Synthesis,crystal structure and two-photon property studies on a series of complexes derived from a novel Schiff base ligand

A new Schiff base ligand derived from S-benzyldithiocarbazate and 4-[N-hydroxy ethyl-N-(methyl)amino]benzaldehyde (HL, where H is a dissociable proton) and its Ni^II, Cu^II, Zn^II and Pd^II complexes were prepared and fully characterized. The structures of HL and Ni(L)₂ were determined by X-ray diffraction analysis, which revealed that the geometry of the Ni^II ion is square-planar with two equivalent Ni=N and Ni=S bonds, and that the two neighboring molecules in two layers have weak contact. The electronic spectra and solution fluorescence of the ligand and the complexes were studied, and the quantum yields of single-photon fluorescence for the compounds were determined. The compounds possess two-photon absorption (t.p.a.) character and the t.p.a. coefficient and t.p.a. cross-section were determined by the Z-scan technique. Especially, the Zn(L)₂complex and the HL ligand exhibit intensive two-photon fluorescence (t.p.f.) at 800 nm laser pulses in the femtosecond regime.     

Theoretical study on the structure and property relationship of the cationic conjugated polyelectrolytes

A theoretical study using density functional theory was performed to understand the structure/property relationship of the cationic conjugated polyelectrolytes, poly[9,9-bis-(6′-N,N,N-trimethylammonium) hexyl] fluorene-alt-4,7-(2,1,3-benzothiadiazole)] (PFBT-X, where X = Br). The torsion angle between the fluorene and benzothiadiazole units in the PFBT monomer was found to substantially affect the structural and electronic properties of the cationic PFBT monomer. The changes of geometrical parameter, HOMO and LUMO energy levels, and band gap, as well as the absorption maximum are discussed in terms of the torsion in the PFBT monomer structure. For comparison, its neutral analogue, the monomer of poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) (F8BT) was also studied. The length of conjugation backbone was also examined.     

Electrodeposition of nanocrystalline zinc from acidic sulfate solutions containing thiourea and benzalacetone as additives

Nanocrystalline zinc coatings were produced by pulse electrodeposition in acid sulfate bath containing thiourea and benzalacetone additives and characterized by X-ray diffraction and scanning electron microscopy techniques. The influence of benzalacetone concentration and pulse peak current density on the grain size and crystallographic orientation of zinc deposits was investigated. Zinc electrodeposited from additive-free solutions or with one of the two additives is not composed of nanosized crystals. The mixture additives of thiourea and benzalacetone give rise to the formation of particle-like nanocrystalline zinc with a (10ī1) random orientation. A change in peak current density from 2 to 1 A/cm² only increases the grain size from 60 to 62 nm.     

Energy transfer rates and impact sensitivities of two classes nitramine explosives molecules

Some explosives are stable molecules with large energy barriers to chemical reaction, and in shock or impact initiation, a sizable amount of phonon energy must be converted to the molecular internal higher vibrations by multiphonon up pumping. To investigate the relationship between impact sensitivities and energy transfer rates, the number of doorway modes of explosive molecules is estimated by a simple theory in which the rate is proportional to the number of normal mode vibrations. We evaluated frequencies of normal mode vibrations of 13 explosive molecules which are CHNO nitramine-contained and have not been analyzed previously. The number of doorway modes in the regions of 200–700 cm⁻¹ was evaluated by the direct counting method. For more clear investigation of the relationship we have classified these 13 nitramine explosive molecules, by the number of nitramine group they contained, into two groups. There are eight molecules that contained one nitramine group and five molecules that contained poly-nitramine groups. It is found that the number of doorway modes shows a linearly correlation to the impact sensitivities derived from drop hammer tests. This result is in agreement with that of several previous works. Besides, it is also noted in our study that in those nitramine explosives molecules with similar molecular structure (similar number nitramine group they contained) and similar molecular weight, the correlation between the sensitivity and the number of doorway modes is higher. We found that the vibrational frequency of ω corresponds to nitro group motions of every molecule is contributed to the number of doorway modes in the regions of 200–700 cm⁻¹.     

Micro-sized Sb2O3 octahedra fabricated via a PEG-1000 polymer-assisted hydrothermal route

The micro-sized Sb₂O₃ octahedra can be synthesized on a large scale via a simple PEG-1000 polymer-assisted hydrothermal route (PAHR) in the temperature range of 160-180 °C for 10-14 h. The structures, compositions, and morphologies of the as-synthesized products are derived from X-ray power diffraction pattern, X-ray photoelectron spectra, and field emission scanning electronic microscope. Meanwhile, the optical properties of the micro-sized Sb₂O₃ octahedra are studied by their photoluminescene spectroscopy and Raman spectrum. Furthermore, the possible growth mechanism of the micro-metered Sb₂O₃ octahedra is discussed on the basis of a series of supplementary experiments. And it has been found that PEG-1000, sodium tartrate, the reaction temperature, and the reaction time have considerable effects on the final morphology of Sb₂O₃, while the pH value has an influence on the formation of the Sb₂O₃ crystals.     

Micellization and morphological characterization of Ag-micelles prepared by poly(vinyl acetate)–silver nitrate in solvent/nonsolvent system

The inducing method for preparing Ag-micelle solution with the use of mixed solvent/nonsolvent, and the morphological characterization of the generated metal–micelles were investigated and reported in this paper. In this method, an Ag containing metal chelate polymer (MCP) raw solution was preprepared by dissolving poly(vinyl acetate) (PVAc)–silver nitrate (AgNO₃) MCP in conc. formic acid, and a mixed solvent of HCOOH/H₂O with specific water composition was then added to induce the micellization of the MCP chain. The critical water concentration (CWC) that was needed for inducing the formation of the Ag-micelles, and the water concentration at which the flocculation of the Ag-micelles occurred in micellar solution, were studied by measuring the transmittance of the dilute MCP solution; the results showed that a long-lasting MCP solution with stable micelles might be prepared by using a H₂O/HCOOH solvent of specific weight ratio 1:1.2. The effect of the AgNO₃ concentration on the morphology of the Ag-micelles was also investigated by transmission electron microscopy (TEM). At AgNO₃ concentration below 0.5 wt%, the Ag-micelles displayed a variety of core-shell structure; but as the AgNO₃ concentration was increased to 1.0–2.0 wt%, micelles that had Ag-solid embedded in the micellar core were observed.     

Energetic preferences for alpha,beta versus beta,gamma unsaturation

Density functional theory has been applied at the B3LYP/6-311+G(d,p)//B3LYP/6-31G(d) level to examine the energetics of alpha,beta- versus beta,gamma-unsaturation for some common organic functional groups. Specifically, the relative stabilities of allyl-X (H2C=CHCH2X) and 1-propenyl-X (H3CCH=CHX) isomers have been computed for X = methyl, vinyl, phenyl, formyl, acetyl, methoxy, methylthio, methylsulfinyl, methylsulfonyl, sulfamoyl, and methoxysulfonyl, and the results are compared to available experimental data. The intrinsic preference of 3 kcal/mol for the 1-propenyl isomer when X = CH3 is exceeded by 2-4 kcal/mol for first-row conjugating groups, but it is not met for the sulfur-containing groups. In particular, alpha,beta-unsaturation is favored by less than 1 kcal/mol for the sulfone and sulfonamide analogues, while it is preferred by 8 kcal/mol for the vinyl-substituted case. Detailed structural results and torsional energy profiles are also reported.     

Liquid Densities and Excess Molar Volumes for Binary Systems (Ionic Liquids + Methanol or Water) at 298.15, 303.15 and 313.15 K,and at Atmospheric Pressure

Binary excess molar volumes, V _m ^E, have been evaluated from density measurements, using a vibrating tube densimeter over the entire composition range for binary liquid mixtures of ionic liquids 1-ethyl-3-methyl-imidazolium diethyleneglycol monomethylethersulphate [EMIM]⁺[CH₃(OCH₂CH₂)₂OSO₃]⁻ or 1-butyl-3-methyl-imidazolium diethyleneglycol monomethylethersulphate [BMIM]⁺[CH₃(OCH₂CH₂)₂OSO₃]⁻ or 1-methyl-3-octyl-imidazolium diethyleneglycol monomethylethersulphate [MOIM]⁺[CH₃(OCH₂CH₂)₂OSO₃]⁻+methanol and [EMIM]⁺[CH₃(OCH₂CH₂)₂OSO₃]⁻+water at 298.15, 303.15 and 313.15 K. The V _m ^E values were found to be negative for all systems studied. The V _m ^E results are explained in terms of intermolecular interactions and packing effects. The experimental data were fitted by the Redlich-Kister polynomial.     

Interference of Copper(II) ions with Non-covalent Interactions in Uridine or Uridine 5′-Monophosphate Systems with Adenosine,Cytidine, Thymidine and their Monophosphates in Aqueous Solution

Coordination reactions of copper(II) ions and their effect on non-covalent interactions in uridine (Urd) or uridine 5′-monophosphate (UMP) systems with nucleosides (Ado, Cyd, Thd) and nucleotides (AMP and CMP) in aqueous solutions have been studied. At high pH the effective coordination centers are deprotonated N(3) atoms from Urd and Thd, whereas at low pH, the N(3) atoms of pyrimidine nucleosides are blocked for coordination and the metallation sites are endocyclic nitrogen atoms from Ado, Cyd, AMP and CMP. Moreover, at low pH, the main reaction center in nucleotide solutions is the phosphate group. The NMR study has proven the occurrence of non-covalent ion-dipole interactions and stacking interactions in the systems considered. Introduction of a copper ion in the majority of systems causes the disappearance of weak interactions between ligands. The structures of the complexes in solution have been inferred from the equilibrium study: an analysis of the pH range of their occurrence with respect to the pH range of deprotonation of particular groups in the compounds studied, using Vis, EPR and ¹³C as well as ³¹P NMR spectral analysis.     

Fast Marching Method for Calculating Reactive Trajectories for Chemical Reactions

We present a method for computing classical Newtonian trajectories that minimize the path length or transit time from reactant to product. Our approach is based on a generalization of the fast-marching method, which allows us to construct the solution of the Hamilton-Jacobi equation for the action that optimizes the desired quantity. The resulting “reactive paths” can be interpreted as reaction coordinates but, unlike more conventional choices, they contain dynamical information about the chemical system of interest.