Acetylacetonate Groups Research Articles

Study on the underpinning mechanisms of microwave-induced synthesis of carbon-coated metal nanoparticles

Microwave-induced metal arc discharge provides an intriguing solution for the synthesis of carbon-coated metal nanoparticles (M@CNPs) due to its fast formation and improved quality of products, however, the underpinning reaction mechanism is not comprehensively revealed. In this work, the effect of arc discharge intensity on the product morphology is firstly investigated by adjusting microwave power. And then, the effects of the organic groups (i.e. cyclopentadienyl v. s Acetylacetonate groups) and metal catalysis on the product morphology are also investigated by selecting ferrocene, iron acetylacetonate, nickelocene, and nickel acetylacetonate as precursors. Specifically, moderate microwave power can not only destroy the precursor to form carbon nanosheets by inducing intense discharge heat release but also provide sufficient intermittency to allow the carbon nanosheets to deposit on the surface of the metal core, which is an important precondition in fabricating M@CNPs. The structure of organic groups in the precursor also plays a predominant role in adjusting product morphology. Cyclopentadienyl groups tend to encapsulate the metal core to form graphitized carbon shells as the coordination bond between cyclopentadienyl and metal is recognized as a very strong covalent bond that confines the cyclopentadienyl collapse to metal core, and the cyclic structure facilitates the formation of graphite. In contrast, the acetylacetonate groups intend to combine randomly due to their open-loop structure. Moreover, for open-loop structures such as acetylacetonate groups, metal catalysis also affects the growth trend, of which Ni is more likely to induce the formation of carbon nanotubes relative to Fe. This work can provide a good reference for the synthesis of M@CNPs with controllable morphology.

N-Donor-Functionalized Acetylacetones for Heterobimetallic Coordination Polymers, the Next Episode: Trimethylpyrazoles

The ditopic molecule 3-(1,3,5-trimethyl-4-1H-pyrazolyl)acetylacetone (HacacMePz) combines an acetylacetone group suitable for deprotonation and O,O′ coordination to a Pearson hard cation with a softer N-donor site. Both binding modes were employed individually: the pyrazolyl moiety was coordinated to ZnII, HgII, and AgI, and with trivalent iron the tris-chelating O,O′ complex [Fe(acacMePz)3] was isolated. The CuII derivative shows shorter O,O′ chelation and N coordination in the more distant Jahn–Teller sites and exists in two alternative crystal forms: namely, as a tetranuclear discrete complex and as a chain polymer. The different Pearson hardnesses of the coordination sites of acacMePz– allow for the design of well-ordered mixed-metal solids. Selective complexation to a hard and soft cations was achieved in coordination polymers combining hard FeIII and softer HgII or AgI. Even slight differences in Pearson hardness based on different oxidation states of the same cation imply sufficient selectivity, as shown by the successful synthesis of a mixed-valence CuII/CuI chain polymer. A synopsis of all structurally characterized compounds confirms that HacacMePz represents a bridging ligand with restricted conformational freedom. No full rotation about the single bond between the pyrazolyl and acetylacetone fragments occurs, and dihedral angles between these moieties are limited to values of 90 ± 17°.

Molecular‐Scale Strategies to Achieve High Efficiency and Low Efficiency Roll‐off in Simplified Solution‐Processed Organic Light‐Emitting Diodes

AbstractSolution‐processed small‐molecule organic light‐emitting diodes (OLEDs) are regarded as next‐generation flat‐panel displays and solid‐state lighting sources due to low material loss and a simple device fabrication process. However, they still suffer from low device efficiency and severe efficiency roll‐off. Here, molecular‐scale strategies are proposed to achieve highly efficient solution‐processed small‐molecule OLEDs with reduced efficiency roll‐off. By combining experiments with ab initio and molecular dynamics simulations, it is shown that an acetylacetonate group in a phosphorescent dopants lowers the dipole moment and molecular interaction energy of dopants, reducing dopant aggregation and increasing charge carrier transport. Furthermore, a charge‐balance assistant molecule is incorporated in the mixed‐host emitting layer to increase the balance of charge carrier transport and to broaden the exciton recombination zone in the center of the emitting layer. The resulting OLEDs have a current efficiency (CE) of 103.7 cd A−1, which is the highest yet reported in solution‐processed OLEDs, and low efficiency roll‐off (CE = 99.68 cd A−1 at a luminance LEL = 100 cd m−2, and CE = 75.00 cd A−1 at LEL = 1000 cd m−2) even with the simplified device architecture. It is expected that this strategy will advance the feasibility of commercialization of low‐cost high‐efficiency OLEDs.

Electrochemistry of Tri‐substituted Porphyrins with β‐Appended Ethyl Acetoacetate and Acetylacetone in Neutral and Basic Nonaqueous Solvents

AbstractThe electrochemistry of β‐substituted tetraphenylporphyrins with a single ethyl acetoacetate (EAA), acetylacetone (acac), or ethyl acetate (EA) group and two antipodal H, Br or Ph groups was investigated in CH2Cl2 containing 0.1 M tetrabutylammonium perchlorate (TBAP) before and after addition of base to solution in the form of tetrabutylammonium hydroxide (TBAOH). The tri‐substituted porphyrins in their neutral form are represented as MTPP(EAA)X2, MTPP(acac)X2 and MTPP(EA)X2, where TPP is the dianion of tetraphenylporphyrin, M=H2, NiII, CuII or ZnII and X=H, Br or Ph. The singly reduced porphyrins are relatively stable on the cyclic voltammetry timescale, but this is not the case for the doubly reduced EAA and acac derivatives, which are highly reactive at room temperature, leading to a porphyrin product assigned as containing a deprotonated EAA− or acac− (enolate) substituent. Enolate‐appended porphyrins were also generated in‐situ by the addition of TBAOH, resulting in mono‐anionic porphyrins that are harder to reduce by 110–160 mV as compared to the neutral compounds with the same β‐substituents, suggesting a high degree of interaction between the deprotonated EAA− or acac− substituent and the porphyrin π‐ring system. The chemically or electrochemically generated enolate‐appended porphyrin could also be irreversibly oxidized by one electron at peak potentials between 0.10 and 0.30 V; the exact value depending upon solvent and type of β‐diketo substituent.

Получение и выделение кремнийсодержащих продуктов из рисовой шелухи

To isolate silicon-containing products from plant materials, the reaction of interaction of rice husks with triethanolamine and ethylene glycol have been investigated. The effect of pretreatment of raw materials and the reaction conditions on the yield of soluble products containing silicon has been studied. It has been shown that the highest enrichment of rice husks with silicon occurs upon its treatment with concentrated hydrochloric acid and the Schweitzer's reagent. The highest degree of silicon extraction (69%) was achieved at using native rice husks and vanadyl acetylacetonate as a catalyst. The resulting solution contained silicon in the form of silatrane fragments. In order to isolate a silicon-containing product from the ethylene glycol solution, which would have the prospect of practical use and the maximum silicon yield, the heterofunctional polycondensation method was applied. It has appeared to be possible to isolate solid products using acetylacetonates of trivalent and tetravalent metals, which formed metal siloxanes. The structure of the obtained compounds has been confirmed by the element and X-ray diffraction analysis, as well as by the IR spectroscopy. When using rice husk chaffs as a silicon source, the product of the reaction with ethylene glycol and triethanolamine has appeared to be an irregular copolymer comprising amorphous silicon dioxide fragments and cyclic fragments similar in structure to that of silatranes. The application of metal acetylacetonates has made it possible to isolate silicon derivatives in the form of organometallic siloxanes. Тhe yield of metalsiloxanes increased in the sequence Zr < Fe < Al. Apparently, this was due to formation of lattice structures in the case of trivalent aluminum and iron, while zirconium had two remaining acetylacetonate groups and, in this case, its functionality was lower than for trivalent metals, which was confirmed by the spectral data.

Proton disorder in a short intramolecular hydrogen bond investigated by single-crystal neutron diffraction at 2.5 and 170 K.

The substituted acetylacetone 3-[2-(pyridin-4-yl)ethyl]pentane-2,4-dione, C12H15NO2, (1), with an ethylene bridge between the acetylacetone moiety and the heteroaromatic ring, represents an attractive linker for mixed-metal coordination polymers. In the crystal, (1) adopts an antiperiplanar conformation with respect to the C-C bond in the central ethylene group and almost coplanar acetylacetone and pyridyl groups. The ditopic molecule exists as the enol tautomer, with proton disorder in the short intramolecular hydrogen bond. Single-crystal neutron diffraction at 2.5 K indicated site occupancies of 0.602 (17) and 0.398 (17). The geometry of the acetylacetone moiety is in agreement with such a site preference of the bridging hydrogen: the O atom associated with the preferred H-atom site subtends the longer [1.305 (2) Å] and the more carbonyl-like O atom the shorter [1.288 (2) Å] C-O bond. Based on structure-factor calculations for the alternative H-atom sites, reflections particularly sensitive for proton distribution were identified and measured in a second neutron data collection at 170 K. At this temperature, 546 independent neutron intensities were used to refine positional and isotropic displacement parameters for a structure model in which parameters for C and O atoms were constrained to those obtained by single-crystal X-ray diffraction at the same temperature. The site occupancies for the disordered proton do not significantly differ from those at 2.5 K.

Acetylacetone Covalent Triazine Framework: An Efficient Carbon Capture and Storage Material and a Highly Stable Heterogeneous Catalyst

We present, for the first time, covalent triazine frameworks functionalized with acetylacetonate group (acac-CTFs). They are obtained from the polymerization of 4,4′-malonyldibenzonitrile under ionothermal conditions and exhibit BET surface areas up to 1626 m2/g. The materials show excellent CO2 uptake (3.30 mmol/g at 273 K and 1 bar), H2 storage capacity (1.53 wt % at 77 K and 1 bar), and a good CO2/N2 selectivity (up to 46 at 298 K). The enhanced CO2 uptake value and good selectivity are due to the presence of dual polar sites (N and O) throughout the material. In addition, acac-CTF was used to anchor VO(acac)2 as a heterogeneous catalyst. The V@acacCTF showed outstanding reactivity and reusability for the modified Mannich-type reaction with a higher turnover number than the homogeneous catalyst. The higher reactivity and reusability of the catalyst come from the coordination of the vanadyl ions to the acetyl acetonate groups present in the material. The strong metalation is confirmed from Fourier trans...

Effect of precursor structure on mixed-crystal phase titanium oxide synthesized by sol-gel reaction in supercritical carbon dioxide

Effects of the precursor structure on crystallinity and morphology of titanium oxide from sol-gel reaction and drying in supercritical carbon dioxide was investigated. The titanium precursors examined in this work are: titanium isopropoxide (TIP), titanium tetrabutoxide (TBO), titanium ethylhexoxide (TEO) and titanium diisopropoxide bis(acetylacetonate) (TDB). A mixed-crystal phases with anatase and rutile phases were formed from the titanium oxide synthesized in supercritical carbon dioxide at the lower calcination temperatures. The formation of the rutile phase in the mixed-crystal titanium oxide was facilitated by using the TEO and TDB precursor with long alkyl chain and acetylacetonate group and the calcination in argon gas. The fibrous titanium oxide was synthesized from the supercritical sol-gel reaction using TIP. The supercritical sol-gel reaction using TBO precursor succeeded the titanium oxide mixed-crystal of anatase and rutile phases with the urchin-like morphology with a surface area of 63 m2 g−1.

Monolithic zirconia aerogel from polyacetylacetonatozirconium precursor and ammonia hydroxide gel initiator: formation mechanism, mechanical strength and thermal properties.

Zirconia (ZrO2) aerogels are potential candidates for use at temperatures higher than those attainable with silica aerogels. However, fabricating a robust ZrO2 aerogel with a high thermal stability is still a challenge. The extreme electronegativity of Zr makes the hydrolysis and polycondensation of zirconium precursors difficult to control, leading to poor structural integrity and unsatisfactory physical properties. In the present research, we prepared a ZrO2 aerogel by using a synthetic zirconium precursor, namely polyacetylacetonatozirconium (PAZ), and ammonia hydroxide as the gel initiator. The ammonia hydroxide catalyzes the cross-linking of PAZ via promotion of the dehydration between hydroxyls in PAZ and the acetylacetonate group in PAZ binds the zirconium ion firmly upon the addition of ammonia hydroxide to avoid a gel precipitate. A monolithic ZrO2 aerogel with a large diameter size of 4.4 cm and high optical transmittance was achieved after drying. The surface area and pore volume of the as-dried ZrO2 aerogel were as high as 630.72 m2 g−1 and 5.12 cm3 g−1, respectively. They decreased to 188.62 m2 g−1 and 0.93 cm3 g−1 after being heat-treated at 1000 °C for 2 h. The best mechanical performances of the ZrO2 aerogels showed a compressive strength of 0.21 ± 0.05 MPa and a modulus of 1.9 ± 0.3 MPa with a density of 0.161 ± 0.008 g cm−3. Both pore structures and mechanical performances varied according to the ammonia hydroxide gel initiator used. The thermal insulating properties of the ZrO2 aerogel performed better than a silica aerogel blanket with a thermal conductivity of 0.020 W (m−1 K−1).

New active meso-porous titania foam as size limiter for metal nanoparticles

We present here a new sustainable method to fabricate peculiar titania mesofoam (mF), showing open cells with homogeneous size and shape for applications in heterogeneous catalysis. The mF was fabricated from an aqueous suspension of monodisperse polystyrene beads in diluted titanium acetylacetonate. The acetylacetonate group is proposed to be the driving force for the adsorption of the metal complex on the polystyrene beads. On top of the obtained anatase foam, we deposited gold nano-particles as an example of catalytically active metal nanoparticles, where the size of the metal nanoparticles was very sensitive to the temperature of catalytic tests. The resulting catalyst was fully characterized for application in the catalytic oxidation of CO and C3H6. The catalytic activity is strongly influenced by thermal treatments which increase the mean Au particle size distribution of the catalyst. Nevertheless, the proposed method for mF fabrication is able to generate mesopores that delimit the size of the gold nanoparticles to the mesopore size of the foam (i.e at average size below 10 nm) even in severe reaction conditions. This unusual attitude of the mF to delimit the gold nanoparticle size might also be effective for other metal nanoparticles. Consequently, we foresee that the proposed method could open a new route foractive inorganic mF, as support for metal nanoparticles.

Position Assignment and Oxidation State Recognition of Fe and Co Centers in Heterometallic Mixed-Valent Molecular Precursors for the Low-Temperature Preparation of Target Spinel Oxide Materials.

A series of mixed-valent, heterometallic (mixed-transition metal) diketonates that can be utilized as prospective volatile single-source precursors for the low-temperature preparation of MxM'3-xO4 spinel oxide materials is reported. Three iron-cobalt complexes with Fe/Co ratios of 1:1, 1:2, and 2:1 were synthesized by several methods using both solid-state and solution reactions. On the basis of nearly quantitative reaction yields, elemental analyses, and comparison of metal-oxygen bonds with those in homometallic analogues, heterometallic compounds were formulated as [FeIII(acac)3][CoII(hfac)2] (1), [CoII(hfac)2][FeIII(acac)3][CoII(hfac)2] (2), and [FeII(hfac)2][FeIII(acac)3][CoII(hfac)2] (3). In the above heteroleptic complexes, the Lewis acidic, coordinatively unsaturated CoII/FeII centers chelated by two hexafluoroacetylacetonate (hfac) ligands maintain bridging interactions with oxygen atoms of acetylacetonate (acac) groups that chelate the neighboring FeIII metal ion. Preliminary assignment of Fe and Co positions/oxidation states in 1-3 drawn from X-ray structural investigation was corroborated by a number of complementary techniques. Single-crystal resonant synchrotron diffraction and neutron diffraction experiments unambiguously confirmed the location of Fe and Co sites in the molecules of dinuclear (1) and trinuclear (2) complexes, respectively. Direct analysis in real time mass spectrometry revealed the presence of FeIII- and CoII-based fragments in the gas phase upon evaporation of precursors 1 and 2 as well as of FeIII, FeII, and CoII species for complex 3. Theoretical investigation of two possible "valent isomers", [FeIII(acac)3][CoII(hfac)2] (1) and [CoIII(acac)3][FeII(hfac)2] (1'), provided an additional support for the metal site/oxidation state assignment giving a preference of 6.48 kcal/mol for the experimentally observed molecule 1. Magnetic susceptibility measurements data are in agreement with the presence of high-spin FeIII and CoII magnetic centers with weak anti-ferromagnetic coupling between those in molecules of 1 and 2. Highly volatile heterometallic complexes 1-3 were found to act as effective single-source precursors for the low-temperature preparation of iron-cobalt spinel oxides FexCo3-xO4 known as important materials for diverse energy-related applications.

Hydrothermal processing of electrospun fibers in the synthesis of 1D ZnO nanoparticles

ZnO fibers were prepared by electrospinning of a viscous solution of zinc acetate and polyvinylpyrrolidone in C2H5OH/H2O followed by their calcination at 400°C. Thus obtained ZnO fibers were hydrothermally processed at 160°C in aqueous medium containing hydrolyzed zinc acetylacetonate. For short times of electrospinning and relatively short times of hydrothermal processing the uniform ZnO nanorods perpendicular to the axis of electrospun fibers were obtained. The adsorption of zinc hydrolytical products as well as an acetylacetonate group on selected crystal planes was considered responsible for the morphology and size of the ZnO produced. For a longer time (8h) of hydrothermal processing the recrystallization of ZnO was noticed with the formation of bigger particles elongated along the c-axis with a±b.

Interaction of polyphenylsiloxane with magnesium acetylacetonate

Interaction of polyphenylsiloxane with magnesium acetylacetonate in boiling toluene has been studied. The products isolated via extraction and fractional precipitation have been characterized with elemental analysis, IR spectroscopy, X-ray diffraction analysis, and thermal analysis. The reaction products are polymers containing acetylacetonate group at magnesium atom. Structure of the major product has been suggested.

Conformational features of meso-tetrathienylporphyrins and photosensitising properties of their β-1-acetyl-2-oxopropyl derivatives

The difference in the site of electrophilic nitration of meso-tetra-thien-2-yl- and thien-3-yl-porphyrins is explained based on the difference in extended conjugation between porphyrin core and meso-thienyl rings. The significance of resonance in dictating the site of substitution is also explained based on the behavior of tetrakis(5-bromothien-2-yl)porphyrin toward electrophilic nitration. Three new β-1-acetyl-2-oxopropyl-substituted porphyrins are synthesized by Michael addition of acetylacetone group on pyrrole β-nitroporphyrins. The photosensitizing properties of these porphyrins is investigated using porphyrin–TiO2 composites in the degradation of 4-nitrophenol. The results showed the importance of the effect of the position of sulfur on the thienyl ring and the orientation of meso-thienyl groups with the central macrocyclic ring of porphyrins in deciding its efficiency as photosensitiser.

Preparation of polyboronphenylsiloxanes by mechanochemical activation

Linear polyboronphenylsiloxanes containing fluorine atom at silicon and acetylacetonate group at boron have been synthesized by mechanochemical activation. Mechanochemical activation of polyphenylsilsesquioxane and boron difluoride acetylacetonate taken in molar ratio 1 : 1 was shown to lead to the formation of polyboronphenylsiloxane with the given Si/B ratio. The products are characterized by gel chromatography, IR, NMR spectroscopy, elemental analysis, and X-ray phase analysis. The increase of the starting ratio Si/B enhances side processes and formation of polydisperse products with the Si/B ratio different from the desired one. The mechanism of the reaction is suggested.

Comparative study of copper complexes with different anchoring groups by molecular modeling and its application to dye-sensitized solar cells

Copper complexes with different anchoring groups (based on biquinoline ligands with acetylacetone, catechol, hydroxamic acid, phosphonic acid and thiocarboxylic acid groups) have been studied by Density Functional Theory and Time-Dependent Density Functional Theory, also the integral equation formalism of the polarizable continuum model has been extended to the calculation of solvent effects. Maximum absorption wavelength reaches the highest value for the complex with hydroxamic acid as anchoring group but a low oscillator strength; the rest of the complexes fulfill both properties. In general, the molecular orbitals energy levels and the schematic representation of them suppose an appropriate electron transfer between the sensitizer and the semiconductor (TiO2), emphasizing more clearly for the copper complex with the thiocarboxylic acid. Chemical reactivity parameters like chemical hardness shows similitude for all molecular systems; but not so in the case of the electrophilicity index and electroaccepting power.

Linker Rectifiers for Covalent Attachment of Transition‐Metal Catalysts to Metal‐Oxide Surfaces

Linkers that favor rectification of interfacial electron transfer are likely to be required for efficient photo-driven catalysis of multi-electron reactions at electrode surfaces. Design principles are discussed, together with the synthesis and characterization of a specific pair of molecular linkers, related by inversion of the direction of an amide bond in the heart of the molecule. The linkers have a terpyridyl group that can covalently bind Mn as in a well-known water oxidation catalyst and an acetylacetonate group that allows attachment to TiO2 surfaces. The appropriate choice of the sense of the amide linkage yields directionality of interfacial electron transfer, essential to enhance electron injection and slow back-electron transfer. Support comes from electron paramagnetic resonance and terahertz spectroscopic measurements, as well as computational modeling characterizing the asymmetry of electron transfer properties.

Monodentate and bridging behaviour of the sulfur-containing ligand 4′-[4-(methylsulfanyl)phenyl]-4,2′:6′,4′′-terpyridine in two discrete zinc(II) complexes with acetylacetonate

The Zn complexes bis(acetylacetonato-κ(2)O,O')bis{4'-[4-(methylsulfanyl)phenyl]-4,2':6',4''-terpyridine-κN(1)}zinc(II), [Zn(C(5)H(7)O(2))(2)(C(22)H(17)N(3)S)(2)], (I), and {μ-4'-[4-(methylsulfanyl)phenyl]-4,2':6',4''-terpyridine-κ(2)N(1):N(1'')}bis[bis(acetylacetonato-κ(2)O,O')zinc(II)], [Zn(2)(C(5)H(7)O(2))(4)(C(22)H(17)N(3)S)], (II), are discrete entities with different nuclearities. Compound (I) consists of two centrosymmetrically related monodentate 4'-[4-(methylsulfanyl)phenyl]-4,2':6',4''-terpyridine (L1) ligands binding to one Zn(II) atom sitting on an inversion centre and two centrosymmetrically related chelating acetylacetonate (acac) groups which bind via carbonyl O-atom donors, giving an N(2)O(4) octahedral environment for Zn(II). Compound (II), however, consists of a bis-monodentate L1 ligand bridging two Zn(II) atoms from two different Zn(acac)(2) fragments. Intra- and intermolecular interactions are weak, mainly of the C-H···π and π-π types, mediating similar layered structures. In contrast to related structures in the literature, sulfur-mediated nonbonding interactions in (II) do not seem to have any significant influence on the supramolecular structure.

Structures of benzoxazine-fused triazoles as potential diuretic agents

6,8-Dinitro-2,4-dihydro-1H-benzo[b][1,2,4]triazolo[4,3-d][1,4]oxazin-1-one, C(9)H(5)N(5)O(6), (I), a potential diuretic, and its acetylacetone derivative (E)-2-(2-hydroxy-4-oxopent-2-en-3-yl)-6,8-dinitro-2,4-dihydro-1H-benzo[b][1,2,4]triazolo[4,3-d][1,4]oxazin-1-one, C(14)H(11)N(5)O(8), (II), both crystallize from methanol but in centrosymmetric and noncentrosymmetric space groups, respectively. To the best of our knowledge, this is the first report of crystal structures of benzoxazine-triazole fused systems. The acetylacetone group in (II) exists as the keto-enol tautomer and is oriented perpendicular to the triazol-3-one ring. Of the two nitro groups present, one is rotated significantly less than the other in both structures. The oxazine ring adopts a screw-boat conformation in (II), whereas it is almost planar in (I). N-H···N and N-H···O hydrogen bonds form centrosymmetric dimers in (I), while C-H···O interactions associate the molecules into helical columns in (II).

(Acetylacetonato-κ2O,O′)bis[2-(naphth[1,2-d][1,3]oxazol-2-yl)phenyl-κ2C1,N]iridium(III)

In the crystal structure of the title compound, [Ir(C17H10NO)2(C5H7O2)], the IrIII atom is O,O′-chelated by the acetyl­acetonate group and C,N-chelated by the 2-aryl­naphth[1,2-d]oxazole groups. The six-coordinate metal atom displays a distorted octa­hedral geometry.