Synthesis, crystal structure and photoluminescent property of an iridium complex with coumarin derivative ligand

Novel iridium complex containing coumarin derivative as a cyclometalated ligand (L) and picolinate (pic) as the ancillary ligand, Ir(III)bis(3-(pyridin-2-yl)coumarinato N,C⁴)(picolinate) [Ir(L)₂(pic)], was synthesized and characterized. It was demonstrated that the iridium (III) ion in Ir(L)₂(pic) is hexacoordinated by two C atoms and two N atoms from 3-(pyridin-2-yl)coumarin ligands and one N atom and one O atom from picolinate ligand, displaying a distorted octahedral coordination geometry. The Ir(L)₂(pic) has very strong absorption and intensive emission at 532 nm. These results show the promising future of that Ir(L)₂(pic) in fabrication organic light-emitting diodes.     

New binuclear model compounds for the study of the 4f-4f exchange interaction

Two new homobinuclear 4f-4f complexes, [Ln^III(L)₃]₂, (Ln=Pr 1; Gd 2) have been synthesized (L⁻=2,6-diformyl-4-methylphenolato). The crystallographic investigation of 1 reveals centrosymmetric binuclear entities with the metallic centers connected by two of the anionic ligands. The praseodymium ions are bridged by the phenoxo oxygen atoms. One carbonyl group of a bridging molecule is coordinated to one Pr(III) ion, while the other one is coordinated to the second Pr(III) ion. The other four L⁻ ions act as terminal chelated ligands, through the phenoxo oxygen atom and one carbonyl group. The distance between the Pr(III) ions within the binuclear entity is 4.0711(4) Å. The supramolecular solid-state architecture is sustained by a system of π-π interactions. The cryomagnetic study of 2 reveals a very weak antiferromagnetic interaction between the Gd(III) ions (J=−0.053 cm⁻¹, ).     

Synthesis, crystal structure and magnetic properties of a novel manganese(III) cluster

A polydentate hydroxy-rich Schiff base ligand, derived from the condensation of 3,5-dibromo-2-hydroxybenzaldehyde and 2-ethanolamine, namely 3,5-dibromo- salicylidene-2-ethanolamine (H₂L), reacts with Mn(ClO₄)₂, NaO₂CPiv and NaOCH₃ to give a novel hexanuclear complex [Na^IMn^III₅(μ₃-O²⁻)(μ₄-O²⁻)L₄(O₂CPiv)₃)(ClO₄)]·1.5CH₃OH·0.25H₂O (1). The complex has been characterized by IR, elemental analyses, crystal structural analyses, and magnetic studies. The core in complex 1 features one μ₃-O²⁻ atom, one μ₄-O²⁻ atom, four L²⁻ ligands, three PivCO₂⁻ groups together with a ClO₄⁻ ion bridging five Mn^III atoms and a Na^I atom to form a distorted cubane extended at one face by an incomplete adamantane unit, which is an unprecedented structural type in Mn chemistry. The variable-temperature solid-state dc magnetic susceptibility studies in the 2-300 K range for complex 1 reveal the presence of overall antiferromagnetic intracluster interactions.     

Syntheses, structures, thermal behavior and solution studies of two types of Hg(II) complexes with [1,3-di(2-methoxy)benzene]triazene

The reaction of [1,3-di(2-methoxy)benzene]triazene, [HL], with Hg(CH₃COO)₂ and Hg(SCN)₂ in methanol as solvent, resulted in the formation of [HgL₂] (1) and [HgL(SCN)] (2), respectively. These compounds were characterized by means of X-ray diffraction, FT-IR spectroscopy, CHN and TGA-DTA analysis. In the lattice of the compound 1, the mono-nuclear complexes were connected to dimer structure by intermolecular non-classical C-H···O hydrogen bonds. Also, weak Hg-η²-arene π-interactions link the dimers into 1D supramolecular chains. The compound 2 is a 2D coordination polymer induced by C-H···π stacking interactions between 1D chains produced by weak Hg-η³-η³-arene π-interactions. The results of studies of the stoichiometry and formation of complexes of 1 and 2 in methanol solution were found to be in support of their solid state stoichiometry.     

Synthesis, characterization, X-ray molecular structure and catalase-like activity of a non-heme iron complex: Dichloro[N-propanoate-N,N-bis-(2-pyridylmethyl)amine]iron(III)

In this work we present the synthesis and characterization of the complex dichloro[N-propanoate-N,N-bis-(2-pyridylmethyl)amine]iron(III) [Fe^III(PBMPA)Cl₂]. The ligand LiPBMPA was synthesized through the Michael reaction of BMPA with methylacrylate, followed by alkaline hydrolysis. The complex [Fe^III(PBMPA)Cl₂] has been synthesized by the reaction of the ligand with FeCl₃ · H₂O and was mainly characterized by cyclic voltammetry, conductivimetry, and electronic, infrared and Mössbauer spectroscopies, and by X-ray structural analysis, which showed an iron center coordinated by one carboxylate oxygen in a monodentate way, one tertiary amine, two pyridine groups and two chloride ions. It has been proposed that in water the chloride ligands are shifted by the solvent molecules and the species [Fe^III(PBMPA)(H₂O)₂]Cl₂ is predominant. The catalase-like activity of the complex was tested in water, and it proved to be active in the hydrogen peroxide dismutation. Kinetics studies were conducted following the initial rates method. The reaction is first order in relation to both the complex and the hydrogen peroxide. Based on the presence of a lag phase that depends on the initial complex concentration, we propose that the active species that shows in situ catalase-like activity, is a binuclear complex.     

Synthesis, characterization, cytotoxic activity and DNA binding properties of the novel dinuclear cobalt(III) complex with the condensation product of 2-acetylpyridine and malonic acid dihydrazide

A novel dinuclear cobalt(III) complex with the condensation product of 2-acetylpyridine and malonic acid dihydrazide, N′,N′²-bis[(1E)-1-(2-pyridyl)ethylidene]propanedihydrazide was synthesized and characterized by elemental analysis, spectroscopy (NMR and infrared), and X-ray crystal analysis. The complex showed a moderate activity towards Artemia salina. The highest cytotoxic potential of the complex was observed on the epithelial breast cancer (MDA-361) cell line. The investigated complex induced apoptosis, the early apoptotic cells comprising 28.18%, compared to 5.64% of control cells in the same phase. The interaction of the complex with calf thymus DNA (CT-DNA) was monitored by blue shift and hyperchromism in the UV-vis spectra. The observed intrinsic binding constant (K_b = 4.2 × 10⁵ M^− 1) together with structural analysis of the complex indicate the groove binding.     

Synthesis and structural characterization of gold(III) dioximates with anions [AuCl4] and [AuCl2]

Two complexes of Au(III) with dimethylglyoxime of compositions [Au^III(HDMG)₂][Au^IIICl₄] (1) and [Au^III(HDMG)₂][Au^ICl₂] (2) were synthesized and characterized by X-ray structural analysis. It was shown that in [Au^III(HDMG)₂]⁺ cation Au(III) has a square-planar environment, and the oxygen atoms of oxime groups are joined by intramolecular H-bond. The secondary Au?Au and Au?Cl interactions in the crystal are discussed.     

A novel tetranuclear lanthanide(III)-copper(II) complex of the macrocyclic oxamide [PrCu3] (macrocyclic oxamide = 1,4,8,11-tetraazacyclotradecanne-2,3-dione): synthesis, structure and magnetism

A novel tetranuclear lanthanide(III)-copper(II) complex of macrocyclic oxamide, [Pr(CuL)₃(H₂O)₂](SCN)₃ · 1.5H₂O (L = 1,4,8,11-tatraazacyclotradecanne-2,3-dione) (1), has been synthesized, structurally characterized and preliminary investigated by magnetic studies. The structure of the title complex consists of a cationic PrCu₃ core, noncoordinated monovalent SCN⁻ anions and H₂O molecules; the packing diagram shows open channels formed through intermolecular weak interactions. The temperature-dependent magnetic susceptibilities were analyzed by an approximate treatment being enlightened by Matsumoto et al. leading to J = −1.62 × 10⁻² cm⁻¹, Δ = 3.12 cm⁻¹, g_Cu = 2.13, respectively.     

Synthesis and structural characterization of a novel diosmium(III) compound: Os2(ap)4Cl2

The reaction between Os₂(OAc)₄Cl₂ and Hap (Hap is 2-anilinopyridine) under prolonged refluxing conditions resulted in a new Os₂(III) compound, Os₂(ap)₄Cl₂ (1). The molecular structure of 1 was determined from a single crystal X-ray diffraction study, which revealed an Os-Os bond length of 2.396[1] Å, and a cis-(2,2) arrangement of the ap ligands. Also reported are magnetic, electrochemical and spectroscopic properties of 1.     

Two new copper(II) polyamine compounds: Synthesis, characterization and crystal structure

Two new compounds of Cu(II) of stoichiometry CuCl₄(polyamineH₂) containing the polyamines (PA): spermidine or spermine were prepared. Their synthesis, spectroscopic and structural characterization are herein described. The obtained complex with spermidine was characterized by elemental and thermogravimetric analysis, electronic and infrared spectroscopy. In the case of the compound with spermine, crystals were obtained. So, beside all other techniques the compound was also characterized by single crystal X-ray diffractometry. In both cases the species [CuCl₄]²⁻ is present and displays a similar polymeric structure. The X-ray, infrared and electronic spectra are herein discussed based on structural peculiarities of the compounds.     

Synthesis, crystal structure and magnetic characterization of a new phenoxo-bridged binuclear manganese(III) Schiff base complex exhibiting single-molecule-magnet behavior

A new phenoxo-bridged binuclear manganese(III) Schiff base complex, [Mn(L)(N₃)]₂ (1) where L = N,N′-bis(salicylidene)-1,2-propanediamine has been synthesized and characterized by IR, elemental analysis, crystal structure analysis and variable temperature magnetic susceptibility measurements. The single crystal X-ray diffraction reveals that the structure is dimeric with each phenolate oxygen atom acting as a bridge between two symmetry equivalent Mn atoms. Low temperature magnetic study shows that the complex exhibits intra-dimer ferromagnetic exchange and single-molecule-magnet (SMM) behavior as well.     

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.     

Functional model for catecholase-like activity: Synthesis, structure, spectra, and catalytic activity of iron(III) complexes with substituted-salicylaldimine ligands

Four new mononuclear iron(III) complexes with the substituted-salicylaldimine ligands, [Fe(L¹)(TCC)] (1), [Fe(L²)(TBC)] (2), [Fe(L³)(TBC)] (3) and [Fe(L⁴)(TCC)](CH₃CN) (4) (HL¹ = N′-(5-OH-salicylaldimine)-diethylenetriamine, HL² = (N′-(5-Cl-salicylaldimine)-diethylenetriamine, HL³ N′-(5-Br-salicyl-aldimine)-dipropylenetriamine, HL⁴ = (N′-3,5-Br-salicylaldimine)-dipropylenetriamine, H₂TCC = tetrachlorocatechol, and H₂TBC = tetrabromocatechol), were prepared and characterized by XRD, EPR, and Mössbauer spectroscopy. The coordination sphere of the Fe(III) in complexes 1-4 is a distorted octahedral with N₃O₃ donors set which constructed by the Schiff-base ligands and the catecholate substrates of TBC or TCC. The in situ prepared Fe(III) complexes [Fe(L¹)Cl₂], [Fe(L²)Cl₂], [Fe(L³)(Cl₂)], and [Fe(L⁴)Cl₂] in absence of TBC or TCC show a high catecholase-like activity for the oxidation of 3,5-DTBC to the corresponding quinone 3,5-DTBQ.     

Synthesis and structure of copper(II) complexes of two new poly(2-pyridylalkyl)diamine ligands

The new pentapyridyldiamine ligand, L¹, which incorporates two bis(2-pyridylethyl)amine donor domains held together by a 2,6-dimethylenepyridine linker, is readily prepared. In the presence of metal salts, L¹ is unstable due to facile elimination of vinyl pyridine. Complexes of L¹ are therefore difficult to isolate. Nonetheless, a novel copper dimer [Cu₂(L¹)(μ-OH)(CH₃CN)](ClO₄)₃ has been isolated in small quantities along with the interesting monomer [Cu(L²)](ClO₄)₂, in which L² is the tetrapyridyldiamine ligand derived from the decomposition of L¹ by loss of one pyridylethyl `arm'. The crystal structures of the two complexes are reported: the [Cu<sub>2</sub>(L<sup>1</sup>)(μ-OH)(CH<sub>3</sub>CN)]<sup>2+</sup> cation exhibits a μ-hydroxo-bridged dicopper(II) core and a coordinated acetonitrile molecule, akin to a putative intermediate in nitrile hydrolysis, and the chiral [Cu(L<sup>2</sup>)]<sup>2+</sup> cation is revealed to have a five-coordinate copper(II) centre that is stabilised by an intramolecular hydrogen-bond between the 2° amine group and a pendant pyridylethyl `arm'.     

Catalytic oxidation of 3,5-di-tert-butylcatechol by a manganese(III) 18-azametallacrown-6 compound: Synthesis, crystal structure, fluorescence, magnetic and kinetic investigation

A new macrocyclic hexanuclear manganese(III) 18-azametallacrown-6 compound, [Mn₆(ashz)₆(CH₃OH)₃(H₂O)₃] · 3H₂O · 3DMF (1), has been prepared using a trianionic pentadentate ligand N-acetylsalicylhydrazide (ashz³⁻) and characterised by various techniques such as elemental analysis, IR, UV-vis and fluorescence spectroscopy, cyclic voltammetry and X-ray diffraction. Six ashz³⁻ ligands connect six metal ions to form the cyclic skeleton based on the M-N-N-M linkage. Due to the meridional coordination of the ligand to the Mn³⁺ ion, the ligand enforces the stereochemistry of the Mn³⁺ ions as a propeller configuration with alternating Δ/Λ forms. The kinetic studies on catecholase activity of 1 for the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) by O₂ were done using UV-Vis absorption spectra method. Compound 1 has been evaluated as a model system for the catechol oxidase enzyme and it is found that the compound shows high catecholase activity. It exhibits the activity with a turnover number of 270 h⁻¹. A kinetic treatment on the basis of the Michaelis-Menten model has been applied. The magnetic susceptibility (300-5 K) study indicates antiferromagnetic exchange interactions with J = −2.6 cm⁻¹ between the adjacent Mn³⁺ ions.     

Synthesis, crystal structure and luminescent properties of two cadmium thiocyanate coordination polymers with benzylpyridyl cations

Two luminescent Cd(II) complexes [RBzPy][Cd(SCN)₃] for R = Cl (1) and Br (2) have been synthesized and structurally characterized. The Cd atoms are all N3S3 hexa-coordinated with six bridging SCN⁻ and form infinite [Cd(SCN)₃]_∞ polymeric chains. The layer arrangement of the anionic chains was obtained using the larger halogenated benzylpyridyl cations. The luminescent properties of 1 and 2 in the solid state were investigated.     

Isolation of a singly oxo-bridged Fe(III) dinuclear complex: Synthesis, crystal structure, spectroscopic and magnetic studies

The μ-oxo dinuclear complex {Fe₂O(tptz)₂[N(CN)₂]₂(NO₃)₂} (1) (where tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine) has been synthesised and characterised by elemental analysis, FT-IR, UV-vis, cyclic voltammetry, Mössbauer spectroscopy, and variable-temperature magnetic susceptibility measurements and single crystal X-ray diffraction. The iron centres have a pentagonal-bipyramidal geometry. The dimeric neutral complex exhibits typical Fe-μ-O bond lengths of 1.763(1) Å and a bridge angle of 180.00°. The Fe?Fe separation is 3.526(3) Å. The Mössbauer spectrum at room temperature consists of one quadrupole doublet with an isomer shift of 0.41 mm/s and a quadrupole splitting of 1.12 mm/s. Variable-temperature magnetic susceptibility measurements have been measured in the temperature range 300-2 K, revealing an intramolecular antiferromagnetic coupling (J = −211.6 cm⁻¹).     

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.     

Formation of a supramolecular ladder using dinuclear dicyanamide bridged Cu(II) species: Synthesis, crystal structure and magnetic property

The reaction of Cu(ClO₄)₂ · 6H₂O with bis(3-aminopropyl)methylamine and sodium dicyanamide in aqueous medium results in the formation of a dimeric dicyanamide complex of Cu(II), [Cu₂(medpt)₂(dca)₂](ClO₄)₂. The single crystal X-ray structure reveals that the dinuclear entities are extended to form a supramolecular 1D ladder by H-bonding. Each dinuclear entity is joined to the adjacent unit via the perchlorate anion. Variable temperature magnetic study was performed and the best-fit parameters are J = −1.20 ± 0.02 cm⁻¹, g = 2.08 ± 0.01 with R = 2 × 10⁻⁵. These clearly indicate the antiferromagnetic interaction between the Cu(II) center.     

Synthesis, characterization and crystal structure of manganese (IV) complex derived from salicylic acid

The binuclear manganese (IV) [Mn₂(Hsal)₄(OH)₄] (H₂sal = salicylic acid) complex has been obtained from a complex reaction mixture in methanol consisting of Mn(II)(OAc)₂ · 4H₂O, GS ( a reagent obtained by refluxing glycine and salicylaldehyde in 1:1 molar ratio in methanol), monosodium salicylate and pyridine. The compound contains a distorted octahedral MnO₆ coordination unit of potential importance to high oxidation state manganese bimolecules.