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Nanomaterials have versatile properties owing to their high surface-to-volume ratio and can thus be used in a variety of applications. This work focused on applying a facile hydrothermal strategy to prepare praseodymium vanadate nanoparticles due to the importance of nanoparticles in today's society and the fact that their synthesis might be a challenging endeavor. The structural and morphological characterizations were carried out to confirm the influence of the optimizations on the reaction's outcomes, which revealed praseodymium vanadate (PrVO

A new praseodymium-based borate crystal Pr2CaB10O19 (PCB) has been grown through the high temperature solution method. PCB crystallizes in monoclinic space group C2 with unit cell parameters of a = 10.9475(10) A, b = 6.5343(7) A, c = 9.0336(8) A, β = 91.652(3)°, and Z = 2, in which B5O12 groups and PrO10 and CaO8 polyhedra constitute the three-dimensional framework. PCB exhibits a similar second harmonic response intensity to that of La2CaB10O19 and an intense orange fluorescence emission with a long fluorescence lifetime at about 610 nm excited by a xenon lamp light of 466 nm. The band gap, partial density of states, and birefringence have been investigated via theoretical calculations.

Here we show that the praseodymium

Physiological storage disorders are caused by ineffective post-harvest handling of horticultural crops, particularly fruits. To address these post-harvest concerns, diphenylamine (DPAH

Apart from perovskites, the development of different types of pyrochlore oxides is highly focused on various electrochemical applications in recent times. Based on this, we have synthesized pyrochlore-type praseodymium stannate nanoparticles (Pr2Sn2O7 NPs) by using a coprecipitation method and further investigated by different analytical and spectroscopic techniques such as X-ray diffraction, Raman spectroscopy, field emission-scanning electron microscopy, high resolution-transmission electron microscopy, and X-ray photoelectron spectroscopy analysis. Followed by this, we have designed a unique and novel electrochemical sensor for nitrofurazone detection, by modifying the glassy carbon electrode (GCE) with the prepared Pr2Sn2O7 NPs. For that, the electrochemical experiments were performed by using cyclic voltammetry and differential pulse voltammetry techniques. The Pr2Sn2O7 NPs modified GCE exhibits high sensitivity (2.11 μA μM−1 cm−2 ), selectivity, dynamic linear ranges (0.01−24 μM and 32−332 μM), and lower detection limit (4 nM). Furthermore, the Pr2Sn2O7 NPs demonstrated promising real sample analysis with good recovery results in biological samples (human urine and blood serum) which showed better results than the noble metal catalysts. Based on these results, the present work gives clear evidence that the pyrochlore oxides are highly suitable electrode materials for performing outstanding catalytic activity toward electrochemical sensors.

Reactions of silicon, carbon, and iron in a low-melting flux mixture of praseodymium and nickel produced two competing intermetallic compounds. Pr62Fe21Si16C32 has a new structure type in tetragonal space group P4/ mmm ( a = 15.584(2) A, c = 11.330(1) A, Z = 1) that features trigonal planar FeC3 units that share corners to form a framework of cylindrical channels encompassing a network of silicon-centered praseodymium clusters. Slight variation of reactant ratio and heating profile produced Pr21Fe8Si7C12 instead; this compound has the previously reported cubic La21Fe8Sn7C12 structure type. Identical Pr/Si clusters and FeC3 subunit motifs are found in both structure types. In addition to reactant ratio and heating profile, size effects play a role in determining which structure forms. Replacing silicon with smaller phosphorus atoms produces only the tetragonal structure; replacement with larger elements (M = Ge, Sn) yields only cubic Pr21Fe8M7C12. Magnetic susceptibility measurements on single crystals of Pr62Fe21Si16C32 indicate antiferromagnetic ordering of the Pr moments below 17 K and no magnetic moment on iron atoms. The behavior of Pr21Fe8Si7C12 is more complex, revealing magnetic contributions from both Pr and Fe atoms and possible spin frustration.

The chemistry of the lanthanides is mostly dominated by compounds in the oxidation state +III. Only few compounds of Ce, Pr, and Tb are known with the metal in the +IV oxidation state. Removal of the last f-electron on praseodymium +IV would lead to a closed-shell system with formal oxidation state V. In this work we investigated the stability of the PrF5 molecule by theory and matrix-isolation techniques through the reaction of laser-ablated praseodymium atoms with fluorine in excess of neon, argon, krypton, or neat fluorine. Besides the known PrF3 molecule, unreported IR bands for PrF4 could be observed, and there is evidence for the formation of PrF and PrF2 but not for the formation of PrF5.

Four new praseodymium alkoxo and amido compounds ([Pr3(μ3-OtBu)2(μ2-OtBu)3(OtBu)4(HOtBu)2] (1), [Pr{OC(tBu)3}3(THF)] (2), [PrCl{N(SiMe3)2}2(THF)]2 (3), and [PrCl{OC(tBu)3}2(THF)]2 (4)) were synthesized and structurally characterized by single-crystal X-ray diffraction analysis. Application of these compounds in solvothermal synthesis of praseodymium oxide/hydroxide nanostructures showed their templating influence on the morphology and phase composition of the resulting solid-state materials. Differential reactivity of the chosen alkoxide ligands toward water and the different arrangements of metal-oxygen units in the studied precursor compounds strongly influenced the kinetics of hydrolysis and cross-condensation reactions as manifested in the morphological changes and phase composition of the final products. Thermal decomposition studies of 1-4 confirmed their conversion into the corresponding oxide phases. Activation of compounds 1, 2, and 4 by either a base or a stoichiometric amount of water showed the distinct influence of their chemical configuration on the obtained nanopowders: whereas 1 solely produced nanorods of Pr(OH)3, 2 predominantly formed a mixture of rod-shaped and spherical particles. The solvothermal decomposition of 4 resulted in Pr(OH)2Cl or PrOCl due to the presence of Cl ligands in the molecular precursor. The resultant materials were thoroughly characterized to demonstrate the relationship between precursor chemistry and the processing parameters that are clearly manifested in the morphology and phase of the final ceramics.

Rare-earth coordination polymers or lanthanide-organic frameworks with hitherto unreported crystal structures have been obtained on the basis of the "light" lanthanides Pr, Nd, Sm, and Eu in combination with terephthalic acid and using a slightly altered literature synthesis procedure. Rietveld refinement has shown that powder XRD patterns of such compounds are largely dominated by the positions of the heavy elements, pointing to isostructural networks for all four terephthalate-based materials. An in-depth luminescence study has been performed on the reported MOFs, showing rare praseodymium and samarium emission in the visible spectrum, aside from the strong europium luminescence and the near-infrared emission from both a terephthalate and 2,5-pyridinedicarboxylate based neodymium-MOF.

New lanthanide N,N-dimethylaminodiboranate (DMADB) complexes of stoichiometry Ln(H(3)BNMe(2)BH(3))(3) and Ln(H(3)BNMe(2)BH(3))(3)(thf) have been prepared, where Ln = yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, and lutetium, except that isolation of the desolvated complexes proved difficult for Eu and Yb. The tetrahydrofuran (thf) complexes are all monomeric, and most of them adopt 13-coordinate structures in which each DMADB group chelates to the metal center by means of four B-H···Ln bridges (each BH(3) group is κ(2)H; i.e., forms two B-H···Ln interactions). For the smallest three lanthanides, Tm, Yb, and Lu, the metal center is 12 coordinate because one of the DMADB groups chelates to the metal center by means of only three B-H···Ln bridges. The structures of the base-free Ln(H(3)BNMe(2)BH(3))(3) complexes are highly dependent on the size of the lanthanide ions: as the ionic radius decreases, the coordination number decreases from 14 (Pr) to 13 (Sm) to 12 (Dy, Y, Er). The 14-coordinate complexes are polymeric: each metal center is bound to two chelating DMADB ligands and to two "ends" of two ligands that bridge in a Ln(κ(3)H-H(3)BNMe(2)BH(3)-κ(3)H)Ln fashion. In the 13-coordinate complexes, all three DMADB ligands are chelating, but the metal atom is also coordinated to one hydrogen atom from an adjacent molecule. The 12-coordinate complexes adopt a dinuclear structure in which each metal center is bound to two chelating DMADB ligands and to two ends of two ligands that bridge in a Ln(κ(2)H-H(3)BNMe(2)BH(3)-κ(2)H)Ln fashion. The complexes react with water, and the partial hydrolysis product [La(H(3)BNMe(2)BH(3))(2)(OH)](4) adopts a structure in which the lanthanum and oxygen atoms form a distorted cube; each lanthanum atom is connected to three bridging hydroxyl groups and to two chelating DMADB ligands. One B-H bond of each chelating DMADB ligand forms a bridge to an adjacent metal center. Field ionization MS data, melting and decomposition points, thermogravimetric data, and NMR data, including an analysis of the paramagnetic lanthanide induced shifts (LIS), are reported for all of the complexes. The Ln(H(3)BNMe(2)BH(3))(3) compounds, which are highly volatile and sublime at temperatures as low as 65 °C in vacuum, are suitable for use as chemical vapor deposition (CVD) and atomic layer deposition (ALD) precursors to thin films.

New estimated standard entropies for some aqueous metal ions are obtained by taking account of magnetic and symmetry contributions. By combining them with an analysis of literature data, improved experimental and estimated values are derived for the standard enthalpies and Gibbs energies of formation of the aqueous ions of titanium, vanadium, chromium, manganese, cerium, and praseodymium. Separate entropy correlations are used for each primary coordination number, and the size dependence is represented by the reciprocal of the metal-oxygen distance in that coordination. The new scheme is consistent with recent work on the coordination of Hg(2+)(aq), Pb(2+)(aq), and tripositive rare earth ions. It differs from its predecessors in indicating a larger variation of the standard molar entropies of aqueous ions with coordination number. The value of S(Θ)(Be(2+), aq) is discussed in this context.

Praseodymium molybdate Pr(2)(MoO(4))(3) was synthesized using the standard ceramic route. The crystal structure of the material has been successfully solved in superspace group I2/b(alphabeta0)00 with lattice constants a = 5.30284(4), b = 5.32699(3), c = 11.7935(1) A, gamma = 90.163(1) degrees , and the modulation vector q = 2/3a* + 0.88810(2)b*. The deviation of the q vector from a rational value allows a description of the structure in terms of nanosize domains with the La(2)(MoO(4))(3)-like structure separated by stacking faults. Under 450 nm excitation, ((3)P(0) level) Pr(2)(MoO(4))(3) exhibits the characteristic red emission, with the most intense band at 649 nm corresponding to a (3)P(0) --(3)F(2) transition. Magnetic susceptibility measurements reveal Curie-Weiss paramagnetism with predominating antiferromagnetic interactions between Pr(3+)-magnetic moments and no evidence of magnetic transitions down to T = 5 K.

The previously proposed concept of "inorganic metallocenes" of group 3 and rare-earth elements has been tested by preparing a series of novel disiloxanediolates with metals displaying different ionic radii. For the smaller scandium and yttrium, approximately planar arrangements of the disiloxanediolate frameworks with solvent and chloride ligands in trans positions were found. Thus, the compounds [{(Ph2SiO) 2 O} 2 {Li(DME)} 2 ]ScCl(THF/DME) (2; DME = 1,2-dimethoxyethane and THF = tetrahydrofuran) and [{(Ph2SiO) 2 O} 2 {Li(THF) 2 } 2 ]YCl(THF) (3) can be described as heterobimetallic inorganic ring systems or metallacrown complexes with "in-plane" coordination of the metal. In contrast, "out-of-plane" geometries with cis coordination of additional ligands were identified in the praseodymium derivatives [{(Ph2SiO) 2 O} 2 {Li(THF)2}{Li(THF)}]Pr(μ-Cl)2Li(THF)2 (4) and [{(Ph2SiO) 2 O} 2 {Li(DME)} 2 ]PrCl(DME) (5). These compounds can be viewed as analogues of the known metallocene derivatives (C 5 Me 5 ) 2 Pr(μ-Cl) 2 Li-(THF) 2 and (C 5 Me 5 ) 2 PrCl(THF). The molecular structures of 2-5 have been determined by X-ray diffraction.

The Pr0.50Sr0.50CoO3 perovskite exhibits unique magnetostructural properties among the rest of the ferromagnetic/metallic Ln0.50Sr0.50CoO3 compounds. Existing reports are largely controversial. We have determined and described its structural evolution, which follows the Pm3̅m → R3̅c → Imma → I4/mcm transformations. The structural changes have been thoroughly described. The results are confronted with distinct nonconventional properties and spin-lattice coupling effects in another half-doped cobaltite based on praseodymium, Pr0.50Ca0.50CoO3. The Imma → I4/mcm symmetry change is responsible for the unexpected second magnetic transition.

Experiments have been performed to enhance negative thermal expansion (NTE) in the La(Fe,Co,Si)13-based compounds by optimizing the chemical composition, i.e., proper substitution of La by magnetic element Pr. It is found that increasing the absolute value of the average coefficient of thermal expansion (CTE) in the NTE temperature region (200-300 K) attributes to enhancement of the spontaneous magnetization and its growth rate with increasing Pr content. Typically, the average CTE of La(1-x)Pr(x)Fe10.7Co0.8Si1.5 with x = 0.5 reaches as large as -38.5 × 10(-6) K(-1) between 200 and 300 K (ΔT = 100 K), which is 18.5% larger than that of x = 0. The present results highlight the potential applications of La(Fe,Co,Si)13-based compounds with a larger NTE coefficient.

Lipophilic lanthanide complexes of fluorinated β-diketonate ligands were demonstrated to bind unprotected phenylalanine, leucine, and other amino acids under neutral conditions. Extraction experiments supported that these lanthanide tris(β-diketonates) formed highly coordinated 1:1 complexes with amino acids, although they were electrically neutralized. NMR and CD spectroscopic studies further suggested that the lanthanide tris(β-diketonates) bound amino acids at two points. Their extraction, transport, and chiral recognition behaviors were significantly controlled by a combination of central lanthanide cation and coordinating ligand: Chiral ytterbium complex offered good enantioselectivity in the extraction of unprotected amino acids, and the related praseodymium complex provided their efficient membrane transport. Thus, these lipophilic lanthanide tris(β-diketonates) were confirmed to be a new class of receptors for amino acids.

Reactions of Pr(NO3)3 with Ph2P(O)-CH2CH2-P(O)Ph2 and Ph2P(O)-C5H3N-P(O)Ph2 yielded layered network coordination polymers with bidentate ligands spanning the lanthanide atoms in a bridging fashion. The praseodymium cations with "spacer" ligands form two-dimensional building blocks assembling into either square grid or herringbone network.

Reactions of Pr turnings, PrBr[sub 3], and metallic Z in Nb containers at 780-910[degrees]C yield Pr[sub 6]Br[sub 10]Z (Y[sub 6]I[sub 10]Ru type) for Z = Co, Ru, Os, monoclinic Pr[sub 3]Br[sub 3]Ru (Pr[sub 3]I[sub 3]Ru type), and cubic Pr[sub 3]Br[sub 3]Z (Ca[sub 3]PI[sub 3]type) for Z = Co, Os, Rh, Ir, Pt. Other Z elements investigated yield the binary Pr[sub 2]Br[sub 5] or unknown phases. The structures of Pr[sub 6]Br[sub 10]CO and Pr[sub 6]Br[sub 10]Ru have been refined (P[bar 1];Z = 1; a = 9.359(4), 9.206(4) [angstrom], b = 9.243(5), 9.505(3) [angstrom], c = 7.538(3), 7.606(4) [angstrom], [alpha] = 97.37(4), 97.08(4)[degrees], [beta] = 107.31(4), 107.47(4)[degrees], [gamma] = 110.17(3), 109.69(4)[degrees], R = 4.3, 5.2%, R[sub w] = 3.8, 6.7%, respectively). The tetragonal compression in the 16-electron Pr[sub 6]Br[sub 10]Ru (0.28 [angstrom] in d(Pr-Ru)) is notably greater than observed in the analogous Y[sub 6]I[sub 10]Ru, probably because of reduced matrix effects (repulsions) between the smaller bromide components. Earlier theoretical predictions regarding a one-over-two splitting of the parent t[sub lu[sup 4]] in the idealized octahedral iodide are therefore supported. The 17-electron Pr[sub 6]Br[sub 10]Co shows a possibly related compression of 0.12 [angstrom].

Reaction of aqueous solutions of the heteropolytungstate [NaP[sub 5]W[sub 30]O[sub 110]][sup 14[minus]] with various cations Z[sup n+] in a sealed container at 120-180[degrees]C for several hours leads to cation exchange and the formation of [ZP[sub 5]W[sub 30]O[sub 110]][sup (15-n-)] when Z = Ca[sup 2+], trivalent Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, or Bi, or tetravalent Ce or U. No exchange occurred for Z = Cd[sup 2+], Sn[sup 2+], Tl[sup 3+], Ce[sup 3+], Pr[sup 3+], or Th[sup 4+] at temperatures up to 180[degrees]C. The lanthanide selectivity appears to be determined by ionic radius. The new complexes, which are hydrolytically stable from pH 0 to pH 9--10, are characterized by cyclic voltammetry, IR spectra, and [sup 31]P NMR spectra (single line in all cases except when Z = Y[sup 3+] which shows [sup 2]J([sup 31]P-O-[sup 89]Y) = 1.6 Hz); [delta] = [minus]68.1 to +17.6 ppM. The lanthanide-induced shifts of the [sup 31]P nucleus are predominantly pseudocontact in origin. The [sup 183]W NMR spectrum of the Eu[sup 3+] derivative has four doublets at +62.5, [minus]201.7, [minus]209.5, and [minus]297.5 ppM (1:2:1:1) consistent with the C[sub 5v] structure found for the Na derivative. The emission spectrum of the Eumore » derivative and the ESR spectrum of the Gd derivative are reported. The low proton relaxivity of the latter complex (ca. 1.0 mM s[sup [minus]1] at 300 MHz) is consistent with the presumed structure in which Gd[sup 3+] is inaccessible to solvent water. 25 refs., 7 figs., 3 tabs.« less

This Article reveals a rare synthesis of pure Pr(2)O(2)CO(3) (POC) nanopowder by thermolysis (700 °C) of a single chemical precursor in an autogenic reaction. The autogenic thermolysis of praseodymium acetate is a solvent-free, efficient, and straightforward approach yielding luminescent POC nanoparticles. The as-prepared POC nanopowder converted to PrO(1.833) (PO) powder via combustion. Methodical morphological, structural, and compositional characterizations of POC and PO powders are carried out, supported by mechanistic elucidation and the photoluminescent properties.

The hydrothermal reaction of 5-aminoisophthalic acid and praseodymium oxide in different acids results in two new praseodymium coordination polymers, {Pr(2)(aip)(3)(H(2)O)(2) x 3 H(2)O}(n) (1) and {Pr(2)(Haip)(2)(aip)(NO(3))(2) x 8 H(2)O}(n) (2) (aip = 5-aminoisophthalate). Complexes 1 and 2 are two distinct three-dimensional metal-organic frameworks constructed from the linkage of rod-shaped praseodymium carboxylate secondary building units and phenyl rings. Both dehydrated coordination frameworks are estimated using a computational method based on Connolly's algorithm, indicating that dehydrated compound 1 cannot host molecules other than water molecules or He, whereas dehydrated compound 2 is able to host molecules with kinetic radii as big as 2.3 A. The potential specific accessible surface of this compound is 792 m(2) g(-1). Meanwhile, N(2) sorption measurements reveal that dehydrated compound 2 having a high 230 cm(3)/g (287 mg/g) N(2) storage capacity at 77 K and 1 atm is in fairly good agreement with our calculation results. Moreover, powder X-ray diffraction measurement results demonstrated that the stable channels of dehydrated compound 2 can reversibly host other small solvent molecules (e.g., water, methanol, and ethanol) and grand canonical Monte Carlo simulation is applied to predict its hydrogen storage capacity.

The first example for an endohedral transition-metal atom (Ru) sequestered in a seven-coordinate surrounding of rare-earth metal atoms (Pr) has been found for {RuPr3}Cl3. The monocapped trigonal prisms of Pr atoms share two rectangular faces, forming a zigzag chain with Ru-Ru distances of 308 pm. Intracluster bonding is dominated by Ru-Pr bonding with very little Ru-Ru bonding.

A deconvolution procedure has been applied to K-edge X-ray absorption near-edge structure (XANES) spectra of lanthanoid-containing solid systems, namely, hexakis(dmpu)praseodymium(III) and -gadolinium(III) iodide. The K-edges of lanthanoids cover the energy range 38 (La)-65 (Lu) keV, and the large widths of the core-hole states lead to broadening of spectral features, reducing the content of structural information that can be extracted from the raw X-ray absorption spectra. Here, we demonstrate that deconvolution procedures allow one to remove most of the instrumental and core-hole lifetime broadening in the K-edge XANES spectra of lanthanoid compounds, highlighting structural features that are lost in the raw data. We show that quantitative analysis of the deconvolved K-edge XANES spectra can be profitably used to gain a complete local structural characterization of lanthanoid-containing systems not only for the nearest neighbor atoms but also for higher-distance coordination shells.

Substitution of calcium for strontium in LnSr2-xCaxCu2GaO7 (Ln = La, Pr, Nd, Gd, Ho, Er, Tm, and Yb) materials at ambient pressure and 975 degrees C results in complete substitution of calcium for strontium in the lanthanum and praseodymium systems and partial substitution in the other lanthanide systems. The calcium saturation level depends on the size of the Ln cation, and in all cases, a decrease in the lattice parameters with calcium concentration was observed until a common, lower bound, average A-cation size is reached. Site occupancies from X-ray and neutron diffraction experiments for LnSr2-xCaxCu2GaO7 (x = 0 and x = 2) confirm that the A-cations distribute between the two blocking-layer sites and the active-layer site based on size. A quantitative link between cation distribution and relative site-specific cation enthalpy for calcium, strontium, and lanthanum within the gallate structure is derived. The cation distribution in other similar materials can potentially be modeled.