Β-diketonato Complexes Research Articles

Functionalization of Nanodiamond Surfaces with Metal β-Diketonato Complexes with Possible Application in Cancer Treatment

Functionalization of Nanodiamond Surfaces with Metal β-Diketonato Complexes with Possible Application in Cancer Treatment

Synthesis, Electrochemistry, XPS, and DFT Calculations of α-Carbon-Bonded Gold(I) Ferrocenyl- and Ruthenocenyl-Containing β-Diketonato Complexes

Synthesis, Electrochemistry, XPS, and DFT Calculations of α-Carbon-Bonded Gold(I) Ferrocenyl- and Ruthenocenyl-Containing β-Diketonato Complexes

Structural and Magnetic Properties of a Drop-Cast C54H34Br4CuO4 β-Diketonato Complex Film on a Graphite Surface.

The structural and magnetic properties of a drop-cast film of flat C54H34Br4CuO4, a β-diketonato complex functionalized with bromine atoms, on a graphite surface are investigated using scanning tunneling microscopy, synchrotron X-ray absorption spectroscopy, and X-ray magnetic circular dichroism. Experimental measurements reveal that the Cu-complexes preferentially lay flat on the graphite surface. The magnetic hysteresis loops show that the organic thin film remains paramagnetic at 2 K with an easy axis of magnetization perpendicular to the graphite surface and is therefore perpendicular to the plane of the Cu-complex skeleton.

XPS photoelectron lines, satellite structures and Wagner plot of Cu(II) β-diketonato complexes explained in terms of its electronic environment

A series of copper(II) β-diketonato complexes [Cu(R1CHCOCHR2)2], with R1 = R2 = C6H5 (1); R1 = C6H5 and R2 = CH3 (2); R1 = R2 = CH3 (3); R1 = C6H5 and R2 = CF3 (4); R1 = CH3 and R2 = CF3 (5) and R1 = R2 = CF3 (6), was subjected to a systematic XPS study of the Cu 2p core-level photoelectron lines, their satellite structures and the LMM Auger lines. The binding energies of the main Cu 2p core-level photoelectron lines are sensitive towards chemical environment (initial state effects) and are described by linear correlations with the combined Gordy scale group electronegativity of the R-groups on the β-diketonato ligands, ΣχR, and the first electrochemical reduction potential, Epc, of the Cu compounds. The modified Auger parameters were determined from the constructed Wagner plot of the copper(II) β-diketonato complexes, which also showed that the initial state effects are dominant during the photoemission process.

The chemistry of spin-coated rhodium-ferrocenyl complexes supported on silanol-capped silicon wafers

A series of rhodium β-diketonato complexes [Rh(FcCOCHCOR)(CO)2] and [Rh(FcCOCHCOR)(CO)(PPh3)] with R = CF3, CH3, Ph = C6H5 and Fc (ferrocenyl = FeII(C5H5)(C5H4)) were spin-coated on two-dimensional silanol-functionalised silicon wafers. Chemical reactions were observed that do not occur in ethanol solutions. Si-OH fragments on the wafers substituted ligands and oxidatively added to the Rh(I) centres. A multitude of different surface species could be identified with X-ray photoelectron spectroscopy (XPS). These included the parent spin-coated rhodium(I) complexes and rhodium(I) species that resulted from β-diketonato displacement from parent rhodium complexes by surface silanol OH’s to generate [wafer-(O)2-Rh-(CO)2]⊝ and [wafer-(O)2-Rh-(CO)(PPh3)]⊝ units. Several RhIII surface species that inter alia resulted from oxidative addition of surface Si-OH groups to surface-coordinated RhI core atoms were also identified. Efficacy of β-diketonato ligand substitution by the silanol surfaces is a kinetically driven process and can be related to the rate of solution-phase β-diketonato substitution by 1,10-phenanthroline from parent [Rh(FcCOCHCOR)(CO)2] and [Rh(FcCOCHCOR)(CO)(PPh3)] complexes. The binding energies of the RhI and RhIII 3d5/2 photoelectron lines were found to be functions of Gordy scale R-group electronegativities and they are also linearly related to electrochemically determined RhI oxidation potentials.

Multinuclear NMR Studies on Lewis Acid–Lewis Base Interactions between Bis(pentafluorophenyl)borinic Acid and Uranyl β-Diketonato Complexes in Toluene

In order to examine the possibility of Lewis acid-Lewis base (LA-LB) interactions between the boron atom of B(C6F5)2OH and the oxo groups ("yl" oxygen atoms) of uranyl β-diketonato complexes, we have measured the 1H, 11B, 17O, 19F NMR and IR spectra of toluene solutions containing β-diketonato complexes [UO2(acac)2DMSO or UO2(dfh)2DMSO, where acac = 2,4-pentanedionate, dfh = 1,1,1,2,2,6,6,7,7,7-decafluoroheptane-3,5-dionate, and DMSO = dimethyl sulfoxide] and B(C6F5)2OH. 11B and 17O NMR spectra of solutions containing UO2(dfh)2DMSO and B(C6F5)2OH showed no change in their chemical shifts regardless of the [B(C6F5)2OH]/[UO2(dfh)2DMSO] ratio. This indicates that there were no apparent interactions between B(C6F5)2OH and UO2(dfh)2DMSO. On the other hand, in the corresponding NMR spectra of solutions containing UO2(acac)2DMSO and B(C6F5)2OH, new signals were observed at a higher field than signals observed in the solutions containing only B(C6F5)2OH or UO2(acac)2DMSO, and their intensity changed with the [B(C6F5)2OH]/[UO2(acac)2DMSO] ratio. These results reveal that a complex with LA-LB interaction (B···O═U) between the boron atom of B(C6F5)2OH and the "yl" oxygen atom of UO2(acac)2DMSO was formed. IR spectra also supported such complex formation; i.e., the asymmetric O═U═O stretching band of UO2(acac)2DMSO was observed to shift from 897 to 810 cm-1 with the addition of B(C6F5)2OH. Moreover, 19F NMR spectra indicated that 1:1 and 2:1 LA-LB complexes exist in equilibrium, UO{OB(C6F5)2OH}(acac)2DMSO + B(C6F5)2OH = U{OB(C6F5)2OH}2(acac)2DMSO. The thermodynamic parameters for this equilibrium were obtained as K = (2.5 ± 0.6) × 102 M-1 (at 25 °C), ΔH = -42.4 ± 5.2 kJ mol-1, and ΔS = -96.7 ± 19.4 J K-1 mol-1. In 1H NMR spectra, the signal due to -CH groups of UO2(acac)2DMSO disappeared, and three signals due to the corresponding -CH groups newly appeared with an increase in the [B(C6F5)2OH]/[UO2(acac)2DMSO] ratio. From these phenomena, it is proposed that 1:1 and 2:1 LA-LB complexes having interactions between the -CH groups of acac and the -OH group of coordinated B(C6F5)2OH are formed depending on the [B(C6F5)2OH]/[UO2(acac)2DMSO] ratio.

Can Electrochemical Measurements Be Used To Predict X-ray Photoelectron Spectroscopic Data? The Case of Ferrocenyl-β-Diketonato Complexes of Manganese(III).

In order to better understand intramolecular communication between molecular fragments, a series of ferrocene-functionalized β-diketonato manganese(III) complexes, [Mn(FcCOCHCOR)3] with R = CF3, 1, CH3, 2, Ph = C6H5, 3, and Fc = FeII(η5-C5H4)(η5-C5H5), 4, the mixed ligand β-diketonato complex [Mn(FcCOCHCOFc)2(FcCOCHCOCH3)], 5, as well as the acac complex [Mn(CH3COCHCOCH3)3], 6, were subjected to an electrochemical and X-ray photoelectron spectroscopy (XPS) study. The ferrocenyl (FeII) and MnIII redox potentials, E°', and photoelectron lines were sufficiently resolved in each complex to demonstrate a linear correlation between E°' and group electronegativities of ligand R groups, χR, or ΣχR, as well as with binding energies of both the Fe 2p3/2 and Mn 2p3/2 photoelectron lines. These relationships are consistent with effective communication between molecular fragments of 1-5. From these relationships, prediction of Mn and Fe core electron binding energies in [Mn(R1COCHCOR2)3] complexes from known manganese and/or ferrocenyl redox potentials are, therefore, now possible. Ligand infrared carbonyl stretching frequencies were successfully related to binding energy as a measure of the energy required for inner-sphere reorganization. In particular it became possible to explain why, upon electrochemical oxidation or photoionization, the ferrocenyl FeII inner-shell of 1-5 needs more energy in complexes with ligands bearing electron-withdrawing (CF3) groups than in ligands bearing electron-donating groups such as ferrocenyl. The XPS determined entity Iratio (the ratio between the intensities of the satellite and main metal 2p3/2 photoelectron lines) is an indication not only of the amount of charge transferred, but also of the degree of inner-sphere reorganization. Just as for binding energy, the quantity Iratio was also found to be related to the energy requirements for the inner-sphere reorganization depicted by the vibrational frequency, vco.

Two-Dimensional Halogen-Bonded Porous Self-Assembled Nanoarchitectures of Copper β-Diketonato Complexes

Two novel copper β-diketonato complexes with halogen atoms are synthesized. The length of complex arms is slightly different. Scanning tunneling microscopy shows that the two complexes self-assemble into porous two-dimensional (2D) nanoarchitectures at the solid–liquid interface on graphite. These arrangements are however stabilized by the formation of two different halogen synthons between neighboring molecules. These synthons are composed of four or two type-II halogen bonds. These observations reveal that a tiny modification of complex design can drastically affect the structure of 2D halogen-bonded nanoarchitectures.

Significance of the electron-density of molecular fragments on the properties of manganese(iii) β-diketonato complexes: an XPS and DFT study

The group electronegativity of the R-groups of the ligand influences the XPS binding energies and the amount of charge transferred in the Mn 2p3/2photoelectron lines. DFT studies illustrated different Jahn–Teller elongation bond stretch isomers.

Synthesis by ligand exchange and electrochemistry of ruthenocenyl-containing β-diketonato complexes of titanocene. Structure of [TiCp2(RcCOCHCOCH3)][ClO4

A new synthetic route involving ligand exchange towards a series of ruthenocenyl-containing β-diketonato titanocene complexes of the type [TiIV(C5H5)2(RcCOCHCOR)][ClO4] with Rc = RuII(C5H5)(C5H4) and R = C10F21 (1), CF3 (2), C6F5 (3), C10H21 (4), CH3 (5), Rc (6) and Fc = FeII(C5H5)(C5H4) (7) are described. The complex [TiIV(C5H5)2(RcCOCHCOCH3)][ClO4], 5, (Z = 4) crystallised in the monoclinic space group P21/n. A cyclic voltammetric electrochemical study in CH2Cl2/0.1 M [NBu4][B(C6F5)4] showed the one-electron transfer redox processes of the TiIII/TiIV and Rc/Rc+ couples exhibited irreversible electrochemical behaviour. In CH3CN/0.1 M [N(nBu)4][PF6], the ruthenocenyl couple switched to an electrochemically and chemically irreversible two-electron transfer redox couple, Rc/Rc2+, involving the RuIV redox centre. The redox potentials of the TiIII/TiIV, Rc/Rc+ and Rc/Rc2+ couples were in the range −642 < Eo′ < −1479 mV (both solvents), 1016 mV < Eo′ < 1034 mV (CH2Cl2) and 609 mV < Eo′ < 832 mV (CH3CN) vs. the free ferrocene couple, FcH/FcH+, respectively. The Fc/Fc+ redox process associated with 7 was observed at Eo′ = 0.259 (CH3CN) and 0.235 V (CH2Cl2). The cytotoxicity of [TiIV(C5H5)2(RcCOCHCOCF3)][ClO4], 2, against CoLo DM320 and HeLa cells, IC50 = 10.2 and 9.7 μmol dm−3 respectively, was found to be in the same order of magnitude as those of the free ligand, RcCOCH2COCF3.

Consequences of Electron-Density Manipulations on the X-ray Photoelectron Spectroscopic Properties of Ferrocenyl-β-diketonato Complexes of Manganese(III). Structure of [Mn(FcCOCHCOCH3)3

Reaction of [Mn3(OAc)6O·3H2O](+) (1) with ferrocenyl β-diketones of the type FcCOCH2COR with R = CF3 (2a) and CH3 (2b), Ph = C6H5 (2c), and Fc = Fe(II)(η(5)-C5H4)(η(5)-C5H5) (2d) yielded a series of ferrocene-functionalized β-diketonato manganese(III) complexes 3a-3d, respectively, of general formula [Mn(FcCOCHCOR)3]. The mixed-ligand β-diketonato complex [Mn(FcCOCHCOFc)2(FcCOCHCOCH3)] (4) was obtained by reacting mixtures of diketones 2b and 2d with 1. A single-crystal X-ray structure determination of 3b (Z = 2, triclinic, space group P1̅) highlighted a weak axial elongating Jahn-Teller effect and a high degree of bond conjugation. An X-ray photoelectron spectroscopic study, by virtue of linear relationships between group electronegativities of ligand R groups, χR, or ∑χR, and binding energies of both the Fe 2p3/2 and Mn 2p3/2 photoelectron lines, confirmed communication between molecular fragments of 2a-2d as well as 3a-3d. This unprecedented observation allows prediction of binding energies from known β-diketonato side group χR values.

Comparison of X-ray photoelectron spectroscopy multiplet splitting of Cr 2p peaks from chromium tris(β-diketonates) with chemical effects

X-ray photoelectron spectra (XPS) measurements of a series of chromium(III) β-diketonato complexes of the Cr 2p spectra was fitted with calculated multiplet peaks. The XPS of these Cr(III) complexes did not exhibit fine structure, however, well-defined line shapes could be fitted to the Cr 2p3/2 envelope. The splitting patterns obtained for the Cr(III) β-diketonato complexes compared well with the multiplet splitting predicted by Gupta and Sen for the free Cr(III) ion. The Cr(III) β-diketonato complexes containing unsymmetrically substituted β-diketonato ligands, which display both the fac and mer isomers, could be fitted with two sets of multiplets and were useful in determining the ratio between the fac and mer isomers, which was compared with the Boltzman calculated ratio obtained from density functional theory energies. The obtained binding energy of the first multiplet splitting peak of the Cr 2p3/2 envelope was found to be dependent on the combined Gordy group electronegativity of the R-groups substituted on the β-diketonato ligand (RCOCHCOR′)−.

Tailoring supramolecular assemblies of β-diketonato Co(II) and Ni(II) complexes

In order not to rely on serendipity when targeting a desired physical property, we need an improved understanding of how metal-complexes can be organized and assembled into 3D solids using relatively weak and reversible interactions. Certain supramolecular synthons have already proved to be promising and reliable tools in engineering of crystalline organic substances. To examine the robustness and reliability of those synthons in metal-organic systems we have opted for β-diketonato complexes. β-Diketonates are a promising class of chelating ligands that eliminate the need for involvement of additional anions into the building of supramolecular assemblies. In this way, the functionalities are not exposed to the (usually) disruptive nature of counter ions commonly encountered in metal-organic systems, and are expected to communicate and interact with each other in the same manner as they do in purely organic systems. Nevertheless, the outcomes of our best theoretical and experimental efforts are often surprising. Here, we report on a series of β-diketonato complexes of Co(II) and Ni(II) with selected structure directing N-heterocyclic ligands with the intention of giving an insight into the requirements that have to be met by the ligand itself, as well as by the complex as a whole, for the expected supramolecular behaviour to be achieved. The data are complemented by CSD data mining and extensive computational methods are used to facilitate the interpretation of the experimental efforts.

Transition Metal Complexes of Phosphinous Acids Featuring a Quasichelating Unit: Synthesis, Characterization, and Hetero-bimetallic Complexes.

Diorganophosphane oxides were employed as preligands for the synthesis of catalytically active transition metal complexes of the phosphinous acids (CF3)2POH and (C2F5)2POH. Their reactions with solid PtCl2 and PdCl2 led to the formation of mononuclear phosphinous acid complexes [Cl2M{P(R(f))2OH}2] (M = Pd, Pt; R(f) = C2F5, CF3), which can be crystallized, for example, as its pyridinium salts, 2[HPy](+)[Cl2Pd{P(CF3)2O}2](2-). In vacuo HCl is liberated from the neutral palladium complexes affording mixtures of di- and polynuclear complexes. Moreover, (C2F5)2POH was reacted with several β-diketonato complexes of palladium, platinum, and nickel yielding air- and moisture-stable complexes [(acac)M{[P(R(f))2O]2H}], featuring a quasichelating phosphinous acid phosphinito unit {P(R(f))2O···H···O(R(f))2P}(-). Treatment of [Ni(Cp)2] (Cp = cyclopentadienyl) and [(cod)RhCl]2 (cod = 1,5-cyclooctadiene) with (C2F5)2POH leads to the substitution of one Cp or chloro ligand by a quasichelating unit. The novel coordination compounds were characterized by NMR and IR spectroscopies, mass spectrometry, and X-ray diffraction analysis. The platinum complex [(acac)Pt{[P(C2F5)2O]2H}] (acac = acetylacetonato) was used for the construction of hetero-bimetallic complexes by the treatment with [(cod)RhCl]2 and [Ni(Cp)2]. The trinuclear bimetallic complex [{(acac)Pt[P(C2F5)2O]2}2Ni] is the first structurally characterized hetero-bimetallic species containing a bis(perfluoroalkyl)phosphinito bridge.

VCD Studies on Chiral Characters of Metal Complex Oligomers

The present article reviews the results on the application of vibrational circular dichroism (VCD) spectroscopy to the study of stereochemical properties of chiral metal complexes in solution. The chiral characters reflecting on the vibrational properties of metal complexes are revealed by measurements of a series of β-diketonato complexes with the help of theoretical calculation. Attention is paid to the effects of electronic properties of a central metal ion on vibrational energy levels or low-lying electronic states. The investigation is further extended to the oligomers of β-diketonato complex units. The induction of chiral structures is confirmed by the VCD spectra when chiral inert moieties are connected with labile metal ions. These results have demonstrated how VCD spectroscopy is efficient in revealing the static and dynamic properties of mononuclear and multinuclear chiral metal complexes, which are difficult to clarify by means of other spectroscopes.

Spectral signature of a Ru(ii, iii, iv) complex: a combined experimental and theoretical investigation

The electronic and geometrical features of a recently synthesized ruthenium β-diketonato complex with a protected ethynyl ligand ([Ru(dbm)2(acac-TIPSA)], dbm = dibenzoylmethanate ion, acac-TIPSA = 3-(triisopropylsilyl)acetylene-2,4-pentanedionate ion), a building block for molecular spintronic devices, were analyzed as a function of its oxidation degree using Density Functional Theory (DFT) and Time Dependent DFT (TD-DFT), for ground and excited state properties, respectively, and compared to the available experimental data. The UV-Vis spectral signature of a native Ru(III) neutral form computed at a TD-DFT level was compared to those of the oxidized Ru(IV) and reduced Ru(II) ones, allowing us to clearly identify the nature of all bands occurring in this spectral region and thus providing important photophysical insights for the use of this complex as a building block in polynuclear organometallic mixed valence molecular systems able to perform a swapping operation under light control.

Fe(II) complexes that mimic the active site structure of acetylacetone dioxygenase: O2 and NO reactivity.

Acetylacetone dioxygenase (Dke1) is a bacterial enzyme that catalyzes the dioxygen-dependent degradation of β-dicarbonyl compounds. The Dke1 active site contains a nonheme monoiron(II) center facially ligated by three histidine residues (the 3His triad); coordination of the substrate in a bidentate manner provides a five-coordinate site for O(2) binding. Recently, we published the synthesis and characterization of a series of ferrous β-diketonato complexes that faithfully mimic the enzyme-substrate intermediate of Dke1 (Park, H.; Baus, J.S.; Lindeman, S.V.; Fiedler, A.T. Inorg. Chem.2011, 50, 11978-11989). The 3His triad was modeled with three different facially coordinating N3 supporting ligands, and substituted β-diketonates (acac(X)) with varying steric and electronic properties were employed. Here, we describe the reactivity of our Dke1 models toward O(2) and its surrogate nitric oxide (NO), and report the synthesis of three new Fe(II) complexes featuring the anions of dialkyl malonates. Exposure of [Fe((Me2)Tp)(acac(X))] complexes (where (R2)Tp = hydrotris(pyrazol-1-yl)borate with R-groups at the 3- and 5-positions of the pyrazole rings) to O(2) at -70 °C in toluene results in irreversible formation of green chromophores (λ(max) ∼750 nm) that decay at temperatures above -60 °C. Spectroscopic and computational analyses suggest that these intermediates contain a diiron(III) unit bridged by a trans μ-1,2-peroxo ligand. The green chromophore is not observed with analogous complexes featuring (Ph2)Tp and (Ph)TIP ligands (where (Ph)TIP = tris(2-phenylimidazoly-4-yl)phosphine), since the steric bulk of the phenyl substituents prevents formation of dinuclear species. While these complexes are largely inert toward O(2), (Ph2)Tp-based complexes with dialkyl malonate anions exhibit dioxygenase activity and thus serve as functional Dke1 models. The Fe/acac(X) complexes all react readily with NO to yield high-spin (S = 3/2) {FeNO}(7) adducts that were characterized with crystallographic, spectroscopic, and computational methods. Collectively, the results presented here enhance our understanding of the chemical factors involved in the oxidation of aliphatic substrates by nonheme iron dioxygenases.

UHV-STM Investigations and Numerical Calculations of a Ruthenium β-Diketonato Complex with Protected Ethynyl Ligand: [Ru(dbm)2(acac-TIPSA)

The quest of molecular electronic devices necessitates addressing model molecular systems as starting points. Among the targeted functions, electron transfer between specific moieties inside a molecule is expected to play a fundamental role for ultimate logical gates. Here we propose a coordination complex exhibiting two inorganic centers (Ru and Si) that constitutes a step toward a more complex architecture. Starting from the complex 1 [Ru(dbm)2(acac-I)] (dbm = dibenzoylmethanate ion, acac-I = 3-iodo-2,4-pentanedionate ion), the complex 2 [Ru(dbm)2(acac-TIPSA)] (acac-TIPSA = 3-(triisopropylsilyl)acetylene-2,4-pentanedionate ion) was obtained through Sonogashira cross coupling reaction under classical conditions. This complex 2 was characterized by elemental analysis, IR, 1H NMR, 13C NMR, UV–vis, cyclic voltammetry, mass spectroscopy as well as X-ray single-crystal diffraction. It crystallized with empirical formula of C46H49O6Ru1Si1 in a monoclinic crystal system and space group P21/c with a = 21.077(3) Å, b = 9.5130(7) Å, c = 21.8790(12) Å, β = 94.125(7)°, V = 4375.5(7) Å3 and Z = 4. Additionally, scanning tunneling microscopy measurements at liquid He temperature and in an ultrahigh vacuum (UHV-STM) were conducted on complex 2 on a Ag(111) surface. The STM images, supported by adsorption and STM image calculations, demonstrate that the molecules exist in two stable forms when adsorbed on the metallic surface.

NMR Spectroscopic Evidence of Lewis Acid–Lewis Base Complex Formation of Perfluoroborane with Uranyl β-Diketonato Complexes

Abstract Interactions between B(C6F5)2OH and [UO2(dfh)2(dmso)] or [UO2(acac)2(dmso)] in toluene have been investigated by 11B- and 19F NMR measurements. The results showed that one or two B(C6F5)2OH molecules coordinate to the oxo ligands of [UO2(acac)2(dmso)] through B, i.e., O=U=O···B (1:1) and B···O=U=O···B (2:1) complexes based on Lewis acid–Lewis base (LA–LB) interactions are formed, while such LA–LB interactions are not observed in [UO2(dfh)2(dmso)]. Furthermore, it was clarified that the 2:1 complex becomes predominant with decreasing temperatures.

Studies on solubility of uranyl complexes in supercritical carbon dioxide and its controlling factors using UV-visible and 17O- and 19F-NMR spectroscopy

Solubility of various β-diketonato complexes [Cu(hfa)2, Cr(hfa)3, Zr(hfa)4, Cu(hfa)2H2O, VO(hfa)2H2O, UO2(hfa)2H2O, UO2(hfa)2DMSO, and UO2(dfh)2DMSO (DMSO = dimethyl sulfoxide, hfa = hexafluoroacetylacetonate, dfh = 4H,4H-decafluoroheptane-3,5-dionate)] in supercritical carbon dioxide (scCO2) at 10.0 MPa and 40°C were measured using ultraviolet-visible and nuclear magnetic resonance (NMR) spectrometers equipped with high-pressure cell. The solubility of UO2(hfa)2H2O (4.0 × 10−2 M) and Cu(hfa)2H2O (2.3 × 10−2 M) with H2O ligands was smaller than that of UO2(hfa)2DMSO (1.2 × 10−1 M), UO2(dfh)2DMSO (3.8 × 10−1 M), and Cu(hfa)2 (2.9 × 10−2 M) (M = mol dm−3). The number of yl-oxygen and fluorine atoms also affected the solubility, i.e. the solubility increased in order of Cu(hfa)2H2O < VO(hfa)2H2O (2.5 × 10−2 M) < UO2(hfa)2H2O and in order of Cu(hfa)2 (2.9 × 10−2 M) < Cr(hfa)3 (3.0 × 10−2 M) < Zr(hfa)4 (4.4 × 10−2 M). Moreover, the intermolecular interactions between CO2 and specific atoms (yl-oxygen and fluorine) in β-diketonato complexes were examined by 17O- and 19F-NMR chemical shifts, and the existence of the apparent van der Waals interactions between CO2 and the specific atoms was identified. These results showed that the solubility of β-diketonato complexes in scCO2 was mainly controlled by the strength of CO2-complex interactions.