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,characterization, and optoelectronic properties of heteroleptic iridium complexes containing substituted 1,3,4-oxadiazole and β-diketone as ligands

The new heteroleptic iridium(III) complexes (BuOXD)₂Ir(tta) and (BuOXD)₂Ir(tmd) [BuOXD?=?2-(4-butyloxyphenyl)-5-phenyl[1,3,4]oxadiazolato-N4,C2, tta?=?1,1,1-trifluoro-4-thienylbutane-2,4-dionato, tmd?=?2,2,6,6-tetramethylheptane-3,5-dionato] have been synthesized and characterized. These complexes have two cyclometalated ligands (C^N) and a bidentate diketone ligand (X) [C^N)₂Ir(X)], where X is a β-diketone with trifluoromethyl, theonyl or t-butyl groups. The color tuning with the change in electronegativity of substituents in the β-diketones has been studied. Photoluminescence spectra of the complexes showed peak emissions at 523 and 549?nm, respectively. The electroluminescent properties of these complexes have been studied by fabricating multi layer devices with device structure ITO/α-NPD/8% iridium complex doped CBP/BCP/Alq₃/LiF/Al. The electroluminescence spectra also showed peak emissions at 526 and 570?nm for (BuOXD)₂Ir(tta) and (BuOXD)₂Ir(tmd), respectively. These metal complexes showed good thermal stability in air to 340°C.     

Synthesis, crystal structures, photophysical properties, and bioimaging of living cells of bis-β-diketonate phenothiazine ligands and its cyclic dinuclear complexes

Two bis-β-diketones, RCOCH(2)CO-EPTZ-COCH(2)COR (EPTZ = 10-ethylphenothiazine; R = C(6)H(5) for H(2)L(1) and CF(3) for H(2)L(2)) and their cyclic dinuclear Zn(II), Cd(II), Ni(II), Mn(II), Cu(II), Co(II) complexes have been synthesized and fully characterized. Their crystal structures were determined by single crystal X-ray diffraction analysis. Their photophysical properties have been further investigated both experimentally and theoretically. The results revealed that significant enhancement of two-photon absorption cross section values were obtained for the cyclic dinuclear Zn(II) and Cd(II) complexes compared with their free ligands. Additionally, confocal microscopy and two-photon microscopy fluorescent imaging of MCF-7 cells labeled with two ligands and Zn(II) complexes reveal their potential applications as a biological fluorescent probe.     

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.     

Syntheses and characterization of η-hexamethylbenzeneruthenium(II)-β-diketone complexes: their reactions with mono- and bidentate neutral ligands

The complex [(η⁶-C₆Me₆)Ru(μ-Cl)Cl]₂1 react with sodium salts of β-diketonato ligands in methanol to afford the oxygen bonded neutral complexes of the type [(η⁶-C₆Me₆)Ru(κ²-O,O′-R¹COCHCOR²)Cl] {R¹, R² = CH₃ (2), CH₃, C₆H₅ (3), C₆H₅ (4), OCH₃ (5), OC₂H₅ (6)}. Complex 4 with AgBF₄ yields the γ-carbon bonded ruthenium dimeric complex 7. Complex 4 also reacts with tertiary phosphines and bridging ligands to yield complexes of the type [(η⁶-C₆Me₆)Ru(κ²-O,O′-C₆H₅COCHCOC₆H₅)(L)]⁺ (L = PPh₃ (8), PMe₂Ph (9)) and [{η⁶-C₆Me₆)Ru(κ²-O,O′-C₆H₅COCHCOC₆H₅)}₂(μ-L)] L = 4,4′-bipyridine (4,4′-bipy) (11), 1,4-dicyanobenzene (DCB) (12) and pyrazine (Pz) (13). Complexes 2-4 react with sodium azide to yield neutral complexes [(η⁶-C₆Me₆)Ru(κ²-O,O′-R¹COCHCOR²)N₃] {R¹, R² = CH₃ (10a), CH₃, C₆H₅ (10b), C₆H₅ (10c). All these complexes were characterized by FT-IR and FT-NMR spectroscopy as well as analytical data. The molecular structures of complexes [(η⁶-C₆Me₆)Ru(κ²-O,O′CH₃COCH-COC₆H₅)Cl] (3) and [(η⁶-C₆Me₆)Ru(κ²-O,O′-C₆H₅COCHCOC₆H₅] (4) were established by single crystal X-ray diffraction studies. The complex 3 crystallizes in the triclinic space group, [a = 7.9517(4), b = 9.0582(4) and c = 14.2373(8) Å, α = 88.442(3)°, β = 76.6.8(3)° and γ = 81.715(3)°. V = 987.17(9) ų, Z = 2]. Complex 4 crystallizes in the monoclinic space group, P2₁/c [a = 7.5894(8), b = 20.708(2) and c = 29.208(3) Å,β = 92.059(3)° V = 4587.5(9) ų, Z = 8].     

Synthesis, structural characterization, and luminescence properties of multinuclear silver complexes of pyrazole-functionalized NHC ligands containing Ag-Ag and Ag-π interactions

A few pyrazole-functionalized imidazolium salts have been prepared via the reactions of N-alkylimidazole and 3,5-bis(chloromethyl)pyrazole or 2-(1-(2-chloroethyl)-5-methyl-1H-pyrazol-3-yl)-6-(5-methyl-1-vinyl-1H-pyrazol-3-yl) pyridine. Reactions of these imidazolium salts with Ag₂O led to the successful isolation of tetranuclear [Ag₄(L)₂](X)₂ (X = PF₆⁻ or BF₄⁻; H₃L1 = 3,5-bis(N-benzylimidazoliumyl)pyrazole, H₃L2 = 3,5-bis(N-(2,4,6-trimethylphenyl)imidazoliumyl)pyrazole, H₃L3 = imidazolium cyclophane from the condensation of 3,5-bis(chloromethyl)pyrazole and 1,4-bis(imidazolyl)butane) and trinuclear silver clusters supported by N-heterocyclic carbene ligands in high yields. The molecular structures of these silver complexes have been confirmed by ¹H, ¹³C NMR, ESI-MS spectroscopy, and X-ray diffraction analyses. The tetranuclear complexes [Ag₄(L1)₂](PF₆)₂ (1) and [Ag₄(L2)₂](BF₄)₂ (2) consist of a pair of Ag-Ag contacts (ca. 3.11 Å) showing weak silver-silver interaction. [Ag₄(L3)₂](PF₆)₂ (3) has a square planar Ag₄ core sandwiched by two NHC cyclophanes with Ag-Ag distances of 3.22 Å. All the silver atoms in 1-3 are located in the same linear C-Ag-N coordination environment. [Ag₃(L4)₂] (PF₆)₃ (HL4 = 2-(1-(2-methylimidazoliumylethyl)-5-methyl-1H-pyrazol-3-yl)-6-(5-methyl-1-vinyl-1H-pyrazol-3-yl) pyridine) (4) is a trinuclear complex in which the three silver are bridged by two L4 molecules, and the Ag₃ units form one-dimensional chain via Ag-π interaction. The luminescence properties of the imidazolium salts and their silver complexes were also studied.     

Synthesis and structural characterization of iron–sulfur complexes with hydrophilic nitrogen–phosphorus ligands

Reaction of the parent complex (μ-PDT)Fe₂-(CO)₆ (A) (PDT = 1,3-SCH₂CH₂CH₂S^2?) with the bidentate N/P ligand [(Ph₂P)₂N(C₆H₄Cl-p)] in the presence of Me₃NO as decarbonylating agent produced an unexpected iron–sulfur complex [(μ-PDT)Fe₂(CO)₅{PPh₂(NHC₆H₄Cl-1,4)}] (1). Extending this chemistry further, two similar complexes [(μ-PDT)Fe₂(CO)₅{PPh₂(NHC₆H₄NO₂-1,4)}] (2) and [(μ-PDT)Fe₂(CO)₅{PPh₂(NHC₆H₄CO₂Et-1,4)}] (3) could be prepared from the simple substitution reactions of the precursor A with the monodentate N/P ligands Ph₂P(NHC₆H₄NO₂-1,4) and Ph₂P(NHC₆H₄CO₂Et-1,4), respectively. These new complexes, which can be considered as active site models of [FeFe] hydrogenases, have been characterized by elemental analysis, FTIR, and NMR (¹H, ¹³C, ³¹P) spectroscopies, as well as by X-ray crystallography for complex 1.     

Tetranuclear copper complexes with new β-diketone and β-iminoketone-containing ligands

Novel tetranuclear copper complexes, Cu4(OH)2(ClO4)3 (HA)·H2O (1) and Cu4(ClO4)5(H3B)·3H2O (2), were synthesized by reacting 1,5-bis(1-phenyl-3-methyl-5-pyrazolone-4)-1 ,5-pentanedione with 1,3-propanediamine and 2-hydroxyl-1,3-propanediamine in the presence of a template reagent copper ion. New [2+2] type open cyclic multidentate ligands are also obtained from the reaction (H4A and H6B stand for new compounds from 1,3-propanediamine and 2-hydroxyl-1,3-propanediamine, respectively). They each contain five C = O, three C = N and one NH2 groups. The complexes were characterized by elemental analyses, conductivity, FT-i.r. (micro-i.r., deconvolution technique), FAB-MS, e.s.r., electronic spectra and extended X-ray absorption fine structure (EXAFS). Copper ions in (1) are basically four coordinate with tetragonal geometry. The average coordination bond distances of Cu–N and Cu–O are 1.91 Å and 2.05 Å. In (2), copper ions are primarily five coordinate with square-based pyramidal geometry. The average coordination bond distances of Cu–N and Cu–O are 1.93Å and 2.08Å. Four copper atoms in molecules may be arranged tetragonally. Both the ligand field and the coordination bonds in complex (1) are stronger than those in (2). Investigations on variable temperature susceptibilities show that some antiferromagnetic exchange interaction exist in the complexes. The plots of –1 versus T obey the Curie-Weiss law only at low temperature. Preliminary results of a bioassay indicate that the two complexes have some antitumour activity in vitro.     

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).     

Synthesis,characterization and magnetic properties of supramolecular metal–organic complexes constructed from flexible–rigid mixed ligands

Two new supramolecular metal–organic complexes have been synthesized under hydrothermal conditions. Complex 1 exhibits a three-dimensional supramolecular network, constructed from [Co₂(H₃BPTC)₂(phen)₂] (H₄BPTC = 3,3′4,4′-benzophenone tetracarboxylate acid, phen = 1,10-phenanthroline) discrete units. Complex 2 similarly exhibits discrete [Cu₂(DPA)₂(bipy)₂(H₂O)₂] (DPA = 1,1′-biphenyl-2,2′-dicarboxylate acid, bipy = 2,2′-bipyridine) units, which are linked to form a three-dimensional supramolecular network through π–π interactions. It is interesting that during the synthesis of complex 1, the H₄BPTC ligands undergo partial decomposition to give 1,2,4-benzenetricarboxylate (H₃BTC) ligands, which react with Co to form [Co₃(BTC)₂]_n (3). Complex 3 shows a three-dimensional covalent network. The magnetic properties of complexes 1 and 2 have been studied.     

Copper complexes of pyridyl–tetrazole ligands with pendant amide and hydrazide arms: synthesis,characterization, DNA-binding and antioxidant properties

Pyridyl–tetrazole ligands 2-(5-(pyridin-2-yl)-1H-tetrazol-1-yl)acetamide (L1), 2-(5-(pyridin-2-yl)-2H-tetrazol-2-yl)acetamide (L2), 2-(5-(pyridin-2-yl)-1H-tetrazol-1-yl)acetohydrazide (L3) and 2-(5-(pyridin-2-yl)-2H-tetrazol-2-yl)acetohydrazide (L4) have been prepared and coordinated with CuCl₂·2H₂O to furnish the corresponding complexes [Cu(L1) ₂ ]–[Cu(L4) ₂ ]. EPR spectra of the complexes are characteristic of square planar geometries, with nuclear hyperfine spin 3/2. DNA-binding studies using UV–Vis absorption spectroscopy, viscosity and thermal denature studies revealed that all of these complexes are avid binders of calf thymus DNA. The antioxidant properties of the free ligands and the Cu(II) complexes were investigated using the p-nitrosodimethyl aniline hydroxyl radical scavenging method, and [Cu(L4) ₂ ] was found to show the highest activity.     

Synthesis,characterization and biological activity of copper(II) complexes with ligands derived from β-amino acids

Transition Metal Chemistry - Two copper(II) complexes with ligands derived from β-amino acids, 2-(1-aminocyclohexyl)acetic acid L1 and 2-(1-amino-4-(tert-butyl)cyclohexyl)acetic acid L2, were...     

Synthesis,characterization and magnetic properties of coordination polymers of manganese with 1,1′-biphenyl-2,2′-dicarboxylic acid ligands

Three new coordination polymers have been synthesized from 1,1′-biphenyl-2,2′-dicarboxylic acid (2,2-dpa), nitrogen-containing coligands and Mn salts under hydrothermal conditions. The X-ray crystal structures of all three complexes are presented. With the change of nitrogen-containing ligand, the structural features of the complexes also change. The complex prepared without a nitrogen coligand exhibits a one-dimensional covalent chain-like structure, composed of the rare pentanuclear Mn building unit. The complex with 4,4′-bipyridine as a secondary ligand shows a two-dimensional layer structure. With the chelating ligand 1,10-phenanthroline, a discrete molecular complex is synthesized. The magnetic properties of the complex with 4,4′-bipyridine in the temperature range 1.99–300 K are reported.     

Studies on characterization, telomerase inhibitory properties and G-quadruplex binding of η6-arene ruthenium complexes with 1,10-phenanthroline-derived ligands

Two arene ruthenium complexes [Ru(η(6)-C(6)H(6))(p-MOPIP)Cl](+)1 and [Ru(η(6)-C(6)H(6))(p-CFPIP)Cl](+)2, where p-MOPIP = 2-(4-methoxyphenyl)-imidazo[4,5f][1,10] phenanthroline and p-CFPIP = 2-(4-trifluoromethylphenyl)-imidazo[4,5f][1,10] phenanthroline, were prepared and the interactions of these compounds with DNA oligomers 5'-G3(T2AG3)3-3'(HTG21) have been studied by UV-vis and circular dichroism (CD) spectroscopy, gel mobility shift assay, fluorescence resonance energy transfer (FRET) melting assay, polymerase chain reaction (PCR) stop assay and telomeric repeat amplification protocol (TRAP) assay. The results show that both complexes can induce the stabilization of quadruplex DNA but complex 1 is a better G-quadruplex binder than complex 2. The two ruthenium complexes tested led to an inhibition of the enzyme telomerase and complex 1 was the significantly better inhibitor. A novel visual method has been developed for making a distinction between G-quadruplex DNA and double DNA by our Ru complexes binding hemin to form the hemin-G-quadruplex DNAzyme. Furthermore, in vitro cytotoxicity studies showed complex 1 exhibited quite potent antitumor activities and the greatest inhibitory selectivity against cancer cell lines.     

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,chemical characterization,X-ray crystal structure and magnetic properties of oxalato-bridged copper(II) binuclear complexes with 2,2′-bipyridine and diethylenetriamine as peripheral ligands

Two new μ-oxalato binuclear copper(II) complexes, [{Cu(NO₃)(H₂O)(bipy)}₂(ox)] (1) and [{Cu(dien)}₂(ox)](NO₃)₂ (2), with ox=oxalate, dien=diethylenetriamine and bipy=2,2′-bipyridine, have been synthesized and their crystal and molecular structures have been determined by single-crystal X-ray diffraction methods. The crystal structure of 1 consists of centrosymmetric neutral dimers where the copper atoms lie in a strongly elongated octahedral environment, surrounded by two nitrogen atoms of a bipy molecule and two oxygen atoms of the bridging oxalato group in the equatorial plane and oxygen atoms of water molecules and nitrate ions in the axial positions. Crystal structure of 2 is made up of non-coordinated nitrate anions and asymmetric binuclear cations in which copper atoms are in a distorted square–pyramidal coordination with three atoms of a diethylenetriamine ligand and an oxygen atom of the asymmetrically coordinated oxalato bridge building the basal plane and the other oxygen atom of the oxalato ligand filling the apical position. Both compounds have been also characterized by Fourier transform infrared (FT-IR) and electron spin resonance (ESR) spectroscopies, thermal analysis and variable temperature magnetic susceptibility measurements. The two compounds exhibit antiferromagnetic exchange with a singlet–triplet separation of −382 and −6.5 cm⁻¹ for 1 and 2, respectively. Magnetic and ESR results are discussed with respect to the crystal structure of the compounds.     

Synthesis,structure, and magnetic properties of lanthanide ferrocenoylacetonates with nitrate and 2,2′-bipyridine ligands

Ferrocenoylacetonate complexes of several lanthanides, [Ln(fca)₂(NO₃)(bpy)]·nMeC₆H₅ (Ln = Sm (1), Dy (3), Er (4), Yb (5), n = 1; Eu (2), n = 0.5; fca = FcC(O)CHC(O)Me; bpy = 2,2′-bipyridine), were synthesized and characterized by X-ray single-crystal analysis. Complexes 1, 4, and 5 are isostructural; 2 has a similar molecular structure with cis-disposition of fca ligands. The molecular structure of 3 is different, with trans-disposition of the fca ligands. Crystal lattices of the complexes are stabilized by π-stacking interactions. The Ln³⁺ ions in the complexes are eight-coordinate. According to mass spectroscopic data, the complexes are unstable in the gas phase. Magnetic properties of 2 and 4 were studied in a DC field; for 4, AC studies were also carried out. The values of spin-orbital parameters obtained using two estimation methods for 2 are in satisfactory agreement. Slow relaxation of the magnetization was found for the Er complex.     

Synthesis, structure, and luminescent properties of three silver(I) complexes with organic carboxylic acid and 4,4′-bipyridine-like ligands

The reactions of AgNO₃ with combinations of 1,2-bis(4-pyridyl)ethane(bpa)/4,4′-bipyridine (bpy), 4,4′-stilbenedicarboxylic acid (H₂sda)/2,2′-diphenylaminedicarboxylic acid (H₂dpadc)/2,6-naphthalenedicarboxylic acid (H₂ndc) in aqueous alcohol/ammonia at room temperature produce block-like crystals of [Ag₂(bpa)_1.5(sda)_0.5](sda)_0.5·7H₂O, [Ag₂(bpa)₂(H₂O)₃](dpadc), [Ag₂(bpy)₂](ndc)·4H₂O. All three complexes consist of 1D infinite silver–ligand cationic chains, interspersed with organic carboxylate anions that provide charge compensation in the crystal structures. The lattice water molecules are situated among the framework of the crystal structure and show rich hydrogen-bonding interactions, which help to orientate the organic carboxylate anions in the crystal packing, and the presence of Ag···N and Ag···Ag contacts contributes to strengthen the frameworks. The luminescent properties and thermogravimetric analyses of the three complexes are also presented.     

Preparation and characterization of inclusion complexes of carvedilol with methyl-β-cyclodextrin

Aim of the present work was to investigate the effect of methyl-β-cyclodextrin (MβCD) on the solubility and dissolution rate of carvedilol (CAR), a drug used orally for the treatment of hypertension. Phase solubility studies showed an A_L-type diagram indicating the formation of inclusion complex in 1:1 molar ratio. Solid binary systems of the drug with MβCD were prepared by various methods. Physicochemical characterizations were performed using Fourier Transformation Infrared Spectroscopy, Differential Scanning Calorimetry and powder X-Ray Diffractometry. It could be concluded that CAR can form inclusion complex with MβCD. The dissolution profiles of inclusion complexes were determined and compared with those of CAR alone and the physical mixture. The dissolution rate of CAR was increased by MβCD inclusion complexation remarkably.