Solution chemistry of lanthanide complexes—III: Spectroscopic studies of lanthanide complexes of glycine and polyglycines

The lanthanide complexes of glycine, diglycine and triglycine have been studied by a variety of physical means. Measurements of differential absorption of Ho(III) complexes, luminescence intensities of Tb(III) complexes, and intermolecular energy transfer from Tb(III) to Eu(III) complexes were all used to characterize the nature of the solution chemistry. The complexes tend to remain mononuclear at low pH, but associate through hydroxide linkages above neutral pH. The degree of association is much less for complexes of diglycine relative to those of glycine, suggesting that the steric nature of the amino acid ligand plays a dominant role in determining the degree of association.     

Syntheses,structures, and luminescent properties of lanthanide complexes with N,N′-bis(p-methoxyphenyl)-3-oxapentanediamide

An amide-type acyclic polyether, N,N′-bis(p-methoxyphenyl)-3-oxapentanediamide (L), and its three lanthanide coordination compounds, [Ln(NO₃)(L)₂(H₂O)₂]?·?(NO₃)₂ [Ln?=?Pr (1), Nd (2), and Dy (3)], have been synthesized and characterized by elemental analysis, IR spectroscopy, thermal analysis, and X-ray diffraction. Single crystal X-ray structure analyses reveal that 1 and 2 have the same structure and crystallize in the monoclinic crystal system with C2/c space group. The coordination geometry around the central atom is a distorted bicapped square antiprism. Extensive intermolecular hydrogen bonds in 1 and 2 result in 3-D supramolecular networks. Complex 3 exhibits luminescence in the visible region upon excitation with UV-rays.     

Two new lanthanide–radical complexes: synthesis,structure, and magnetic properties

Two new lanthanide–radical complexes, [Tb(hfac)₃(EtVNIT)₂] (1) and [Dy(hfac)₃(EtVNIT)₂] (2) (EtVNIT?=?2-(4′-ethoxy-3′-methoxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, hfac?=?1,1,1,5,5,5-hexafluoroacetylacetonate), were synthesized; both display radical–Ln(III)–radical (Ln=Tb (1), Dy (2)) tri-spin structures. Magnetic studies reveal that interactions between the lanthanide ions and radicals are ferromagnetic.     

Ruthenium(II) complexes of 2-(2′-pyridyl)naphthoimidazole: synthesis,characterization and DNA-binding studies

The perchlorate salts of two new ruthenium(II) complexes incorporating 2-(2′-pyridyl)naphthoimidazole are synthesized in good yield. Complexes [Ru(phen)₂(PYNI)]²⁺ (phen = 1,10-phenanthroline) 1 and [Ru(dmp)₂(PYNI)]²⁺ (dmp = 2,9-dimethyl-1,10-phenanthroline, PYNI = 2-(2′-pyridyl)naphthoimidazole) 2 are fully characterized by elemental analysis, FAB-MS, ES-MS, ¹H NMR and cyclic voltammetric methods. The DNA-binding behavior of the complexes have been studied by spectroscopic titration, viscosity measurements and thermal denaturation. Absorption titration and thermal denaturation studies reveal that these complexes are moderately strong binders of calf-thymus DNA (CT-DNA), with their binding constants spanning the range (2.73–5.35) × 10⁴ M^?1. The experimental results show that 1 interacts with calf thymus DNA (CT-DNA) by intercalative mode, while 2 binds to CT-DNA by partial intercalation.     

Complexation and extraction studies of lanthanide ions by 1,1′-(3,6,9-Trioxaundecanedionyl)Diphenothiazine

Solid complexes of lanthanide picrates with 1,1′-(3,6,9-trioxaundecanedionyl)diphenothiazine (L), [Ln(pic)₃L] (Ln = La, Nd, Eu, Gd, Er, Y), have been prepared and characterized by elemental analysis, IR and ¹H NMR spectra. The molecular structure of [Er(pic)₃L]·1/2C₂H₅OH shows that five oxygens of L form a ring-like coordination structure. Er(III) is 9-coordinated by L together with the other two unidentate and one bidentate picrate anions, revealing a tri-capped distorted trigonal prism geometry. Solvent extraction of Ln(III) with L has been carried out in a water–nitrobenzene system by use of the multitracer method. The relationship between the complex structure and extractabilities of the ligand is discussed.     

Ruthenium(II)-CO complexes of N-[(2-pyridyl)methyliden]-α(or β)-aminonaphthalene: Synthesis, spectral studies, crystal structure, redox properties and DFT calculation

The characterization and properties of trans-(X)-[RuX₂(CO)₂(α/β-NaiPy)] (1, 2) (α-NaiPy (a), β-NaiPy (b); X = Cl (1), I (2)) are described in this work. The structures are confirmed by single crystal X-ray diffraction studies. Reaction of these compounds with Me₃NO in MeCN has isolated monocarbonyl trans-(X)-[RuX₂(CO)(MeCN)(α/β-NaiPy)] (3, 4). The complexes show intense emission properties. Quantum yields of 1 and 2 (? = 0.02-0.08) are higher than 3 and 4 (? = 0.006-0.015). Voltammogram shows higher Ru(III)/Ru(II) (1.3-1.5 V) potential of 1 and 2 than that of 3 and 4 (0.8-0.9 V) that may be due to coordination of two π-acidic CO groups in former. The electronic spectra and redox properties of the complexes are compared with the results obtained by density functional theory (DFT) and time-dependent density functional theory (TD-DFT) using polarizable continuum model (CPCM).     

Catecholato complexes of palladium(II)–naphthylazoimidazoles: synthesis,spectral characterization,electrochemistry and solvatochromic studies

[Pd(-NaiR)(O,O)] [-NaiR = 1-alkyl-2-(naphthyl--azo)imidazoles; R = Me (a), Et (b), CH₂Ph (c) and O,O = pyrocatecholato (cat) (3), 4-t-butylcatecholato (tbcat) (4), 3,5-di-t-butylcatecholato (dtbcat) (5), and tetracholorocatecholato (tccat) (6)] complexes were characterized by elemental analyses, i.r. and ¹H-n.m.r. spectral data. Studies by cyclic voltammetry suggest the existence of two redox couples, positive saturated calomel electrode (s.c.e.) that are due to catecholes to semiquinone, and semiquinone to quinone oxidations, respectively; two couples at negative to s.c.e. are associated with azo reductions. The complexes exhibit ligand-to-ligand charge-transfer transition in the near-i.r. region. The band position is largely dependent upon the substituent on the catechole frame and exhibits a negative solvatochromic effect. The transition is qualitatively assigned to the HOMO (cat) LUMO (-NaiR) transition.     

Lanthanide complexes with pyridine-2,6-dicarboxylic acid: synthesis,crystal structure,thermal and magnetic properties of [LnPDA)2(PDAH2)] · (DMAH2)2(DMAH0.5)2

Mild solvothermal synthesis, structures, thermal and magnetic properties of coordination complexes [Ln(PDA)₂(PDAH₂)] · (DMAH₂)₂(DMAH_0.5)₂(I–IV) (PDA = pyrdine-2,6-dicarboxylate anion, DMAH = dimethylamine, Ln = Ce, Nd, Sm, and Ho) are described. The DMAH molecules in I–IV, generated in situ from hydrolysis of N,N-dimethylformamide, are responsible to assemble three dimensional coordination polymers through N–H···O and C–H···O hydrogen bonds. Distorted tricapped trigonal prismatic LnO₆N₃ geometry having 14 triangular faces is attributed to mean deviation of dihedral angles while nitrogen shows fairly triangular faces having dihedral angle close to 60°C (CIF files CCDC nos. 872065 (I), 872070 (II), 872069 (III), and 872066 (IV)). Curie–Weiss law and the overall magnetic behavior are typical for the presence of antiferromagnetic exchange coupling interactions between lanthanide. Thermal decomposition analyses reveal removal of ammonia and resultant complexes showthermal stability. Complexes have been further characterized by using elemental analyzer and FT-IR spectroscopy.     

Design,synthesis,characterization,cytotoxic and structure activity relationships of novel Ru(Ⅱ) complexes

Platinum containing compounds have shown antineoplastic potential, but their clinical applications have been limited by high toxicity. Ruthenium containing complexes have long been known to be well suited for biological applications, and have long been utilized as replacements to popular platinum based-drugs. Here, we report a novel series of ruthenium(II) arene compounds bearing thiosemicarbazone and isonicotinylhydrazone ligands with potent anticancer activity their structure activity relationships and apoptosis was studied. The cytotoxic activity of the new ruthenium(II) arene compounds has been evaluated in several cell lines (Molt 4/C8, L1210, CEM, HL60 and BEL7402). Among them, ten complexes were found to be excellent in vitro growth inhibitory activity against various cell lines with IC50 in the sub-micromolar range.     

Spectroscopic and extraction studies of new transition metal complexes with N,N ′- bis (2-aminothiophenol)-1, 4- bis (2-carboxaldehydephenoxy)butane

Metal complexes of La(III), Cu(II) and Ni(II) with a thio Schiff base derived from 1,4-bis(2-carboxaldehydephenoxy)butane and 2-aminothiophenol have been synthesized in absolute ethanol and characterized by microanalytical data, magnetic measurements, ¹H NMR, ¹³C NMR, UV-visible, IR-spectra, mass spectra and conductance measurements. The extractability of divalent cations was evaluated as a function of relationship between distribution ratios of the metal and pH or ligand concentration. The highest extraction percentage of Cu⁺² and Ni⁺² were at pH 7.0 and 6.4, respectively. The ligand can effectively be used in solvent extraction of copper(II) and nickel(II) from aqueous phase to organic phase.     

Copper(II) halide complexes of aminopyridines: Syntheses,structures and magnetic properties of [(5CAP)2CuX2] and [(5BAP)nCuX2] (X = Cl,Br)

Abstract

Reaction of 2-amino-5-halopyridine molecules with Cu(II) halides in the solid state via mechanochemical techniques produced four coordination complexes, (5BAP)₂CuBr₂ (2a), (5BAP)₂CuCl₂ (3), (5CAP)₂CuCl₂ (4), (5CAP)₂CuBr₂ (5) [5BAP?=?2-amino-5-bromopyridine; 5CAP?=?2-amino-5-chloropyridine]. In all compounds, the 5BAP or 5CAP ligands are coordinated to the Cu(II) ion through the pyridine N atom along with two halide ions. Compounds 2 and 3 crystallized in the P-1 and P2₁/c space groups, respectively. Temperature dependent magnetic susceptibility data for 2 were fit to the antiferromagnetic rectangle model (J?=?–4.5(2) K; α?=?0.89(17)), while the data for 3 were fit to the uniform chain model (J?=?–4.20(6) K), indicating a significant difference in the interchain interactions. Both 4 and 5 crystallize with the 5CAP ligands in the syn-conformation in the space groups I2/a and P21/n, respectively. Compound 4 formed the expected dimeric structure via bridging chloride ions and the magnetic data were successfully fit to the dimer model (J?=?–2.57(5) K), while 5 unexpectedly formed a structural chain via Br…Br contacts which exhibits very weak antiferromagnetic interactions. An intermediate structure, (5BAP)(H₂O)CuBr₂ (1), was prepared and characterized via mechanochemical methods along with an isomer of (5BAP)₂CuBr₂ (2b).     

Theoretical studies on electronic structures and spectroscopic properties of a series of novel β-diketonate Os(II) complexes

The geometries, electronic structures, and spectroscopic properties of a series of [Os^(II)(CO)₃(tfa)(acac(X)₂)] (tfa = trifluoroacetate; acac = acetoylacetonate; X = H (1), CF₃ (2), C₆H₅ (3), and C₁₀H₇ (4)) complexes have been investigated theoretically. The ground and excited state geometries were optimized at the B3LYP/LANL2DZ and CIS/LANL2DZ levels, respectively. The optimized geometry structural parameters agreed well with the corresponding experimental results. As indicated in this paper, the highest occupied molecular orbitals were dominantly localized on the Os atom, ctfa (abbv. of CO and tfa), and acac ligand for 1 and 2, acac ligand and X substituent for 3 and 4, while the lowest unoccupied molecular orbitals were mainly composed of acac ligand and X substituent. Under the time-dependent density functional theory (TDDFT) level with the polarized continuum model (PCM), the absorption and phosphorescence in CH₂Cl₂ media were calculated based on the optimized ground- and excited-state geometries, respectively. The calculated results show that the lowest energy absorptions at 317 (1), 342 (2), 377 (3), and 420 nm (4) are attributed to a change of ππ*/MLCT mixing transition to pure ππ* transition for 1–4, while their phosphorescence emission have similar transition properties. This indicates that the absorption and emission transition characters could be altered by adjusting the π electron-donating ability.     

Synthesis, characterization and magnetic properties of novel μ-isophthalato oxovanadium(IV) binuclear complexes

Four novel oxovanadium(IV) binuclear complexes have been synthesized, namely [(VO)₂(IPHTA) (L)₂SO₄ (L denotes 2,2′-bipyridine (bpy); 1,10-phenanthroline (phen); 4,4′-dimethyl-2,2′-bipyridine (Me₂bpy) and 5-nitro-1,10-phenanthroline (NO₂-phen)), where IPHTA is the isophthalate dianon. Based on elemental analyses, molar conductivity measurements, IR and electronic spectra studies, it is proposed that these complexes have IPHTA-bridged structures and consist of two vanadium(IV) atoms in a square-pyramidal environment. The complexes [(VO)₂(IPHTA)(Me₂bpy)₂]SO₄ (1) and [(VO)₂(IPHTA)(bpy)₂]SO₄ (2) were characterized by variable temperature magnetic susceptibility (4–300 K) and the data could be well fitted by the least-squares method to a susceptibility equation derived from the spin Hamiltonian operator, . The exchange integral, J, was found to be −26.8 cm⁻¹ for (1) and −31.0 cm⁻¹ for (2). These results are commensurate with antifferomagnetic interactions between two oxovanadium(IV) ions within each molecule. The influence of different terminal ligands on magnetic interactions between the metals of this kind of complexes is also discussed.     

Synthesis,crystal structure and luminescent properties of two complexes containing [Au(CN)2] − building blocks

Two supramolecular complexes, {{Ni(H₂O)(phen)₂[Au(CN)₂]}[Au(CN)₂]?·?1.5H₂O} _n (1) (phen?=?1,10-phenanthroline) and [H₂teta][Au₂(CN)₄]?·?2H₂O (2) (teta?=?5,7,7,12,14,14-hexamethyl-1,4,8,11-tetra-azacyocloteradeca-4,11-diene) have been synthesized and structurally characterized. Complex 1 was a one-dimensional infinite chain constructed by [Au(CN)₂]^? building blocks. In complex 2, there are one cation, one anion, and two water molecules in the asymmetric unit. The two complexes are interconnected through a combination of aurophilic attractions and hydrogen bonds and formed into 3D supramolecular structures. The aqueous solutions of 1 and 2 display interesting luminescence at room temperature.     

Crystal structures, luminescent properties and thermal decomposition kinetics of some binuclear lanthanide complexes with 2,3-dichlorobenzoic acid anion and 2,2′-bipyridine

Some binuclear lanthanide complexes with the general formula [Ln(2,3-DClBA)₃bipy]₂ (Ln = Sm(1), Eu(2), Tb(3), Dy(4), and Ho(5); 2,3-DClBA = 2,3-dichlorobenzoate; bipy = 2,2′-bipyridine) were synthesized and characterized by elemental analysis, molar conductance, infrared, ultraviolet, luminescent spectroscopy, thermogravimetry, and different thermogravimetry (TG–DTG) techniques. The single crystals of the complexes have been obtained except the complex 2 and their structures have been determined by single-crystal X-ray diffraction. The four complexes are isostructural and the rare earth ions are all nine coordinated. The two rare earth ions in each complex are linked by two bridging bidentate and two chelating-bridging tridentate carboxylate groups. Under ultraviolet light excitation, the europium and terbium complexes exhibited characteristic red fluorescence of Eu³⁺ ion and green fluorescence of Tb³⁺ ion at room temperature. The non-isothermal kinetics was investigated by using the integral isoconversional non-linear (NL-INT) and the Popescu methods. The mechanism functions of the first decomposition step of the complexes 3–5 were determined. Meanwhile, the thermodynamic parameters (ΔG ^≠ , ΔH ^≠, and ΔS ^≠) at DTG peak temperatures were also calculated.     

The synthesis and spectroscopic properties of some (π-allyl) dicarbonyl-semicarbazonatohalogenomolybdenum(II) complexes

Reaction of [MoX(CO₂(NCMe)₂(η³-C₃H₄R)] in CH₂Cl₂ at room temperature with an equimolar quantity of (R′R″)CNNHCONH₂ gave high yields of the bidentate coordinated semicarbazone complexes [MoX(CO)₂{(R′R″)CNNHCONH₂}(η³-C₃H₄R)] (X = Cl, Br or I; R = H or Me; R′,R″ = H or Me and Me, Et, ⁿPr or Ph) via displacement of two acetonitrile ligands.     

Hydrothermal synthesis, thermal and luminescent investigations of lanthanide(III) coordination polymers based on the 4,4′-oxybis(benzoate) ligand

In this study, new series of lanthanide 4,4??-oxybis(benzoates) of the general formula Ln₂oba₃·nH₂O, where Ln = lanthanides from La(III) to Lu(III), oba?=?C₁₂H₈O(COO) ₂ ^2? and n?=?3?C6, has been prepared under hydrothermal conditions. The compounds were characterized by elemental analysis, infrared spectroscopy, X-ray diffraction patterns measurements and different methods of thermal analysis (TG, DSC, and TG-FTIR). In addition, photoluminescence properties of the selected complexes have been investigated. Crystalline compounds are isostructural in the whole series. Both carboxylate groups are deprotonated and engaged in the coordination of Ln(III) ions. Heating of the complexes leads to the dehydration and next decomposition processes. Although of the same structure, the removal of water molecules proceeds in different ways. In the nitrogen atmosphere, they decompose releasing water, carbon oxides and phenol molecules. The complexes of Eu(III), Tb(III) and Dy(III) exhibit photoluminescence in the visible range, whereas the compounds of Nd(III) and Yb(III) in the near-infrared region upon excitation by UV light.