM interface and thus acid and base formation occurred. [ABSTRACT FROM AUTHOR]

Abstract: Various hierarchical porous titania with high surface area over 600m2/g have been synthesized via a spontaneous self-formation process from titanium alkoxides by a water adjusting approach using acetonitrile as reaction medium. The reactivity of metal alkoxides and the water content in acetonitrile medium on the resultant structure have been investigated. The porosities of the products were characterized by SEM, TEM and N2 adsorption–desorption measurements. The observation on the evolution of porous structure with increasing water content in reaction system is essential for a better understanding of hierarchical porous structure formation over different length scales by this self-formation process. The creation of macro/micropores in photocatalytic titania materials has been found to enhance the photocatalytic activity due to both the action of macrochannels as light harvester and the easy diffusion effect of organic molecules. The present work shows clearly that hierarchically porous titania with the presence of macroporous structure and high surface area can be very efficient photocatalysts, suggesting their potential applications in water treatment as decontamination materials. [Copyright &y& Elsevier]

Investigation of the coordination behavior of 4,4′-methylenebis(2,6-di-tert-butylphenol) (or H2-4DBP) with a series of metal alkoxides led to isolation of [(OR)3M]2(µ-4DBP), where M/OR = Ti/OBut (2), Ti/ONep (3), Zr/OBut (4), Hf/OBut (5), and [(py)(OR)3M]2(µ-4DBP) · py (5a), where py = pyridine and ONep = OCH2C(CH3)3. Metal alkyl derivatives of 4DBP were also studied and found to form similar di-substituted species: [(py)2(Et)Zn]2(µ-4DBP) · py (6), [(THF)3(Br)Mg]2(µ-4DBP) (7), [(THF)2(Br)Mg](µ-4DBP)[Mg(Br)(THF)3] · (THF, tol) (7a), and [(py)(R)2Al]2(µ-4DBP), where R = CH3 (8), Et (9), CH2CH(CH3)2 (10); tol = toluene and THF = tetrahydrofuran. All structures demonstrate the bridging nature of 4DBP and the ability to bind a variety of metal centers. Solution state NMR indicates that the structures of 2–10 are retained in solution. Thermal analyses indicate that 4DBP is preferentially lost during heating. [ABSTRACT FROM AUTHOR]

Cu-doped TiO was prepared by the refluxing of a mixture of copper and titanium alkoxides. The refluxing improved the Cu dispersion in the TiO and formed effective Ti-O-Cu bonds. The impurity states due to the highly dispersed Cu were presumed to trap the electrons in the conduction band of the TiO and prevent charge recombination of the electrons and holes. Consequently, the prolonged charge separation duration was suggested to enhance the photocatalytic activity of the Cu-doped TiO. This enhancement was confirmed by the hydroxyl radical generation and organic compound degradation. The Ti-O-Cu bonds and electronic interaction between Cu and Ti should effectively promote the electron trapping. The Cu-doped TiO exhibited a visible light-induced activity due to the transition from the TiO valence band to the Cu impurity states. [ABSTRACT FROM AUTHOR]

The invention of electrospinning has solved the problem of producing micro- and nanoscaled metal oxide fibres in bulk quantities. However, until now no methods have been available for preparing a single nanofibre of a metal oxide. In this work, the direct drawing method was successfully applied to produce metal oxide (SnO2, TiO2, ZrO2, HfO2 and CeO2) fibres with a high aspect ratio (up to 10 000) and a diameter as small as 200 nm. The sol-gel processing includes consumption of precursors obtained from alkoxides by aqueous or non-aqueous polymerization. Shear thinning of the precursors enables pulling a material into a fibre. This rheological behaviour can be explained by sliding of particles owing to external forces. Transmission (propagation) of light along microscaled fibres and their excellent surface morphology suggest that metal oxide nanofibres can be directly drawn from sol precursors for use in integrated photonic systems. [ABSTRACT FROM AUTHOR]

The sol-gel-derived host matrices are well known for biosensor applications where various types of organic and biological molecules can be immobilized and can act as recognition elements. The molecular imprinting technology is an attractive alternative method where expensive and labile biorecognition elements can be replaced by molecular imprinted polymers (MIPs), which are capable of recognizing a target molecule of an interest. In the present study, hybrid sol-gel MIPs were synthesized in the form of crushed powder (CP) by both non-hydrolytic and hydrolytic method for cholesterol recognition. These MIPs were characterized by scanning electron microscopy (SEM), fourier transform-infrared (FT-IR), liquid chromatography-mass spectrometry (LC-MS) and nitrogen adsorption-desorption isotherm measurements. The template molecule was extracted by means of soxhlet extraction and calcination method. The cholesterol adsorption experiments were performed by using non-imprinted (NI) and extracted crushed powder (ExCP) and the percentage of adsorption was determined by measuring the residual quantity in the analyte solution using Liebermann-Burchard (L-B) reagent. The adsorption studies with non-imprinted crushed powder (NICP) showed interference with L-B reagent as well as non-specific binding between analyte molecules and silica matrix. The percentage of adsorption or rebinding was found to be higher for phenyl triethoxysilane (PhTEOS)-derived ExCP (composition 3) which was synthesized by the aqueous sol-gel processing method at low pH as compared to PhTEOS-derived (composition 1) and 3-aminopropyltriethoxysilane (APTES)-derived ExCP (composition 2) prepared by non-hydrolytic method. The reusability of used ExCP after re-extraction was also investigated. The various factors affecting rebinding of template molecules were discussed along with interference study. The study provided information on molecular imprinting of cholesterol in sol-gel matrix and highlighted the importance of characterization of MIPs before applying it for sensing applications. [ABSTRACT FROM AUTHOR]

This article reviews the progress made in the sub-10 nm electron beam patterning of metal oxides over the last thirty years. The patterning of inorganic resists began with metal halides, they were soon taken over by metal oxides due to their excellent environmental stability. However, these inorganic materials, both halides and oxides, suffered from the requirement of very steep dose, thus rendering them useless for practical applications. This gave way to highly electron beam-sensitive stabilized metal alkoxides and metal naphthenates, with sensitively close to conventional electron beam resists such as poly(methylmethacrylate) (PMMA) and calixarene. Furthermore, they show excellent line edge roughness characteristics at sub-10 nm scale, which is currently unmatched by any other electron beam resist. Recent applications of these resists such as an etch mask and their suitability as gate oxides will be highlighted. [ABSTRACT FROM AUTHOR]

Abstract: Non-agglomerated hybrid particles of 200nm diameter with an outer metal oxide shell were prepared by reacting the COOH groups of poly((S)-N-dicarbazolyl-lysine)-covered silica particles with metal alkoxides, such as titanium, zirconium and aluminum alkoxides, followed by sol–gel processing. With tetraethoxysilane (Si(OEt)4), the silica particle core was growing rather than forming an external metal oxide shell, as observed for the other tested metal alkoxides. [Copyright &y& Elsevier]

Abstract: An investigation of a series of substituted pyridyl-based ligands was undertaken using 2-mercapto pyridine n-oxide (H-2MPO) and 3,3′-dihydroxy-2,2′-bipyridine (H2-OBPy) as the modifying reagents of a series of titanium alkoxides. The resultant products were identified as (2MPO)2Ti(OR)2 [OR=OCHMe2 (1), OCH2CMe3 (2), OCMe3 (3)] and [(OR)2M(μc-OBPy)]3 where M⧹OR=Ti⧹OCH2CMe3 (4) along with Zr⧹OCMe3 (5) from Zr(OCMe3)4 (μc =chelating bridging). The structure of 1–3 were found to adopt similar monomeric structures with octahedrally (Oh) bound Ti metal centers using two terminal OR and two chelating 2MPO derivatives. Switching to the OBPy ligand, cyclic trinuclear species with Oh bound metals that employed two terminal OR and two μc-OBPy ligands were isolated. The two rings of the bridging OBPy were rotated such that one O and one N from different rings chelate to a single metal. The synthesis and characterization of these compounds and comparison to appropriate literature species are presented. [Copyright &y& Elsevier]

Organic-inorganic hybrid materials are derived from the chemical reaction of silane coupling reagents and metal alkoxides, involving O-Si-C bonds in the matrix. They offer superior characters of combined organic groups and inorganic linkages for various optical applications. This paper reviews preparation and characterization of optical devices and materials derived from these hybrid materials. We mainly describe three topics for micrometer-nanometer scale optical components in our laboratories using organic-inorganic hybrid materials: 1) film formation; 2) patterning by the photolithography techniques; and 3) laser emission from dye-doped hybrid spheres and coated glass spheres. [ABSTRACT FROM PUBLISHER]

Since its inception five decades ago, imprinted sol-gel materials went practically unnoticed, until in the 1970s the conceptual introduction of molecular imprinting in synthetic polymers triggered a new interest in this field. The recent growth in interest in organic-inorganic hybrid materials prepared by sol-gel chemistry and the development of a variety of new strategies for imprinting polymeric matrices have led to a growing activity in what became known as molecularly imprinted sol-gel materials. This paper intends to give an overview of recent progress in molecular imprinting in sol-gel matrices, the potential analytical applications of these tailor-made materials and their limitations, with the aim of drawing attention to useful information and to enhancing interest in this practically unexplored but promising field. [ABSTRACT FROM AUTHOR]

Sol–gel derived Bi2Ti2O7 ceramic powders have been prepared from methoxyethoxides of bismuth and titanium (molar ratio of Ti/Bi = 1.23 and water/alkoxides = 1.31). The Bi2Ti2O7 phase was stable at a low temperature (700 °C), but it then transformed into mixed phases of Bi4Ti3O12 and Bi2Ti4O11 at 850–1150 °C. The single phase of Bi2Ti2O7 reoccurred at 1200 °C. Dielectric properties and ferroelectric behavior of samples sintered at 1150 and 1200 °C were examined. Under frequency of 1 MHz, samples sintered at 1150 and 1200 °C had a dielectric constant of 101.3 and 104.2, and a loss tangent of 0.0193 and 0.0145, respectively. Only the sample sintered at 1150 °C showed ferroelectric behavior, where remanent polarization is 3.77 μC cm−2 and coercive field is 24 kV cm−1. Thus, the Bi2Ti2O7 did not exhibit ferroelectricity, but the mixed phase of Bi4Ti3O12 and Bi2Ti4O11 did. [Copyright &y& Elsevier]