Synthesis,spectroscopic, thermal,free radical scavenging ability,and antitumor activity studies of cobalt(II) metformin complex

New [Co(Mfn-HCl)₂(NO₃)₂] · 6H₂O complex has been synthesized and characterized using microanalytical, molar conductance, spectroscopic (IR and UV-Vis), effective magnetic moment, and thermal analyses. The infrared spectroscopic results data received from the comparison between free Mfn · HCl ligand and its cobalt(II) complex proved that Metformin forms complex with cobalt(II) ions as a bidentate ligand through its two imino groups. The antioxidant activity of the Mfn · HCl and Co(II)-2Mfn · HCl complex were evaluated by using 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging method. Antitumor activity for Mfn · HCl ligand and its cobalt(II) complex was determined using Ehrlich Ascites carcinoma cell (EACC) line. It has been shown that the Co(II)-Mfn · HCl complex is much more effective as free radical scavenger and has higher antitumor activity than the free Mfn · HCl ligand.     

Synthesis and characterization of a Eu-containing polymer precursor featuring thenoyltrifluoroacetone and 5-acrylamido-1,10-phenanthroline

A polymerizable ligand, 5-acrylamido-1,10-phenanthroline (L), was synthesized. Its Eu(III) complex with 2-thenoyltrifluoroacetone (HTTA) was prepared and characterized by elemental analysis, IR, MS, and ¹H NMR spectra. The photophysical properties of the complex were studied in detail by using UV, luminescence spectra, luminescence lifetime and quantum yield. The complex shows a remarkable luminescence quantum yield at room temperature (40.1%) upon ligand excitation and a long ⁵D₀ lifetime (590 μs), which makes it not only a promising light-conversion molecular device but also an excellent luminescent polymer precursor.     

Zinc complexes with 1-(1H-benzimidazol-1-ylmethyl)-1H-benzotriazole: the structure,quantum chemical calculations,and luminescence properties

An organic ligand 1-(1H-benzimidazol-1-ylmethyl)-1H-benzotriazole (bta) and two zinc complexes of the composition [Zn(bta)₂Hal₂] (Hal = Cl, Br) were synthesized. The crystal structure of the complex [Zn(bta)₂Cl₂] was determined and its features were discussed. According to X-ray diffraction data, the central atom has a tetrahedral environment composed of two nitrogen atoms from two ligand molecules coordinated in monodentate mode and two terminal chloride ions. Density functional theory (DFT) calculations of the ligand and complex [Zn(bta)₂Cl₂] were carried out. A study of the luminescence properties of the compounds synthesized suggests that excitation of the zinc complexes gives rise to a dual-band luminescence similar to that of the free ligand. Most probably, the emission originates from π—π* and π—π* intra-ligand transitions.

     

Synthesis,structure, and optical properties of iridium(III) complex with 1-benzyl-2-phenylbenzimidazole and 4,4'-dicarboxy-2,2'-bipyridyne

A new cyclometalated iridium(III) complex [Ir(L)₂(Hdcbpy)] (1) has been synthesized, where L is 1-benzyl-2-phenylbenzimidazole and Hdcbpy is monoprotonated 4,4′-dicarboxy-2,2′-bipyridine. The structure of complex 1 has been determined by X-ray diffraction. The optical properties of complex 1 have been studied, and the quantum yield of luminescence has been measured.     

Anionically Substituted 1,1′,1″‐Methylidynetris[1H‐pyrazole] Ligands for the Formation of Neutral Lanthanide Complexes in Water: Synthesis,Characterization, and Photophysical Properties

The six‐step synthesis of the new podand‐type ligand 6,6′,6″‐[methylidenetri(1H‐pyrazole‐1,3‐diyl)]tris[pyridine‐2‐carboxylic acid] (LH₃) is described. Reaction of LH₃ with LnCl₃ ?6 H₂O (Ln=Eu, Gd, Tb) in MeOH resulted in the isolation of [LnL]?HCl complexes characterized by elemental analysis, mass and IR spectroscopy. Photophysical studies of the Eu and Tb complexes in aqueous solutions revealed the characteristic luminescence features of the metal atoms, indicative of an efficient ligand‐to‐metal energy‐transfer process. Determination of the luminescence quantum yields in H₂O showed the Tb complex to be highly luminescent (?=15%), while, for the Eu complex, the quantum efficiency was only 2%. Excited‐state‐lifetime measurements in H₂O and D₂O evidenced the presence of ca. three H₂O molecules in the first coordination sphere of the complexes. Investigation of the Gd complex allowed the determination of the ligand‐centered triplet state and showed the ligand to be well suited for energy transfer to the metal. The luminescence properties of the complexes are described, and the properties of the ligand as a suitable complexation pocket is questioned.     

A new ligand system containing sulfanilamide and quinazolinone fragments: Synthesis,structure, and properties

A new Schiff base ligand, 4-methyl-N-{2-[(2-methyl-4-oxo-3,4-dihydroquinazolin-3-yl)iminomethyl]-phenyl}benzenesulfonamide (L), and its complexes with transition metals [Cd(L)₂], [Zn(L)₂], and [CuLOAc] have been synthesized. The structure and electronic properties of the ligand have been studied by quantum chemical methods, and its zinc and cadmium complexes have been found to exhibit luminescence properties.     

Synthesis,spectral characterization,and luminescence properties of a cup-like ligand and its magnesium(II) complex

A new tripodal ligand, N,N′,N″-tri(salicylaldehyde)triaminotriethylamine (1) has been synthesized and characterized by elemental analysis, IR and UV spectroscopy, MS, and X-ray crystallography. X-ray diffraction analysis reveals that the three chains of the ligand form a cup-like structure. The ligand’s magnesium(II) complex has been synthesized and characterized by elemental analysis, conductivity, and IR and UV spectroscopy. The luminescence properties of the ligand and its magnesium(II) complex were investigated in DMF, CH₃OH, and CH₃CH₂OH solution and in the solid state at room temperature.     

Luminescence properties of fluorene-substituted porphyrinates of magnesium(II) and aluminum(III)

Aluminum(III) (AlClTFP) and magnesium(II) (MgTFP) porphyrinates were synthesized from free meso-tetra(fluoren-2-yl)porphyrin, aluminum chloride and the MgBr₂Et₂O complex. The structure of the synthesized compounds was established on the basis NMR and absorption spectroscopy data. The luminescence properties of the new compounds were studied in a toluene solution at 300 K, and the quantum yields of fluorescence were determined by relative method. The quantum yields of fluorescence of MgTFP and AlClTFP (37 and 35%, respectively) are higher than that of parent porphyrin (22%).     

Transition metal complexes with thiosemicarbazide-based ligands. Part LVI: Nickel(II) complex with 1,3-diphenylpyrazole-4-carboxaldehyde thiosemicarbazone and unusually deformed coordination geometry

Synthesis of a new nickel(II) complex, [Ni(Ph₂PzTSC-H)₂] with 1,3-diphenylpyrazole-4-carboxaldehyde thiosemicarbazone (Ph₂PzTSC), is described. The compounds have been characterized by elemental and thermal analysis, molar conductivity and spectral (UV–Vis, IR, ¹H NMR, and ¹³C NMR) measurements. In the case of complex the magnetic measurement has been also performed. Crystal and molecular structures of both the free ligand and the complex have been determined by single crystal X-ray analysis. It was found that the ligand coordinates in a bidentate NS fashion, in its deprotonated thioenolato form. The cis-square-planar geometry of the complex is significantly distorted tetrahedrally. The Cambridge Structural Database (CSD) study has been performed to obtain geometrical and structural informations on similar nickel(II) complexes in order to compare structural data.     

Synthesis and Properties of Acyclic and Cryptate Europium(III) Complexes Incorporating the 3,3′-Biisoquinoline 2,2′-Dioxide Unit

The lithium and europium(III) cryptates of a macrobicyclic ligand 1 incorporating the 3,3′-biisoquinoline 2,2′-dioxide 2 have been prepared. The Eu(III) complex [Eu(2)₂]Cl₃ has also been obtained. These Eu(III) complexes present characteristic ¹H-NMR spectra containing markedly shifted resonances. They are strongly luminescent; the emission spectra, quantum yields, and lifetimes have been determined.     

Synthesis,crystal structures,antibacterial activities,and fluorescence properties of Schiff base ligand and its nickel(II) complex

A complex [Ni(L · CH₃OH)₂] · CH₃OH was synthesized, in which a Schiff base ligand HL · CH₃OH, was derived from condensation of 1-phenyl-3-methyl-4-(p-methylbenzoyl)-5-pyrazolone with L-Valine methyl ester. They were characterized by IR and single crystal X-ray diffraction. The ligand contains three independent molecules L · CH₃OH. The complex has a dissociative methanol and nickel six-coordinated compound. Every fragment is a distorted octahedron with four oxygen atoms and two nitrogen atoms. The HL · CH₃OH ligand and its complex have been tested in vitro to evaluate their antibacterial activity against bacteria Escherichia coli and Bacillus subtilis. It has been found that the complex has higher activity than the corresponding free ligand HL · CH₃OH against the same bacteria. The HL · CH₃OH ligand and its complex have been tested by liquid fluorescent. It has been found that the complex has higher fluorescence property than ligand.     

Protonation and solvation effects in the reaction of zinc 1,2,3,7,8,12,13,17,18,19-Decamethylbiladien-<Emphasis Type="Italic">a,c</Emphasis> complex formation

The reactions of protonated (H₄L²⁺) and free (H₂L) forms of the ligand 1,2,3,7,8,12,13,17,18,19-decamethylbiladien-a,c with zinc(II) acetate in dimethyl sulfoxide was studied by the spectrophotometric method. It was found that the mononuclear complex [ZnL] is formed in the studied systems. Constants of its formation were determined from the spectral data. Unlike H₂L, the protonated [H₄L²⁺] form has extremely low reactivity, because the initial stages of the complex formation mechanisms of the free and protonated forms of the ligand are different. Regularities of the solvent nature influence on the free energy of formation of biladien chelates were revealed.     

Crystal structures and luminescence properties of two new terbium complexes with aromatic carboxylic acid

Two new terbium complexes with aromatic carboxylic acids, [(Tb)₂(L₁)₆(H₂O)₄] (1) and [(Tb)₂(L₂)₆(H₂O)₂(DMF)₂] (2) (HL₁: nicotinic acid; HL₂: 4-hydroxybenzoic acid), with different coordination geometries have been synthesized and their crystal structures determined. The luminescence properties of the two complexes, including the phosphorescence lifetime, have been investigated. The effect of a secondary ligand on luminescence of the ternary terbium complex with carboxylic acid and the relationship between luminescence properties and crystal structure, including coordination mode of the carboxyl groups from HL₁ and HL₂ and coordination mode of a secondary ligand, are discussed.     

Optical properties of a tetradentate bis(beta-diketonate) europium(III) complex

Eu₂(BPOPB)₃H₂O, an europium complex chelated with bis(β-diketone), was synthesized. Its properties have been investigated by absorption spectrum, emission spectrum and luminescence lifetime measurement. The complex displays strong red luminescence upon irradiation at the ligand band around 355 nm, which indicates that the bis-β-diketonate ligand BPOPB is an efficient sensitizer. The Judd–Ofelt parameters obtained from the emission spectrum of Eu₂(BPOPB)₃H₂O have been used to calculate the total spontaneous emission probabilities (A), the radiative lifetime (τ_rad), the fluorescence branching ratio (β) and the stimulated emission cross-sections (σ). The luminescence lifetimes are determined to be 402 and 169 μs for Eu₂(BPOPB)₃H₂O and Eu(DBM)₃(H₂O)₂, respectively. The relationship between the structures of rare-earth complexes and luminescence lifetimes was analyzed. The radiative properties reveal that Eu₂(BPOPB)₃H₂O is potential to be an efficient luminescent material.     

Structure Determination of Alkynyl-Protected Gold Nanocluster Au22(tBuC≡C)18 and Its Thermochromic Luminescence

An alkynyl-protected gold nanocluster, Au₂₂(^tBuC≡C)₁₈ ( 1 ), has been synthesized and its structure has been determined by single-crystal X-ray diffraction. The molecular structure consists of a Au₁₃ cuboctahedron kernel and three [Au₃(^tBuC≡C)₄] trimeric staples. The cluster 1 has strong luminescence in the solid state with a 15 % quantum yield, and it displays interesting thermochromic luminescence as revealed by temperature-dependent emission spectra. The enhanced room-temperature emission is characterized as thermally activated delayed fluorescence.     

Synthesis, characterization, and molecular structure of Ru(II) complex containing 2,5-pyridinedicarboxylic acid

This article presents a combined experimental and computational study of Ru(II) complex containing 2,5-pyridinedicarboxylic acid ligand. The novel complex [Ru(py-2,5-COOH)₂(PPh₃)₂]·3H₂O has been obtained in the reaction of [RuCl₂(PPh₃)₃] with 2,5-pyridinedicarboxylic acid in methanol and has been studied by IR, ¹H, ³¹P NMR, UV–Vis spectroscopy, and X-ray crystallography. The electronic structure of [Ru(py-2,5-COOH)₂(PPh₃)₂] has been calculated with the density functional theory (DFT) method. The spin-allowed electronic transitions of the complex have been calculated with the time-dependent DFT method, and the UV–Vis spectrum has been discussed on this basis and rationalized by determination of ligand field splitting (10Dq) and Racah’s parameters from the experimental spectrum. The luminescence property of the complex has been examined.     

Photophysical properties of lanthanide complexes with 5-nitro-1,10-phenanthroline

Abstract  

Five novel lanthanide (Eu³⁺, Tb³⁺, Sm³⁺, Dy³⁺, and Gd³⁺) complexes with 5-nitro-1,10-phenanthroline (phenNO₂) have been synthesized and characterized by elemental analysis, IR, UV, and luminescence spectra. The triplet state energy of phenNO₂ was determined to be 20,048 cm⁻¹ via the phosphorescence spectra of phenNO₂ and its gadolinium complex. The photophysical properties of these complexes indicated that the triplet state energy of the ligand is suitable for the sensitization of the luminescence of Eu³⁺ and Sm³⁺, especially the former.     

Structure Determination of Alkynyl‐Protected Gold Nanocluster Au22(tBuC≡C)18 and Its Thermochromic Luminescence

An alkynyl‐protected gold nanocluster, Au₂₂(^tBuC≡C)₁₈ ( 1 ), has been synthesized and its structure has been determined by single‐crystal X‐ray diffraction. The molecular structure consists of a Au₁₃ cuboctahedron kernel and three [Au₃(^tBuC≡C)₄] trimeric staples. The cluster 1 has strong luminescence in the solid state with a 15 % quantum yield, and it displays interesting thermochromic luminescence as revealed by temperature‐dependent emission spectra. The enhanced room‐temperature emission is characterized as thermally activated delayed fluorescence.     

The photophysics of a luminescent ruthenium polypyridyl complex with pendant β-cylodextrin; pH modulation of lifetime and photoinduced electron transfer

At room temperature, [Ru(bpy)₂(phen-CD)][PF₆]₂, (phen-CD is 6 ^A -(5-amino-1, 10-phenanthroline)-6 ^A -deoxy- β-Cyclodextrin and bpy is 2,2'-bipyridine) exhibits an intense metal ligand charge transfer (MLCT) transition at 452 nm and a long lived luminescence, centred at 618 nm. We demonstrate, for the first time, that the luminescence quantum yield and lifetime of the Ru (II) polypyridyl centre depends markedly on the solution pH. The pH sensitive range extends from pH 3.9 to pH 13.2 and the luminescence quantum yield changes by more than 60% over this range. This pH sensitivity is attributed to protonation/deprotonation of the secondary amine group bridge between the phenanthroline unit and CD. The complex exhibits strong host-guest binding to anthraquinone and anthraquinone-2-carboxylic acid, with concomitant quenching of the [Ru(bpy)₂(phen-CD)]²⁺ excited state. This quenching arises from efficient intramolecular electron transfer. The sensitivity of this photoinduced process to the protonation state of the bridge is discussed.     

Homo‐ and Heteronuclear Compounds with a Symmetrical Bis‐hydrazone Ligand: Synthesis,Structural Studies,and Luminescent Properties

Nine new coordination compounds have been synthesized by the reaction of salts of bivalent metal ions (a=Zn^II, b=Cu^II, c=Ni^II, d=Co^II) with the bis(benzoylhydrazone) derivative of 4,6‐diacetylresorcinol (H₄L). Three kinds of complexes have been obtained: homodinuclear compounds [M₂(H₂L)₂]?nH₂O ( 1 a , 1 b , 1 c , and 1 d ), homotetranuclear compounds [M₄(L)₂]?n(solv) ( 2 a and 2 c ), and heterotetranuclear compounds [Zn₂M₂(L)₂]?n(solv) ( 2 ab , 2 ac , and 2 ad ). The structures of the free ligand H₄L?2 DMSO and its complexes [Zn₂(H₂L)₂(DMSO)₂] ( 1 a* ), [Zn₄(L)₂(DMSO)₆] ( 2 a* ), and [Zn_0.45Cu_3.55(L)₂(DMSO)₆]?2 DMSO ( 2 ab* ) were elucidated by single‐crystal X‐ray diffraction. The ligand shows luminescence properties and its fluorimetric behavior towards M^II metals (M=Zn, Cu, Ni and Co) has been studied. Furthermore, the solid‐state luminescence properties of the ligand and compounds have been determined at room temperature. ¹H NMR spectroscopic monitoring of the reaction of H₄L with Zn^II showed the deprotonation sequence of the OH/NH groups upon metal coordination. Heteronuclear reactions have also been monitored by using ESI‐MS and spectrofluorimetric techniques.