Femtosecond-Picosecond Laser Photolysis Studies on Proton Transfer Process of Excited 1-Pyrenol-Triethylamine Hydrogen Bonding Complex in Solutions

The proton transfer (PT) process in the excited hydrogen bonding (HB) complex of 1-pyrenol and triethylamine, leading to the formation of a hydrogen-bonded ion pair (HBIP*) of excited pyrenolate anion and triethylammonium cation, PyO^−* ··· H-N⁺(C₂H₅)₃, and subsequent reaction processes of HBIP* in various solvents were investigated by picosecond and femtosecond laser photolysis, as well as by steady-state absorption and fluorescence measurements. Time constants for the PT process taking place in the time region of a few picoseconds were almost independent of the polarity of the solvent and it was suggested that the intermolecular slow motion in the HB complex, such as the intermolecular vibration and/or the torsional motion of the two moieties, might regulate the PT process. Moreover, the ionic dissociation process following the photoinduced PT process in polar solvent was directly measured. The dynamic behaviors of the excited intermolecular HB complex and underlying mechanisms are discussed by comparing these results with those on the intramolecular photoinduced PT process and with results of investigations of electron transfer systems.     

Dissociation et hydratation de nitrates alcalins dans le carbonate de propylene aqueux

Dissociation of lithium, sodium, potassium and tetraethylammonium nitrates and perchlorates in propylene carbonate has been studied by conductometry. Dissociation constants of alkali nitrates are 3·14 × 10^?3 (LiNO₃), 8·35 × 10^?3 (NaNO₃ and 1·92 × 10^?2 (KNO₃) at 25°C. The perchlorates and tetraethylammonium nitrate are strong electrolytes. The solubility products are 4·1 × 10^?4 (LiNO₃), 1·2 × 10^?5 (NaNO₃ and 2·5 × 10^?5 (KNO₃). The conductivity of saturated solutions of nitrates in the aqueous solvent has been determined up to 0·6 M water. Results are used to calculate the equilibrium constants for the reaction I^± + H₂O = I^± H₂O; Li⁺ 6·5, Na⁺ 2·5, K⁺ 0·5 and NO^?₃ 2·4. Dissociation constants, solubility products and hydration constants are compared with values reported for other solvents.     

Acides forts dans le dimethylsulfoxide

Dissociation of acids in dimethylsulfoxide has been studied by conductometry. Trifluoromethanesulphonic acid is completely dissociated. Dissociation constants of the other acids are: picric acid 10^+0·3, methanesulphonic acid 10^?1·76, hydrochloric acid 10^?2·01, trifluoroacetic acid 10^?3·45 and sulphuric acid ? 10^?1·41. The proton ionic conductivity is “normal”. The acids dissociation is compared in dimethylsulfoxide and other solvents.     

Synergistic Extraction of Plutonium (IV) from Nitric Acid Medium by Mixtures of TOPO and HTTA

Abstract

Synergistic solvent extraction of Pu(IV) from nitric acid medium by mixtures of thenoyltrifluoroacetone (HTTA) and tri-n-octylphosphine oxide (TOPO) in benzene was investigated by a method developed for such studies. The species involved in the extraction were identified as Pu(NO₃)₄ · 2TOPO, Pu-(N0₃)₃(TTA) · 2TOPO, Pu(NO₃)₂(TTA)₂ · TOPO, and Pu(NO₃)(TTA)₃ · TOPO. The concentration equilibrium constants for the extraction of all the suggested species from 1.0 M nitric acid were calculated from the data obtained, and the concentration equilibrium constants for their formation in the organic phase were estimated.     

SOME METHODS FOR ANALYSIS OF SOLVENT EXTRACTION DATA AND THEIR APPLICATIONS

Abstract

Three programs develpoed to analyze data for liquid-liquid extraction of metal have been applied to the calculation of the stability constants of aqueous cadmium(II)-thiocyanato complexes by using the data for the extraction of tricaprylmethylammonium salt in benzene. The resulting stability constants of the aqueous thiocyanato complexes determined were: for the trial and error method log β₁ = 2·97, log β₂ = 3·70, log β₃ =3·50 and log β₄ =3·28; for the Gauss method log β₁ = 2·91, log β₂ = 3·70, log β₃ =3·35 and log β₄ = 3·29; for the Newton-Gauss method for log β₁ = 2·47, log β₂ =3·24, log β₃ =2·29 and log β₄ = 2·85     

ADDUCT FORMATION OF β-DIKETONATO LANTHANOIDS(III) WITH CARBOXYLIC ACIDS HAVING HYDROXYL AND METHOXYL GROUPS

Adduct formation of 2-thenoyltrifluoroacetonato(tta) lantha-num(III), europium(III), and ytterbium(I II) with α-pheny 1 1 actic, α-methoxy phenyl acetic, salicylic, and o-methoxy benzoic acids in chloroform has been studied by solvent extraction technique. It has been found that 1anthanoid(111) chelates form more stable adducts with these carboxylic acids in the sequence: Yb(tta)₃ < Eu(tta) ₃ < La(tta) ₃. The adduct formation constants as well as the separation factors obtained as the ratio of the constants between a pair of metals are the largest for α-phenyl lactic acid among these acids. The characteristics with α-phenyl 1actic acid would be caused by the action as bidentate unlike benzoic acid derivatives which work as monodentates owing to the internal complexa-tion through hydrogen bonding.     

Synergistic Extraction of Trivalent Actinides by Mixtures of 1-Phenyl-3-methyl-4-benzoyl-pyrazolone-5 and Neutral Oxo Donors

Abstract

The synergistic extraction of trivalent actinides Am, Cm, Bk, and Cf with mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (HPMBP) and TBP or TOPO has been investigated in xylene at 30°C. With HPMBP alone, all four trivalent actinides form M(PMBP)₃· HPMBP-type self-adducts. Bk(III) shows an abnormally high extraction with HPMBP alone. With TBP or TOPO(S) as neutral donor, except in the Bk/HPMBP/TBP system where Bk(PMBP)₃· HPMBP·TBP was extracted, all metal ions were extracted as M(PMBP)₃·S and M(PMBP)₃·(S)₂ into the organic phase. The equilibrium constants (β₁, β₂, and K ₂ for the organic phase synergistic reactions have been calculated. The β₁, β₂ values for Bk(III)/HPMBP/TOPO system are much lower as compared to the corresponding values for other trivalent actinides. The reasons for this extraordinary behavior of Bk(III) have been discussed. The extraction behavior of the M(III)/HPMBP/S and the M(III)/HTTA/S systems has also been compared.     

SELECTIVE EXTRACTION OF PALLADIUM(II) FROM CHLORIDE SOLUTIONS WITH NONYLTHIOUREA DISSOLVED IN CHLOROFORM

ABSTRACT

The extraction of Palladium(II) [Pd(II)] from hydrochloric acid solutions with nonylthiourea (NTH) dissolved in chloroform at a constant ionic strength of 1.0?M has been studied. The extraction of Pd(II) has been investigated as a function of the concentration of the extractant, chloride ion, and proton concentrations as well as extraction temperature. The distribution data have been treated graphically and numerically. The analysis of the experimental data has shown that Pd(II) is extracted as PdCl₂·(NTH) and PdCl₂·(NTH)₂ species with the respective extraction constants of log?K ₁₁=5.0±0.1 and log?K ₁₂=9.1±0.1. The back-extraction of Pd(II) from the organic phase using different stripping reagents has been examined. The selectivity of NTH for Pd(II) against Pt(IV), Rh(III), Cu(II), Fe(III), and Zn(II) has also been investigated.     

Extraction of Benzene and Naphthalene Carboxylic Acids Using Quaternary Ammonium Salts As a Model Study for the Separation of Coal Oxidation Products

Abstract

The ion‐pair solvent extraction of benzene‐ and naphthalene‐carboxylic acids has been investigated as a model study for the separation of coal oxidation products, which are formed by treatment with alkaline solutions at high temperatures. It was possible that benzene‐ and naphthalene‐dicarboxylic acids are extracted into several types of organic solvents with quaternary ammonium ions. The extraction equilibrium constants (K_ex) for benzoic acid, 1,2‐benzenedicarboxylic acid, 1,3‐benzenedicarboxylic acid, 1‐naphthoic acid, 2‐naphthoic acid, 2,3‐naphthalenedicarboxylic acid, and 2,6‐naphthalenedicarboxylic acid into chloroform were determined at 20°C. The difference of K_ex among the aromatic acids was sufficiently large for designing a separation method for these aromatic acids. It was unexpected that the extraction of dicarboxylic acids was slower than that of monocarboxylic acids, although the ion‐pair formation of aromatic carboxylate ion with quaternary ammonium ion is normally considered as a diffusion control reaction in aqueous phase. Thus, this fact suggests that the phase transfer of the ion‐pair from aqueous to organic phase is the rate‐determining step. Liner‐free‐energy relationship was observed for the monocarboxylic acids using different quaternary ammonium salts while that was ambiguous for the dicarboxylic acids. This is due to the steric influence of the counter ions for the magnitude of K_ex.     

Hydrothermal Synthesis of Metal–Organic Coordination Polymers Constructed from Asymmetric Semi-rigid V-shaped Dicarboxylate and Nitrogen-Contained Mixed Ligands

Three new coordination polymers, [Ni(2,4′-oba)(1,10-phen)] _n (1), {[Ni (2,4′-Hoba)₂(4,4′-bipy)(H₂O)₂]·2H₂O} _n (2) and [Zn(2,4′-oba) (4,4′-bipy)] _n (3) (2,4′-H₂oba = 2-(4-carboxyphenoxy)benzoic acid, 1,10- phen = 1,10-phenanthroline, and 4,4′-bipy = 4,4′-bipyridine) have been obtained by hydrothermal synthesis. The framework structures of these polymeric complexes have been determined by single-crystal X-ray diffraction studies. Complex 1 exhibits double-helical chains formed by π–π stacking interactions from the phenyl rings of the 1,10-phen ligands. Complex 2 forms a two-dimensional supramolecular architecture directed by hydrogen bonding. Complex 3 exhibits a three-dimensional structure; Schl?fli symbol of {4⁴·6¹⁰·8}. The luminescent property of compound 3 is discussed.     

3D Supramolecular Polymer Constructed from Agostic, Polyhapto and Thallophillic Interactions: A New Precursor for Preparation of Tl2O3 Nanoflowers

A new thallium(I) supramolecular polymer, [Tl₄(μ₃-2,4-cfp)₄] _n (1) [2,4-Hcfp = 2-chloro-4-fluorophenol] (1) with disordered cubic cage structural unit has been synthesized and characterized. The single-crystal X-ray data of 1 shows four types of Tl^I ions in the tetranuclear cubic cage unit with a coordination number three. In addition to an intra-cage thallophillic interaction, an inter-cage thallophillic interaction also exists and results in formation of 1D supramolecular polymer. Short contacts, Tl···H and Tl···C, make 1 a 3D supramolecular polymer. Short Tl···F and Tl···Cl secondary interactions also exist. Finally the Tl-ions attain O₃Tl1···C₆Tl₂, O₃Tl2···TlClF, O₃Tl3···Tl₂ and O₃Tl4···C₂TlH coordination spheres with a stereochemically ‘active’ electron lone pair of electrons on the metal ions. The thermal stability of 1 was studied by thermogravimetric and differential thermal analyses. Nanostructures of thallium(III) oxide were prepared from calcination of fine powders of 1 at 570 and 630 °C. These nanostructures were characterized by X-ray powder diffraction and scanning electron microscopy .     

Conductometric studies on the dissociation constants of phosphoric acid in methanol-water mixtures

The dissociation constants of phosphoric acid have been determined in methanol-water mixtures (8.0–87% by weight of methanol) by the method suggested by Gelb. The results have been verified by Fuoss—Kraus method. Δ⁰ values of HClO₄, KClO₄ and KH₂PO₄ (and hence of H₃PO₄) in mixed solvents have been determined in the usual way. The role of solvents on the dissociation constants has been discussed.     

Solutions of benzoic acid in formamide—I: The activity coefficients of the undissociated part of benzoic acid in potassium benzoate solutions at 25°C

The emf of the buffered cell Pt. H₂ |;HBz(m₂)|; Hg₂Bz₂|; Hg, has been measured at 25°C using formamide as the solvent. The standard potential of the HG, Hg₂Bz₂ electrode is 0·2545 ± 0·0005 V in good agreement with the value, 0·2541 ± 0·0003 V, obtained from the study of the cell Pt, H₂ HBz(m) Hg₂Bz₂, Hg. From the standard potential of the Hg, Hg₂Bz₂ electrode, the standard free energy charge, ΔG° for the cell reaction in formamide medium has been calculated. In addition, the activity coefficients of the undissociated benzoic acid in potassium benzoate solutions have been evaluated for 25°C.     

Solvent extraction of Zn(II) by Cyanex 923 and its application to a solid‐supported liquid membrane system

The extraction of zinc(II) by Cyanex 923 (phosphine oxides mixture) in Solvesso 100 from hydrochloric acid solution has been investigated. The extraction reaction is exothermic. The numerical analysis of metal distribution data suggests the formation of ZnCl₂·L₂,HZnCl₃·2L and H₂ZnCl₄·2L(L = ligand) in the organic phase with formation constants K_ext = 4.1,5.6 × 10⁹ and 6.7 × 10⁹, respectively. The results obtained for zinc(II) distribution have been implemented in a solid‐supported liquid membrane system. The influence of source phase stirring speed, membrane composition and metal concentration on zinc transport have been investigated. © 2001 Society of Chemical Industry     

A computational investigation on the molecular structure,electronic properties and intramolecular hydrogen bonding interaction of 1,1,1-trifluoro-4-mercaptobut-3-ene-2-thione in ground and electronic excited state

The hydrogen bond (HB) strength, geometry optimization, vibrational frequencies and several well-established indices of aromaticity in 1,1,1-trifluoro-4-mercaptobut-3-ene-2-thione and its 15 derivatives in two positions, R1 and R2, have been investigated by means of the density functional theory (DFT) method with 6-311++G** basis set in the gas phase. The obtained results show that the HB strength is mainly governed by resonance variations inside the chelate ring induced by the substituent groups. The following substituents have been taken into consideration: NO₂, SCF₃, Ph, PhOCH₃, SCOCH₃, CH₂OCH₃ and CH₂OH. The strongest S–H···S HBs belong to PhOCH₃-substituted system in both positions, whereas NO₂ and H substitutions in R1 and R2 positions, respectively, produce the weakest S–H···S hydrogen bridges. The excited-state properties of intramolecular hydrogen bonding in substituted systems have been investigated theoretically using the time-dependent DFT method. Natural bond orbital analysis is also performed for a better understanding of the nature of intramolecular interactions. The electron density and Laplacian (?²ρ) properties, estimated by atoms in molecule calculations, indicate that the H···S bond possesses low ρ, positive ?² ρ and H_C<0, which are in agreement with the partially covalent character of HBs.     

Removal of Lead from Aqueous Solutions Using Rice Husk

ABSTRACT

Rice husk, an agricultural waste, was studied as a potential scavenger of lead from various aqueous solutions. Physicochemical parameters such as selection of appropriate electrolyte, shaking time, and the concentrations of adsorbent and adsor-bate were studied to optimize the conditions to be utilized on a commercial scale for the decontamination of effluents using a batch technique. Maximum adsorptionwas observed with 0.01 mol·dm?³ acid solutions (HNO₃, HC1, H₂SO₄ and HC1O₄) using 1000 mg of adsorbent for a 4.82 × 10?⁵ mol·dm?³ lead concentration in less than 10 minutes equilibration time. Studies show that the adsorption decreases with an increase in the concentrations of all the acids. The adsorption data follows the Freundlich isotherm over the 9.65 × 10?⁵to4.83 × 10?³ mol·dm?³ range of lead concentration. The characteristic Freundlich constants, i.e.,l/n = 0.93 ± 0.04 and A = 19.86 ± 0.82 m·mol·g?¹, have been computed for the sorption system. Thermo- dynamic parameters, i.e.,ΔG°ΔSdeg;,and ΔHdeg; have also been calculated for the system.     

Hydrothermal Synthesis and Crystal Structures of Cd(II)-Based 1D Coordination Polymer and Mn(II) Coordination Complex with Mixed N- and O-donor Ligands: [Cd2(4-4′-bpy)2(pa)4]n·0.25(H2O) and [Mn(4-4′-bpy)2(pa)(H2O)3]ClO4·2(H2O)

Two new complexes, [Cd₂(4-4′-bpy)₂(pa)₄] _n ·0.25H₂O (1) (pa = phenylacetate), and [Mn(4-4′-bpy)₂(pa)(H₂O)₃]ClO₄·2H₂O, (2), have been obtained from hydrothermal reaction of Cd(NO₃)₂·4H₂O and Mn(ClO₄)₂·6H₂O with a mixture of the ligands, 2-phenylmalonic acid (2-phmalH₂) and 4-4′-bipyridine (4-4′-bpy). The pa is formed in situ by decarboxylation of phenylmalonic acid. These complexes have been characterized by elemental analysis, FT-IR spectroscopy, thermogravimetric analysis and single-crystal X-Ray diffraction. The Cd(II) center is seven-coordinate and linked via pa ligands to form a binuclear complex in the asymmetric unit of 1. A ladder-like 1D chain of binuclear units is formed by Cd(II)–N coordination bond through 4-4′-bpy ligands. Complex 2 consists of a mononuclear manganese center based on a distorted octahedral geometry and exhibits a supramolecular structure containing hydrogen bonds and extensive π···π and C–H···π interactions.     

NUCLEAR SIZE AND SHAPE EFFECT IN CHEMICAL ISOTOPE EFFECT OF GADOLINIUM USING DICYCLOHEXANO-18-CROWN-6

ABSTRACT

Gadolinium isotopes were fractionated in a liquid-liquid extraction system using dicyclohexano-18-crown-6. The isotope enrichment factors showed breakdowns of the conventional Bigeleisen-Mayer approximation for every condition of the initial phases; the concentrations of gadolinium and hydrochloric acid and the type of organic solvents. The nuclear mass effect and the field shift effect were estimated by use of the isotope pairs ¹⁵²Gd-¹⁶⁰Gd and ¹⁵⁴Gd-¹⁶⁰Gd. Since both isotopes, ¹⁵²Gd and ¹⁵⁴Gd, have the unique characteristics of the nuclear charge radii, <r²>'s, the unusual isotope effects due to the field shifts took place, while the mass effects of the other isotopes canceled the field shift effects. The maximum isotope effect was observed to be ε_160,152 =0·0252 ± 0·0024 whose initial aqueous phase was 0·023 M GdCl₃ in 12 M HC1, and its organic phase was 0·2 M DC18C6 in chloroform: this was 0·00315 ± 0·00030 in terms of the enrichment factor for unit mass.     

A novel 3D Zn(II) coordination polymer for highly luminescent sensing of nitro compounds

A novel 3D coordination polymer [Zn_2.5(L)(trz)₂(H₂O)₂]·2H₂O (1) (H₃L = 5-(4-carboxybenzyloxy)isophthalic acid, trz = 1,2,4-triazole) has been synthesized hydrothermally. Compound 1 displays a 3D (3,8)-connected net with (5³)₂(5⁸·6⁴·7⁸·8⁴·9⁴) topology. The luminescent property of 1 dispersed in different solvents as well as nitro compounds have been investigated systematically, demonstrating high detection sensitivity via a fluorescence quenching mechanism.     

Solvent Control Over Structural Diversity of Two Copper (II) Complexes Based on Polyaromatic Acid Ligand

Abstract  

A new bipod polyaromatic acid ligand H₂bcm (H₂bcm = {2, 4-bis [(2′-carboxyphenoxy) methyl]-1,3,5-trimethylbenzene}) is prepared and its two novel binuclear coordination compounds, [Cu₂(bcm)₂(CH₃OH)₂]·2CH₃OH (1) and [Cu₂(bcm)₂(CH₃CH₂OH)₂]·2CH₃CH₂OH (2), have been synthesized with copper acetate and H₂bcm ligand in methanol solvent and ethanol solvent respectively, and characterized by the element analysis, IR, TGA and single crystal X-ray diffraction. The results of structural analysis indicate that 1 crystallizes in the triclinic system with space group P1, while 2 crystallizes in the monoclinic system with space group P2₁ /c. Furthermore, 1 adopts μ ₂ -COO⁻ and syn–syn coordination mode with Cu (II)···Cu (II) separation of 2.5868(11) ? and forms 1D zigzag chain structure by O···O interactions. The coordination of 2 is similar to that of 1 except that ethanol molecules are coordinated instead of methanol molecules with Cu (II)···Cu (II) separation of 2.5973(13) ?. Two-dimensional network structures of 1 and 2 are formed through π–π interactions.