Synthesis,characterization and redox properties of mono- and bis-β-diketonate ruthenium complexes

Complexes of the type [RuIII(L)Cl2(PPh3)2] and [RuII(L)2(PPh3)2] (HL=benzoylacetone or acetylacetone) have been synthesized by the reaction of [RuCl2(PPh3)3] with HL under various experimental conditions. The [RuIII(L)Cl2(PPh3)2] complexes are one-electron paramagnetic species and, in solution, they show intense LMCT transitions in the visible region together with weak ligand-field transitions at lower energies. The [RuII(L)2(PPh3)2] complexes are diamagnetic and their solutions show sharp 1H n.m.r. signals and also show intense MLCT transitions in the visible region. In MeCN solution, the [RuIII(L)Cl2(PPh3)2] complexes show a reversible RuIII-RuII reduction near –0.3V and an irreversible RuIII- RuIV oxidation near 1.2 V versus s.c.e. A reversible RuII-RuIII oxidation is displayed by the [RuII(L)2(PPh3)2] complexes in MeCN solution near 0.3 V versus s.c.e. followed by another reversible RuIII-RuIV oxidation near 1.1 V versus s.c.e. The [RuII(L)2(PPh3)2] complexes have been oxidized to the corresponding [RuIII(L)2(PPh3)2]+ analogues and isolated as ClO4– salts in the solid state. The oxidized complexes are one-electron paramagnetic. They are 1:1 electrolytes in solution and show intense LMCT transitions in the visible region along with weak ligand-field transitions at lower energies.     

Synthesis and photophysical properties of europium pentafluorinated β-diketonate complexes

Research on Chemical Intermediates - Two pentafluorinated β-diketone ligands, 4,4,5,5,5-pentafluoro-1-(4-methoxyphenyl)pentane-1,3-dione (PFMP) and 4,4,5,5,5-pentafluoro-1-(4-dimethyl...     

Synthesis and crystal structures of dichlorocyclopentadienyl β-diketonate titanium complexes

Complexes of acetylacetonatodichlorocyclopentadienyltitanium(IV) (1) and dichlorocyclopentadienyl(2,2,6,6-tetramethyl-3,5-heptanedionato)titanium(IV) (2) have been prepared and their crystal structures determined by X-ray diffraction methods. Complex 1 crystallizes in space group P2₁/m with a?=?7.1893(10), b?=?11.7680(17), c?=?7.6129(11) Å, β?=?109.901(12)°; complex 2 crystallizes in space group P2₁/n with a?=?10.065(2), b?=?16.322(3), c?=?12.219(2) Å, β?=?110.99(3)°. The molecular structures of 1 and 2 can be described as square-based pyramidal, with the centroid of the C₅H₅ ring occupying the apical site and the bidentate β-diketonate and two chloride ligands occupying the basal positions. The average distances between titanium and oxygen atoms are 1.991(2) and 1.967(3) Å in compounds 1 and 2, respectively.     

Synthesis,characterization, and photoluminescence properties of difluoroboron complexes with bis-β-diketone ligands

Some novel difluoroboron bis-β-diketonates containing a pyridyl moiety were synthesized from diethyl 2,6-pyridinedicarboxylate via Claisen condensation with the corresponding aryl methyl ketones and followed by complexation with boron trifluoride etherate. Their spectroscopic behaviors were studied by FTIR, ¹H NMR, UV–Vis, and fluorescence spectroscopic techniques. The results indicated that difluoroboron bis-β-diketonates exhibited violet or blue fluorescence emission at 428–454 nm under UV illumination in DMSO and possessed high extinction coefficients. It was found that the nature of the substituents at benzene ring in bis-β-diketone ligands had a significant impact on the photoluminescence behaviors of difluoroboron complexes. The complex 5b exhibited the strongest photoluminescence intensity and highest quantum yield (Φ _u = 0.93), due to two strong electron-donating methoxyl moieties in molecule and the compound 4b displayed the lowest photoluminescence intensity and quantum yield, assigned to the heavy atom effect of the chlorine atom in its molecule. The photoluminescence intensity and quantum yield of these difluoroboron complexes decreased in the sequence, 5b > 2b > 1b > 3b > 4b.     

Synthesis,characterization and photophysical properties of homoleptic platinum(II) complexes with 2,2′-biimidazole-based ligands

Eight pairs of cis–trans isomeric homoleptic platinum(II) complexes based on N-alkyl- or aryl-substituted 2,2′-biimidazole ligands were synthesized, and their photophysical properties were investigated. The cis and trans isomers readily interconvert at slightly elevated temperature, implying that the activation barrier for this process is low. Single crystal X-ray diffraction analysis revealed that the complexes have an ideal square-planar geometry. Their UV–Vis spectra showed lower energy absorption bands in the range of 345–378 nm, which are assigned to the typical MLCT mixed with LC transitions. In frozen glass solution at 77 K and also in the powder state, these complexes exhibit green emission ranging from 440 to 540 nm with photoluminescence quantum yields of 3.3–24.4%. The emitting excited state is dominated by ³ππ* character with some contributions from ³MLCT according to the excitation spectra.     

New luminescent cyclometalated iridium(Ⅲ) complexes containing fluorinated phenylisoquinoline-based ligands: Synthesis,structures,photophysical properties and DFT calculations

Two new fluorinated phenylisoquinoline-based iridium(Ⅲ) complexes,[Ir(f_2piq)_2(bipy)][PF_6](3a) and[Ir(fmpiq)_2(bipy)][PF_6](3b)(f_2piq = l-(2,4-difluorophenyl)isoquinoline,fmpiq = 1-(4-fluoro-2-methylphenyl)isoquinoline,bipy = 2,2'-bipyridine),have been synthesized and fully characterized.Single crystal X-ray diffraction study has been undertaken on complexes 3a and 3b,which show that each adopts the distorted octahedral coordination geometry with the cis-C,C' and trans-N,N' configuration.The photoluminescence spectra of 3a and 3b exhibit yellow and orange emission maxima at 584 and 600 nm,respectively.The frontier molecular orbital diagrams and the lowest-energy electronic transitions of 3a-3b have been calculated with density functional theory(DFT) and time-dependent DFT(TD-DFT).The absorption and emission spectra of complex 3b is red-shifted relative to those of complex 3a,as a consequence of the nature of the methyl group.     

Synthesis,crystal structures,and photophysical properties of dibromo-2-(2′-pyridyl)imidazole and its corresponding boron–fluorine complex

2-(2′-Pyridyl)imidazole L1 and its corresponding boron–fluorine complex, 1, were synthesized and their crystal structures correlated with their photophysical properties. L1 forms a rigid supramolecular network through hydrogen bonds and halogen bond in the single crystal, which induces amplified spontaneous emission in crystals; it emits rather poor fluorescence in solution and powder states. Its boron chelate 1 emits intense fluorescence in solution since boron chelate is an excellent chromophore, and it exhibits large Stokes shift (136?nm in acetonitrile), due to the charge-transfer transition from the electron-donating π system to the electron-accepting boron moiety. Interestingly, 1 is also highly fluorescent in amorphous powder and crystal states; C–C rotation between pyridyl and imidazole groups is inhibited by the formation of a five-member ring containing BF₂, and the formation of intermolecular non-covalent bonds is the key factor. Solid emission with large Stokes shift makes it a valuable chromophore for synthesis of functional materials.     

Star-shaped triphenylamine terminated difluoroboron β-diketonate complexes: synthesis,photophysical and electrochemical properties

Two new star-shaped difluoroboron β-diketonate complexes (TBC)₃Ph and (TBF)₃Ph, in which the terminal groups of triphenylamine functionalized difluoroboron β-diketonates were bridged by carbazole or fluorene to the core of 1,3,5-benzene, have been synthesized. It was found that they gave high molar extinction coefficients, meaning strong light-harvesting ability, and emitted intense yellow light with fluorescence quantum yields (Φ_F) of 0.73 and 0.67 for (TBC)₃Ph and (TBF)₃Ph, respectively, in toluene as well as red light in solid states with Φ_F of 0.36 and 0.27, respectively. The electrochemical behaviors suggested that they had considerably higher electron affinities than tris(8-hydroxyquinoline)aluminum (AlQ₃), which indicated that they could be used as electron-transporting materials besides emitting materials.     

Syntheses,crystal structures,and magnetic properties of three one-dimensional metal–nitroxide complexes linked by 1,4-cyclohexanedicarboxylate ligands

Three one-dimensional metal–nitroxide complexes [Cu(NIT4Py)₂(1,4-chdc)] _n (1), {[Cu(IM4Py)₂(1,4-chdc)(H₂O)]·H₂O} _n (2) and {[Zn(IM4Py)₂(1,4-chdc)(H₂O)₂]·H₂O} _n (3) (NIT4Py = 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, IM4Py = 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl and 1,4-chdc = 1,4-cyclohexanedicarboxylate anion) have been synthesized and characterized structurally as well as magnetically. All three complexes crystallize in neutral one-dimensional chains in which the nitroxide–metal–nitroxide units are linked by linear 1,4-cyclohexanedicarboxylate anions. The 1,4-chdc ligands only present the e,e-trans-configuration in these complexes, although there are both cis- and trans-isomers in the free ligand. Magnetic measurements show that complexes 1 and 2 both exhibit weak antiferromagnetic interactions between the copper atoms and nitroxide radicals.     

Synthesis, characterization and crystal structures of manganese (Ⅱ) complexes containing nitronyl nitroxide and its reduced derivative

Two novel adducts of formula Mn(hfac)2( NITPhCl )2 (1) and [Mn(hfac)2(IMHPhCl)]2(NIT-PhCl)·0.5H2O (2), where hfac = hexafluoroacetylacetonate, NITPhCl = 2-(3-chlorophenyl)-4,4,5,5-tetram-ethylimidazolyl-1-oxyl-3-oxide, IMHPhCl = 2-(3-chlorophenyl)-4, 4, 5, 5-tetramethylimidazolyl-3-oxide, have been prepared by the reaction of Mn(hfac)2·2H2O with NITPhCl. Compound 1 is triclinic, space group P-1with a = 1.3003(3) nm, 6 = 1.3138(3) nm,c = 1.4931 (3) nm, α = 83.74(3)°, β = 77.77(3)°, γ = 60.59(3)°, V=2.171(1)nm3, Z = 2. Compound 2 is triclinic, space group P-1 with a = 1.2994(3) nm, b = 1.4841(3) nm, c = 2.1031 (4) nm, a = 92.30(3)° ,p = 98.68(3)°, γ = 97.89(3)°, V= 3.964(2)nm3, Z = 2. Each manganese atom is hexacoordinated in both compounds and compound 2 is organized inchains by hydrogen bonds between neighboring pairs of NITPhCl and IMHPhCl.     

Synthesis,properties and crystal structures of volatile β-ketoiminate Pd complexes,precursors for palladium chemical vapor deposition

The β-aminovinylketone ligands CH₃C(NH₂)CHC(O)CH₃ (1) and CH₃C(NHCH₃)CHC(O)CH₃ (2) were synthesized from 2,4-pentandione by amination with a water solution of the appropriate amine in toluene at room temperature. The reactions of 1 and 2 with the PdCl₂ salt in amine medium gave the volatile chelate metal complexes Pd[CH₃C(NH)CHC(O)CH₃]₂ (3) and Pd[CH₃C(NCH₃)CHC(O)CH₃]₂ (4). The obtained compounds were identified by elemental analysis, ¹H and ¹³С NMR, IR-spectroscopy and were characterized by TGA and a single-crystal X-ray diffraction study. In compounds 3 and 4, the Pd atom has a square coordination environment Pd O₂N₂.     

Discotic metallomesogens: Synthesis and properties of square planar metal bis(β-diketonate) complexes

Abstract

Discotic β-diketonate liquid crystals containing palladium(II), and oxovanadium(IV), (V[tbnd]0), analogous to known copper complexes (which display discotic lamellar and columnar mesophases), have been prepared and characterized. These are the first enantiotropic discotics containing Pd(II) and among the earliest examples containing VO(IV). The best-behaved Pd(II) complex is [Pd(DK 10, 10)₂], and it also is probable that the complexes [Pd(DKn,n)₂] (n = 7–9) are mesomorphic, however their characterization is difficult due to decomposition in the isotropic phase. The mesophase of [Pd(DK 10²,10²)₂], which appears below 100°C, is suggested to be an example of the rare N_d phase on the basis of optical microscopy. The complex [VO(DK8,8)₂] is an enantiotropic discotic vanadyl complex; the monotropic behaviour of [VO(DK 10,10)₂] was also confirmed. It is suggested that the discotic phase which occurs for [VO(DK 8,8)₂] is more organized than that of [Cu(DK 8,8)₂].     

Ruthenium(II) complexes of azoimine and α-diimine ligands: synthesis,spectroscopic and electrochemical properties,crystal structures and DFT calculations

Five octahedral ruthenium(II) complexes with azoimine–quinoline (Azo) and α-diimine (L) ligands having the general formula [Ru^II(L)(Azo)Cl](PF₆) (1–5) {Azo: PhN=NC(COMe)=NC₉H₆N, L = 4,4′-dimethoxy-2,2′-bipyridine (dmeb) (1), 4,4′-di-tertbutyl-2,2′-bipyridine (dtb) (2), 1,10-phenanthroline (phen) (3), 5-chlorophenanthroline (Clphen) (4), or 3,4,7,8-tetramethyl-1,10-phenanthroline (tmphen) (5)} were prepared by stepwise addition of the tridentate azoimine (H₂Azo) and α-diimine (L) pro-ligands to RuCl₃ in refluxing EtOH. The tridentate azoimine–quinoline ligands coordinate to ruthenium via the Azo-N′, N′-imine and N″-quinolone nitrogen atoms. The spectroscopic properties (IR, UV/Vis, ¹H, ¹³C and ¹⁹F NMR) and electrochemical behavior of complexes 1–5 and the X-ray crystal structures of complexes 2 and 3 are presented. The coordination of Ru(II) to these strong π-acceptor ligands (Azo and L) results in a large anodic shift for the Ru(III/II) couples of 1.63–1.72 V versus NHE. The electronic spectra in MeCN and IR spectra in CH₂Cl₂ for complex 3 in its oxidized 3 ⁺ and reduced 3 ^? forms were investigated. The calculated absorption spectrum of 3 in MeCN was used to assign the UV–Vis absorption bands.     

Synthesis, characterization and magnetic properties of μ-iodanilato dinuclear oxovanadium (Ⅳ) complexes

Five oxovanadium(Ⅳ) dinuclear complexes described by the overall formula [(VO)2(IA)L2]-SO4, where IA represents the dianion of iodanilic acid and L denotes 2,2'-bipyridine (bpy) ; 4,4'-dimethyl-2,2'-bipyridine (Me2-bpy); 1,10-phenanthroline (phen); 4,7-diphenyl-1, 10-phenanthroline (Ph2-phen) and 5-nitro-l, 10-phenanthroline (NO2-phen) , have been synthesized and characterized by elemental analyses, molar conductivity and room-temperature magnetic moment measurements, IR and electronic spectral studies. It is proposed that these complexes have IA-bridged structures and consist of two oxovanadium(Ⅳ) ions each in a square- pyramidal environment. The complexes [ ( VO)2 (IA) (bpy )2 ] SO4 (1) and [ ( VO )2 ( IA) ( phen)2 ] -SO4 (2) were further characterized by variable temperature (4.2-300 K) magnetic susceptibility measurements and the observed data were fitted to the modified Bleaney-Bowers equation by the least-squares method, giving the exchange integral J = -2.15 cm-1 for 1 and J = - 9.88 cm-1 for 2     

Synthesis,structure, and magnetic properties of iron — yttrium complexes containing acetylacetonate ligands

Two new compounds have been obtained by the synthesis of heteronuclear iron-yttrium acetylacetonate, using the modified electrochemical dissolution of the [YFe₂] alloy. One of these compounds, with the Fe(acac)₂ · 2H₂O composition, has been studied by X-ray diffraction analysis. X-ray diffraction data: a=11.002(5), b=5.412(2), c=11.179(5) Å;=106.39(4)°;V=638.6 ų, space group P2₁/c, Z=2. According to the data on magnetic susceptibility, Mössbauer spectroscopy, and X-ray electron microanalysis, single crystals of this complex are covered with an amorphous film containing finely dispersed [Y_1–aFe_a]n clusters and, probably, superparamagnetic -Fe₂O₃ species. The second oligomeric acetylacetonate complex contains ions of high-spin two-valence iron, yttrium, and finely dispersed ferromagnetic [Y_1–aFe_a)n intermetallide clusters.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1454–1458, August, 1995.The studies were financially supported by the International Science Foundation (Grants Nos. MI 8000, MI 8300).     

Structural investigations of copper(II) complexes containing unsymmetrical β-diketonate and monothio-β-diketonate ligands

The crystal structures of the complexes Cu(txhd)₂ and Cu(S-tmhd)₂ (where txhd is the anion of 2,2,6-trimethylheptane-3,5-dione and S-tmhd is the anion of 5-mercapto-2,2,6,6-tetramethyl-4-hepten-3-one) were determined. In the solid state, both complexes are square planar. In each case, only one geometrical isomer (trans or cis) was observed in the crystals; arguments are presented that both isomers are present in bulk samples of Cu(txhd)₂, while from electronic considerations, the monothio-β-diketonate ligands probably have cis geometry in Cu(S-tmhd)₂. Calculations of molecular volumes for structurally similar Cu[t-BuC(O)CHC(O)R]₂ complexes showed that there is a slight decrease in packing efficiency as the steric bulk of R increases. More importantly, strong ring-stacking interactions, such as those found for Cu(acac)₂ are not observed, or are greatly attenuated, in complexes with bulkier peripheral substituents. [Cu(txhd)(μ₃-OEt)]₄, an impurity that co-sublimed with Cu(txhd)₂, was isolated in low yield. The tetrameric structure, which is isomorphous with known [Cu(tmhd)(μ₃-OEt)]₄ (where tmhd is the anion of 2,2,6,6-tetramethylheptane-3,5-dione), has a cubane-like core.     

Synthesis,crystal structures and characterization of iron(III) and cobalt(III) complexes bearing 2,2′-bipyridylcarboxylate ligands

Transition Metal Chemistry - The Fe(III) complex [FeIII(bpdc)(Hbpdc)] (1) (bpdc?=?2,2′-bipyridyl-6,6′-dicarboxylate and...     

Synthesis,crystal structure and properties of two terbium complexes with 2,2′-bipyridine

Two new complexes {[Tb(2-IBA)₃ · 2,2′-bipy]₂ · C₂H₅OH} (1) and [Tb(2-ClBA)₃ · 2,2′-bipy]₂ (2) (2-IBA = 2-iodobenzoate; 2-ClBA = 2-chlorobenzoate; 2,2′-bipy = 2,2′-bipyridine) were prepared and their crystal structures determined by X-ray diffraction. Complex 1 is composed of two types of binuclear molecules, [Tb(2-IBA)₃ · 2,2′-bipy]₂ (a) and [Tb(2-IBA)₃ · 2,2′-bipy]₂ (b), and an uncoordinated ethanol molecule. In molecule (a), two Tb³⁺ ions are linked by four 2-IBA groups, all bidentate-bridging. In molecule (b), two Tb³⁺ ions are held together by four 2-IBA groups in two coordination modes, bidentate-bridging and chelating-bridging. In the two molecules, each Tb³⁺ ion is further bonded to one chelating 2-IBA group and one chelating 2,2′-bipy molecule, resulting in coordination numbers of eight for (a) and nine for (b). The structural characteristics of 2 are similar to that of molecule (b) in 1. The two complexes, 1 and 2, both emit strong green fluorescence under ultraviolet light with the ⁵D₄ → ⁷F _j (j = 6–3) emission of Tb³⁺ ion observed.     

Synthesis,properties and crystal structures of volatile dimethylgold(III) complexes based on phenyl-containing β-diketones and β-iminoketone

We have synthesized and studied volatile dimethylgold(III) complexes based on phenyl-containing β-diketones and β-iminoketone, namely (CH₃)₂Au(C₆H₅–CO–CH–CO–CH₃), (CH₃)₂Au(bac) (1); (CH₃)₂Au(C₆H₅–CO–CH–CO–CF₃), (CH₃)₂Au(btfa) (2); and (CH₃)₂Au(C₆H₅–CO–CH–C(NH)–CH₃), (CH₃)₂Au(i-bac) (3). The obtained compounds were identified by elemental analysis, ¹H NMR and IR-spectroscopy, and were characterized by DTA and single-crystal X-ray diffraction studies. In compounds 2 and 3, the Au atom has a square coordination environment AuC₂O₂ and AuC₂NO, respectively.     

Synthesis, electrochemical and photophysical properties of β-carboxy triaryl corroles

An unswerving one-pot conversion of 3-formyl-5,10,15-triaryl substituted corroles and their copper(III) derivatives to the corresponding 3-carboxy-5,10,15-triaryl substituted corroles was achieved by adopting mild reaction conditions by using hydroxylamine hydrochloride and phthalic anhydride. All these substituted carboxy corroles were completely characterized by using Mass, CHN analysis, IR, ¹H NMR, UV-vis., Fluorescence spectroscopies, and cyclic voltammetry. Both the absorption maxima and emission maxima of carboxy corroles were red shifted by 5-13 nm. The LUMO level of these corroles is above the TiO₂ conduction band and HOMO level was below the redox electrolytes. These β-carboxy corroles confined with may find applications as sensitizers in dye-sensitized solar cells.