An Overview of Metal Acetylacetonates: Developing Areas/Routes to New Materials and Applications in Organic Syntheses

Distinct baseline toxicity of volatile organic compounds (VOCs) in gaseous and liquid phases: Mixture effects and potential molecular mechanisms

Volatile organic compounds (VOCs) are significant pollutants found in various environments, posing health risks. Traditionally, the gaseous VOCs are adsorbed and eluted in liquid phases, and then subjected to toxicity testing, which deviates from the actual exposure scenarios of gaseous VOCs. How the physical states of VOCs (gaseous or liquid) affect their toxicity has not been well understood. This study examined the baseline toxicity of VOCs in both gaseous and liquid phases using a self-assembled passive colonization hydrogel (SAPCH) with luminous bacteria (Vibrio fischeri). The findings revealed that gaseous VOCs exhibited higher baseline toxicity than their liquid counterparts, attributed to the higher free energy and electronic activity of gaseous VOC molecules. Furthermore, the study elucidated that the differences in electronic transitions and energy gaps significantly impact the combined toxicity of VOC mixtures in different phases. Understanding these differences is crucial for assessing the real-world impact of VOCs on health and the environment.

Nonaqueous G-Quadruplex Ionogels

Supramolecular ionogels, as an emerging class of materials, utilize the intriguing properties of ionic liquids (ILs) and offer a promising method for constructing functional materials in anhydrous solvents. G-Quadruplex, assembled from guanine-rich nucleic acid building blocks, is an important structure closely associated with life and leads to the gelation for constructing versatile materials, such as the electrolytes of supercapacitors. Herein, we design and fabricate G-quadruplex ionogels using an unreported cation. Among the metal acetylacetonates under investigation, iron(III) acetylacetonate is distinctive in its capacity to stabilize G-quadruplexes through a reaction with the solvent ethylammonium nitrate (EAN), resulting in the formation of Fe(acac)2+. The ionogel displays high ionic conductivity (6.43 mS·cm-1), a wide electrochemical stability window (2.86 V), and self-healing properties. The supercapacitor based on the G-quadruplex ionogel electrolyte delivers a gravimetric capacitance of 91.8 F·g-1, a high energy density of 32.6 W h/kg, and a power density of 319.8 W/kg at a current density of 0.2A·g-1. Therefore, the present findings have important implications for deepening the understanding of G-quadruplex structures and metal acetylacetonate complexes and provide an approach to fabricating ionogel electrolytes for high-performance supercapacitors.

Osmium(III) Acetylacetonate and Its Missing Polymorph: A Magnetic and Structural Investigation

Despite the potential for their application, the magnetic behavior of complexes containing 4d and 5d metal ions is underexplored, evidencing the need for benchmark multi-technique studies on simple molecules. We report here a structural and magnetic study on osmium(III) acetylacetonate [Os(acac)3]. X-ray single crystal diffraction did not allow us to determine the structure of the β-polymorph of [Os(acac)3]. The combined magnetic (dc magnetic measurements on powder and cantilever torque magnetometry on single crystal) and spectroscopic (electron paramagnetic resonance, EPR) characterization is here used to provide further evidence that its structure is indeed the one of the orthorhombic "missing polymorph", analogous to the ruthenium(III) derivative. Our study shows that all acetylacetonate complexes of the eighth group of the periodic table show dimorphism and are isomorphic. The EPR characterization allowed the experimental assessment of the easy axis nature of the ground doublet and the determination of the first hyperfine coupling in an osmium complex. Torque magnetometry, applied here for the first time on an osmium-based molecule, determined the orientation of the easy axis along the pseudo C3 axis of the complex. Ac magnetometric measurements revealed in-field slow relaxation of the magnetization further slowed by the suppression of dipolar fields via magnetic dilution in the isostructural gallium(III) analogue.

Synthesis of a Palladium Dimer Supported by a C-Bound Trifluoroacetonate Bridge Formed by Cleavage of a Hexafluoroacetylacetonate Ligand

Palladium(II) hexafluoroacetylacetonate (Pd(Hfacac)2) is known to form adducts of bases, such as lutidine (2,6-dimethylpyridine). When treated with approximately 3 equiv of lutidine, Pd(Hfacac)2 yields a 1:1 complex as reported in the literature, Pd(O,O-Hfacac)(C-Hfacac)(lutidine), 1. However, when the amount of excess lutidine is increased, a new complex, 2, is formed. A single-crystal X-ray structure of 2 proves it is a rare example of a dimeric palladium complex containing two Pd(Hfacac)(lutidine) fragments bridged by a dianionic trifluoroacetonate ligand, μ-CHC(O)CF3. The formation of 2 is accompanied by a white precipitate determined to be a mixture of trans-Pd(O2CCF3)2(lutidine)2 (3), confirming the fate of the missing trifluoroacetate fragment from the cleavage of the Hfacac ligand, and [lutidinium][Hfacac] (4). Subsequent experiments revealed the determinative role that water played in this reaction. The mechanism of cleavage of the Hfacac ligand was explored by DFT methods.

Liquid-Phase Cyclic Chemiluminescence for the Identification of Cobalt Speciation

Accurate discrimination of metal species is a significant analytical challenge. Herein, we propose a novel methodology based on liquid-phase cyclic chemiluminescence (CCL) for the identification of cobalt speciation. The CCL multistage signals (In) of the luminol-H2O2 reaction catalyzed by different cobalt species have different decay coefficients k. Thereby, we can facilely identify various cobalt species according to the distinguishable k values, including the complicated and structurally similar cobalt complexes, such as analogues of [Co(NH3)5X]n+ (X = Cl-, H2O, and NH3), Co(II) porphyrins, and bis(2,4-pentanedione) cobalt(II) derivatives. Especially, the number of substituent atoms also influences the k value greatly, which allows excellent discrimination between complexes that only have a subtle difference in the substituent group. In addition, linear discriminant analysis based on In provides a complementary solution to improve the differentiating ability. We performed density functional theory calculations to investigate the interaction mode of H2O2 over cobalt species. A close negative correlation between the adsorption energy and the k value is observed. Moreover, the calculation of energy evolutions of H2O2 decomposition into a double hydroxide radical shows that a high level of consistency exists between the activation energy barrier and the k value. The results further demonstrate that the decay coefficient of the CCL multistage signal is associated with the catalytic reactivity of the cobalt species. Our work not only broadens the application of chemiluminescence but also provides a complementary technology for speciation analysis.

Formation of intermetallic PdIn nanoparticles: influence of surfactants on nanoparticle atomic structure

Bimetallic nanoparticles have been extensively studied as electrocatalysts due to their superior catalytic activity and selectivity compared to their monometallic counterparts. The properties of bimetallic materials depend on the ordering of the metals in the structure, and to tailor-make materials for specific applications, it is important to be able to control the atomic structure of the materials during synthesis. Here, we study the formation of bimetallic palladium indium nanoparticles to understand how the synthesis parameters and additives used influence the atomic structure of the obtained product. Specifically, we investigate a colloidal synthesis, where oleylamine was used as the main solvent while the effect of two surfactants, oleic acid (OA) and trioctylphosphine (TOP) was studied. We found that without TOP included in the synthesis, a Pd-rich intermetallic phase with the Pd3In structure initially formed, which transformed into large NPs of the CsCl-structured PdIn phase. When TOP was included, the syntheses yielded both In2O3 and Pd3In. In situ X-ray total scattering with Pair Distribution Function analysis was used to study the formation process of PdIn bimetallic NPs. Our results highlight how seemingly subtle changes to material synthesis methods can have a large influence on the product atomic structure.

Electronic Structure of the Complete Series of Gas-Phase Manganese Acetylacetonates by X-ray Absorption Spectroscopy

Metal centers in transition metal-ligand complexes occur in a variety of oxidation states causing their redox activity and therefore making them relevant for applications in physics and chemistry. The electronic state of these complexes can be studied by X-ray absorption spectroscopy, which is, however, due to the complex spectral signature not always straightforward. Here, we study the electronic structure of gas-phase cationic manganese acetylacetonate complexes Mn(acac)1-3+ using X-ray absorption spectroscopy at the metal center and ligand constituents. The spectra are well reproduced by multiconfigurational wave function theory, time-dependent density functional theory as well as parameterized crystal field and charge transfer multiplet simulations. This enables us to get detailed insights into the electronic structure of ground-state Mn(acac)1-3+ and extract empirical parameters such as crystal field strength and exchange coupling from X-ray excitation at both the metal and ligand sites. By comparison to X-ray absorption spectra of neutral, solvated Mn(acac)2,3 complexes, we also show that the effect of coordination on the L3 excitation energy, routinely used to identify oxidation states, can contribute about 40-50% to the observed shift, which for the current study is 1.9 eV per oxidation state.

Ligand Decomposition during Nanoparticle Synthesis: Influence of Ligand Structure and Precursor Selection

Aliphatic amine and carboxylic acid ligands are widely used as organic solvents during the bottom-up synthesis of inorganic nanoparticles (NPs). Although the ligands' ability to alter final NP properties has been widely studied, side reactivity of these ligands is emerging as an important mechanism to consider. In this work, we study the thermal decomposition of common ligands with varying functional groups (amines and carboxylic acids) and bond saturations (from saturated to polyunsaturated). Here, we investigate how these ligand properties influence decomposition in the absence and presence of precursors used in NP synthesis. We show that during the synthesis of inorganic chalcogenide NPs (Cu₂ZnSnS₄, Cu _x S, and SnS _x ) with metal acetylacetonate precursors and elemental sulfur, the ligand pyrolyzes, producing alkylated graphitic species. Additionally, there was less to no ligand decomposition observed during the sulfur-free synthesis of ZnO and CuO with metal acetylacetonate precursors. These results will help guide ligand selection for NP syntheses and improve reaction purity, an important factor in many applications.

Facile Modification of Flexible Electrodes via Laser Transfer

In this work, we report the modification of commercially available electrochemical electrodes with tin oxide (SnO₂) and Pd doped SnO₂ (Pd-SnO₂) via pulsed laser-induced forward transfer (LIFT). The pulsed light irradiation working as in situ pulsed photo-thermal treatment allows for the transfer of SnO₂ and Pd-SnO₂ from UV absorbing metal complex precursors onto flexible, commercially available screen-printed electrodes. The laser transfer conditions are optimized and the material transferred under different conditions is evaluated morphologically and chemically, and its functionality is tested against the detection of copper ions. For example, by applying laser fluences in the range 100–250 mJ/cm², the shape and the size of the transferred features ranges from nano-polyhedrons to near corner-grown cubic Pd-SnO₂ or near cubic Pd-SnO₂. In addition, the EDX analysis is consistent with the XPS findings, i.e., following laser transfer, Pd amounts lower than 0.5% are present in the Pd-SnO₂ pixels. First sensing tests were carried out and the transferred Pd-SnO₂ proved to enhance the cathodic peak when exposed to Cu(II) ions. This photo-initiated fabrication technology opens a promising way for the low-cost and high-throughput manufacturing of metal oxides as well as for electrodes for heavy metal ion detection.

Fluorinated β-diketonate complexes M(tfac)2(TMEDA) (M = Fe, Ni, Cu, Zn) as precursors for the MOCVD growth of metal and metal oxide thin films

Novel trifluoroacetylacetonate complexes M(tfac)2·TMEDA (M = Fe, Ni, Cu, Zn) were used as precursors for the MOCVD growth of metal and metal oxide thin films.

La(III)-Catalysed degradation of polyesters to monomers via transesterifications

Tris(acetylacetonato)lanthanum(III) (1 mol%) catalyses the degradation of poly(butylene succinate) (Mw = 90,700) by transesterification in MeOH at 90 ˚C for 4 h, thus affording dimethyl succinate (>99% yield) and 1,4-butanediol...

Solventless synthesis of nanospinel Ni1−xCoxFe2O4 (0 ≤ x ≤ 1) solid solutions for efficient electrochemical water splitting and supercapacitance

The formation of solid solutions represents a robust strategy for modulating the electronic properties and improving the electrochemical performance of spinel ferrites. However, solid solutions have been predominantly prepared via wet chemical routes, which involve the use of harmful and/or expensive chemicals. In the present study, a facile, inexpensive and environmentally benign solventless route is employed for the composition-controlled synthesis of nanoscopic Ni_1−xCo_xFe₂O₄ (0 ≤ x ≤ 1) solid solutions. The physicochemical characterization of the samples was performed by p-XRD, SEM, EDX, XPS, TEM, HRTEM and UV-Vis techniques. A systematic investigation was also carried out to elucidate the electrochemical performance of the prepared nanospinels towards energy generation and storage. Based on the results of CV, GCD, and stability tests, the Ni_0.4Co_0.6Fe₂O₄ electrode showed the highest performance for the supercapacitor electrode exhibiting a specific capacitance of 237 F g⁻¹, superior energy density of 10.3 W h kg⁻¹ and a high power density with a peak value of 4208 W kg⁻¹, and 100% of its charge storage capacity was retained after 4000 cycles with 97% coulombic efficiency. For HER, the Ni_0.6Co_0.4Fe₂O₄ and CoFe₂O₄ electrodes showed low overpotentials of 168 and 169 mV, respectively, indicating better catalytic activity. For OER, the Ni_0.8Co_0.2Fe₂O₄ electrode exhibited a lower overpotential of 320 mV at a current density of 10 mA cm⁻², with a Tafel slope of 79 mV dec⁻¹, demonstrating a fast and efficient process. These results indicated that nanospinel ferrite solid solutions could be employed as promising electrode materials for supercapacitor and water splitting applications.

The formation of solid solutions represents a robust strategy for modulating the electronic properties and improving the electrochemical performance of spinel ferrites.

Adsorption and Dissociation of Ni(acac)2 on Iron by Ab Initio Calculations

Among metal β-diketonates, nickel acetylacetonate (Ni(acac)₂) has been widely employed as a precursor for many chemical structures, due to its catalytic properties. Here, we investigate, by means of density functional theory (DFT) calculations, the adsorption and dissociation of this complex: after an evaluation of the structural and electronic properties of Ni(acac)₂, a comparison between different dissociation patterns reveals that the most favorable pattern for the complex adsorbed on iron is different from the one suggested by considering the strength of the bonds in the isolated complex and an attempt to generalize this dissociation model is made in this work. Moreover, the most favorable adsorption configurations turned out to be a long bridge positioning of the nickel atom along with an on top positioning of the oxygen atoms of Ni(acac)₂, while a short bridge positioning is the most favorable for the central metallic unit alone.

Manganese oxide doped carbon dots for temperature-responsive biosensing and target bioimaging

We report on the synthesis of manganese oxide doped CDs (MnOx-CDs) by a hydrothermal strategy using manganese (III) acetylacetonate (Mn(III) (C5H7O2)3) as the only raw materials. The MnOx-CDs exhibit water solubility, favorable biocompatibility, low cytotoxicity, and show blue fluorescence with excitation/emission maxima at 326/442 nm with a quantum yield of 11.3%, allowing efficient cellular imaging. The MnOx-CDs have a reversible temperature-sensitive fluorescent property in vitro within 10-60 °C, which can also be used as a sensitive thermometer in living cells. By a scratch assay, the MnOx-CDs can restrain the migration of HepG2 cancer cells, which make the MnOx-CDs be attractive candidates for liver cancer adjuvant treatment. Besides, the fluorescence of the MnOx-CDs is quenched in the presence of Fe3+ due to the formation of a nonfluorescent MnOx-CDs-Fe3+ complex between oxygen-containing groups on the surface of MnOx-CDs and Fe3+, and the quenched fluorescence of MnOx-CDs can be turn-on by dissociation of MnOx-CDs-Fe3+ complexes by biothiols including L-cysteine, homocysteine and glutathione. Therefore, the Fe3+ and biothiols can be sequentially detected with high reliability and accuracy via exploiting the on-off-on nanosensor at room temperature, respectively. Further application to detection biothiols in human serum indicated that the probe was practicality and feasibility in medical field.

Developing Conductive Highly Ordered Zinc Oxide Nanorods by Acetylacetonate-Assisted Growth

Highly ordered vertically grown zinc oxide nanorods (ZnO NRs) were synthesized on ZnO-coated SiO₂/Si substrate using zinc acetylacetonate hydrate as a precursor via a simple hydrothermal method at 85 °C. We used 0.05 M of ZnO solution to facilitate the growth of ZnO NRs and the immersion time was varied from 0.5 to 4 h. The atomic force microscopy revealed the surface roughness of ZnO seed layer used to grow the ZnO NRs. The morphology of vertically grown ZnO NRs was observed by field emission scanning electron microscopy. X-ray diffraction examination and transmission electron microscopy confirmed that the structure of highly ordered ZnO NRs was crystalline with a strong (002) peak corresponded to ZnO hexagonal wurtzite structure. The growth of highly ordered ZnO NRs was favorable due to the continuous supply of Zn²⁺ ions and chelating agents properties obtained from the acetylacetonate-derived precursor during the synthesis. Two-point probe current–voltage measurement and UV–vis spectroscopy of the ZnO NRs indicated a resistivity and optical bandgap value of 0.44 Ω.cm and 3.35 eV, respectively. The photoluminescence spectrum showed a broad peak centered at 623 nm in the visible region corresponded to the oxygen vacancies from the ZnO NRs. This study demonstrates that acetylacetonate-derived precursors can be used for the production of ZnO NRs-based devices with a potential application in biosensors.

3-(4-Methylthiophenyl)acetylacetone – ups and downs of flexibility in the synthesis of mixed metal–organic frameworks. Ditopic bridging of hard and soft cations and site-specific desolvation

Different Pearson-hardness of O and S donors leads to well-ordered mixed metal–organic frameworks.

Tantalum(v) 1,3-propanediolate β-diketonate solution as a precursor to sol–gel derived, metal oxide thin films

Tantalum oxide is ubiquitous in everyday life, from capacitors in electronics to ion conductors for electrochromic windows and electrochemical storage devices. Investigations into sol–gel deposition of tantalum oxide, and its sister niobium oxide, has accelerated since the 1980s and continues to this day. The aim of this study is to synthesize a near UV sensitive, air stable, and low toxicity tantalum sol–gel precursor solution for metal oxide thin films – these attributes promise to reduce manufacturing costs and allow for facile mass production. By utilizing 1D and 2D nuclear magnetic resonance, this study shows that by removing ethanol from the precursor solution at a relatively low temperature and pressure, decomposition of the photosensitive complex can be minimized while obtaining a precursor solution with sufficient stability for storage and processing in the atmosphere. The solution described herein is further modified for inkjet printing, where multiple material characterization techniques demonstrate that the solution can be utilized in low temperature, photochemical solution deposition of tantalum oxide, which is likely amorphous. Tested substrates include amorphous silica, crystalline silicon wafer, and gold/titanium/PET foil. The hope is that these results may spark future investigations into electronic, optical, and biomedical device fabrication with tantalum oxide, and potentially niobium oxide, based films using the proposed synthesis method.

Synthesis of tantalum(v) 1,3-propanediolate β-diketonate solution and use in photochemical solution deposition to form tantalum oxide films.

One-pot synthesis of sub-10 nm LiNbO3 nanocrystals exhibiting a tunable optical second harmonic response

Nanophotonics, dealing with the properties of light interacting with nanometer scale materials and structures, has emerged as a sought after platform for sensing and imaging applications, and is impacting fields that include advanced information technology, signal processing circuits, and cryptography. Lithium niobate (LiNbO3) is a unique photonic material, often referred to as the "silicon of photonics" due to its excellent optical properties. In this article, we introduce a solution-phase method to prepare single-crystalline LiNbO3 nanoparticles with average diameters of 7 nm. This one-pot approach forms well-dispersed LiNbO3 nanocrystals without additional organic additives (e.g., surfactants) to control growth and aggregation of the nanoparticles. Formation of these LiNbO3 nanocrystals proceeds through a non-aqueous sol-gel reaction, in which lithium hydroxide and niobium hydroxide species were generated in situ. The reaction proceeded through both a condensation and crystallization of these reactants to form the solid nanoparticles. These nanocrystals of LiNbO3 were active for optical second harmonic generation (SHG) with a tunable response from 400 to 500 nm. These nanoparticles could enable further development of non-linear optical techniques such as SHG microscopy for bioimaging, which requires the dimensions of nanoparticles to be well below 100 nm.

New insights into the crystallization of polymorphic materials: from real-time serial crystallography to luminescence analysis

This article unravels reaction conditions governing the formation of polymorphic structures in solution down to the single particle level applying, for instance, unprecedented real-time serial crystallography measurements during a synthesis process.