Β-diketonate Ligands Research Articles

Cyclometalated N-Difluoromethylbenzimidazolylidene Platinum(II) Complexes with Built-in Secondary Coordination Spheres: Photophysical Properties and Bioimaging.

Bidentate Pt(II) complexes with cyclometalated N-heteroarene or N-heterocyclic carbene (NHC) ligands have been extensively studied as phosphorescent emitters over the past two decades. Herein, we introduce a difluoromethyl group (CF2H) into the wingtip of NHCs, where CF2H acts as a lipophilic hydrogen bond (HB) donor. Their cyclometalated Pt(II) complexes show excellent PLQYs (up to 93%) and phosphorescence lifetimes mainly due to the rigid structure with hydrogen bonding between the CF2H group and the adjacent O atom at the β-diketonate ligand. Bioimaging studies demonstrate high cellular uptake efficiency and deep tumor penetration capability of complex 7 in HeLa cells and multicellular tumor spheroids, highlighting their potential as bioimaging probes.

Full Picture of Energy Transfer in a Trivalent Europium Complex with Bidentate β-Diketonate Ligand.

Trivalent europium (Eu(III)) complexes emit narrow-band luminescence as a result of energy transfer following the photoexcitation of antenna ligands. Bidentate β-diketonates are typically used as antenna ligands; however, their entire energy transfer mechanism to Eu(III) remains unknown. We used time-resolved photoluminescence spectroscopy and femtosecond transient absorption spectroscopy to map the complete intramolecular energy transfer process in the [Eu(hfa)3(TPPO)2] (hfa = hexafluoroacetylacetonate, TPPO = triphenylphosphine oxide) complex; hfa is a β-diketonate antenna ligand. Our analysis provides a "full picture" of energy transfer, tracing each step from initial photoexcitation to final relaxation: intersystem crossing in the ligands, energy transfer from the ligands to the metal center, and multiple internal conversion of Eu(III). We demonstrated that the direct bonds of the bidentate ligands enabled a quick and near-unity-efficiency energy transfer from the triplet state of the ligand to the 5D2 state of Eu(III). We also revealed that the loss of the ligand-centered intersystem crossing process reduces the overall sensitization efficiency. Our findings provide a foundation for the rational design of advanced luminescent materials, paving the way for advances in lanthanide-based luminescence research.

STUDY OF COPPER COMPLEXES [Cu(LCF3)2] AND [Cu(Lcur)2]H2O AS RADIOPROTECTIVE COMPOUNDS

One of the first and direct signs of the impact of ionizing radiation (IR) on a cell is the destabilization of chromosomes. Radiation-induced damage to the karyotype is an important indicator both for biological indication of the severity of radiation injuries and for predicting the development of long-term adverse effects of IR. The search for new, effective radioprotective compounds is a priority task of modern radiobiology. In this area, metal-based compounds with high antioxidant activity are of particular interest. The purpose of this work is to determine the possible radioprotective properties of Cu(II) complexes, [Сu(LCF3)2] and [Cu(Lcur)2]H2O, supported by the anions of the β-diketone ligands 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (HLCF3) and 1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione or curcumin (HLcur). In this research work we determined survival, life expectancy and cytogenetic parameters: mitotic index, chromosome aberrations and % of polyploid cells in the bone marrow cells of the femur (count in 1000 cells in each preparation). Group I included intact animals; Group II consisted of animals exposed to the radioisotope technetium; Group III consisted of animals that were intraperitoneally injected with copper complex [Cu(LCF3)2] at a dose of 50 mg/kg in a volume of 2 mL one hour before the administration of the Tc isotope (“irradiation + copper compound [Cu(LCF3)2]); Group IV included animals that received the compound [Cu(Lcur)2]H2O before irradiation. The groups with the injection of [Cu(LCF3)2] complex had the highest survival. In terms of chromosomal aberrations and number of polyploid cells, as indicators, a significant difference was found in those irradiated compared with the “irradiation + [Cu(LCF3)2]” group (both after 15 and after 30 days), which indicates the radioprotective property of the compound. In terms of the mitotic index, a tendency towards normalization was noted after 15 days and a significant difference between Groups 2 and 3 by the end of the study (after 30 days), which also proves the beneficial effect of this compound. Analysis of survival and changes in cytogenetic parameters multiregression analysis using both complexes confirms the greatest efficiency of the [Cu(LCF3)2] complex with respect to [Cu(Lcur)2]H2O, because when using [Cu(Lcur)2]H2O in Group IV and comparing it with “pure irradiation” only a tendency toward normalization of cytogenetic parameters was observed. Multiregression analysis of cytogenetic parameters also confirmed the highest efficiency of the [Cu(LCF3)2] compound in comparison with [Cu(Lcur)2]H2O. The results of the research indicate the need to continue work in the direction of searching for agents that have a therapeutic effect in radiation injuries.

Syntheses, crystal structures, luminescence properties and Hirshfeld surface analyses of two mononuclear 2,2′:6′,2′’-terpyridine lanthanide complexes with different β-diketones

Six ternary lanthanide complexes with different β-diketones as primary “antenna” ligand and 2,2’:6’,2’’-terpyridine as neutral ancillary ligand, namely [Ln(hfac)3(tpy)] [Ln(III) = Eu (1), Gd (2), Tb (3); hfac = hexafluoroacetylacetone; tpy = 2,2’:6’,2’’-terpyridine] and [Ln(btfa)3(tpy)] [Ln(III) = Eu (4), Gd (5), Tb (6); btfa = 4,4,4-trifluoro-1-phenyl-1,3-butanedione], were synthesized and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, single crystal X-ray diffraction and powder X-ray diffraction. The three-dimensional Hirshfeld surface map and two-dimensional fingerprint analysis reveal that the substitution of hfac with btfa result in the decrease of the H···F/F···H and F···F interactions and the increase of the C···H/H···C and H···H interactions. Solid-state luminescence investigations indicate that the Eu(III) complexes (1-Eu and 4-Eu) and the Tb(III) complexes (3-Tb and 6-Tb) display the characteristic lanthanide-centered luminescence upon UV excitations. 1-Eu and 4-Eu emit red light at CIE: 0.6827, 0.3172 and CIE: 0.6819, 0.3179 with the quantum yields (QY) of 78.70 % and 68.85 % and the lifetimes (τ) of 0.768 and 0.808 ms, respectively. 3-Tb and 6-Tb emit green light at CIE: 0.2677, 0.7221 and CIE: 0.2680, 0.7217 with the QY values of 7.56 % and 1.38 % and the τ values of 0.076 and 0.022 ms, respectively. For the Eu(III) complexes, the substitution of hfac by btfa makes the QY value lower from 78.70 % to 68.85 % and slightly prolong the τ value from 0.768 to 0.808 ms, while for the Tb(III) complexes, both of the QY and τ values decrease. The results suggest that the structures of the primary β-diketone ligands could affect the luminescence performances such as QY and τ values of the Eu(III) and Tb(III) complexes.

Mechanistic investigation of iron-catalyzed cross-coupling using sterically encumbered β-diketonate ligands

Iron β-diketonate compounds are reported using the hindered 2,6-dimesitylbenzoyl pinacolone (Aracac), which sterically precludes formation of tris-Aracac complexes. Fe(Aracac)2 (1), Fe(Aracac)2Cl (2) were synthesized and characterized using crystallographic, spectroscopic, elemental analysis, and electrochemical techniques. Iron complexes with only one Aracac ligand form dimers [Fe(Aracac)(THF)2]2(μ-OTf)2 (3) and [(Aracac)Fe(μ-mesityl)]2 (4). Complexes 1–4 were evaluated in a Kumada cross-coupling reaction and compared with the parent FeIII(acac)3 complex. Whereas the bis-acac complexes 1 and 2 show only modest activity (∼50 % yield after 60 min), the mono-acac complexes 3 and 4 are nearly as effective as the parent compound (∼90 % yield). DFT computations, in conjunction with catalytic results and electrochemical observations, suggest a catalytic cycle involving an oxidative addition of an aryl-chloride to Fe(II) to produce a high-spin Fe(IV) complex that could alternately be described as a high-spin Fe(II) stabilizing two coordinated organoradicals. These results suggest that a unique aspect of acac as a ligand for this reaction is its ability to support high-spin organoiron complexes, which can provide low-barrier pathways for C–Cl bond cleavage and CC bond formation reactions.

Time-gated luminescence indicators for lysosome and endoplasmic reticulum in living cells based on β-diketonate-europium(III) complexes

Lysosome and endoplasmic reticulum (ER) play essential roles for the digestion, synthesis and transportation of biological macromolecules in living cells. For the better visualization and tracking of them, effective luminescence indicators that can specifically locate into them are necessary. In this work, using a visible light-excitable ternary β-diketonate-europium(III) complex, 4,4,5,5,5-pentafluoro-1-(thiophen-2-yl)pentane-1,3-dionate-Eu3+-2-(N,N-diethylanilin-4-yl)-4,6-bis(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine, as the luminophore, and morpholine and p-toluenesulfonamide moieties that covalently bound to the β-diketonate ligands as organelle-anchoring motifs, two time-gated luminescence (TGL) indicators for lysosome and ER, Lyso-TGL-indicator and ER-TGL-indicator, were designed and synthesized. Two TGL indicators exhibited strong and long-lived emissions at 608 nm, with wide excitation wavelength ranges from UV to visible light (∼320–450 nm, maximum at 396 nm). In addition, two indicators showed low cytotoxicity and excellent lysosome/ER-location performances (Pearson's coefficients >0.97 after being co-localized with commercial lysosome and ER staining agents in cells). These features enabled them to be successfully used for the background-free TGL tracking of lysosomes and ERs in living cells, respectively.

Luminescent Ln3+-based silsesquioxanes with a β-diketonate antenna ligand: toward the design of efficient temperature sensors.

We report the synthesis and single-crystal X-ray diffraction, magnetic, and luminescence measurements of a novel family of luminescent cage-like tetranuclear silsesquioxanes (PhSiO1.5)8(LnO1.5)4(O)(C5H8O2)6(EtOH)2(CH3CN)2⋅2CH3CN (where Ln = Tb, 1; Tb/Eu, 2; and Gd, 3), featuring seven-coordinated lanthanide ions arranged in a one-capped trigonal prism geometry. Compounds 1 and 2 exhibit characteristic Tb3+ and Tb3+/Eu3+-related emissions, respectively, sensitized by the chelating antenna acetylacetonate (acac) ligands upon excitation in the UV and visible spectral regions. Compound 3 is used to assess the energies of the triplet states of the acac ligand. For compound 1, theoretical calculations on the intramolecular energy transfer and multiphonon rates indicate a thermal balance between the 5D4 Stark components, while the mixed Tb3+/Eu3+ analog 2, with a Tb:Eu ratio of 3:1, showcases intra-cluster Tb3+-to-Eu3+ energy transfer, calculated theoretically as a function of temperature. By utilizing the intensity ratio between the 5D4→7F5 (Tb3+) and 5D0→7F2 (Eu3+) transitions in the range 11-373K, we demonstrate the realization of a ratiometric luminescent thermometer with compound 2, operating in the range 11-373K with a maximum relative sensitivity of 2.0% K-1 at 373K. These findings highlight the potential of cage-like silsesquioxanes as versatile materials for optical sensing-enabled applications.

A strategy to enhance the water solubility of luminescent β-diketonate-Europium(III) complexes for time-gated luminescence bioassays

Luminescent β-diketonate-europium(III) complexes have been found a wide range of applications in time-gated luminescence (TGL) bioassays, but their poor water solubility is a main problem that limits their effective uses. In this work we propose a simple and general strategy to enhance the water solubility of luminescent β-diketonate-europium(III) complexes that permits facile synthesis and purification. By introducing the fluorinated carboxylic acid group into the structures of β-diketone ligands, two highly water-soluble and luminescent Eu3+ complexes, PBBHD-Eu3+ and CPBBHD-Eu3+, were designed and synthesized. An excellent solubility exceeding 20 mg/mL for PBBHD-Eu3+ was found in a pure aqueous buffer, while it also displayed strong and long-lived luminescence (quantum yield φ = 26%, lifetime τ = 0.49 ms). After the carboxyl groups of PBBHD-Eu3+ were activated, the PBBHD-Eu3+-labeled streptavidin-bovine serum albumin (SA-BSA) conjugate was prepared, and successfully used for the immunoassay of human α-fetoprotein (AFP) and the imaging of an environmental pathogen Giardia lamblia under TGL mode, which demonstrated the practicability of PBBHD-Eu3+ for highly sensitive TGL bioassays. The carboxyl groups of PBBHD can also be easily derivatized with other reactive chemical groups, which enables PBBHD-Eu3+ to meet diverse requirements of biolabeling technique, to provide new opportunities for developing functional europium(III) complex biolabels serving for TGL bioassays.

Structure and Thermal Properties of Silver Complexes with 2,2′-Bipyridine and Fluorinated β-Diketonate Ligands

Structure and Thermal Properties of Silver Complexes with 2,2′-Bipyridine and Fluorinated β-Diketonate Ligands

Structural Information on Supramolecular Copper(II) β-Diketonate Complexes from Atomic Force Microscopy and Analytical Ultracentrifugation.

Supramolecular Cu(II) complexes were prepared from two trifunctional β-diketone ligands. The ligands (CH3Si(phacH)3 and CH3Si(phprH)3, represented by LH3) contain three aryl-β-diketone moieties joined by an organosilicon group. The complexes have the empirical formula Cu3L2, as expected for combinations of Cu2+ and L3-. Several metal-organic polyhedra (MOPs) [Cu3L2]n are possible (n = 1-10); a dodecahedron (Cu30L20; n = 10; estimated diameter of ca. 5 nm) should be the most stable because its internal bond angles would come closest to ideal values. Atomic force microscopy (AFM), performed on samples deposited from solution onto mica substrates, revealed a distribution of sample heights in the 0.5-3.0 nm range. The most commonly observed heights were 0.5-1.5 nm, corresponding to the smallest possible molecules (Cu3L2, i.e., n = 1). Some molecular cubes (Cu12L8; ca. 2.5 nm) or larger molecules or aggregates may be present as well. Equilibrium analytical ultracentrifugation (AUC) was also used to probe the compounds. A previously reported reference compound, the molecular square Cu4(m-pbhx)4 (M = 2241 g mol-1), behaved well in AUC experiments in four nonpolar organic solvents. AUC data for the new tris(β-diketonate) MOPs [Cu3L2]n in toluene and fluorobenzene did not agree well with the theoretical results for a single solute. The data were fit well by a two-solute model, but these results were not consistent in the two solvents used, and some run-to-run variability was noted even in the same solvent. Also, the calculated molecular weights differed significantly from those expected for [Cu3L2]n ([Cu3(CH3Si(phac)3)2]n, multiples of 1322 g mol-1; or [Cu3(CH3Si(phpr)3)2]n, multiples of 1490 g mol-1).

Chemical and redox non-innocence in low-valent molybdenum β diketonate complexes: novel pathways for CO2 and CS2 activation.

The investigation of fundamental properties of low-valent molybdenum complexes bearing anionic ligands is crucial for elucidating the molybdenum's role in critical enzymatic systems involved in the transformation of small molecules, including the nitrogenase's iron molybdenum cofactor, FeMoco. The β-diketonate ligands in [Mo(acac)3] (acac = acetylacetonate), one of the earliest low-valent Mo complexes reported, provide a robust anionic platform to stabilize Mo in its +III oxidation state. This complex played a key role in demonstrating the potential of low-valent molybdenum for small molecule activation, serving as the starting material for the preparation of the first reported molybdenum dinitrogen complex. Surprisingly however, given this fact and the widespread use of β-diketonate ligands in coordination chemistry, only a very limited number of low-valent Mo β-diketonate complexes have been reported. To address this gap, we explored the redox behavior of homoleptic molybdenum tris-β-diketonate complexes, employing a tertiary butyl substituted diketonate ligand (dipivaloylmethanate, tBudiket) to isolate and fully characterize the corresponding Mo complexes across three consecutive oxidation states (+IV, +III, +II). We observed marked reactivity of the most reduced congener with heterocumulenes CE2 (E = O, S), yet with very distinct outcomes. Specifically, CO2 stoichiometrically carboxylates one of the β-diketonate ligands, while in the presence of excess CS2, catalytic reductive dimerization to tetrathiooxalate occurs. Through the isolation and characterization of reaction products and intermediates, we demonstrate that the observed reactivity results from the chemical non-innocence of the β-diketonate ligands, which facilitates the formation of a common ligand-bound intermediate, [Mo( tBudiket)2( tBudiket·CE2)]1- (E = O, S). The stability of this proposed intermediate dictates the specific reduction products observed, highlighting the relevance of the chemically non-innocent nature of β-diketonate ligands.

Enhancing the single-molecule magnetic performance of β-diketonate Dy(III) complexes by modulating the coordination microenvironment and magnetic interaction: from a mononuclear to a dinuclear structure.

Based on a β-diketonate ligand, a mononuclear Dy(III) complex, [Dy(dmpd)3(bpy)] (1) (dmpd = 4,4-dimethyl-1-phenylpentane-1,3-dione, bpy = 2,2'-dipyridyl), of [DyN2O6] type has been synthesized with a capping nitrogen-containing coligand. Then, a dual capping coligand 2,2'-bipyrimidine (bmp) is introduced to be a bridge to link two β-diketonate-Dy(III) motifs, leading to a new dinuclear Dy(III) complex, [Dy2(dmpd)6(bmp)] (2). Dy(III) centers in both complexes feature an N2O6 octacoordinated environment with an approximate square-antiprism geometry (D4d). Without a dc field, the SMM behaviour is absent in complex 1, but can be clearly observed in dinuclear 2 with a Ueff of 87.29 K. The significantly improved magnetism arising in 2 is mainly due to the modulation of the coordination environment around the Dy(III) ions and the superexchange magnetic interactions inside the dinuclear units, thus allowing for the effective inhibition of the quantum tunneling of magnetization at low temperatures and promotion of the uniaxial magnetic anisotropy. For 1, a diamagnetic Y(III) analogue [Y(dmpd)3(bpy)] (3) and diluted sample 1@Y were constructed to further perform the dilution experiment, coupled with theoretical calculations further supporting that the synergetic contributions of intermolecular dipole-dipole interactions, intramolecular coupling and uniaxial magnetic anisotropy cause the enhancement of dynamic magnetic relaxation.

Bifunctional heterobimetallic 3d-4f [Co(II)-RE, RE = Dy, Eu, and Y] ionic complexes: modulation of the magnetic-luminescence behaviour.

This work reports the engineering and functional properties of an emerging class of heterobimetallic 3d-4f ionic complexes designed with cobalt and rare-earth (RE) metals. We present a comprehensive examination of the structural, magnetic, optical, and thermal properties of the heterobimetallic ionic complexes with the general formula [Co(hfa)3]-[RE(hfa)2tetraglyme]+ (RE = Dy, Eu, and Y), where the metal centres are coordinated by hexafluoroacetylacetonate (Hhfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione), β-diketone and tetraglyme (2,5,8,11,14-pentaoxapentadecane) polyether. Structural analysis reveals an octahedral coordination geometry enveloping the cobalt(II) centre, characterized by inherent symmetry properties consistent across the derivatives, while a capped square-antiprism coordination polyhedron is observed for the RE ions. Electron paramagnetic resonance (EPR) spectroscopy confirms the constancy of the electronic structure of the cobalt(II) moiety and the significant contribution of the lanthanide ions to the magnetic properties of the compounds. The non-trivial single-ion magnetic properties of cobalt(II), dysprosium(III), and europium(III) centres, and the effect of their interactions are investigated by a detailed static and dynamic magnetic susceptibility study. Moreover, optical analyses have been carried out showing the π-π* intraligand (IL) transition of the β-diketonate ligand and the d-d cobalt(II) transitions. Luminescence characterization of dysprosium(III) and europium(III) derivatives exhibits their characteristic emission bands, indicative of the unique photophysical properties conferred by the lanthanide ions. Thermal studies using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) reveal good thermal stability and volatility properties, underscoring the interesting nature of these ionic complexes for potential deposition on suitable substrates. In summary, these heterobimetallic complexes show intriguing optical and magnetic properties with potential implications across diverse scientific disciplines, including molecular magnetism, optoelectronics, and materials science.

Automated Structural Activity Screening of β-Diketonate Assemblies with High-Throughput Ion Mobility-Mass Spectrometry.

Embracing complexity in design, metallo-supramolecular self-assembly presents an opportunity for fabricating materials of economic significance. The array of accessible supramolecules is alluring, along with favourable energy requirements. Implementation is hampered by an inability to efficiently characterise complex mixtures. The stoichiometry, size, shape, guest binding properties and reactivity of individual components and combinations thereof are inherently challenging to resolve. A large combinatorial library of four transition metals (Fe, Cu, Ni and Zn), and six β-diketonate ligands at different molar ratios and pH was robotically prepared and directly analysed over multiple timepoints with electrospray ionisation travelling wave ion mobility-mass spectrometry. The dataset was parsed for self-assembling activity without first attempting to structurally assign individual species. Self-assembling systems were readily categorised without manual data-handling, allowing efficient screening of self-assembly activity. This workflow clarifies solution phase supramolecular assembly processes without manual, bottom-up processing. The complex behaviour of the self-assembling systems was reduced to simpler qualities, which could be automatically processed.

New Heteroleptic Germanium Precursors for GeO2 Thin Films by Atomic Layer Deposition.

This study describes the synthesis of 12 new germanium complexes containing β-diketonate and/or N-alkoxy carboxamidate-type ligands as precursors for GeO2 through atomic layer deposition (ALD). A series of Ge(β-diketonate)Cl complexes such as Ge(acac)Cl (1) and Ge(tmhd)Cl (2) were synthesized by using acetylacetone (acacH) and 2,2,6,6-tetramethyl-3,5-heptanedione (tmhdH). N-Alkoxy carboxamidate-type ligands such as N-methoxypropanamide (mpaH), N-methoxy-2,2-dimethylpropanamide (mdpaH), N-ethoxy-2-methylpropanamide (empaH), N-ethoxy-2,2-dimethylpropanamide (edpaH), and N-methoxybenzamide (mbaH) were used to afford further substituted complexes Ge(acac)(mpa) (3), Ge(acac)(mdpa) (4), Ge(acac)(empa) (5), Ge(acac)(edpa) (6), Ge(acac)(mba) (7), Ge(tmhd)(mpa) (8), Ge(tmhd)(mdpa) (9), Ge(tmhd)(empa) (10), Ge(tmhd)(edpa) (11), and Ge(tmhd)(mba) (12), respectively. Thermogravimetric analysis curves, which mostly exhibited single-step weight losses, were used to determine the evaporation properties of complexes 1-12. Interestingly, liquid complex 2 has no residue at 198 °C and therefore exhibits excellent vaporization properties and high volatility. Single-crystal X-ray diffraction studies of 1 and 7 demonstrated that the complexes had monomeric molecular structures with germanium chelated by the oxygen atoms of one or two bidentate ligands, respectively. An ALD process was developed for the growth of GeO2 using Ge(tmhd)Cl (2) as a new precursor and H2O2 as an oxidant. This study demonstrates the achievement of self-limiting growth of GeO2 films by varying the duration of injection/purge, with an observed ALD window at deposition temperatures ranging from 300 to 350 °C. The saturated growth per cycle of the GeO2 film was determined as 0.27 Å/cycle at a deposition temperature of 300 °C. The deposited films were observed to be amorphous consisting of GeO2.

Towards the MOCVD’s paradise: Thermodynamics of phase transitions of new scandium precursors

Scandium complexes with β-diketonate ligands are valuable precursors for the metal–organic chemical vapour deposition (MOCVD) of scandia based materials. The technology has been constantly developing and demanding novel precursors with accurately defined thermal properties, which could be used in MOCVD as well as related gas phase processes. Two new complexes with 1,1-difluoroacetylacetone (dfac) and 5,5,6,6,6-pentafluorohexane-2,4-dione (5Fac) have been synthesized, isolated, and characterized. The volatility and condensed phase behaviour including thermal stability and phase transitions of the obtained compounds have been studied; the saturated vapour pressures over crystalline Sc(dfac)3 and liquid Sc(5Fac)3 complexes have been measured. As a result, the standard molar thermodynamic characteristics of melting, sublimation, and vaporization processes have been calculated. Thermal properties of these compounds have been compared with literature data on scandium(III) β-diketonates already used as MOCVD precursor. These new compounds can be successfully used as precursors in the gas-phase deposition processes, and the set of obtained thermodynamic data can help in choosing the optimal deposition conditions.

Investigating the long-term stability of photoluminescence lifetimes in PMMA films doped with β-diketonate europium complexes based on bipyridine and terpyridine derivatives

In this work, two β-diketonate ligands: dibenzoylmethane (DBM) and Hexafluoroacetone (hfac) have been selected to synthesize a series of β-diketonate europium complexes based on bipyridine and terpyridine derivatives. These complexes were then incorporated into PMMA films to comprehensively investigate their thermal and long-term photoluminescence stability. Comparatively, Eu(hfac)3L1-5 demonstrated higher heat resistance than Eu(DBM)3L1-5, as indicated by their respective initial decomposition temperatures. Various aspects including absorbance, excitation, and emission were examined in solution, powder, and within the PMMA-doped films. Notably, the complexes exhibited a remarkable red emission peak at 613nm and a high photoluminescence quantum yield. To assess their stability, the films were subjected to light, indoor, and dark storage conditions for 720h, with photoluminescence measurements recorded at both 0h and 720h. The results revealed that the hfac-based europium complexes (Eu(hfac)3L1-5) demonstrated good stability under light, indoor, and dark conditions compared to the DBM-based europium complexes (Eu(DBM)3L1-5). This study highlights the direct impact of the β-diketonate ligand structure on the stability of such complexes in films, thus showcasing their potential for future applications in stable optoelectronic devices.

Ligand-Enabled NiII -Catalyzed Hydroxylarylation of Alkenes with Molecular Oxygen.

The use of molecular oxygen as the terminal oxidant in transition metal catalyzed oxidative process is an appealing and challenging task in organic synthetic chemistry. Here, we report a Ni-catalyzed hydroxylarylation of unactivated alkenes enabled by a β-diketone ligand with high efficiency and excellent regioselectivity employing molecular oxygen as the oxidant and hydroxyl source. This reaction features mild conditions, broad substrate scope and incredible heterocycle compatibility, providing a variety of β-hydroxylamides, γ-hydroxylamides, β-aminoalcohols, γ-aminoalcohols, and 1,3-diols in high yields. The synthetic value of this methodology was demonstrated by the efficient synthesis of two bioactive compounds, (±)-3'-methoxyl citreochlorol and tea catechin metabolites M4.

Regulating Magnetic Relaxations of Cyano-Bridged {DyIII MoV } Systems by Tuning the N-Sites in β-Diketone Ligands.

Cyano-bridged 4d-4f molecular nanomagnets have re-called increasing research interests in molecular magnetism since they offer more possibilities in achieving novel nanomagnets with versatile structures and magnetic interactions. In this work, four β-diketone ligands bearing different substitution N-sites were designed and synthesized, namely 1-(2-pyridyl)-3-(3-pyridyl)-1,3-propanedione (HL1 ), 1,3-Bis (3-pyridyl)-1,3-propanedione (HL2 ), 1-(4-pyridyl)-3-(3-pyridyl)-1,3-propanedione (HL3 ), and 1,3-Bis (4-pyridyl)-1,3-propanedione (HL4 ), to tune the magnetic relaxation behaviors of cyano-bridged {DyIII MoV } systems. By reacting with DyCl3 ⋅ 6H2 O and K4 Mo(CN)8 ⋅ 2H2 O, four cyano-bridged complexes, namely {[Dy[MoV (CN)8 ](HL1 )2 (H2 O)3 ]} ⋅ 6H2 O (1), {[Dy[MoV (CN)8 ](HL2 )(H2 O)3 (CH3 OH)]}2 ⋅ 2CH3 OH ⋅ 3H2 O (2), {[Dy[MoV (CN)8 ](HL3 )(H2 O)2 (CH3 OH)] ⋅ H2 O}n (3), and {[Dy[MoV (CN)8 ](HL4 )2 (H2 O)3 ]} ⋅ 2H2 O⋅CH3 OH (4) were obtained. Structural analyses revealed that 1 and 4 are binuclear complexes, 2 has a tetragonal structure, and 3 exhibits a stair-like polymer chain structure. The DyIII ions in all complexes have eight-coordinated configurations with the coordination spheres DyO7 N1 for 1 and 4, DyO6 N2 for 2, and DyO5 N3 for 3. Magnetic measurements indicate that 1 is a zero-field single-molecule magnet (SMM) and complexes 2-4 are field-induced SMMs, with complex 4 featuring a two-step relaxation process. The magnetic characterizations and ab initio calculations revealed that changing the N-sites in the β-diketone ligands can effectively alter the structures and magnetic properties of cyano-bridged 4d-4f nanomagnets by adjusting the coordination environments of the DyIII centers.

Cytotoxicity of Ruthenium(II) Arene Complexes Containing Functionalized Ferrocenyl β-Diketonate Ligands.

The synthesis and characterization of 24 ruthenium(II) arene complexes of the type [(p-cym)RuCl(Fc-acac)] (where p-cym = p-cymene and Fc-acac = functionalized ferrocenyl β-diketonate ligands) are reported, including single-crystal X-ray diffraction for 21 new complexes. Chemosensitivity studies have been conducted against human pancreatic carcinoma (MIA PaCa-2), human colorectal adenocarcinoma p53-wildtype (HCT116 p53+/+) and normal human retinal epithelial cell lines (APRE-19). The most active complex, which contains a 2-furan-substituted ligand (4), is 5x more cytotoxic than the analogs 3-furan complex (5) against MIA PaCa-2. Several complexes were screened under hypoxic conditions and at shorter-time incubations, and their ability to damage DNA was determined by the comet assay. Compounds were also screened for their potential to inhibit the growth of both bacterial and fungal strains.