Synthesis, crystallography and photoluminescence of a new pyrazolonato iridium complex

By using 1-phenyl-3-methyl-4-isobutyryl-5-pyrazolone (pmip) as the ancillary ligand, the cyclometalated complex: bis-(2-phenylpyridine)-(pmip)-iridium [(ppy)₂Ir(pmip)] was synthesized. Its crystal structure, absorption and emission were compared with those of its analogue, the frequently used electrophosphorescent material (ppy)₂Ir(dbm) [bis-(2-phenylpyridine)-(dibenzoylmethane) iridium]. For (ppy)₂Ir(pmip) in dichloromethane, the emission is highly structured and the intensity is 5 times higher than that of (ppy)₂Ir(dbm). It is a result of the higher triplet energy level of pmip relative to that of dbm. In solid state, green emission of (ppy)₂Ir(pmip) peaked at 550 nm was observed with a quantum efficiency 0.31% in contrast to the emission at 626 nm with a quantum efficiency of 0.76% for (ppy)₂Ir(dbm). The bathochromical shift and higher efficiency in crystallized (ppy)₂Ir(dbm) was explained by the stronger π-π intermolecular interactions which is unique to in solid state (ppy)₂Ir(dbm) crystals.     

Synthesis, structural characterization, and photo and electroluminescence of a novel terbium(III) complex: {Tris(acetylacetonate) [1,2,5]thiadiazolo[3,4-f][1,10]phenanthroline}terbium(III)

Lanthanides ion complexes have been intensively investigated as light emitting materials due to their interesting photophysical properties, such as narrow line luminescence with a long lifetime, large Stokes shift and high luminescence quantum efficiency. Here we report the synthesis, structural and photophysical properties of a new Tb(III) complex. This complex showed strong photoemission of green light both in solution and in the solid state as well as the characteristic emission lines of the Tb(III) ion. The electroluminescence properties of the complex were also studied and we obtained bright green light emission through the use of a co-deposited structure. The fabricated device showed a typical diode behavior with a low threshold bias voltage (around 10 V).     

Hydrogen bonding in diruthenium(II,III) tetraacetate complexes with biologically relevant axial ligands

Three diadduct complexes of the mixed-valent form of diruthenium tetraacetate, [Ru₂(μ-O₂CCH₃)₄L₂](PF₆), where L are the biologically relevant ligands imidazole, 1, 7-azaindole, 2, and caffeine, 3, were synthesized and characterized by elemental analysis, IR and UV-Vis spectroscopy and X-ray crystallography. In order to further elucidate the potential interactions of these dimers with DNA, the nature of the ligand coordination and the secondary inter- and intramolecular hydrogen-bonding interactions in all three complexes were assessed. Complex 1 · CH₂Cl₂ shows, exclusively, intermolecular interactions with the counterion whereas complexes 2 · ClCH₂CH₂Cl and 3 · OC(CH₃)₂ · H₂O, in addition to extensive intermolecular interactions, show intramolecular hydrogen bonding from the axial ligand to the bridging acetate oxygens, locking the ligand mean planes in place between the bridging acetate mean planes. In addition, all three complexes display π-π stacking of axial ligand rings on adjacent diadduct units.     

Synthesis, structure and magnetic properties of an oxo-bridged dinuclear iron(III) complex [(TPyA)FFeOFeF(TPyA)](BF4)2 · 0.5MeOH (TPyA = tris(2-pyridylmethyl)amine) containing the FFeOFeF linkage

The reaction of [Fe^II(H₂O)₆](BF₄)₂ with tris(2-pyridylmethyl)amine (TPyA) and triethylamine in methanol under aerobic conditions forms [(TPyA)FFe^IIIOFe^IIIF(TPyA)](BF₄)₂ · 0.5MeOH (1), in which each Fe(III) ion is coordinated to a TPyA and an F⁻ ion as well as an oxo ion (O²⁻) linking two Fe(III) ions. 1 has offset face-to-face π-π interactions between the dimers, and possesses a supramolecular network structure. The magnetic susceptibility of 1 can be fit with g = 2.0, J/k_B = − 153 K (106 cm⁻¹), and θ = − 0.3 K [H = − 2JS_a · S_b]. These indicate that very strong antiferromagnetic interactions occur via the oxo bridge within the Fe(III) dimer and weak antiferromagnetic interactions between the dimers.     

Synthesis, characterization and supramolecular structures of two Ni(II) complexes with potentially heptadentate ligand N,N-bis(2-hydroxybenzyl)-1,3-bis[(2-aminoethyl)amino]-2-propanol

A potentially heptadentate ligand H₃L (N,N^′-bis(2-hydroxybenzyl)-1,3-bis[(2-aminoethyl)amino]-2-propanol) and its two Ni(II) complexes, [Ni(H₂L)H₂O](H₂O)₃ClO₄ (1) and [Ni(H₂L)(H₂O)](H₂O)Cl (2) were prepared and characterized. X-ray structural analyses indicate that complex 1 has a distorted octahedral coordination geometry, with four amine N atoms of H₂L⁻ defining the equatorial plane, one aqua O atom and one phenoxo O atom of the ligand occupying two axial positions, respectively. The Ni(II) center of 2 has coordination geometry similar to that of 1. IR and electronic spectra of 1 and 2 are in agreement with their crystal structural features. Approximately along the ab plane, 2D supramolecular structure of 1 is assembled through multiple hydrogen bonds between hydroxy groups of the ligands, coordinated and crystal lattice H₂O and π-π stacking interactions between adjacent phenyl rings of the ligands, while for that of 2, probably along the a axis, 1D chain structure is also formed by multiple hydrogen bonds, but lack of π-π stacking interactions.     

Synthesis, characterization, and magnetic properties of new binuclear CuCu bis(oxamato) complexes

Two new neutral, binuclear Cu^IICu^II bis(oxamato) complexes with the formula [Cu₂(opba)(pmdta)(MeOH)] · 1/2MeOH · dmf (3) and [Cu₂(nabo)(pmdta)(MeOH)] (4), with opba = o-phenylene-bis(oxamato), nabo = 2,3-naphthalene-bis(oxamato), pmdta = N,N,N′,N″,N″-pentamethyldiethylenetriamine and dmf = dimethylformamide have been synthesized and their crystal structures have been determined. The structure of 3 consists of dimeric [Cu₂(opba)(pmdta)(MeOH)] entities, joined together by mutual intermolecular Cu?O contacts of the Cu²⁺ ion of one [Cu(opba)]²⁻ complex fragment and one carboxylate atom of the oxamato group of a second [Cu(opba)]²⁻ complex fragment. The structure of 4 consists of neutral binuclear complexes joined together by hydrogen bonds and π-π interactions, giving rise to an unique supramolecular 1D-chain. The magnetic properties of 3 and 4 were studied by susceptibility measurements versus temperature. For the intramolecular J parameter, identical values of (−114 ± 2) cm⁻¹ (3) and (−112 ± 2) cm⁻¹ (4) were obtained.     

Synthesis, characterization and cytotoxic activity of gallium(III) complexes anchored by tridentate pyrazole-based ligands

Reactions of GaCl₃ with pyrazole-containing ligands of the pyrazole-imine-phenol (HL¹-HL³) or pyrazole-amine-phenol (HL⁴-HL⁶) types led to the synthesis of well-defined [GaL₂]⁺ homoleptic complexes (1-6). Complexes 1-6 were characterized by elemental analysis, ESI-MS (electrospray ionization-mass spectrometry), IR and NMR spectroscopies, and in the case of Complex 1 also by X-ray diffraction analysis. In complexes 1-3, the pyrazole-imine-phenolate ligands act as monoanionic chelators that coordinate to the metal in a meridional fashion, while 4-6 contain monoanionic and facially coordinated pyrazole-amine-phenolate ligands. Complexes 1-3 have a greater stability in solution compared to 4-6, which have shown a more pronounced tendency to release the respective ancillary ligands. The cytotoxicity of 1-6 and of the respective ligands (HL¹-HL⁶) was evaluated against human prostate cancer cells PC-3 and human breast cancer cells MCF-7. The substituents of the phenolate rings strongly influenced the cytotoxicity of the compounds. Complexes 3 and 6 that contain chloride substituents at the phenolate rings have shown the highest cytotoxicity, including in the cisplatin-resistant PC-3 cell line. The cytotoxic profile of 3 and 6 is very similar to the one displayed by the respective anchor ligands, respectively HL¹ and HL⁶. The cytotoxic activity of 3 and 6 is slightly increased by the presence of transferrin, and both complexes provoke cell death mainly by induction of apoptotic pathways.     

Synthesis, solid-state characterization and antimicrobial activities of three different polymorphs of a copper(II) complex with 4-isopropyltropolone (hinokitiol)

There exist at least three different polymorphs in the copper(II) complex [Cu(hino)₂] with a hinokitiol ligand (Hhino; 4-isopropyltropolone¹). In addition to deep-green plate crystals 1a and deep-green rod crystals 1b, whose crystal structures have been recently reported, novel green needle crystals 1c of [Cu(hino)₂] were found, the crystal structure of which was here determined by single-crystal X-ray analysis. Since only one crystal structure has been reported for the copper(II) complex [Cu(trop)₂] with a tropolone ligand (Htrop), the polymorphism found in the crystals of [Cu(hino)₂] would be due to the presence of the isopropyl group on the tropolone ring. The synthetic conditions giving the three polymorphs in good yields were found and the crystals were characterized with elemental analysis, FT-IR, TG/DTA and X-ray powder diffraction (XPD) measurements, as well as solution molecular weight measurements for 1a. The solid-state magnetic behaviors or the temperature-dependent magnetic susceptibilities were measured with Superconductivity Quantum Interference Devices (SQUID): 1a showed a weak ferromagnetic interaction, 1b showed a paramagnetic nature with S=1/2, while 1c showed a weak antiferromagnetic interaction. The antimicrobial activities for selected bacteria, yeasts and molds were also measured in the water-suspension system: 1a and 1b showed no activity, while 1c showed modest activities, and these activities were compared with those of the neutral Hino and the anionic hino⁻ ligands.     

An azomethin-zinc complex for organic electroluminescence: Crystal structure, thermal stability and optoelectronic properties

An azomethin-zinc complex, bis[salicylidene(4-dimethylamino)aniline]zinc(II) (Zn(sada)₂) was synthesized and structurally characterized by single-crystal X-ray crystallography. Crystal data for Zn(C₁₅H₁₅N₂O)₂ was determined as follows: space group, triclinic, ; a = 10.2791(9) Å, b = 16.5008(14) Å, c = 17.5984(15) Å, α = 114.830(2)°, β = 96.579(2)°, γ = 97.674(2)°, Z = 4. Through thermal analysis characterization and FT-IR spectra, this complex was proved to have good thermal stability. The vapor-deposited films exhibited uniform and environment-stable morphology. The light emission and charge transporting performance of Zn(sada)₂ in organic light emitting diodes (OLEDs) were investigated preliminarily, and the results indicated the superior electron transporting property of this complex. Compared with the typical bilayer device of N,N′-diphenyl-N,N′-bis(1-naphthyl)-benzidine (NPB)/tris-(8-hydroxyquinoline)aluminum (Alq₃), the device with Zn(sada)₂ as the electron transporting layer exhibited a much lower turn-on voltage of 2.5 V (it is usually 3.5 V for an NPB/Alq₃ device).     

Supramolecular networks of hexanuclear cadmium (II): Synthesis, crystal structure and emission property

A new hexanuclear cadmium(II) complex of Cd₆(pyim)₄(Hpyim)₆(sal)₄ (Hpyim = 2-pyridylbenzimidazole, H₂sal = salicylic acid) (1) has been synthesized under hydrothermal condition and characterized by element analysis, FT-IR spectroscopy and luminescent analysis. X-ray crystallographic studies reveal that complex 1 displays a novel hexanuclear unit in which six cadmium ions are bridged by deprotonated salicylic and pyridylbenzimidazole ligands. In 1, the hexanuclear units are further assembled into a 3D supramolecular framework by hydrogen bonding, π-π and C−H?π stacking interactions. In the solid state, complex 1 shows blue photoluminescent property at room temperature.     

Synthesis, structures and properties of macrocyclic nickel(II) supramolecules with imidazole pendants

Two new nickel(II) complexes with the composition [Ni(L+H)(CH₃CN)₂](ClO₄)₃ (1) and [Ni(L)(tp)]·6H₂O (2), (L = 3,10-bis{3-(1-imidazolyl)propyl}-1,3,5,8,10,12-hexaazacyclotetradecane, tp = terephthalate) have been synthesized and structurally characterized by a combination of analytical, spectroscopic and X-ray diffraction methods. The structure of 1 consists of monomeric cations of the formula [Ni(L+H)(CH₃CN)₂]³⁺ and perchlorate ions. The nickel(II) ion is six-coordinate with bonds to the four nitrogen atoms of the macrocycle and two nitrogen atoms of the axial acetonitrile ligands. One of the protonated imidazole pendants of the macrocycle is hydrogen bonded to the imidazole group of the neighboring nickel(II) macrocycle, forming an undulated 1D supramolecule. Then, the two 1D supramolecular chains are further interconnected by C-H···π interactions between the methyl group of the acetonitrile ligand and one of the imidazole groups to form a 2D double stranded supramolecular polymer. In the structure of 2, the 1D coordination polymer is formed with nickel(II) macrocycles and bridging terephthalate ions, where each 1D chain is interconnected with π-π interactions of pendant imidazole moieties of the macrocycles, resulting in the formation of a 2D supramolecule.     

Synthesis, characterization and luminescence study of dimethyl[2-(arylmethyleneimino)phenolato]gallium complexes. Crystal structure of dimethyl[3,4-dimethoxyphenylmethyleneiminophenolato]gallium

Three dimethylgallium complexes of type Me₂GaL [L = 3,4-dimethoxyphenylmethyleneiminophenolato (1), 4-butoxylphenyl methyleneiminophenolato (2), 2-pyridylphenolato (3)] have been synthesized by the reaction of trimethylgallium with appropriate N-arylmethyleneiminophenol. The complexes obtained have been characterized by elemental analysis, ¹H NMR, FT-IR and mass spectroscopy, respectively. The solid structure of 1 has been determined by X-ray single crystal analysis. The gallium atom was bonded by an oxygen atom and coordinated by an imine nitrogen atom forming one five-membered ring. The stable dimmer was formed by the coordination of bridging oxygen atom of phenolate to another gallium atom. The photoluminescence of complexes 1-3 were studied. The maximum emission wavelengths of 1-3 are between 338 and 362 nm upon radiation by UV light. The Electroluminescent properties of diodes using 1-3 as emitters were measured. The blue/green electroluminescence has been observed.     

Synthesis and characterization of gallium complexes bearing N-arylmethylenethiobenzahydrazone ligands; crystal structure of diethyl[N-(4-N,N-dimethylamino)benzylidene thiobenzahydrazonato]gallium

Five diethylgallium complexes of type Et₂GaL [(L = N-(4-methoxy) benzylidenethiobenzahydrazonato (1), N-(3,4-dimethoxy)benzylidenethio benzahydrazonato (2), N-(4-N,N-dimethylamino)benzylidenethiobenza hydrazonato (3), N-(2-naphthyl)methylenethiobenzahydrazonato (4), N-(9-anthryl)methylenethiobenzahydrazonato (5)] have been synthesized by the reaction of triethylgallium with appropriate N-arylmethylene thiobenzahydrazones. The compounds obtained have been characterized by elemental analysis, ¹H NMR, IR and mass spectroscopies, respectively. The solid structure of 3 has been determined by X-ray single crystal analysis, in which Ga atom is four coordinate. The photoluminescent property of complex 1 was studied. The maximum emission wavelength is 475 nm upon radiation by UV light.     

Structures and magnetic properties of one-dimensional polymers constructed with copper(II) salts and pyridinecarboxamide-type ligands

Three complexes of the composition {[Cu(μ_1,5-dca)₂(mppca)₂] · H₂O}_n (1), [Cu(μ_1,5-dca)₂(nppca)₂]_n (2) and [Cu(μ-Cl)₂(mppca)₂]_n (3) (dca = dicyanamide, ; mppca = N-(4′-methylphenyl)-4-pyridinecarboxamide; nppca = N-(4′-nitrophenyl)-4-pyridinecarboxamide) have been synthesized and characterized by single crystal X-ray crystallography and magnetic susceptibility studies. Different supramolecular structures of the complexes have been constructed by different non-covalent motifs in the crystalline solids. In complex 1, adjacent copper(II) atoms are connected by double μ_1,5-dca(end-to-end) bridges to form a chain-like structure. The chains are linked by π-π interactions and hydrogen bonds between the ligands and water molecules to form a 3D network. In complex 2, copper(II) atom has a coordination environment similar to 1, but water molecules have not been found. Weak C-H?N hydrogen bonding and π-π interaction yield a 3D supramolecular network which is different from that of complex 1. Complex 3 is a 1D polymeric chain in which Cu(II) ions are bridged by Cl⁻, and only CH/π interactions had been found. Magnetic measurements revealed antiferromagnetic properties of 1, 3 and ferromagnetic behavior of 2.     

Tuning of emission: Synthesis, structure and photophysical properties of imidazole, oxazole and thiazole-based iridium (III) complexes

Three new iridium (III) complexes with two cyclometalated C^∧N ligands (imidazole, oxazole and thiazole-based, respectively) and one acetylacetone (acac) ancillary ligand have been synthesized and fully characterized. The structure of the thiazole-based complex has been determined by single crystal X-ray diffraction analysis. The Ir center was located in a distorted octahedral environment by three chelating ligands with the N-N in the trans and C-C in the cis configuration. By changing the hetero-atom of C^∧N ligands the order S, O and N, a marked and systematic hypsochromic shift of the maximum emission peak of the complexes was realized. The imidazole-based complex emits at a wavelength of 500 nm, which is in the blue to green region. The tuning of emission wavelengths is consistent with the variation of the energy gap estimated from electrochemistry results. An electroluminescent device using the thiazole-based complex as a dopant in the emitting layer has been fabricated. A highly efficient yellow emission with a maximum luminous efficiency of 9.8 cd/A at a current density of 24.2 mA/cm² and a maximum brightness of 7985 cd/m² at 19.6 V has been achieved.     

Synthesis and crystal structures of mono- and dinuclear silver(I) complexes bearing 1,8-naphthyridine ligand

Mononuclear and dinuclear silver(I) complexes bearing 1,8-naphthyridine (napy) were prepared. The crystal structures of [Ag(napy-κN)₂](PF₆) (1) and [Ag₂(μ-napy)₂](PF₆)₂ · 3CH₃CN (2 · 3CH₃CN) were determined by X-ray diffraction studies. In complex 1, intermolecular π-π interaction of napy ligands between neighboring molecules forms left-handed hexagonal columns in the solid state. On the other hand, two napy ligands bridging two Ag ions in the dinuclear complex 2 shape a face-to-face π-π stacking with those of the neighboring molecule to form the dimeric unit. Besides, two of four napy ligands, which are located in a diagonal position in the dimeric unit, build intermolecular back-to-back π-π stackings with those of the adjacent dimeric unit, and a ladder-like stairway structure is generated in the solid state. Irrespective of such characteristic structures of 1 and 2 in the solid state, both complexes show very rapid dynamic behavior in solutions. No conversion between 1 and 2 took place even in the presence of excess amounts of Ag⁺ or napy in solutions.     

Synthesis, structure, photoluminescence and theoretical studies of an In(III) complex with 2-(2′-hydroxylphenyl)benzoxazole

The synthesis and characterization of [In(pbx)₃] (1) (Hpbx = 2-(2′-hydroxylphenyl)benzoxazole) are presented. The ground and low lying excited electronic states in 1 are studied using density functional theory level (DFT). The optimized geometry is compared to the experimentally observed structure. Time-dependent density functional theory level (TDDFT) is employed to investigate the excited singlet states. The calculated energies of the low lying singlet states in 1 are in considerable agreement with the experimental data. All the low lying transitions are categorized as π → π∗ ligand-to-ligand charge transfer transitions (LLCT) in nature. The emissive state of 1 is assigned as a singlet metal-perturbed π → π∗ ligand-to-ligand charge transfer transition (LLCT).     

Coordination behaviour of ferrocenylthiosemicarbazone in a novel hetero trinuclear nickel(II) complex: Synthesis, spectral, electrochemistry and X-ray crystallography

The coordination behaviour of ferrocenylthiosemicarbazone was investigated in a trinuclear [Ni(Fctsc)₂] complex. The structure of the complex has been studied by X-ray crystallography. The complex crystallizes in rhombohedral space group with six molecules per unit cell has the dimensions of a = 28.8042(2) Å, b = 28.8042(2) Å and c = 19.5131(3) Å, α = 90°, β = 90°, γ = 120°. The electronic communication between the metal centers has been studied by cyclic voltammetry.     

Synthesis, characterization and X-ray structure of [Pd(SO4)(dppp)] · H2O, a catalyst for the CO-ethene copolymerization [dppp = 1,3-bis(diphenylphosphino)propane]

The title complex has been synthesized by first reacting dppp with Pd(AcO)₂ in acetone and then with NaHSO₄ in water. It has been characterized by IR, NMR and X-ray diffraction studies. The ³¹P NMR spectrum in DMSO shows a singlet at 16.62 ppm indicating that the two P atoms are equivalent and that the sulfate anion is weakly coordinating. The X-ray structure shows that the Pd atom is surrounded in an almost regular square planar environment by the two P atoms and by two O atoms of the sulfate anion and that the neutral complex is accompanied by a water molecule of crystallization. The Pd-P distances (2.217(1) and 2.233(1)) and the P-Pd-P angle (90.78(3)°) are close to those found in other complexes where the chelating diphosphine is the same. Also the Pd-O distances and the O-Pd-O bond angle are comparable to those of other relevant chelating ligands.In MeOH, the title complex, in combination with H₂SO₄, catalyses the CO-ethene copolymerization. The productivity reaches a maximum upon increasing the H₂SO₄/Pd ratio up to ca. 470 (7650 g of polyketone/g Pd h at 90 °C and 45 atm, CO/ethene 1/1). The viscosity of the polyketone passes through a maximum of 0.95 dL/g in m-cresol when the above ratio is ca. 100. It has been proposed that acid promotes the copolymerization process by destabilizing the β- and γ-chelates intermediates involved in chain growing process, thus favoring the insertion of the monomers. At relatively high acid concentration the lowering of productivity and viscosity suggests that the sulfate anion competes with the monomers for the coordination to the metal center.In H₂O-CH₃COOH as a solvent the productivity strongly depends on the H₂O/CH₃COOH ratio, as it passes through a maximum of 12 000 g polymer/g Pd h in the presence of ca. 60% of H₂O. The productivity is significantly lower than that found when the acetate and chloride analogues are used (27 000 g polyketone/g Pd · h). Thus, it is likely that the sulfate anion assists significantly the copolymerization process even though the concentration of CH₃COOH/CH₃COO⁻ is much preponderant.     

Luminescence and structural studies of yttrium and heavier lanthanide-picrate complexes with pentaethylene glycol

The monoclinic structural isomers with molecular formula of [M(Pic)₂(EO5)](Pic) where EO5 = pentaethylene glycol, Pic = picrate anion, and M = Gd, Tb, Er, Tm, Yb, and Y have been synthesized and characterized. The current study was conducted in the solid state to evaluate the coordination pattern of the central metal ion with the EO5 ligand in the presence of Pic anion. The photoluminescence (PL) spectra of the Tb and Yb complexes have the typical 4f-4f transition emissions of Tb(III) and Yb(III) ions. The Gd, Er, Tm, and Y complexes had broad bands resulting from the ligands. The counteranion factor influenced the emission intensity in the Tb-Pic-EO5 and Tb-NO₃-EO5 complexes in several solvents also were studied. The Pic anion acts as a quencher in the [Tb(Pic)₂(EO5)](Pic) complex due to the nitro withdrawing groups was clearly observed both in solution and the solid state.