Engineering of molecular architectures of β-diketonate precursors toward new advanced materials

Novel Volatile Heteroleptic Barium Complexes Using Tetradentate Ligand and β-Diketonato Ligand

Novel barium heteroleptic complexes were synthesized through the substitution of the bis(trimethylsilyl)amide of Ba(btsa)₂·2DME with aminoalkoxide and β-diketonate ligands. Compounds [Ba(ddemap)(tmhd)]₂ (1) and [Ba(ddemmp)(tmhd)]₂ (2) were obtained and analyzed through Fourier transform infrared spectroscopy, nuclear magnetic resonance, thermogravimetric analysis, and elemental analysis (ddemapH = 1-(dimethylamino)-5-((2-(dimethylamino)ethyl) (methyl)amino)pentan-3-ol and ddemmpH = 1-(dimethylamino)-5-((2-(dimethylamino)ethyl) (methyl)amino)-3-methylpentan-3-ol). In single-crystal X-ray crystallography, complex 1 exhibited a dimeric structure with μ₂-O bonds of the ddemap ligand. All complexes exhibited high volatility and could be sublimed under reduced pressure (0.5 Torr) at 160 °C, indicating that these complexes are promising candidates as atomic layer deposition or chemical vapor deposition precursors for the growth of barium-containing thin films.

Combining tetraphenylethene (TPE) derivative cations with Eu3+-β-diketone complex anions for tunable luminescence

Tetraphenylethene (TPE) derivative cations (TPE⁺) and Eu³⁺-β-diketone complex anions (Eu(ABM)₄^-) were combined to construct a novel dual energy transfer system (TPE⁺ to Eu³⁺ and ABM to Eu³⁺). Our system exhibits tunable luminescence in DMF/water mixtures under different f_w conditions owing to the AIE and ACQ properties of TPE⁺ and ABM, respectively. Its luminescence can be also regulated by adding P-containing oxysalts or polyacrylic acids.

Heterometallic Molecular Architectures Based on Fluorinated β-Diketone Ligands

This review summarizes the data on the synthesis of coordination compounds containing two or more different metal ions based on fluorinated β-diketonates. Heterometallic systems are of high interest in terms of their potential use in catalysis, medicine and diagnostics, as well as in the development of effective sensor devices and functional materials. Having a rich history in coordination chemistry, fluorinated β-diketones are well-known ligands generating a wide variety of heterometallic complexes. In this context, we focused on both the synthetic approaches to β-dicarbonyl ligands with additional coordination centers and their possible transformations in complexation reactions. The review describes bi- and polynuclear structures in which β-diketones are the key building blocks in the formation of a heterometallic framework, including the examples of both homo- and heteroleptic complexes.

Sodium β-Diketonate Glyme Adducts as Precursors for Fluoride Phases: Synthesis, Characterization and Functional Validation

Very few sodium complexes are available as precursors for the syntheses of sodium-based nanostructured materials. Herein, the diglyme, triglyme, and tetraglyme (CH₃O(CH₂CH₂O)_nCH₃, n = 2–4) adducts of sodium hexafluoroacetylacetonate were synthesized in a single-step reaction and characterized by IR spectroscopy, ¹H, and ¹³C NMR. Single-crystal X-ray diffraction studies provide evidence of the formation of the ionic oligomeric structure [Na₄(hfa)₆]²⁻•2[Na(diglyme₂]⁺ when the diglyme is coordinated, while a mononuclear seven-coordinated complex Na(hfa)•tetraglyme is formed with the tetraglyme. Reaction with the monoglyme (CH₃OCH₂CH₂OCH₃) does not occur, and the unadducted polymeric structure [Na(hfa)]_n forms, while the triglyme gives rise to a liquid adduct, Na(hfa)•triglyme•H₂O. Thermal analysis data reveal great potentialities for their applications as precursors in metalorganic chemical vapor deposition (MOCVD) and sol-gel processes. As a proof-of-concept, the Na(hfa)•tetraglyme adduct was successfully applied to both the low-pressure MOCVD and the sol-gel/spin-coating synthesis of NaF films.

Structural Diversity of Silver Fluorinated β-Diketonates: Effect of the Terminal Substituent and Solvent

In order to demonstrate the role of the fluorination and some solvents in the structural organization of the Ag(I) coordination polymers with β-diketonate ligands (R1C(O)CαHC(O)R2)- we synthesized a series of the compounds containing tfac- (R1 = CH3, R2 = CF3) and pfpac- (R1 = CH3, R2 = C2F5) anions. Solvent-free [Ag(L)]∞ (L = tfac 1, pfpac 2) compounds and the corresponding acetonitrile and toluene adducts have been characterized by elemental analysis and/or NMR, IR and single-crystal XRD. This series includes five new coordination polymers. Compound 1 is a 3D coordination framework based on Ag-Ochelate/bridge, Ag-Cα bonds, and argentophilic interactions. An increase in the fluorinated group leads to a chain coordination polymer 2 of an unusual structural organization. These chains can be represented as a "DNA-type", where two intertwined helices based on Ag-Ochelate and Ag-Cα bonds are connected through Ag-Obridge ones. Two structural types of chain coordination polymers, [Ag(tfac)(CH3CN)] and [Ag2(L)2(solvent)], have been revealed for the adducts. The latter structural type differs significantly from the previously studied toluene and acetonitrile adducts of fluorinated Ag(I) β-diketonates of the same stoichiometry. Thermal analysis in helium showed that both 1 and 2 decompose to metallic silver with the compound of pfpac-ligand being slightly more stable.

Journey of a molecule from the solid to the gas phase and vice-versa: direct estimation of vapor pressure of alkaline-earth metalorganic precursors for atmospheric pressure vapor phase deposition of fluoride films

Atmospheric pressure (AP) vapor phase processes such as spatial atomic layer deposition (S-ALD) and AP-metalorganic chemical vapor deposition (AP-MOCVD) are becoming increasingly important for their use in a variety of...

Investigations into the structure, reactivity, and AACVD of aluminium and gallium amidoenoate complexes

Amidoenoate (AME = {ethyl-3-(R-amido)but-2-enoate}) complexes of aluminium and gallium, of the type: [AlCl₂(AME^R)] R = iPr (1-Al); [AlCl(AME^R)₂] R = iPr (2-Al), Dip (3-Al); [GaCl₂(AME^R)] R = iPr (1-Ga) and [GaCl(AME^R)₂] R = iPr (2-Ga), Dip (3-Ga), have been synthesised (iPr = isopropyl, Dip = 2,6-diisopropylphenyl). The coordination chemistry of these complexes has been studied in relation to precursor suitability. Investigations into the reactivity of the aluminium and gallium amidoenoate complexes involved reactions with hydride sources including alkali metal hydride salts, alkylsilanes, and magnesium hydride species and magnesium(I) dimers. The isolation of alkyl metal amidoenoate precursors including an aluminium hydride amidoenoate, [AlH(AME^Dip)₂] (4-Al) and dimethyl gallium amidoenoates [GaMe₂(AME^Dip)] (4-Ga), [GaMe₂(AME^iPr)] (5-Ga) concluded the synthetic studies. A selection of the isolated complexes were used as precursors for aerosol assisted chemical vapour deposition (AACVD) at 500 °C. Thin films of either amorphous Al₂O₃ or Ga₂O₃ were deposited and subsequently annealed at 1000 °C to improve the materials' crystallinity. The films were characterised by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV-visible (UV-vis) spectroscopy and energy dispersive X-ray analysis (EDXA).

Error or exemption to the rule? Development of a diagnostic check for thermochemistry of metal-organic compounds

Volatile metal β-diketonates are well-known precursors used in Metal-Organic Chemical Vapour Deposition (MOCVD) for manufacturing film materials. Knowledge of vapour pressures and sublimation/vaporization thermodynamics of the MOCVD precursors is indispensable for optimization of deposition. However, the spread of available data could be unacceptably large for the same precursor for several reasons related to its chemical nature or incorrectly configured conditions of tensimetric investigation. In this work, we have developed an algorithm for a general diagnostic check, based on principles of group-additivity, for thermochemistry on solid-gas, liquid-gas, and solid-liquid phase transitions of metal-organic compounds and applied it to tris(beta-diketonato)iron complexes. The diagnostic tool helps to localize general "healthy" thermochemical interconnected data, and, subsequently, isolate molecules with definitely "ill" properties from the data pool. This diagnostic tool could be expanded and adapted for β-diketonate complexes with metals other than iron.

Facile synthesis of novel lithium β-diketonate glyme adducts: the effect of molecular engineering on the thermal properties

Novel adducts of lithium hexafluoroacetylacetonato {Li(hfa)} with polyethers (monoglyme = {CH₃OCH₂CH₂OCH₃}, diglyme = {CH₃O(CH₂CH₂O)₂CH₃}, triglyme = {CH₃O(CH₂CH₂O)₃CH₃} and tetraglyme {CH₃O(CH₂CH₂O)₄CH₃} have been synthesized through a single step reaction and characterized by FT-IR spectroscopy, ¹H, and ¹³C NMR, single crystal X-ray diffraction studies along with thermal analysis.

A versatile nitrogen ligand for alkaline-earth chemistry

A readily available and versatile bis(imino)carbazolate ligand is shown to allow for the synthesis of a broad range of solution stable heteroleptic complexes of the alkaline-earth metals Mg, Ca, Sr and Ba.

The deposition of cadmium selenide and cadmium phosphide thin films from cadmium thioselenoimidodiphosphinate by AACVD and the formation of an aromatic species

Aerosol-assisted chemical vapour deposition (AACVD) of Cd[(SPiPr2)(SePiPr2)N]2 yields hexagonal cadmium selenide and monoclinic cadmium phosphide films on glass substrates between 475 and 525 °C at different argon flow rates. The films were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis of X-rays (EDAX) and X-ray photoelectron spectroscopy (XPS). All the results of XRD, EDAX and XPS are in agreement with our previous investigations on Cd[(SePiPr2)2N]2. A breakdown mechanism is proposed based on mass spectra and density functional theory calculations. A large peak at m/z 207 in the mass spectra, previously assigned by us as a new aromatic species, is also observed for this complex.

Dinuclear lanthanide–lithium complexes based on fluorinated β-diketonate with acetal group: magnetism and effect of crystal packing on mechanoluminescence

A convenient and straightforward synthesis of a novel type of Ln–Li β-diketonates with a discrete molecular structure is presented.

Lewis acidic alkaline earth metal complexes with a perfluorinated diphenylamide ligand

Alkaline earth metal chemistry with the anion [N(C₆F₅)₂]⁻ has been explored. Complexes are stabilized by metal⋯F interactions. Mg[N(C₆F₅)₂]₂ is a stronger Lewis acid than B(C₆F₅)₃.

Ten-fold boost of catalytic performance in thiol–yne click reaction enabled by a palladium diketonate complex with a hexafluoroacetylacetonate ligand

Palladium complexes with fluorinated acetylacetonate chelating ligands were studied as catalysts for alkyne hydrothiolation.

Synthesis, metal binding and spectral properties of novel bis-1,3-diketone calix[4]arenes

Novel bis-1,3-diketone calix[4]arenes provide good antenna effects on Tb³⁺- and Yb³⁺-centered luminescence.

Asymmetrically substituted triazenes as poor electron donor ligands in the precursor chemistry of iron(ii) for iron-based metallic and intermetallic nanocrystals

First as precursors: Heteroleptic Fe^II complexes derived from new asymmetric triazene ligands t-BuNN-NHR (R = Et, i-Pr, n-Bu) show interesting molecular and precursor chemistry.

The quest towards epitaxial BaMgF4 thin films: exploring MOCVD as a chemical scalable approach for the deposition of complex metal fluoride films

Conventional and Pulsed Liquid Injection MOCVD processes (C-MOCVD and PLI-MOCVD) have been explored as synthetic routes for the growth of BaMgF₄ on Si (100) and single crystalline SrTiO₃ (100) substrates. For the two applied approaches, the volatile, thermally stable β-diketonate complexes Ba(hfa)₂tetraglyme and Mg(hfa)₂(diglyme)₂(H₂O)₂ have been used as single precursors (C-MOCVD) or as a solution multimetal source (PLI-MOCVD). Structural characterization through X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM) analyses confirmed the formation of epitaxial BaMgF₄ films on SrTiO₃ substrates. Energy dispersive X-ray (EDX) analyses have been used to confirm composition and purity of deposited films. The impact of process parameters on film properties has been addressed, highlighting the strong influence of precursor ratio, deposition temperature and oxygen partial pressure on composition, microstructure and morphology of the films. Both methods appear well suited for the growth of the BaMgF₄ phase, but while PLI-MOCVD yields a more straightforward control of the precursor composition that reflects on film stoichiometry, C-MOCVD provides easier control of the degree of texturing as a function of temperature.

Pure white-light and colour-tuning of Eu3+–Gd3+-containing metallopolymer

The first example of Eu³⁺–Gd³⁺-containing metallopolymer Poly(2-co-NVK-co-4) was constructed to exhibit tunable photoluminescence and even direct white-light emission.

Solution based CVD of main group materials

This critical review focuses on the solution based chemical vapour deposition (CVD) of main group materials with particular emphasis on their current and potential applications. Deposition of thin films of main group materials, such as metal oxides, sulfides and arsenides, have been researched owing to the array of applications which utilise them including solar cells, transparent conducting oxides (TCOs) and window coatings. Solution based CVD processes, such as aerosol-assisted (AA)CVD have been developed due to their scalability and to overcome the requirement of suitably volatile precursors as the technique relies on the solubility rather than volatility of precursors which vastly extends the range of potentially applicable compounds. An introduction into the applications and precursor requirements of main group materials will be presented first followed by a detailed discussion of their deposition reviewed according to this application. The challenges and prospects for further enabling research in terms of emerging main group materials will be discussed.

Bidirectional non-innocence of the β-diketonato ligand 9-oxidophenalenone (L-) in [Ru([9]aneS3)(L)(dmso)]n, [9]aneS3 = 1,4,7-trithiacyclononane

The new compound [Ru(II)([9]aneS3)(L)(dmso)]ClO4 ([]ClO4) ([9]aneS3 = 1,4,7-trithiacyclononane, HL = 9-hydroxyphenalenone, dmso = dimethylsulfoxide) has been structurally characterised to reveal almost equal C-O bond distances of coordinated L(-), suggesting a delocalised bonding situation of the β-diketonato ligand. The dmso ligand is coordinated via the sulfur atom in the native (1+) and reduced states (1 and 1-) as has been revealed by X-ray crystallography and by DFT calculations. Cyclic voltammetry of 1+ exhibits two close-lying one-electron oxidation waves at 0.77 V and 0.94 V, and two similarly close one-electron reduction processes at -1.43 V and -1.56 V versus SCE in CH2Cl2. The electronic structures of 1n in the accessible redox states have been analysed via experiments (EPR and UV-vis-NIR spectroelectrochemistry) and by DFT/TD-DFT calculations, revealing the potential for bidirectional non-innocent behaviour of coordinated L(˙/-/˙2-). Specifically, the studies establish significant involvement of L based frontier orbitals in both the oxidation and reduction processes: [([9]aneS3)(dmso)Ru(III)-L˙](3+) (1(3+)) ⇌ [([9]aneS3)(dmso)Ru(III)-L(-)](2+)/[([9]aneS3)(dmso)Ru(II)-L˙](2+) (1(2+)) ⇌ [([9]aneS3)(dmso)Ru(II)-L(-)](+) (1(+)) ⇌ [([9]aneS3)(dmso)Ru(II)-L(˙2-)] (1) ⇌ [([9]aneS3)(dmso)Ru(II)-L(3-)](-)/[([9]aneS3)(dmso)Ru(I)-L(˙2-)](-) (1-).

Ruthenium complexes as precursors for chemical vapor-deposition (CVD)

The progress in precursor chemistry for the chemical vapor deposition of ruthenium containing thin films is reviewed.

Experimental and DFT evidence for the fractional non-innocence of a β-diketonate ligand

New compounds [Ru(pap)(2)(L)](ClO(4)), [Ru(pap)(L)(2)], and [Ru(acac)(2)(L)] (pap = 2-phenylazopyridine, L(-) = 9-oxidophenalenone, acac(-) = 2,4-pentanedionate) have been prepared and studied regarding their electron-transfer behavior, both experimentally and by using DFT calculations. [Ru(pap)(2)(L)](ClO(4)) and [Ru(acac)(2)(L)] were characterized by crystal-structure analysis. Spectroelectrochemistry (EPR, UV/Vis/NIR), in conjunction with cyclic voltammetry, showed a wide range of about 2 V for the potential of the Ru(III/II) couple, which was in agreement with the very different characteristics of the strongly π-accepting pap ligand and the σ-donating acac(-) ligand. At the rather high potential of +1.35 V versus SCE, the oxidation of L(-) into L(⋅) could be deduced from the near-IR absorption of [Ru(III)(pap)(L(⋅))(L(-))](2+). Other intense long-wavelength transitions, including LMCT (L(-) → Ru(III)) and LL/CT (pap(⋅-) → L(-)) processes, were confirmed by TD-DFT results. DFT calculations and EPR data for the paramagnetic intermediates allowed us to assess the spin densities, which revealed two cases with considerable contributions from L-radical-involving forms, that is, [Ru(III)(pap(0))(2)(L(-))](2+) ↔ [Ru(II)(pap(0))(2)(L(⋅))](2+) and [Ru(III)(pap(0))(L(-))(2)](+) ↔ [Ru(II)(pap(0))(L(⋅))(L(-))](+). Calculations of electrogenerated complex [Ru(II)(pap(⋅-))(pap(0))(L(-))] displayed considerable negative spin density (-0.188) at the bridging metal.

(μ-1,2-dimethoxyethane-κ2O:O')bis[(1,2-dimethoxyethane-κ2O,O')tris(1,1,1,5,5,5-hexafluoro-4-oxopent-2-en-2-olato-κ2O,O')cerium(III)]

A previous analysis [Fatila et al. (2012). Dalton Trans. 41, 1352-1362] of the title complex, [Ce(2)(C(5)HF(6)O(2))(6)(C(4)H(10)O(2))(3)], had identified it as Ce(hfac)(3)(dme)(1.5) according to the (1)H NMR integration [hfac = 1,1,1,5,5,5-hexafluoroacetylacetonate (1,1,1,5,5,5-hexafluoro-4-oxopent-2-en-2-olate) and dme = 1,2-dimethoxyethane]; however, it was not possible to determine the coordination environment unambiguously. The structural data presented here reveal that the complex is a binuclear species located on a crystallographic inversion center. Each Ce(III) ion is coordinated to three hfac ligands, one bidentate dme ligand and one monodentate (bridging) dme ligand, thus giving a coordination number of nine (CN = 9) to each Ce(III) ion. The atoms of the bridging dme ligand are unequally disordered over two sets of sites. In addition, in two of the -CF(3) groups, the F atoms are rotationally disordered over two sets of sites. This is the first crystal structure of a binuclear lanthanide β-diketonate with a bridging dme ligand.

Volatile single-source molecular precursor for the lithium ion battery cathode

The first single-source molecular precursor for a lithium-manganese cathode material is reported. Heterometallic β-diketonate LiMn(2)(thd)(5) (1, thd = 2,2,6,6-tetramethyl-3,5-heptanedionate) was obtained in high yield by simple one-step solid-state reactions employing commercially available reagents. Substantial scale-up preparation of 1 was achieved using a solution approach. The crystal structure of the precursor contains discrete Li:Mn = 1:2 trinuclear molecules held together by bridging diketonate ligands. The complex is relatively stable in open air, highly volatile, and soluble in all common solvents. It was confirmed to retain its heterometallic structure in solutions of non-coordinating solvents. The heterometallic diketonate 1 was shown to exhibit clean, low-temperature decomposition in air/oxygen that results in nanosized particles of spinel-type oxide LiMn(2)O(4), one of the leading cathode materials for lithium ion batteries.

9-Oxidophenalenone: a noninnocent β-diketonate ligand?

The redox systems [Ru(L)(bpy)(2)](k), [Ru(L)(2)(bpy)](m), and [Ru(L)(3)](n) containing the potentially redox-active ligand 9-oxidophenalenone = L(-) were investigated by spectroelectrochemistry (UV-vis-near-IR and electron paramagnetic resonance) in conjunction with density functional theory (DFT) calculations. Compounds [Ru(L(-))(bpy)(2)]ClO(4) ([1]ClO(4)) and [Ru(L(-))(2)(bpy)]ClO(4) ([2]ClO(4)) were structurally characterized. In addition to establishing electron-transfer processes involving the Ru(II)/Ru(III)/Ru(IV) and bpy(0)/bpy(•-) couples, evidence for the noninnocent behavior of L(-) was obtained from [Ru(IV)(L(•))(L(-))(bpy)](3+), which exhibits strong near-IR absorption due to ligand-to-ligand charge transfer. In contrast, the lability of the electrogenerated anion [Ru(L)(2)(bpy)](-) is attributed to a resonance situation [Ru(II)(L(•2-))(L(-))(bpy)](-)/[Ru(II)(L(-))(2) (bpy(•-))](-), as suggested by DFT calculations.

The gas-phase ligand exchange reactions of cobalt and zinc acetylacetonate, hexafluoroacetylacetonate, and trifluorotrimethylacetylacetonate complexes

The gas-phase ligand exchange reactions between Co(II) and Zn(II) complexes containing the acetylacetonate (acac), hexafluoroacetylacetonate (hfac), and trifluorotrimethylacetylacetonate (tftm) ligands were investigated using a triple quadrupole mass spectrometer. The gas-phase mixed ligand products of [Cu(acac)(tftm)](+), [Ni(acac)(tftm)](+), [Cu(hfac)(tftm)](+), and [Ni(hfac)(tftm)](+) were formed following the co-sublimation of either homo-metal or hetero-metal precursors and are reported herein for the first time. The fragmentation patterns of these mixed ligand species along with those of Cu(tftm)(2) and Ni(tftm)(2) are also presented. The collision cell of the instrument was utilized to examine the gas-phase reactions between mass-selected ions and specific neutral target compounds.

How does Cu(II) convert into Cu(I)? An unexpected ring-mediated single-electron reduction

Cu(x)O (x=1,2) nanomaterials with tailored composition and properties-a hot topic in sustainable technologies-may be fabricated from molecular sources through bottom-up processes that involve unexpected changes in the metal oxidation state and open intriguing challenges on the copper redox chemistry. How copper(II) sources may lead to copper(I) species in spite of the absence of any explicit reducing agent, and even in the presence of oxygen, is one such question-to date unanswered. Herein, we study copper "reduction without reductants" within one molecule and reveal that the actual reducing agent is abstracted atomic hydrogen. By investigating the fragmentation of a copper(II) precursor for copper oxide nanostructures by combined ESI-MS with multiple collisional experiments (ESI/MS(n)) and theoretical calculations, we highlight a copper-promoted C-H bond activation, leading to reduction of the metal center and formation of a Cu(I)-C-NCCN six-membered ring. Such a novel ring system is the structural motif for a new family of cyclic copper(I) adducts, which show a bonding scheme, herein reported for the first time, that may shed unprecedented light on copper chemistry. Beyond the relevance for the preparation of copper oxide nanostructures, the hydrogen-abstraction/proton-delivery/electron-gain mechanism of copper(II) reduction disclosed herein appears to be a general property of copper and might help to understand its redox reactivity.