Pr Complexes Research Articles

Synthesis, structure and thermal behavior of volatile mononuclear mixed ligand complexes of rare-earth dipivaloylmethanates with diethylenetriamine

Highly volatile and stable complexes of rare-earth elements with mononuclear structure are of great importance for gas phase deposition of functional thin film materials. Mixed ligand complexes with β-diketonate anions (e.g. thd− = 2,2,6,6-tetrametylheptane-3,5-dionate) and ancillary neutral donor ligands demonstrate mononuclear structure and sufficient volatility, however, they are unstable to neutral ligand elimination especially in case of light rare earth elements. Here diethylenetriamine (deta) has been applied as tridentate neutral ligand to improve the stability of mixed ligand complexes due to macrochelate effect and additional weak intramolecular interactions, e.g. hydrogen bonds. Synthesis of a series of mixed-ligand [Ln(thd)3(deta)], Ln = La (1L), Pr (2L), Nd (3L), Sm (4L) and Gd (5L) complexes, their X-ray single crystal structure characterization, DFT calculations, and thermal behavior study have been performed. Compounds 1L-5L demonstrate similar mononuclear molecular structure, but different molecular packing of three types, which may undergo mutual transformation. Compounds 1L-4L sublime intact in temperature range of 140–160 °C in vacuum without decomposition. 1L was successfully applied as volatile precursors for MOCVD preparation of epitaxial complex oxide thin films, (0 0 l) LaMnO3 and (0 0 l) LaAlO3, on (0 0 l) MgO and (0 0 l) SrTiO3 substrates.

Cyclodextrin potentiometric sensors based on selective recognition sites for procainamide: Comparative and theoretical study

AbstractPolyvinyl chloride (PVC) membrane sensors were constructed and developed for the determination of procainamide HCl (PR). Three membrane sensors incorporating α-, β- and γ- cyclodextrin (CD) as ionophores with potassium tetrakis (4-chlorophenyl) borate (KTpClPB) as the ion additive, o-nitro phenyl ether (o-NPOE) as the plasticizer and a PVC matrix. The reaction mechanisms were based on inclusion complexes. The developed α- and β- CD sensors exhibited near-Nernstian profile, whereas γ- CD showed a non-Nernstian response. At pH 4 -8, the sensors exhibited a calibration range for PR of 10-3to 10−6, and the detection limits were 2.40 × 10-6, 2.12 × 10-6, 2.40 × 10-6for α-, β- and γ- CD sensors, respectively. Interference was investigated by studying the selectivity coefficient values of the test sensors, which indicated that the methods were free from interference from investigated species. The determination of PR exhibited high recovery and favorable relative standard deviation using the investigated sensors. The sensors were subsequently used for the quantification of PR in a pharmaceutical formulation and the potentiometric results agreed with those of a spectrophotometric method. A molecular docking (MD) study was used to predict the structure of the inclusion complexes of PR (guest) and α- or β- or γ-CD (host). The study results indicated that the formed complexes were stable with sufficient binding energy.

Planar and sandwich-type Pr(III) and Nd(III) chlorinated phthalocyaninates: Synthesis, thermal stability and optical properties

A direct synthetic approach to four single-decker and one double-decker novel Pr(III) and Nd(III) complexes with 2,3,9,10,16,17,23,24-octachlorophthalocyaninate and 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecachlorophthalocyaninate has been developed. Synthesis of hexadeca-Cl-substituted Nd(III) bisphthalocyaninate has been carried out utilizing two preformed synthetic blocks: Nd(III) octachlorophthalocyaninate acetate and octachlorophthalocyanine ligand. Due to the electron withdrawing effect of 16 chlorine groups, this Nd(III) bisphthalocyaninate was obtained as a redox stable anionic form. Upfield lanthanide-induced shifts of the aromatic proton signals (up to 2.04 ppm for Pr(III) octachlorophthalocyaninate acetate) were observed in the 1H NMR spectra of the obtained phthalocyaninates. Thermal stability of the lanthanide (III) complexes was examined using thermogravimetric analysis combined with mass-spectrometry. The double-decker compound was shown to possess an increased thermal stability in comparison with the single-deckers up to ~400 °C. Linear and nonlinear optical properties of the Cl-substituted Nd(III) and Pr(III) phthalocyaninates have been investigated using z-scan technique. The best nonlinear optical response with the highest excited state absorption cross-section (σ1 = 1.1 × 10−15 cm−2) was found for the hexadeca-Cl-substituted Nd(III) monophthalocyaninate.

Investigation of Photocatalytic Activity of Anchored Dysprosium and Praseodymium Complexes on CoFe2O4 in Synthesis of Pyrano[2,3‐d]pyrimidine Derivatives

AbstractTwo hitherto unknown magnetic nanoparticles were prepared through the immobilization of Dysprosium (Dy) and Praseodymium (Pr) Complexes on the surface of CoFe2O4, using commercially available or easily accessible materials under green conditions. They were fully characterized, using, FT‐IR, SEM, EDX, ICP‐OES, XRD and TGA techniques. Photocatalytic activity of these nanocomposites were successfully examined in the high yielding synthesis of pyrano[2,3‐d]pyrimidines, via MCR, involving, barbituric acid, malononitrile and differently substituted benzaldehydes in the UV region (250 nm) at room temperature. The above‐mentioned photocatalysts showed excellent recoverability and reusability under the optimal reaction conditions.

Potent antiviral HIV-1 protease inhibitor combats highly drug resistant mutant PR20

Drug-resistance threatens effective treatment of HIV/AIDS. Clinical inhibitors, including darunavir (1), are ineffective for highly resistant protease mutant PR20, however, antiviral compound 2 derived from 1 with fused tricyclic group at P2, extended amino-benzothiazole P2’ ligand and two fluorine atoms on P1 shows 16-fold better inhibition of PR20 enzyme activity. Crystal structures of PR20 and wild-type PR complexes reveal how the extra groups of 2 counteract the expanded ligand-binding pocket, dynamic flaps, and faster dimer dissociation of PR20.

Synthesis and 4f 4f absorption studies of tris(acetylacetonato)praseodymium(III) and holmium(III) complexes with imidazole and pyrazole in non-aqueous solvents. Structure elucidation by Sparkle / PM7

The complexes [Pr(acac)3(im)2], [Pr(acac)3(pz)], [Ho(acac)3(im)] and [Ho(acac)3(pz)] (acac is the anion of acetylacetone, im is imidazole and pz is pyrazole) were synthesized and characterized by elemental and thermal analyses, IR and NMR spectroscopy. The ground state molecular structures were obtained using semi-empirical Sparkle/PM7 method. The optimized structures reflect the effect of lanthanide contraction along the lanthanide series as the average Ho—O and Ho—N distances are found shorter than the average Pr—O and Pr—N distances. The size of the lanthanide also affects the overall geometry of the complex. It can be seen in the homologous [Pr(acac)3(pz)] and [Ho(acac)3(pz)] complexes with pentagonal bipyramidal (D5h) and capped trigonal prism (C2v) geometries, respectively. The 4f 4f absorption spectra of the complexes recorded in different non-aqueous solvents are presented and analyzed. The oscillator strength of 3P2 ← 3H4,1D2 ← 3H4 transitions in the case of Pr(III) complexes and 5G6 ← 5I8 transition in the case of Ho(III) complexes, show remarkable changes upon a change in the ancillary ligand and/or solvent. The band shape of 3P2 ← 3H4 transition of both the Pr(III) complexes in pyridine show remarkable change and suggests influence of pyridine in changing the inner-coordination sphere of the complexes. The band shape of the hypersensitive 5G6 ← 5I8 transition of the Ho(III) complexes show appreciable change on changing the ligand/solvent. The paramagnetic shift obtained for these complexes are predominantly dipolar in nature.

Structural studies of antiviral inhibitor with HIV-1 protease bearing drug resistant substitutions of V32I, I47V and V82I

HIV-1 protease inhibitors are effective in HIV/AIDS therapy, although drug resistance is a severe problem. This study examines the effects of four investigational inhibitors against HIV-1 protease with drug resistant mutations of V32I, I47V and V82I (PRTri) that model the inhibitor-binding site of HIV-2 protease. These inhibitors contain diverse chemical modifications on the darunavir scaffold and form new interactions with wild type protease, however, the measured inhibition constants for PRTri mutant range from 17 to 40 nM or significantly worse than picomolar values reported for wild type enzyme. The X-ray crystal structure of PRTri mutant in complex with inhibitor 1 at 1.5 Å resolution shows minor changes in interactions with inhibitor compared with the corresponding wild type PR complex. Instead, the basic amine at P2 of inhibitor together with mutation V82I induces two alternate conformations for the side chain of Arg8 with new interactions with inhibitor and Leu10. Hence, inhibition is influenced by small coordinated changes in hydrophobic interactions.

Mechanism of Enhanced Immature Dengue Virus Attachment to Endosomal Membrane Induced by prM Antibody

Dengue virus (DENV) particles are released from cells in different maturation states. Fully immature DENV (immDENV) is generally non-infectious, but can become infectious when complexed with anti-precursor membrane (prM) protein antibodies. It is unknown how anti-prM antibody-coated particles can undergo membrane fusion since the prM caps the envelope (E) protein fusion loop. Here, we determined cryoelectron microscopy (cryo-EM) maps of the immDENV:anti-prM complex at different pH values, mimicking the extracellular (pH 8.0) or endosomal (pH 5.0) environments. At pH 5.0, there are two structural classes with fewer antibodies bound than at pH 8.0. These classes may represent different maturation states. Molecular simulations, together with the measured high-affinity pr:antibody interaction (versus the weak pr:E interaction) and also the low pH cryo-EM structures, suggest how antibody:pr complex can dislodge from the E protein at low pH. This exposes the E protein fusion loop enhancing virus interaction with endosomes.

Electronic and fluorescent studies on the interaction of DNA and BSA with a new ternary praseodymium complex containing 2,9-dimethyl 1,10-phenanthroline and antibacterial activities testing

In this study, fluorescence emission spectra, UV–vis absorption spectra, ethidium bromide (EB)-competition experiment, and iodide quenching experiment were used for the interaction study of the Fish salmon DNA (FS-DNA) with [Pr(dmp)2Cl3(OH2)] where dmp is 2,9-dimethyl 1,10-phenanthroline. The binding constant and the number of binding sites of the complex with FS-DNA were 6.09 ± 0.04 M−1 and 1.18, respectively. The free energy, enthalpy, and entropy changes (ΔG°, ΔH°, and ΔS°) in the binding process of the Pr(III) complex with FS-DNA were –8.02 kcal mol−1, +39.44 kcal mol−1, and +159.56 cal mol−1 K−1, respectively. Based on these results, the interaction process between FS-DNA with [Pr(dmp)2Cl3(OH2)] was spontaneous and the main binding interaction force was groove binding mode. Also, Fluorescence and electronic absorption spectroscopy were used in order to evaluate the binding characteristics, stoichiometry, and interaction mode of praseodymium(III) (Pr(III)) complex with bovine serum albumin (BSA). Title complex showed good binding propensity to BSA presenting moderately high Kb values. The fluorescence quenching of BSA by Pr(III) complex has been observed to be the static process. The positive ΔH° and ΔS° values showed that the hydrophobic interaction is the main force in the binding of Pr(III) complex and BSA. Eventually, the average aggregation number, <J>, of BSA potentially induced by title complex confirmed the 1:1 stoichiometry for title complex-BSA adducts. In vitro, antimicrobial activity of title complex was indicated that the complex is more active against both Escherichia coli and Enterococcus faecalis bacterial strains than Staphylococcus aureus, and Pseudomonas aeruginosa.Communicated by Ramaswamy H. Sarma

Mononuclear Lanthanide(III)-Salicylideneaniline Complexes: Synthetic, Structural, Spectroscopic, and Magnetic Studies

The reactions of hydrated lanthanide(III) [Ln(III)] nitrates and salicylideneaniline (salanH) have provided access to two families of mononuclear complexes depending on the reaction solvent used. In MeCN, the products are [Ln(NO3)3(salanH)2(H2O)]·MeCN, and, in MeOH, the products are [Ln(NO3)3(salanH)2(MeOH)]·(salanH). The complexes within each family are proven to be isomorphous. The structures of complexes [Ln(NO3)3(salanH)2(H2O)]·MeCN (Ln = Eu, 4·MeCN_Eu, Ln = Dy, 7·MeCN_Dy; Ln = Yb, 10·MeCN_Yb) and [Ln(NO3)3(salanH)2(MeOH)]·(salanH) (Ln = Tb, 17_Tb; Ln = Dy, 18_Dy) have been solved by single-crystal X-ray crystallography. In the five complexes, the LnIII center is bound to six oxygen atoms from the three bidentate chelating nitrato groups, two oxygen atoms from the two monodentate zwitterionic salanH ligands, and one oxygen atom from the coordinated H2O or MeOH group. The salanH ligands are mutually “cis” in 4·MeCN_Eu, 7·MeCN_Dy and 10·MeCN_Yb while they are “trans” in 17_Tb and 18_Dy. The lattice salanH molecule in 17_Tb and 18_Dy is also in its zwitterionic form with the acidic H atom being clearly located on the imine nitrogen atom. The coordination polyhedra defined by the nine oxygen donor atoms can be described as spherical tricapped trigonal prisms in 4·MeCN_Eu, 7·MeCN_Dy, and 10·MeCN_Yb and as spherical capped square antiprisms in 17_Tb and 18_Dy. Various intermolecular interactions build the crystal structures, which are completely different in the members of the two families. Solid-state IR data of the complexes are discussed in terms of their structural features. 1H NMR data for the diamagnetic Y(III) complexes provide strong evidence that the compounds decompose in DMSO by releasing the coordinated salanH ligands. The solid complexes emit green light upon excitation at 360 nm (room temperature) or 405 nm (room temperature). The emission is ligand-based. The solid Pr(III), Nd(III), Sm(III), Er(III), and Yb(III) complexes of both families exhibit LnIII-centered emission in the near-IR region of the electromagnetic spectrum, but there is probably no efficient salanH→LnIII energy transfer responsible for this emission. Detailed magnetic studies reveal that complexes 7·MeCN_Dy, 17_Tb and 18_Dy show field-induced slow magnetic relaxation while complex [Tb(NO3)3(salanH)2(H2O)]·MeCN (6·MeCN_Tb) does not display such properties. The values of the effective energy barrier for magnetization reversal are 13.1 cm−1 for 7·MeCN_Dy, 14.8 cm−1 for 17_Tb, and 31.0 cm−1 for 18_Dy. The enhanced/improved properties of 17_Tb and 18_Dy, compared to those of 6_Tb and 7_Dy, have been correlated with the different supramolecular structural features of the two families. The molecules [Ln(NO3)3(salanH)2(MeOH)] of complexes 17_Tb and 18_Dy are by far better isolated (allowing for better slow magnetic relaxation properties) than the molecules [Ln(NO3)3(salanH)2(H2O)] in 6·MeCN_Tb and 7·MeCN_Dy. The perspectives of the present initial studies in the Ln(III)/salanH chemistry are discussed.

Reactivity of Ln(II) Complexes Supported by (C5H4Me)1– Ligands with THF and PhSiH3: Isolation of Ring-Opened, Bridging Alkoxyalkyl, Hydride, and Silyl Products

Reduction of CpMe3Ln(THF), 1-Ln (Ln = La and Gd; CpMe = C5H4Me), with KC8 in the presence of 2.2.2-cryptand (crypt) generates dark solutions, 2-Ln, with EPR spectra consistent with Ln(II) complexes: an eight-line hyperfine pattern for La at g = 1.971 and a broad single line for Gd at g = 1.988. The solutions decompose within minutes, and in the La system, a decomposition product was isolated in which a molecule of THF had been reduced by two electrons and ring-opened to generate an alkoxyalkyl-bridged bimetallic La(III) complex, [K(crypt)]2[(CpMe3La)2(μ-OCH2CH2CH2CH2)], 3-La. An analogous Pr complex, 3-Pr, was also crystallographically characterized. Since decomposition products were not readily isolated from the analogous yttrium CpMe3Y(THF)/KC8/crypt reaction, the composition of the solution of 2-Y was probed by addition of the hydrogen delivery reagent, PhSiH3, which had previously been reported to form U(III) hydrides from tris(cyclopentadienyl) U(II) complexes. This generated an Y(III) silyl complex,...

New complexes of light lanthanides with the valsartan in the solid state: Thermal and spectroscopic studies

New lanthanides complexes with valsartan drug (H2Val) with stoichiometry Ln2(Val)3⋅nH2O (Ln = La, Ce, Pr, Nd and Sm) were obtained by reacting a solution of the lanthanide nitrate with a solution of valsartan sodium salt. The complexes were characterized by simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC) in dry air and nitrogen atmospheres, Evolved gas analysis (EGA) by TG-DSC-FTIR, Elemental Analysis (EA), complexometry with EDTA, Fourier transform Infrared and Raman (FTIR and FT-Raman) spectroscopy, UV–vis spectroscopy and Powder X-Ray Diffraction (PXRD). The thermal decomposition of the complexes differed in dry air atmosphere with four steps for Ce, five for La and Pr and six for Nd and Sm. In nitrogen atmosphere all the complexes had a similar behavior, with three mass loss steps up to 1000 °C, leading to the formation of a mixture of carbonized material and metal oxide. The main gaseous products released during the thermal decomposition of these compounds were nitrous oxide, carbon dioxide and carbon monoxide (in air atmosphere), ammonia, nitrous oxide, carbon dioxide, carbon monoxide, and an unsaturated ketone or a mixture of unsaturated hydrocarbon and a ketone (in nitrogen atmosphere). The PXRD data suggest that the compounds are amorphous; the FTIR spectra suggests coordination of the ligand by the tetrazole ring, and by the carboxylate group as monodentate ligand; finally, the UV–vis spectra of the Pr, Nd and Sm complexes provided information about the degree of covalence of each compound.

An 17 O NMR study of diamagnetic and paramagnetic lanthanide-tris(oxydiacetate) complexes in aqueous solution.

17 O-enriched complexes between oxydiacetate ligand and several diamagnetic and paramagnetic lanthanide(III) metal ions (Ln) were investigated by solution-state 17 ONMR spectroscopy. The bound-state signals of chelating (Oin ) and nonchelating (Oout ) oxygen atoms of the carboxylate groups were observed for all the samples investigated. The data indicate that the 17 Oline width is dominated by contributions from both quadrupole relaxation and chemical exchange in the case of Pr and Nd complexes. Dissection of the chemical shift induced by metal ions on Oin into Fermi contact and pseudocontact contributions was performed , and the hyperfine coupling constant (A/ℏ) was estimated. No evidence of structural changes within the series was detected.

Synthesis, crystal structure and optical properties of new (Nd, Sm) and other lanthanide (Ln = Pr) complexes with 1,10-phenanthroline and thiocyanate

New types of neodymium, samarium and other light lanthanide (Pr) mixed complexes with thiocyanate (NCS) and 1,10-phenanthroline (Phen) were synthesized in solution and as crystals. It was found that these complexes crystallized with the formulae: (phen)·[Nd(phen)2(NCS)4] (1) and [Ln(phen)3(NCS)3]·EtOH (Ln = Sm(2), Pr(3)). The Pr and Sm complexes are isostructural (space group P1¯), but the Nd compound was different (space group P21/n). Compound (1) crystallizes in a monoclinic system with space group P21/n and the following unit cell parameters: a = 12.097(2), b = 16.444(3), c = 19.202(3)Å, β = 93.46(2)°.The optical spectra of these two types of rare-earth compounds were performed at room and low temperatures in order to understand the electrostatic nature of the Ln3+N coordination bonds. The high values of absorption spectral intensities at 293 K for Nd3+ or Pr3+ show low symmetries for these metal centres. The absorption spectrum analysis at 4.2 K and the correlation of the results with the IR spectra of the monocrystals of (phen)·[Nd(phen)2(NCS)4] and [Pr(phen)3(NCS)3]·Et(OH) make it possible to account for vibronic transitions. The observed Stark splitting of f–f transitions for Ln3+ ions in the emission spectra at 77 K for Sm3+ is in agreement with that predicted by group theory for a single low-symmetry Ln3+ ion site. In the absorption spectra, a ‘red shift’ was observed for hypersensitive transitions of lanthanide ions. The variation of the spectroscopic parameters of the title compounds, calculated based on the absorption spectra, the nephelauxetic ratio β, Sinha’s parameter δ and their correlation with the nature of the Ln3+N bond, are discussed.

Metal versus Ligand Reduction in Ln3+ Complexes of a Mesitylene-Anchored Tris(Aryloxide) Ligand.

The synthesis of 4f n Ln3+ complexes of the tris(aryloxide) mesitylene ligand, ((Ad,MeArO)3mes)3-, with Ln = La, Ce, Pr, Sm, and Yb, and their reduction with potassium have revealed that this ligand system can be redox active with some metals. Protonolysis of [Ln(N(SiMe3)2)3] (Ln = La, Ce, Pr, Sm, Yb) with the tris(phenol) (Ad,MeArOH)3mes yielded the Ln3+ complexes [((Ad,MeArO)3mes)Ln] (Ln = La, Ce, Pr, Sm, Yb), 1-Ln. Single electron reduction of each 4f n complex, 1-Ln, using potassium yielded the reduced products, [K(2.2.2-cryptand)][((Ad,MeArO)3mes)Ln] (Ln = La, Ce, Pr, Sm, Yb), 2-Ln. The Sm and Yb complexes have properties consistent with the presence of Ln2+ ions with traditional 4f n+1 electron configurations. However, the La, Ce, and Pr complexes appear to formally contain Ln3+ ions and ((Ad,MeArO)3mes)4- ligands. Structural comparisons of the [((Ad,MeArO)3mes)Ln] and [((Ad,MeOAr)3mes)Ln]1- complexes along with UV-vis absorption and EPR spectroscopy as well as density functional theory calculations support these ground state assignments.

Structural Basis for Dengue Virus Antibody Dependent Maturation

Event Abstract Back to Event Structural basis for dengue virus antibody dependent maturation Jan K. Marzinek1 and Peter J. Bond1* 1 Bioinformatics Institute (A*STAR), Singapore Background Dengue virus (DENV) is responsible for millions of infections a year around the world. DENV is composed of an RNA genome complexed with capsid (C) proteins, which are surrounded by envelope (E) and membrane (M) proteins embedded within a lipid bilayer. In nascent viral particles, the pre-membrane (prM) protein caps the fusion loop of the E protein, making it non-fusogenic. During maturation, cleavage of prM into the M protein and release of pr leads to a conformational change in the E protein that makes it fusion-competent. Interestingly, DENV is known to be released from cells under different states of maturation. Fully immature DENV (immDENV) is non-infectious. However, its infectivity can be enhanced when DENV is targeted by host anti-prM antibodies. The molecular basis for this antibody-dependent enhancement has until recently been unknown. Methods In this work, cryo-electron microscopy (cryo-EM) structures of the immDENV:anti-prM complex at acidic and neutral pH conditions mimicking the endosomal and extracellular environments respectively were analyzed via integrative modeling and simulation approaches. Results At acidic pH, an intermediate structure of the DENV maturation pathway has been solved with fewer antibodies bound in comparison to neutral pH. Based on previously developed multiscale models of the DENV particle, we employed sets of targeted molecular dynamics (TMD) simulations in order to trigger the maturation transition at low pH. Hydrogen-deuterium exchange mass spectroscopy and Elisa measurements confirmed that the affinity of the antibody:pr complexes are stronger than those of the pr:E complexes, and the TMD simulations revealed dislodgement of antibody:pr from the E protein surface during the conformational transition due to steric clashes. Conclusion Here, we provide the detailed molecular mechanism by which anti-prM antibodies enhance maturation of DENV in the acidic endosomal environment, leading to exposure of the E protein fusion loops for subsequent endosomal membrane binding and fusion. Acknowledgements National Research Foundation: CRP Grant Number: NRF2017-CRP001-027 Keywords: Dengue virus maturation, cryo-electron microscopy, antibody, PRM, Molecular dynamic simulations Conference: International Conference on Drug Discovery and Translational Medicine 2018 (ICDDTM '18) “Seizing Opportunities and Addressing Challenges of Precision Medicine”, Putrajaya, Malaysia, 3 Dec - 5 Feb, 2019. Presentation Type: Oral Presentation Topic: Infectious diseases Citation: Marzinek JK and Bond PJ (2019). Structural basis for dengue virus antibody dependent maturation. Front. Pharmacol. Conference Abstract: International Conference on Drug Discovery and Translational Medicine 2018 (ICDDTM '18) “Seizing Opportunities and Addressing Challenges of Precision Medicine”. doi: 10.3389/conf.fphar.2018.63.00082 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 30 Sep 2018; Published Online: 17 Jan 2019. * Correspondence: Dr. Peter J Bond, Bioinformatics Institute (A*STAR), Singapore, Singapore, peterjb@bii.a-star.edu.sg Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Jan K Marzinek Peter J Bond Google Jan K Marzinek Peter J Bond Google Scholar Jan K Marzinek Peter J Bond PubMed Jan K Marzinek Peter J Bond Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Synthesis, Crystal Structure, Gas Absorption, and Separation Properties of a Novel Complex Based on Pr and a Three-Connected Ligand

A novel Pr complex, constructed from a rigid three-connected H3TMTA and praseodymium(III) ion, has been synthesized in a mixed solvent system and characterized by X-ray single crystal diffraction, infrared spectroscopy, a thermogravimetric analysis, an element analysis, and powder X-ray diffraction, which reveals that complex 1 crystallizes in a three-dimensional porous framework. Moreover, the thermal stabilities and the fluorescent and gas adsorption and separation properties of complex 1 were investigated systematically.

Preparation, spectral properties and thermal decomposition of new ternary complexes of La(III), Ce(III), Pr(III) and Nd(III) ions with N-phenylanthranilic acid and 1,10-phenanthroline

The new ternary complexes of the formula Ln2(nfa)5(phen)(OH)·nH2O (where n = 1 or 1.5; nfa – N-phenylanthranilate anion (C13H10NO2), phen – 1,10-phenanthroline (C12H8N2), Ln = La(III), Ce(III), Pr(III) and Nd(III)) were synthesized and characterized by elemental analysis, complexometry, infrared spectroscopy, XRD technique, simultaneous thermogravimetry and differential scanning calorimetry (TG–DSC), evolved gas analysis by TG–DSC coupled with FTIR and MS spectroscopy. The detailed thermogravimetic analysis showed that thermal decomposition of the complexes in nitrogen and air atmosphere occurs in several stages including water elimination, neutral ligand loss and N-phenylanthranilate anion decomposition, respectively. It was found that the thermal stability and the decomposition path of the studied compounds depend on the metal ion and the applied atmosphere. Low values of the dehydration enthalpies indicate that dehydration is connected with the release of crystallization water. By the use of the coupled TG–FTIR–MS techniques the decomposition pathways of the synthesized compounds were examined and the gaseous products released during pyrolysis and thermal oxidation of the complexes were identified.

Tuning Intrinsic and Extrinsic Proton Conduction in Metal-Organic Frameworks by the Lanthanide Contraction.

Seven isomorphous lanthanide metal-organic frameworks in the PCMOF-5 family, [Ln(H5L)(H2O)n](H2O) (L = 1,2,4,5-tetrakis(phosphonomethyl)benzene, Ln = La, Ce, Pr, Nd, Sm, Eu, Gd) have been synthesized and characterized. This family contains 1-D water-filled channels lined with free hydrogen phosphonate groups and gives a very low activation energy pathway for proton transfer. The lanthanide contraction was employed to systematically vary the unit cell dimensions and tune the proton conducting pathways. LeBail fitting of the crystalline series shows that the crystallographic a-axis, along the channel, can be varied in increments less than 0.02 Å correspondingly shortening the proton transfer pathway. The proton conductivities for the La and Pr complexes were roughly an order of magnitude higher than other members of the series (10-3 S cm-1 versus 10-4 S cm-1). Single crystal structures of the high and low conducting members of the series (La, Pr for high and Ce for low) affirm the structural similarities extend beyond the unit cell parameters to positions of free acid groups and included water molecules. Scanning electron microscopy reveals marked differences in particle size of the different members of the Ln series owing to lattice strain effects induced by changing the lanthanide. Notably, the high conducting La and Pr complexes have the largest particle sizes. This result contradicts any notion that degradation of the MOF at grain boundaries is enabling the observed conductivity as proton conduction dominated by extrinsic pathways would be enabled by small particles (i.e., the La and Pr complexes would be the worst conductors). Proton conductivity measurements of a ball milled sample of the La complex corroborate this result.

Synthesis and characterization of Pr(III), Nd(III) and Er(III) complexes with 2,6-pyridinedimethanol

The reactions of Ln(NO3)3∙6H2O (Ln=Pr, Nd or Er) with the potentially tridentate O,N,O chelating ligand 2,6-pyridinedimethanol (H2pydm) in a 1:2 M ratio were investigated, and complexes with the formula [Ln(H2pydm)2(NO3)2](NO3) (Ln=Pr or Nd) (1 and 2) and [Er(H2pydm)3](NO3)3 (3) were isolated. The compounds contain 10-coordinate Pr(III) and Nd(III) ions that crystallize in the triclinic space group P-1 while the 9-coordinate Er(III) complex crystallizes in the monoclinic system (P21/n). A new lanthanide complex, [Pr(H2pydm)3](Cl)3∙DMF (4), has been synthesized by reaction of PrCl3∙6H2O and H2pydm. The nine-coordinate Pr(III) is bound to three H2pydm ligands. X-ray crystal structures of 1–4 reveal that the ligand coordinates tridentate via the pyridyl nitrogen and the two hydroxyl oxygens. The electronic absorption spectra of 1–4 show 4f–4f transitions.