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Leishmaniasis is a group of parasitic diseases with the potential to infect more than 1 billion people; however, its treatment is still old and inadequate. In order to contribute to changing this view, this work consisted of the development of complexes derived from MI metal ions with thioureas, aiming to obtain potential leishmanicidal agents. The thiourea ligands (HLR) were obtained by reactions of p-toluenesulfohydrazide with R-isothiocyanates and were used in complexation reactions with AgI and AuI, leading to the formation of complexes of composition [M(HLR)2]X (M = Ag or Au; X = NO3− or Cl−). All compounds were characterized by FTIR, 1H NMR, UV-vis, emission spectroscopy and elemental analysis. Some representatives were additionally studied by ESI-MS and single-crystal XRD. Their properties were further analyzed by DFT calculations. Their cytotoxicity on Vero cells and the extracellular leishmanicidal activity on Leishmania infantum and Leishmania braziliensis cells were evaluated. Additionally, the interaction of the complexes with the Old Yellow enzyme of the L. braziliensis (LbOYE) was examined. The biological tests showed that some compounds present remarkable leishmanicidal activity, even higher than that of the standard drug Glucantime, with different selectivity for the two species of Leishmania. Finally, the interaction studies with LbOYE revealed that this enzyme could be one of their biological targets. [ABSTRACT FROM AUTHOR]

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Phosphino hydrazones represent a versatile class of nitrogen‐containing phosphine ligands. Herein, we report a modular synthesis of phosphino hydrazone ligands by hydrazone condensation reaction of three different aryl hydrazines with 3‐(diphenylphosphino)propanal (PCHO). Complexation reactions of these phosphino hydrazone ligands with palladium(II) and platinum(II) were investigated and the catalytic activity of the palladium(II) complexes was explored in a Cu‐free Sonogashira cross‐coupling reaction achieving yields up to 96 %. Additionally it was shown that the catalytically active species is homogeneous. [ABSTRACT FROM AUTHOR]

New complexes of manganese(II) hexafluoroacetylacetonate [Mn(hfac)2] with 2-(1-R-3-pyrazol-4-yl)-4,4,5,5-tetramethyl-2-imidazoline-3-oxide-1-oxyl (R = CHF2, CH2CH2F, CH2CHF2 or CH2CF3) were synthesised and characterised structurally and magnetically. All complexes were prepared under similar conditions. Nonetheless, their crystal structures were considerably different. Depending on the structure of fluorinated alkyl substituent R, the complexation reaction led to complexes of three types: chain-polymeric complexes with the head-to-head or head-to-tail motif and complexes of molecular structure. All complexes show strong antiferromagnetic behaviour in a high-temperature region (150–300 K) and weak ferro- or antiferromagnetic exchange interactions at low temperatures. The stronger antiferromagnetic exchange, −101.7 ± 1.5 or −136 ± 10 cm−1, −82.3 ± 1.3 cm−1 and −87.4 ± 1.3 cm−1, was attributed to the magnetic interaction in three- or two-spin clusters: {>N∸O–Mn2+–O∸N<} or {>N∸O–Mn2+}, respectively. The weaker antiferromagnetic interaction, −0.005, between three-spin clusters or ferromagnetic interactions, 0.18–0.81 cm−1, between two-spin clusters are realised through the pyrazole ring or intermolecular contacts. [ABSTRACT FROM AUTHOR]

Polymeric chelating ligands based on styrene and unsaturated -diketone 5-methyl-5-hexene-2,4-dione (MHD) were prepared by radical copolymerization initiated by benzoyl peroxide in benzene solution at the volume ratios of monomers styrene:MHD=1:30 and 1:10. In this case, β-diketone was added to the system by conventional (simultaneous) and compensatory (equal portions at conversions of 0, 5, and 10%) methods. The resulting products were studied by IR and ¹H NMR spectroscopies. It has been shown that macrochelates obtained on the basis of such ligands differ in their structure and as a consequence in their macroinitiating ability in the grafting of vinyl monomers. Polymeric ligands synthesized at the ratio of 1:10, regardless of the preparation method, form mixedligand complexes in the subsequent complexation reaction with cobalt(II) acetate, which exhibit weak activity in styrene grafting and are not effective in the case of methyl methacrylate. The use of a small amount of MHD (1:30) in combination with the compensatory synthesis method leads to the predominant formation of intramolecular complexes of the β-diketonate type, which are more active macroinitiators in the graft polymerization of styrene and methyl methacrylate than those obtained by the traditional simultaneous method of adding MHD. [ABSTRACT FROM AUTHOR]

The complexes of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II) and Pt(II) were prepared from the complexation reaction between the new Schiff base ligand and selected metal ions. Ligand was derived from the condensation reaction of Oxo(4-(pyridin-2-yl)phenyl) methyline, 4-amino antipyrine, and (6- amino Penicillanic acid). The ligand and its complexes were characterized by C.H.N elemental analysis, Uv-Vis, FT-IR, and molar conductivity, Atomic absorption, magnetic moment measurements and mass spectra studies. The results of their studies show the coordination sites for the ligand with the metal ion were to be through oxygen, nitrogen atoms of 6-amino penicillic acid, and the nitrogen atom of 4-amino antipyrine. The complexes were found to have the general formula [(M)(L)2]Cl2 where M = Co(II), Ni(II), Cu(II), Zn(II), Hg(II), and Cd(II), except the [Pt(L)Cl]Cl. The electronic spectral and magnetic measurement data indicated that the complexes exhibited octahedral geometry, except the Pt(II) complex suggested a square planar geometry around the central metal ion. The ligand forms shape as natural tridentate manner. The biological activity results showed the inhibitory effect for platinum(II) the complex. In this study the cytotoxicity of Pt(II) complex on human colon cancer cell line LS 174 T CRC was investigated and African green monkey kidney cells normal cells were MTT assay. The metal complex showed selective cytotoxicity against colorectal, this metal Complex excelled in halting proliferation of LS 174 T CRC cancer cells line with median inhibitory concentration (IC50) values of Pt(II) complex. The results indicate undoubtedly the possibility of using them as antitumor drugs in the pharmacy colon field cancer. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new ligand (2a) was synthesized by using a coupling agent N,N′- dicyclohexylcarbodiimide. • The geometry of a new mononuclear Zn(II) complex (3a) is tetrahedral. • 2a and 3a emitted a blue and a strong greenish-blue fluorescent, respectively in pure DMSO. • This fluorescence displayed very low emission efficiency in aqueous and acidic DMSO–H 2 O. • 1a–3a have weaker DPPH radical scavenging activity than ascorbic acid. Novel amido-Schiff base 3,5-bis((2-hydroxybenzylidene)amino)- N -(2-hydroxyphenyl)benzamide (2a) has been obtained by the reaction of Schiff base 1a with 2-hydroxyaniline in the presence of coupling agent N,N′- dicyclohexylcarbodiimide. Schiff base (1a) which serves as the starting compound in amide synthesis was produced from the condensation of 3,5-diaminobenzoic acid with salicylaldehyde in a 1:2 mol ratio. Tetrahedral geometry with 1:1 [M:L] stoichiometry Zn(II) complex (3a) was newly synthesized by the complexation reaction of ligand 2a with zinc(II) nitrate. 1a and 2a displayed a broad emission band at λ em = 456 and 472 nm with a blue fluorescent in pure DMSO, while 3a emitted a strong greenish-blue fluorescent with the λ em = 485 nm (λ exc = 365 nm). The fluorescence efficiency of 1a was poor compared to the others. The λ em in aqueous DMSO solution (v/v, 1:1) had ∼8–33 nm red-shift with respect to that of pure solution. The λ em gave ∼1–15 nm red-shift with very low emission efficiency in acidic DMSO media. The results suggested that the aggregation caused quenching properties of 1a–3a in pure, aqueous, and acidic DMSO system with a 50 % water fraction. The fluorescence of the compounds appeared to be visibly very bright in basic DMSO media. All the compounds were also screened for antioxidant activity using UV–Vis spectroscopy. They were found to be not effective DPPH radical scavengers in DMSO. [ABSTRACT FROM AUTHOR]

• A multidonor amidophosphine ligand was prepared using an alternative route. • The ligand reacts with group 10 metal dichloride precursors to produce P,N,N-chelate complexes. • Spontaneous HCl elimination occurs during the complexation. • Terminal chloride ligand can be replaced for a phosphine. • The complexes were fully characterized and possess similar molecular structures. The multidonor amidophosphine 2-Ph 2 PC 6 H 4 NHC(O)C 5 H 4 N, where C 5 H 4 N is a 2-pyridyl substituent, reacted with the synthetic equivalents of group 10 metal dichlorides, viz. [NiCl 2 (dme)], [PdCl 2 (MeCN) 2 ] or [PtCl 2 (cod)] (dme = 1,2-dimethoxyethane, cod = cycloocta-1,5-diene), to produce neutral bis-chelate complexes [MCl(Ph 2 PC 6 H 4 NC(O)C 5 H 4 N-κ3 P,N,N ′)] (M = Ni, Pd, and Pt). During the complexation reaction, spontaneous HCl elimination occurred, possibly as the result of overall structural stabilization by the deprotonation of the amide nitrogen, which is brought toward the metal centers by initial P,N(pyridine)-coordination of the amidophosphine ligand. Subsequent reaction of 3 as the representative with AgClO 4 and triphenylphosphine produced the cationic bis(phosphine) complex [Pd(PPh 3)(Ph 2 PC 6 H 4 NC(O)C 5 H 4 N-κ3 P,N,N ′)]ClO 4 (5), which converted back to parent chloride complex in the presence of chloride ions. All complexes were fully characterized using NMR and IR spectroscopy, mass spectrometry, and elemental analysis. X-ray diffraction analysis for 2, 3, 4 ·½ CH 2 Cl 2 and 5 ·Me 2 CO revealed that compounds 2 – 4 exhibit similar coordination geometry, which is rather marginally affected upon replacement of the chloride for a bulkier phosphine ligand. [Display omitted] [ABSTRACT FROM AUTHOR]

Some podand sulfonamides were designed to Cu2+ ion recognition. Some green chemistry metrics were evaluated in order to know the environmental impact of the reactions. Cu2+ complexes studio with the ligands were done, given adequate complexation constants for Cu2+ recognition by ligands LA2 y LA6. All complexes precipitated instantaneously when directly react with copper ions resulting in blue complexes. For LA2 a color change to olive green in 8 minutes was observed maybe due to a molecular reorganization. LA2 can be used as a part of an ion recognition kit that detect concentration in the order of 10-3 mol·dm-3. [ABSTRACT FROM AUTHOR]

Heteroleptic platinum(II) complexes find wide application in supramolecular and photochemistry. Nevertheless, efficient methods for their preparation are limited. Herein, we report a novel synthetic approach toward heteroleptic trans‐bis(iminopyrrolyl)Pt(II) complexes with N‐propyl, ‐pentyl, ‐methoxyethyl, and ‐phenyl substituents using a Zeise's dimer analog as the platinum source. The developed route, which consists of two sequential complexation reactions with the corresponding sodium salt of the iminopyrrolyl ligand, is operationally simple and delivered the mono and trans‐bis coordinated products quantitatively and highly stereoselectively. The obtained Pt(II) complexes exhibited crystallization‐induced phosphorescent emission enhancement behavior. Furthermore, the luminescence properties were dependent on the substituents on the nitrogen atoms of the iminopyrrolyl ligands. Hence, this study is expected to have important implications in the fields of supramolecular and photochemistry. [ABSTRACT FROM AUTHOR]

The copper coordination chemistry of N2S2 Schiff base ligands derived from acetylacetone and S-methyl or S-benzyl dithiocarbazate (H3acacsR, R = Me, Bn) reveals a rich variety of products depending on the reaction conditions. The free ligands spontaneously cyclise to their pyrazoline isomers but ring-open upon complexation with CuII. In the absence of oxygen, the ligands form CuIIN2S2 complexes ([CuII(HacacsR)]) that have been characterised electrochemically, spectroscopically and structurally. Intermediates in the complexation reaction are observed with time-resolved UV-Vis spectroscopy. Upon exposure to air, a number of different complexes are formed. Facile oxidation of [CuII(HacacsR)] to the trivalent analogue [CuIII(acacsR)] occurs in air. This compound is the precursor to two further oxidation reactions; one to the ketone [CuII(acacsRO)] where a carbonyl group has been installed at the apical C atom of the acetylacetone moiety and another to afford the novel dinuclear complex [(CuIII(acacsR))2]. The presence of excess base (Et3N) favours formation of the dimer. [ABSTRACT FROM AUTHOR]

In this paper we report a series of Al(III) complexes supported by N,O-bidentate β-pyrazyl functionalized enolate ligands HL1–HL5 (L = (6-Me-2,5-C4H2N2)–CH＝C(R)–O–), (R = tBu, Ph, p-tolyl, p-OMePh, o-tolyl) and their exploitation for the ring-opening polymerization of ε-caprolactone (ε-CL) and rac-lactide (rac-LA). The structures of the form LAlMe2 (1a–5a) or L2AlMe (1b–4b) were isolated depending on the ligand or stoichiometry of complexation. The investigation of these complexes toward the ROP of both ε-CL and rac-LA under the same conditions showed that dimethyl-aluminum complexes LAlMe2 (1a–5a) gave a higher activity than monomethyl-aluminum complexes L2AlMe (1b–4b). Meanwhile, monomethyl-aluminum complexes 1b–4b promoted the ring-opening polymerization with a better control over molecular weights and polydispersities than 1a–5a. Moreover, all of the LAlMe2 and L2AlMe produced PLA with strong isotactic bias (Pm up to 0.77) and narrow distributions. Generally, a β-pyrazyl enolate system exhibited significantly higher catalytic activity for the ROP of ε-CL and rac-LA than the analogous β-quinolyl enolate systems reported recently. The results are discussed in terms of electronic and steric properties affected by the substituents on the ligands. [ABSTRACT FROM AUTHOR]

Abstract New Mn(II)-thioantimonate compounds [Mn(NH 3) 6 ] 2 [{Mn(NH 3) 3 } 2 (μ 3 -SbS 4) 2 ]Cl 2 (1), [Mn(NH 3) 6 ][{Mn(NH 3) 4 } 2 (μ-SbS 4) 2 ]·2H 2 O (2), [Mn(NH 3) 6 ][{Mn 2 (μ-SbS 4) 2 }(μ-N 2 H 4) 2 ] (3), and [{Mn(N 2 H 4)} 2 {Mn(μ-SbS 3) 2 (μ-N 2 H 4) 2 }(μ-N 2 H 4) 2 ] n (4) were prepared in different hydrazine solution under solvothermal conditions. In 1 , the tetrahedral SbS 4 unit acts as a tridentate bridging ligand to connect the [Mn(NH 3) 3 ]2+ units into a 2-D lamellar anion [Mn(NH 3) 3 (μ 3 -SbS 4)2−] n containing 12-membered Mn 3 Sb 3 S 6 heterorings. Two SbS 4 ligands join two [Mn(NH 3) 4 ]2+ units with monodentate μ-1κ1 S 1: 2κ1 S 1 bridging mode, forming a binuclear [{Mn(NH 3) 4 } 2 (μ-SbS 4) 2 ]2− anion in 2. In 3 , the SbS 4 ligand links [Mn 2 (μ-N 2 H 4) 2 ] units with tridentate bridging mode, to form a 1-D [{Mn 2 (μ-SbS 4) 2 }(μ-N 2 H 4) 2 2−] n chain-like anion. Octahedral [Mn(NH 3) 6 ]2+ complex cation acts as the counter ion in compounds 1 – 3. In 4 , the Mn(N 2 H 4) units are interconnected into a neutral infinite [{Mn(N 2 H 4)} 2 {Mn(μ-SbS 3) 2 (μ-N 2 H 4) 2 }(μ-N 2 H 4) 2 ] n chain by μ-SbS 3 and μ-N 2 H 4 bridging ligands. The trigonal pyramidal SbS 3 unit adopts a tridentate bridging coordination mode μ-1κ2 S 1, S 2:2κ2 S 1, S 3. Compounds 1 – 4 exhibit tunable semiconducting band gaps varying in the range of 2.38–2.55 eV. Compounds 1 and 2 display higher photocatalytic activity in the degradation of crystal violet than in the degradation of methyl orange under visible light irradiation. Graphical abstract Mn(II)-thioantimonate [Mn(NH 3) 6 ] 2 [{Mn(NH 3) 3 } 2 (μ 3 -SbS 4) 2 ]Cl 2 (1), [Mn(NH 3) 6 ][{Mn(NH 3) 4 } 2 (μ-SbS 4) 2 ]·2H 2 O (2), [Mn(NH 3) 6 ][{Mn 2 (μ-SbS 4) 2 }(μ-N 2 H 4) 2 ] (3), and [{Mn(N 2 H 4)} 2 {Mn(μ-SbS 3) 2 (μ-N 2 H 4) 2 }(μ-N 2 H 4) 2 ] n (4) were prepared in different hydrazine solution under solvothermal conditions. fx1 Highlights • Mn(II) complexes with SbS 4 and SbS 3 ligands were synthesized by solvothermal method. • Four new coordination modes for the SbS 4 and SbS 3 ligands are obtained in 1 – 4. • 1 and 2 perform catalytic activity in the photodegradation of CV. [ABSTRACT FROM AUTHOR]

The complexation of hexavalent plutonyl Pu(vi) with N,N,N′,N′-tetramethyl-3-oxa-glutar-amide (TMOGA) and its carboxylate analogs, N,N-dimethyl-3-oxa-glutaramic acid (DMOGA) and oxydiacetic acid (ODA), has been studied in 1.0 M NaClO4 by absorption spectrophotometry and density functional theory (DFT). Both 1 : 1 and 1 : 2 complexes of Pu(vi) with TMOGA, DMOGA and ODA have been identified and their stability constants were obtained and compared with those of hexavalent U(vi) and pentavalent Np(v). The resultant stability constants indicate that the ability of the three ligands to complex with Pu(vi) decreases in the order of ODA ＞ DMOGA ＞ TMOGA. While for one given ligand, the stability constants of both the 1 : 1 and 1 : 2 complexes decrease generally in the order U(vi) ＞ Pu(vi) ＞ Np(v). The trends of the complexation strength have been elucidated by the calculated Mulliken atomic charges of the central metal cations. Furthermore, the coordination modes of the Pu(vi) complexes with TMOGA, DMOGA and ODA have been illustrated by analyses of the optical features of the complexes as well as by DFT calculations. The results demonstrate that the 1 : 2 Pu(vi)/TMOGA complex is centrosymmetric, while the 1 : 2 complexes of Pu(vi) with DMOGA and ODA are non-centrosymmetric. Moreover, different coordination modes have been observed in actinyl complexes with the same ligand, suggesting the structurally similar actinyl ions (U(vi), Pu(vi) and Np(v)) could exhibit quite different coordination behavior due to the variation of cation size and electronic structure. [ABSTRACT FROM AUTHOR]

Two hexadentate bipyridine ligands and their RuII and NiII complexes were prepared. The helical alignment of the three electron‐donor–π‐bridge–electron‐acceptor (d‐π‐A) single‐strands with bundle architecture in cooperation with the metal center can strongly enhance the nonlinear optical (NLO) properties. The complexation of the novel cage‐type hexadentate ligands with a paramagnetic NiII‐core almost doubles the βHRS values compared with the corresponding diamagnetic RuII complexes. The hyper‐Rayleigh scattering (HRS) was performed with a highly sensitive setup for simultaneous discrimination between multi‐photon fluorescence and the molecular first hyperpolarizability. Nonlinear optics: Increasing the number of unpaired electrons in a dendritic structured hexadentate bipyridine complex can lead to a dramatic enhancement of the SHG effect. [ABSTRACT FROM AUTHOR]

1-(2-Chlorophenyl)-3-methyl-4-propionyl-1H-pyrazol-5(4H)-one was synthesized and characterized by Fourier transform infrared (FT-IR) spectroscopy, 1H nuclear magnetic resonance, and single-crystal X-ray analysis. Its Cu(II) complex was prepared and characterized by FT-IR, thermo gravimetric analysis-differential thermal analysis, ultraviolet-visible spectroscopy, cyclic voltammetry, and single-crystal X-ray structure determination. On the basis of analytical and spectroscopic techniques, a distorted square planar geometry of the complex has been found. [ABSTRACT FROM AUTHOR]

In this study, the coordination chemistry of unsymmetrical 1,n′‐substituted ferrocene (Fc) peptide conjugates is explored, where the peptide substituents are two different histidine‐containing peptides. The resulting Fc‐conjugates serve as ligands for the formation of metal complexes, with the intention to generate complexes that possess a labile coordination site. The following Fc[CO‐His(Trt)‐OMe][COOMe] (1), Fc[CO‐His(Trt)‐Gly‐OMe][CO‐Gly‐OMe] (2), Fc[CO‐His(Trt)‐His(Trt)‐OMe][CO‐His(Trt)‐OMe] (3), and Fc[CO‐His(Trt)‐Gly‐His(Trt)‐OMe][CO‐Gly‐His(Trt)‐OMe] (4) were synthesized and characterized. Each compound forms discrete complexes with metal divalent metal ions Zn2+, Co2+ and Cd2+, where a single metal ion is complexed by the metallo‐ligand, as was confirmed spectroscopically. The redox properties of the Fc group are influenced by metal coordination to the peptide substituents and anodic shifts occur upon the addition of metal ions. These follow the order Zn2+ > Cd2+ > Co2+. NMR experiments indicated imidazole rings are the site of metal coordination. Fc‐peptide conjugates display a switchable axial chirality that is dependent on metal complexation. [ABSTRACT FROM AUTHOR]

Cadmium(II) chelates with 4-iodo-, 5,5´-, and 4,4´-dibromo-2,2´-dipyrromethenes (HL1, HL2, and HL3, respectively) with the composition of [CdL2] were synthesized. The influence of structural features of their molecules and properties of the medium on the characteristics of absorption and fluorescence spectra, and also on the thermodynamic stability constants in solutions was evaluated. The results of quantum chemical calculations revealed that the additional coordination interactions between the bromine atoms at the α-positions of dipyrromethene ligands and the complexing atom are possible in the molecular structure of α,α´- dibromosubstituted dipyrromethenate [Cd(L2)2] in contrast with β-halogenated analogues [Cd(L1)2] and [Cd(L3)2]. [ABSTRACT FROM AUTHOR]

The initial synthesis of two β-cyclodextrin derivatives bearing seven carboxylate ligands was optimized in order to improve the production of contrast agents. A speciation study using potentiometric analysis was performed on a gadolinium(III) complex. The i n vivo myocardic activity was evaluated on mice. This study highlights the best efficiency for the cyclodextrin derivative having free hydroxyl groups and validated the biomedical potential of the flexible cyclodextrin scaffold as a cardiac MRI probe. [ABSTRACT FROM AUTHOR]

Anti-microbial effect is produced when the ligand (L) S-ethyl- l -cysteine sulfoxide (Ethiin) makes coordination complex with metal ‘M’ (M = Cu, Co, Ni), while, ethiin did not show any antimicrobial effect. The synthesized complexes have 1:2 metal to ligand ratio (ML 2 ). The spectro-chemical analysis revealed that the ligand coordinates with the metals through oxygens of the carboxylate and sulfoxide groups resulting in octahedral geometry around the central metal atom. Techniques like 1 H NMR, thermal analysis, mass spectrometry, UV-Vis spectroscopy, XAFS, FTIR, EPR and magnetic moments were used to elucidate the structure of the ligand and the metal complexes. The expected reasons for the creation of anti-microbial effect are, either the disturbance of the ionic environment within the microbial cytoplasm when the complex enters into it or interaction of the complex with the DNA. [ABSTRACT FROM AUTHOR]

Abstract: Chiral cyclopentadienyl (Cpx) ligands have a large application potential in enantioselective transition‐metal catalysis. However, the development of concise and practical routes to such ligands remains in its infancy. We present a convenient and efficient two‐step synthesis of a novel class of chiral Cpx ligands with tunable steric properties that can be readily used for complexation, giving CpxRhI, CpxIrI, and CpxRuII complexes. The potential of this ligand class is demonstrated with the latter in the enantioselective cyclization of azabenzonorbornadienes with alkynes, affording dihydrobenzoindoles in up to 98:2 e.r., significantly outperforming existing binaphthyl‐derived Cpx ligands. [ABSTRACT FROM AUTHOR]

Two new chiral bis-bidentate, C2-symmetrical ligands belonging to the Chiragen family have been synthesised and characterised. They are designed for polynuclear self-assemblies since the two (−)-5,6-pinenebipyridines units are connected by bridges whose length and rigidity avoids the coordination of the bipyridine moieties to the same metal centre. The ligand L1 with a 1,4-dimethylene naphthalene bridge leads, by complexation with Ag(I) cations, to a polymeric, single stranded helix. The helical pitch contains five metal centers, two consecutive metal centers being connected by a bis-bidentate, helically wrapped ligand, one up and the other down resulting in a coordination number four. The chirality (Λ) around each metal centre is controlled by the six asymmetric carbons of the ligands and the homochirality of the metal centers gives rise to a P orientation at the helix level. The 1 H-NMR measurements of these species in solution indicate a temperature dependent behaviour pointing out possible equilibria between various [Ag n L n ] n+ fragments as confirmed by MS-spectroscopy. The ligand L2 with a 4,4′-dimethylene-1,1′-biphenyl bridge reacts with Ag(I) and lead to well resolved and temperature independent 1 H-NMR spectra suggesting the formation of a circular helicate. [ABSTRACT FROM AUTHOR]

Novel Pd nanoparticles were prepared in five successive stages: 1) preparation of the Fe3O4 magnetic nanoparticles (Fe3O4 MNPs), 2) coating of Fe3O4 MNPs with SiO2 (Fe3O4@SiO2), 3) functionalization of Fe3O4@SiO2 with 3‐chloropropyltrimethoxy‐ silane (CPTMS) ligand (Fe3O4@SiO2@CPTMS), 4) further functionalization with 3,5‐diamino‐1,2,4‐triazole (DAT) ligand (Fe3O4@SiO2@CPTMS @DAT), and 5) the complexation of Fe3O4@SiO2@CPTMS@DAT with PdCl2 (Fe3O4@SiO2@CPTMS@ DAT@Pd). Then, the obtained Pd nano‐catalyst characterized by different methods such as the elemental analysis (CHN), FT‐IR, XRD, EDX, SEM, TEM, TG‐DTA and VSM. Finally, the Pd catalyst was applied for the synthesis of various 2‐imino‐3‐phenyl‐2,3‐dihydrobenzo[d]oxazol‐5‐ols. [ABSTRACT FROM AUTHOR]

Complexation of a new macrocyclic compound, 2,6-dimethylformamide-calix[4]pyridine (L1), with Eu(III) was studied by spectrophotometry. Stability constants of the Eu(III)/L1 complex in different solvents were determined. The results reveal that L1 forms moderately strong complexes with Eu(III) and other lanthanides in aprotic solvents and shows little binding ability with transition metals. Moreover, the binding strength of L1 weakens significantly in protic solvents. Using 2-bromodecanoic acid as the synergistic reagent, L1 extracts Am(III) and Eu(III) successfully with a separation factor of SFAm/Eu=1.3, and the distribution ratios of Am(III) and Eu(III) increases as the aqueous acidity is decreased. DFT computational studies were conducted to corroborate the solvent extraction data, and compare the coordination properties of Am(III)/Eu(III) complexes with L1 and a related, 2,6-diformamide-calix[4]pyridine (L2). The computational results suggest that L2 could form stable complexes [ML]3+ and ML(NO3)3 [where M represent Am(III) or Eu(III)] in aqueous phase, in sharp contrast to the case of L1 where such complexes in aqueous phase are not stable. [ABSTRACT FROM AUTHOR]

A ligand system containing three carbamoyl moieties secured onto a triphenylphosphine oxide platform (2-R 2 NC(O)CH 2 OC 6 H 4 ) 3 PO, where R = Me ( 1 ), Bu ( 2 ), and cyclo -Hex ( 3 ) has been developed for lanthanide complexation and extraction from aqueous solutions. The influence of non-coordinating alkyl substituents at the nitrogen atoms in the carbamoyl side arms on coordination and extraction properties of tripodal ligands 1 – 3 was studied. Two new ligands 1 and 3 with alkyl substituents of different bulkiness were synthesized and characterized by spectroscopic methods. Single-crystal X-ray structures have been determined for ligands 1 and 2 . The selected coordination chemistry of ligands 1 – 3 with Ln(NO 3 ) 3 (Ln = La, Nd, Lu) has been evaluated. The 1:1 complexes of all ligands 1 – 3 were synthesized and characterized via elemental analysis and IR spectroscopy; in addition, the crystal structure of the ligand 1 complex with neodymium nitrate was determined by X-ray diffraction. Solution structure of 1:1 complexes was examined by IR and multinuclear ( 1 H, 13 C, and 31 P) NMR spectroscopy. A formation of 1:2 complexes with lanthanum and lutetium nitrates (IR, NMR, ESI-MS ) has been examined and structure of the major components of 1:2 complexes solutions has been suggested for ligands 1 – 3 . Preliminary extraction studies of Ln(III) (Ln = La, Nd, Eu, Lu) from 3 M NH 4 NO 3 into 1,2-dichloroethane show that ligands 2 and 3 recover lanthanides much better than their mono analog [2-(Bu 2 NC(O)CH 2 O)-5-Et-C 6 H 3 ]P(O)Ph 2 and known extractant Ph 2 P(O)CH 2 C(O)NBu 2 . [ABSTRACT FROM AUTHOR]

Four new 1-D coordination polymers [Zn(acac)2(L1)] n ( 1 ), [Co(acac) 2 (L1)] n ( 2 ), [Co(acac) 2 (L2)] n ( 3 ) and [Co(acac) 2 (L3)] n ( 4 ) were afforded by the complexation reaction of appropriate zinc and cobalt metal salts, acetylacetone co-ligand as well as three linear electron rich and bi-functional N,N ′-bipyridyl-base ligands of N,N ′-bis(pyridin-4-ylmethylene)naphthalene-1,5-diamine (L1), N,N ′-bis(pyridin-4-ylmethylene) phenylene-1,4-diamine (L2) and N,N ′-bis(pyridin-4-ylmethylene)hydrazine (L3). The structures of these compounds were characterized by FT-IR spectroscopy, elemental analysis, X-ray powder and single crystal X-ray diffractions. X-ray crystallography analyses revealed that these compounds have 1-D linear chain structures a containing {N 2 O 4 } metal coordination environment in which the N -donor Lx (x = 1–3) bridges occupy trans positions. The acetylacetone (acac) ancillary ligands control the coordination number of the metal cation and adopt chelating binding mode on octahedral metal center. Furthermore, 1-D chains are held together with their neighboring ones by C–H⋯O, C–H⋯π and π-π stacking intermolecular interactions to stabilize 2-D supramolecular networks. The two former cases 1 and 2 , containing same L1 spacer ligand generate isomorphous structures. Theoretical calculations invoking electronic properties, frontier molecular orbital description and the strength of interactions between metal ion and coordinated atoms via second order perturbation energies were carried out using natural bond orbital analysis (NBO). Finally, thermal stability of compound 2 – 4 was examined by thermogravimetric (TGA) analysis. [ABSTRACT FROM AUTHOR]

Seeking to increase the selectivity of antimicrobial peptides for prokaryotic cells, we incorporated a bis-dipicolyl amine (bis-DPA) ligand at the N -terminus of de novo designed model peptides. The Zn 2 ·bisDPA complex increases the interaction of peptides with anionic model membranes, while decreasing interactions with zwitterionic model membranes. Further, it improves the peptides’ antimicrobial activity and decreases their hemolytic activity without substantial changes to their secondary structure. Therefore, incorporating a Zn 2 ·bisDPA complex is a useful strategy to enhance the selectivity of antimicrobial peptides. [ABSTRACT FROM AUTHOR]

To gain insight on the role of mixed solvents on the thermodynamic driving forces for the complexation between trivalent f-elements and organic ligands, solution phase thermodynamic parameters were determined for Eu(III) complexation with 2-hydroxyisobutyric acid (HIBA) and 2-aminoisobutyric acid (AIBA) in mixed methanol (MeOH)-water and N,N-dimethylformamide (DMF)-water solvents. Included in this study were the determination of mixed solvent autoprotolysis constants (pK s ) as well as the thermodynamic formation constants: log β, ΔG, ΔH, and ΔS, for ligand protonation and Eu(III)-ligand complexation utilizing potentiometry and calorimetry techniques. The results presented are conditional thermodynamic values determined at an ionic strength of 1.0 M NaClO 4 and a temperature of 298 K. It was found that moving from an aqueous solution to a binary aqueous-organic solvent affected all solution equilibria to some degree and that the extent of change depended on both the type of mixed solvent and the ligand in each study. The ability to understand and predict these changes in thermodynamic values as a function of solvent composition provides important information about the chemistry of the trivalent f-elements. [ABSTRACT FROM AUTHOR]

The stability constants for the Tc(IV) and V(IV) complexation with the polyamino polycarboxylate ligands IDA, NTA, HEDTA and DTPA were determined using liquid-liquid extraction techniques. These stability constants were then used to evaluate the validity of using V(IV) as a chemical analogue for Tc(IV). Results suggest that Tc(IV), as TcOOH, will form β complexes with the selected ligands, while V(IV), as VO, will form β complexes. The values for these determined stability constants are (in log unit) 10.9 ± 0.1, 11.4 ± 0.1, 14.9 ± 0.1, and 20.1 ± 0.1 for Tc(IV) in 0.5 mol·L NaCl at 25 °C, for IDA, NTA, HEDTA and DTPA, respectively, they are 9.3 ± 0.1, 11.6 ± 0.2, 15.8 ± 0.1, and 20.8 ± 0.1 for V(IV) in 0.5 mol·L NaCl at 25 °C, for the same suite of ligands. The incorporation of a hydroxide into the metal ligand complexes formed by Tc(IV) is proposed as the largest factor differentiating the apparent stability constants of Tc(IV) and V(IV). This work shows that V(IV) is a poor analog for Tc(IV); however, despite the differences in complexation mechanism between V(IV) and Tc(IV), V(IV) still appears to have some use for predicting Tc(IV) complexation behavior. [ABSTRACT FROM AUTHOR]

The complexation of the bismalonamide ligand 2,2'-[1,2-phenylenebis(methylene)]bis(N,N,N',N'-tetraethylmalonamide) (L), bearing two C-alkylated N,N,N',N'-tetraethylmalonamide groups, onto an ortho-xylylene [C6H4(CH2)2] platform with trivalent lanthanides was investigated, both in solid and solution states. The crystal structures [Nd2(NO3)6L2]·(CH3CN)3 (2), [Nd2(NO3)4L2]·[Nd(NO3)5]·(CH3CN)1.5 (3), Ce(NO3)3L2 (4), and [NdL2]·(ClO4)3·C2H5OH (5) were analyzed by single-crystal X-ray diffraction. The ortho-bismalonamide (L) is tetradentate in structures 2, 3, and 5 and bidentate in 4 only. It was found that structures 2 and 3 are composed of dimeric species. According to electrospray-ionization mass spectrometry, the dimers are prevailing in acetonitrile solutions. The polydentate coordination of the ortho-bismalonamide (L) with trivalent lanthanides suggests that an entropy effect favors liquid-liquid extraction of metal ions with this type of ligand. [ABSTRACT FROM AUTHOR]

Iron (Fe) bioavailability depends upon its solubility and oxidation state, which are strongly influenced by complexation with natural organic matter (NOM). Despite observations of Fe(II)-NOM associations under conditions favorable for Fe oxidation, the molecular mechanisms by which NOM influences Fe(II) oxidation remain poorly understood. In this study, we used X-ray absorption spectroscopy to determine the coordination environment of Fe(II) associated with NOM (as-received and chemically reduced) at pH 7, and investigated the effect of NOM complexation on Fe(II) redox stability. Linear combination fitting of extended X-ray absorption fine structure (EXAFS) data using reference organic ligands demonstrated that Fe(II) was complexed primarily by carboxyl functional groups in reduced NOM. Functional groups more likely to preserve Fe(II) represent much smaller fractions of NOM-bound Fe(II). Fe(II) added to anoxic solutions of as-received NOM oxidized to Fe(III) and remained organically complexed. Iron oxidation experiments revealed that the presence of reduced NOM limited Fe(II) oxidation, with over 50% of initial Fe(II) remaining after 4 h. These results suggest reduced NOM may preserve Fe(II) by functioning both as redox buffer and complexant, which may help explain the presence of Fe(II) in oxic circumneutral waters. [ABSTRACT FROM AUTHOR]

The results of a potentiometric and calorimetric study on the complexation reactions of neutral N-donor ligands with silver(I) in propylenecarbonate (PC) and dimethylformamide (DMF) are reported. The ligands concerned in DMF are butylamine ( n-but), 1,2-diaminoethane (EN), bis(2-aminoethyl)amine (DIEN) and N, N'-bis(2-aminoethyl)ethane-1,2-diamine (TRIEN) whereas in PC results are provided for EN and DIEN, because of side reactions occurring for n-but and TRIEN. The data are compared to those previously reported in dimethylsulfoxide (DMSO), acetonitrile (AN) and water solvent media which present quite different dielectric constants ( ε) and donor numbers (Dn). The trend of stabilities of the mononuclear AgL and AgL formed is discussed in terms of different cation and amines solvation in the different solvents. TRIEN can form bimetallic species in DMF, but not in DMSO. Given the lower ε value for DMF than for DMSO, AgTRIEN formation is evidently more influenced by the lower solvation of Ag(I) ion in DMF, rather than by difference in dielectric constants of these two solvents. In PC in addition to mononuclear complexes of higher stability with respect to the former solvents, also polynuclear AgL and AgL species are found. [ABSTRACT FROM AUTHOR]

Three new bipyridyl– and pyridylquinolyl–phenothiazine structures were synthesized through Pd-catalyzed C–N couplings between phenothiazine and the corresponding bromo-heteroaryls. For the 2-( N -phenothiazine)-bipyridine, boat conformation was determined for the phenothiazine moiety by X-ray diffraction analysis. Single well-defined palladium acetate complexes were observed by 1 H NMR analysis with the 4-( N -phenothiazine)-bipyridine and the pyridyl-5-( N -phenothiazine)-quinoline. Compared to the naked ligands, the UV–visible absorption spectra showed, in these cases, significantly red shifted λ max upon coordination. Preliminary modeling experiments with the free and the coordinated 4-( N -phenothiazine)-bipyridine suggested for both the occurrence of electronic transfers from the phenothiazine to the bipyridine. Potentially enabling the tuning of the electron density of the coordinating moiety upon near-UV irradiation, this bipyridyl–phenothiazine structure could be the origin of a novel class of photo-active ligands for applications in organometallic catalysis. [ABSTRACT FROM AUTHOR]

The complexation of the Fe ion with 2-hydroxybenzamide (salicylamide, HL) has been studied, at 25.0 °C, by potentiometric measurements with a glass electrode in 1 mol·dm NaClO medium. The concentration of salicylamide ( C ) has been varied between (1 × 10 and 10 × 10) mol·dm, while the concentration of metal cation ( C ) ranged within (0.5 × 10 and 10 × 10) mol·dm. The ligand to metal concentration ratio has been varied between 1 and 10 and the hydrogen ion concentration was decreased stepwise until the incipient precipitation of a basic salt of the metal, which occurred at different values depending on the specific ligand to metal ratio. The experimental data were consistent with the formation of the complexes FeL, Fe(HL)L and $$ {\text{FeL}}_{2}^{ + } $$ . Equilibrium formation constants have been given for the investigated ionic medium as well as for the infinite dilution reference state, evaluated according to the Specific Interaction Theory. The predominant species in neutral solution are $$ {\text{FeL}}_{2}^{ + } $$ and $$ {\text{Fe}}\left( {\text{OH}} \right)_{2}^{ + } $$ . [ABSTRACT FROM AUTHOR]

The superbulky N-heterocyclic carbenes (NHCs) 2,6-bis(diphenylmethyl)-4-methylimidazol-2-ylidene (IDip*Me) and its 4-methoxy analogue (IDip*OMe) reacted instantaneously with carbon disulfide to afford the corresponding imidazolium-2-dithiocarboxylate zwitterions in high yields. These new dithiolate ligands were fully characterized and their coordination chemistry toward common Re(i) and Ru(ii) metal sources was thoroughly investigated. Neutral [ReBr(CO)3(S2C·NHC)] chelates featured three facially-arranged carbonyl groups on a distorted octahedron, whereas cationic [RuCl(p-cymene)(S2C·NHC)]PF6 complexes displayed a piano-stool geometry. The molecular structures of the six new compounds revealed that the NHC·CS2 inner salts were highly flexible. Indeed, the torsion angle between their anionic and cationic moieties varied between ca. 63° in the free ligands and 3° in the ruthenium complexes. Concomitantly, the S–C–S bite angle underwent a contraction from 131° to 110–113° upon chelation. Computation of the %VBur parameter showed that the dithiocarboxylate unit of the NHC·CS2 betaines chiefly determined the steric requirements of the imidazolium moieties, irrespective of the metal center involved in the complexation. The replacement of the p-methyl substituents of IDip*Me with p-methoxy groups in IDip*OMe did not significantly affect the ligand bulkiness. The more electron-donating methoxy group led, however, to small changes in various IR wavenumbers used to probe the electron donor properties of the carbene moiety. [ABSTRACT FROM AUTHOR]

This paper reports the complexation of a series of tetraalkyl diglycolamides (TRDGA) with trivalent f-cations in a room temperature ionic liquid, viz., 3-octyl-1-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C8mim][Tf2N]). The stability constants of TRDGA/Nd3+ complexes (where R = n-pentyl, n-hexyl, n-octyl, n-decyl and 2-ethylhexl) were determined by absorbance spectroscopy. All the DGA ligands formed a 1 : 3 (Nd3+/DGA) complex as the limiting species. Solvent extraction data on Am3+ and Eu3+ were obtained with the TRDGA ligands in [C8mim][Tf2N] to arrive at a correlation between their extraction behaviour and complexation constant. The nature of the complex formed in the single phase titration (in [C8mim][Tf2N]) and those extracted in the [C8mim][Tf2N] medium from the aqueous phase were found to be identical. Fluorescence lifetime data confirmed that, in both single phase titration and biphasic solvent extraction, the complexation proceeded via replacement of water molecules from the primary coordination sphere of the metal ion. The spectroscopic data confirmed the absence of NO3− and Tf2N− ions or H2O in the extracted complexes. [ABSTRACT FROM AUTHOR]

Three 1,4,7-triazacyclononane-based (tacn-based) ligands containing picolyl and picolinate pendant arms (no3py, no2pa1py, and no3pa) were synthesized, and their copper(II) complexation properties were studied to evaluate their potentials as chelators for copper radioisotopes. The thermodynamic stability constants of the complexes were determined by potentiometric titrations. These studies evidenced the formation of mononuclear species for no3py and mono- and dinuclear species for no2pa1py and no3pa. The pCu values decreased as the number of carboxypicolyl arms increased. The [Cu(no3py)]2+ complex presented a very high stability constant (log KCuL = 27.4) and a very high selectivity towards Zn2+ ions (log KZnL = 17.25). Vis/NIR (NIR = near-infrared) absorption and electron paramagnetic resonance (EPR) spectroscopy indicated that the three complexes present distorted octahedral geometries with two paramagnetic species, which were identified as the Δ(δδδ) and Λ(δδδ) isomers [and their corresponding enantiomeric forms Λ(λλλ) and Δ(λλλ)] by DFT calculations. The electrochemical properties were investigated by cyclic voltammetry, which revealed quasireversible behavior for the [Cu(no3py)]2+ complex but irreversible Cu2+Cu+ systems for [Cu(no2pa1py)] and [Cu(no3pa)]-. [ABSTRACT FROM AUTHOR]

Copper(II) complexation reactions with neutral N-donor ligands (Bipy, Phen, NH 3 ) in the presence of the bulky decachloro- closo -decaborate dianion were studied. Copper(II) complexes can be prepared from copper(II) salts or copper(I) salts by redox reactions proceeding in air. The complexes [Cu(Bipy) 3 ][B 10 Cl 10 ]·2CH 3 CN ( 1 ·2CH 3 CN), [Cu(Bipy) 3 ][B 10 Cl 10 ]·2Bipy ( 1 ·2Bipy), [Cu(Bipy) 2 Cl] 2 [B 10 Cl 10 ]·2DMF ( 2 ·2DMF), [Cu(Phen) 2 Cl] 2 [B 10 Cl 10 ]·DMSO·1.25H 2 O ( 3 ·DMSO·1.25H 2 O) and [Cu(NH 3 ) 4 (CH 3 CN) 2 ][B 10 Cl 10 ] ( 4 ) were prepared and characterized by X-ray diffraction as well as IR and 11 B NMR spectroscopies. Complexes 1 ·2CH 3 CN, 2 ·2DMF, and 4 were also studied using 35 Cl NQR spectroscopy. Secondary interactions were selected from all the interatomic contacts found in these crystals by X-ray diffraction. Hydrogen N–H⋯Cl–B, C–H⋯Cl–B and p⋯π (B–Cl⋯C) secondary bonds were identified in all the compounds, the spectroscopic data being generally in accordance with the results of the X-ray diffraction. [ABSTRACT FROM AUTHOR]

The synthesis, characterization, and stability study of the first uranium complex bearing 2,6-diacetylpyridine dioxime (dapdoH 2 ) is reported. The dimeric complex [UO 2 (dapdoH)Cl] 2 is stable in solution as shown by ESI-MS and NMR spectrometry, and its solid-state structure was further analyzed by X-ray crystallography, IR, Raman and luminescence studies. [ABSTRACT FROM AUTHOR]

The shift toward bioavailability-based standards for metals such as copper and zinc not only improves the ecological relevance of the standard but also introduces significant complexity into assessing compliance. This study examined differences in the copper and zinc complexation characteristics of effluents from a range of different sewage treatment works and in relation to so-called 'natural' samples. This information is essential to determine whether the inclusion of effluent-specific complexation characteristics within the regulatory framework could enhance the environmental relevance of compliance criteria. The data show that for copper, binding affinity was not greater than that measured for materials derived from the receiving water environment, with a mean log K of between 4.4 and 5.15 and mean complexation capacity ranging from 38 to 120 μg/mg dissolved organic carbon (DOC) for effluents compared with a log K of 5.6 and complexation capacity of 37 μg/mg DOC for the Suwannee River fulvic acid. For zinc, however, effluents exhibited a much higher complexation capacity, with effluent means ranging from 3 to 23 μg/mg DOC compared with the Suwannee River fulvic acid, for which the complexation capacity could not be determined. Synthetic ligands in sewage effluent, such as ethylenediaminetetraacetic acid (EDTA), are implicated as contributing to these observed differences. This suggests that the current biotic ligand models for zinc might overstate the risk of harm in effluent-impacted waters. The data also show that the copper and zinc complexation characteristics of effluent samples obtained from the same sewage treatment works were less different from one another than those of effluents from other treatment works and therefore that sewage source has an important influence on complexation characteristics. The findings from this study support the case that the contribution to complexation from effluent-derived ligands could enhance the environmental relevance of bioavailability-based compliance criteria, in particular for zinc, owing to the additional complexation capacity afforded by effluent-derived ligands. [ABSTRACT FROM AUTHOR]

A combined experimental and theoretical study has been put forward to investigate the complexation behaviour of tetravalent Pu 4+ and hexavalent UO 2 2+ ions with the N,N-dihexyloctanamide (DHOA) ligand in different diluents. Solvent extraction experiments were conducted with Pu 4+ and UO 2 2+ ions using DHOA in different diluents, namely dodecane, toluene, chloroform, octanol, nitrophenyl-octyl ether (NPOE) and nitrobenzene (NB). The experimentally measured distribution coefficients (D) of both the Pu 4+ and UO 2 2+ ions followed the order: nitrobenzene > NPOE > octanol > chloroform > toluene > dodecane. In order to complement the experimental distribution data, the structure, energetic and thermodynamic parameters of the Pu 4+ and UO 2 2+ complexes with DHOA have been calculated using density functional theory. The free energy of extraction, Δ G ext , for the Pu 4+ and UO 2 2+ ions with DHOA was calculated using the Born–Haber thermodynamic cycle in the different experimentally studied diluents. The value of Δ G ext for the Pu 4+ ion in dodecane was found to be higher than that of the UO 2 2+ ion, as measured in the experiments. The value of Δ G ext was shown to increase with the increase in the dielectric constant of the diluent for both Pu 4+ and UO 2 2+ ions, similar to the experimental studies. Thus, the combined experimental and theoretical studies help to understand the underlying complexation mechanism of the UO 2 2+ and Pu 4+ ions with DHOA, which explains its selectivity towards the Pu 4+ ion. [ABSTRACT FROM AUTHOR]

Four new Schiff base ligands carrying naphthalene groups were prepared from the reaction of 2,4-diamino-6-methyl-1,3,5-triazine and 2,4-diamino-6-undecyl-1,3,5-triazine with 2-hydroxy-1-naphthaldehyde. The influence of a series of metal ions including Cu, Co, Hg, Al, Cr, Fe, Pb, Ni, Cd, Zn, Mn, Ag, Ba, Ca and Mg on the spectroscopic properties of the ligands was investigated by means of absorption and emission spectrometry. The results of spectrophotometric and spectrofluorimetric titrations disclosed the complexation stoichiometry and complex stability constant of the ligands with metal ions. A simple spectrofluorimetric method was developed using the Schiff base derived from 2,4-diamino-6-undecyl-1,3,5-triazine to determine Hg ion. No cleanup or enrichment of the tap water sample was required. A modified standard addition method was used to eliminate matrix effect. The standard addition graph was linear between 0.2 and 2.6 mg/L in determination of Hg. Detection and quantification limits were 0.08 and 0.23 mg/L, respectively. The simple and cost-effective method can be applied to water samples. [ABSTRACT FROM AUTHOR]

The fluorescence quantum yield of the 5,10,15,20-tetraphenylporphyrin, 5,10,15,20-tetra(4-OH-phenyl)porphyrin, 5,10,15,20-tetra(4-Cl-phenyl)porphyrin, 5,10,15,20-tetra(4-NH-phenyl)porphyrin and their complexes with Zn have been determined and the kinetic rate constants of the porphyrins ligands complexation with Zn in acetonitrile have been estimated. It was shown that the substituents on the tetrapyrrolic macrocycle periphery have a strong influence on the fluorescent and coordination properties of the investigated porphyrins. [ABSTRACT FROM AUTHOR]

One of the bipyridines of a [Ru(bpy) 3 ] 2+ core has been substituted at its 5 position by a terpyridine chelating unit through an ether bridge. The modification has only a minor influence on the photophysical and electrochemical properties of the Ru(II) complex. This metallo-ligand ( C1 ) is used to obtain two trimetallic structures [Ru II –Co III –Ru II ] 7+ and [Ru II –Fe II –Ru II ] 6+ in solution by complexation of the corresponding metallic ion to the terpyridine site. Under irradiation, an efficient intramolecular electron transfer process occurs in [Ru II∗ –Co III –Ru II ] 7+ with a kinetic rate constant of 9 × 10 6 s −1 resulting in the formation of [Ru III –Co II –Ru II ] 7+ . In the presence of a sacrificial electron donor, continuous irradiation leads to the reduced species [Ru II –Co II –Ru II ] 6+ . On the other hand, [Ru II∗ –Fe II –Ru II ] 6+ follows a deactivation pathway through an energy transfer process with a rate constant of 2 × 10 8 s −1 . This energy transfer is not total and can be short-circuited in the presence of an external electron acceptor to form the oxidized [Ru II –Fe III –Ru II ] 7+ . Based on these results in solution, C1 has been used in a stepwise approach to construct two photoelectrodes on ITO taking advantage of the strong self-assembling interaction between phosphonates with ITO surface and terpyridine ligands with first row transition metals. The luminescence lifetimes of the resulting dyads on surface are drastically lowered compared to the systems in solution. ITO/[Co III –Ru II ] 5+ behaves as a photoanode in presence of TEOA as sacrificial electron donor and ITO/[Fe II –Ru II ] 4+ as a photocathode in presence of ArN 2 + as sacrificial electron acceptor. The photocurrent magnitude depends on the coverage value and increases linearly with the power of the irradiation light, proving the good photostability of these ITO-dyads modified surfaces. Association of both photoelectrodes in a photoelectrochemical cell would result in a gain of 0.8 V. [ABSTRACT FROM AUTHOR]

Enthalpies of complexation of diglycine (HL±) with Pr3+ and Sm3+ ions at 303.15 K and I = 0.5 (KNO3) have been determined by means of calorimetry. The thermodynamic parameters of the formation of diglycine complexes with Pr3+ and Sm3+ ions have been calculated at different molar ratios between metal and the ligand. [ABSTRACT FROM AUTHOR]

The new ligand L was prepared and features a 13-membered tetraaza macrocyclic ring with a 1,8-naphthalimide fluorophore appended to a C atom of its backbone. The protonation constants of L as well as its complexation constants with Zn2+ ions were determined in 1:1 water/methanol solutions by potentiometric titrations. Fluorimetric pH titrations were performed with L alone and L in the presence of Zn2+ ions (1:1), and the species distributions (%) versus pH were compared. A window-shaped fluorescence trend was observed with pH for the L/Zn2+ system, which behaves as an off-on-off pH sensor. The on window is centred in the 6.5-7.5 pH range, in correspondence with the formation of [ZnL]2+. The ligand L also works as a sensor for Zn2+ ions in this pH window, which includes the physiological pH value (7.4). Accordingly, L was used as a probe for the visualization of the Zn2+ pools in Saccharomyces cerevisiae yeast cells at pH 7.4 and has the additional ability to distinguish between living and dead cells. [ABSTRACT FROM AUTHOR]

By complexing a nonionic G-quadruplex ligand with hybrid dual-emission quantum dots (QDs), a ratiometric fluorescent nanoprobe is developed for G-quadruplex detection in a sensitive and specific manner. The QDs nanohybrid comprised of a green-emission QD (gQD) and multiple red-emission QDs (rQDs) inside and outside of a silica shell, respectively, is utilized as the signal displaying unit. Only the presence of G-quadruplex can displace the ligand from QDs, breaking up the QDs--ligand complexation, and inducing the restoration of the rQDs fluorescence. Since the fluorescence of embedded gQD stays constant, variations of the dual-emission intensity ratios display continuous color changes from green to bright orange, which can be clearly observed by the naked eye. Furthermore, by utilizing competitive binding of a cationic ligand versus the nonionic ligand toward G-quadruplex, the nanoprobe is demonstrated to be applicable for assessing the affinity of a G-quadruplex-targeted anticancer drug candidate, exhibiting ratiometric fluorescence signals (reverse of that for G-quadruplex detection). By making use of the specificity of the ligand binding with G-quadruplex against a double helix, this nanoprobe is also demonstrated to be capable of sensitive detection of one-base mutation, exhibiting sequence-specific ratiometric fluorescence signals. By functionalizing with a nuclear localization peptide, the nanoprobe can be used for visualization of G-quadruplex in the nucleus of human cells. [ABSTRACT FROM AUTHOR]

In the present work the modular synthesis of new chelating bisphosphite ligands based on 9,10-brigded 9,10-dihydroanthracenes as ligand backbones is presented. The complexation behavior of these ligands in rhodium metal complexes as well as mechanistic studies of the preformation step of the rhodium-catalysed hydroformylation is investigated. Ratio of coordination isomers in the Rh complexes of these ligands has been determined using NMR based calculation technique. Modular synthesis route was established allowing for a variety of ligands to be synthesized in a standard procedure The new ligands were tested in the hydroformylation of 4-pentenal under optimized conditions to give adipic aldehyde a promising starting material for the polyamide nylon-6,6. Ligand L3 showed the best selectivity towards adipic aldehyde with selectivity of 10.2/1 n/iso aldehyde. [ABSTRACT FROM AUTHOR]

A series of tridentate, ONO- and ONN-chelating β-ketiminate ligands were synthesised via condensation reactions, and complexed with iron(ii) using [Fe(N(SiMe3)2)2THF]. The complexation reactions proceeded in high yields to generate novel, monomeric, tetracoordinate iron(ii) complexes, each bearing a bis(trimethylsilyl)amide ligand, as confirmed by X-ray crystallography. These complexes were amenable to further reaction (protonolysis) with alcohols and phenols, generating alkoxide/phenolate-containing complexes that were dimeric in the solid state. All complexes synthesised were screened as potential mediators of the controlled radical polymerisation (CRP) of styrene and methyl methacrylate under both atom transfer radical polymerisation (ATRP) and organometallic mediated radical polymerisation (OMRP) conditions. Whilst all of the complexes were relatively poor ATRP mediators under the conditions used here, regardless of monomer choice, dispersities (Đ) as low as 1.58 for styrene and 1.23 for methyl methacylate polymerisation under OMRP conditions could be achieved. The better performance in methacrylate polymerisation suggests the formation of a stronger metal–carbon bond in these systems. In particular, the use of a β-ketiminate ligand functionalised with an N,N-dimethylethylene pendant arm and a 2,6-diphenylphenolate ligand affords a potential Fe-based mediator of methyl methacrylate OMRP. [ABSTRACT FROM AUTHOR]

A straightforward synthesis of a sterically hindered and electron rich bidentate monophosphine biaryl ligand Sym -Phos of C,P-type of complexation was realised in a high yield starting from simple substrates in easily affordable conditions. In combination with a palladium source, the obtained ligand formed a highly active catalyst mediating sterically demanding Suzuki–Miyaura coupling reactions in aqueous media even at 60 °C and with no need to protect the reaction mixture by an inert gas. [ABSTRACT FROM AUTHOR]