Competition between chalcogen bond and halogen bond interactions in YOX<Subscript>4</Subscript>:NH<Subscript>3</Subscript> (Y = S,Se; X = F,Cl, Br) complexes: An ab initio investigation

Using ab initio calculations, the geometries, interaction energies and bonding properties of chalcogen bond and halogen bond interactions between YOX₄ (Y = S, Se; X = F, Cl, Br) and NH₃ molecules are studied. These binary complexes are formed through the interaction of a positive electrostatic potential region (σ-hole) on the YOX₄ with the negative region in the NH₃. The ab initio calculations are carried out at the MP2/aug-cc-pVTZ level, through analysis of molecular electrostatic potentials, quantum theory of atoms in molecules and natural bond orbital methods. Our results indicate that even though the chalcogen and halogen bonds are mainly dominated by electrostatic effects, but the polarization and dispersion effects also make important contributions to the total interaction energy of these complexes. The examination of interaction energies suggests that the chalcogen bond is always favored over the halogen bond for all of the binary YOX₄:NH₃ complexes.     

On the rate of complete convergence for weighted sums of NSD random variables and an application

In this paper, the complete convergence is established for the weighted sums of negatively superadditive-dependent random variables. As an application, the Marcinkiewicz-Zygmund strong law of large numbers for the random weighted average is also achieved, and a simulation study is done for the asymptotic behaviour of random weighting estimator.     

Chlorofluorofullerenes (CFFs)

We have applied density functional theory calculations to devise stable arrangements of chlorofluorofullerenes (CFFs). In the case of C₆₀ClF and C₆₀Cl₂F₂, an extensive isomer search shows that the most stable configurations are those with two halogens located on the corannulene-like structure. In general, 1,2-adduct is more stable than 1,4-adduct and 1,2 addition across 6–6 bonds is more stable than 1,2 addition across 5–6 bonds. The formation of a CFF from chlorofullerene is exothermic while chlorination of a fluorofullerene is endothermic. For C₆₀Cl_18-3nF_3n (n = 0, 1, 2, 3, 4, 5, and 6), the binding energies decrease as the number of Cl atoms increases and the energy differences between isomers with the same formula are small. The ¹³C NMR patterns of C₆₀Cl_18-3nF_3n (n = 0, 1, 2, 3, 4, 5, and 6) are divided into two parts: δ_iso values of chlorinated and fluorinated carbons shift to low field and appear in the range of 65.1–100.2 and 84.5–97.4 ppm; two peaks related to C sites on the cyclohexatriene pole and the flattened equatorial belt separating the two hemispheres appear at 120.2–123.4 and 125.8–129.1 ppm, respectively. Negative nucleus independent chemical shift (NICS) in interior positions of rings or cages indicates the presence of induced diatropic ring currents which suggests that cyclohexatriene poles can be considered as benzenoid fragments. NICS yields minor value (?2.7 ppm) at the ring center of polar pentagons of C₆₀Cl₁₀F₁₀, and significantly negative values in the cage center.     

Effects of Solvent and Reaction Time in Sonochemical Synthesis of Cadmium(II) Compounds and Use them as Template for Synthesis of Cadmium(II) Oxide Nano Structures

Abstract . A cadmium(II) zero-dimensional supramolecular compound [Cd(L)₂(I)₂] ( 1 ), {L = 2-picolylamine}, was fabricated by branch tube and sonochemical irradiation techniques. Regardless of the method utilized, the same crystallographic structure is obtained for the complex. To investigate the effects of reaction time and solvent on the creation of [Cd(L)₂(I)₂] ( 1 ) supramolecule compound, certain tests were designed and four specimens of 1 were fabricated through sonochemical process. Less reaction time led to the creation of smaller particles with mixed morphologies. To prepare cadmium(II) oxide micro-crystals via calcination, four samples were utilized as new precursors. Micro- and nano-sphere of cadmium(II) oxide could be fabricated from 1. The morphology and structure of micro- and nano-crystals were identified by using Scanning Electron Microscopy (SEM), IR spectroscopy, and X-ray powder diffraction (XRD).     

Organosoluble and thermally stable polyimides derived from a new diamine containing bulky-flexible triaryl pyridine pendent group

A novel kind of aromatic diamine,N-(4-(4-(2,6-diphenyl pyridine-4-yl)phenoxy)phenyl)-3,5-diaminobezamide (DPDAB),was synthesized via aromatic nucleophilic substitution of 3,5-dinitrobenzoylchloride with 4-(4-(2,6- diphenylpyridine-4-yl)phenoxy)aniline(DPPA),followed by palladium-catalyzed hydrazine reduction.This monomer was used to prepare polyimides(PIs)based on reaction with several commerically avaiable tetracarboxylic dianhydrides such as pyromellatic dianhydride(PMDA),benzophenone tetracarboxylic acide dianhydride(BTDA)and bicycle[2.2.2]oct-7-enc- 2,3,5,6-tetracarboxylic dianhydride(BCDA).These PIs had inherent viscosity in the range of 0.34-0.76 dL/g and showed good solubility in various aprotic polar solvents.The glass-transition tempratures(T_gs)of the PIs were in the range of 184-302℃,and showed high thermal stability with 10%weight loss in the temperature range of 360-500℃under nitrogen atmosphere.     

Design of a coupled bioluminescent assay for a recombinant pyruvate kinase from a thermophilic Geobacillus

A simple and rapid method using coupled bioluminescent assay was developed to determine level of ADP. ADP is involved in many biological reactions and ADP assay can be used for assaying some reactions universally by monitoring ADP formation or depletion. ADP analysis involves incubation of ADP or extracts containing ADP with pyruvate kinase (PK) and PEP. The ATP formed by this reaction is determined by measuring the intensity of the initial light flash produced when luciferin-luciferase preparation injected into the reaction mixture. In regard to the main role of the PK in this assay, the gene of PK from a Geobacillus species has been cloned in expression vector pET28a (+), sequenced and overexpressed in Escherichia coli. Recombinant protein was purified using Ni-NTA column and then the purified PK was used in a coupled bioluminescent assay for ADP measurement. Kinetic properties of PK are determined according to a bioluminescent assay using firefly luciferase.     

Synthesis and characterization of polyamides derived from (4-(4-(2, 6-diphenylpyridin-4yl)phenoxy)phenyl)-3, 5-diaminobezamide

New types of polyamides containing pendent triaryl pyridine groups were successfully synthesized by direct polycondensation of a symmetry diamine,（4-（4-（2,6-diphenylpyridin-4yl）phenoxy）phenyl）-3,5-diaminobezamide（DPDAB）, and various aromatic and aliphatic dicarboxylic diacids in NMP using triphenyl phosphate（TPP） and pyridine as catalyst. The diamine and all the prepared polyamides were fully characterized by using FT-IR,¹H-NMR,UV-Vis spectroscopy, fluorimetry and elemental analysis.The inherent viscosity of polyamides ranged from 0.45 dL/g to 0.68 dL/g.All the polymers exhibited solubility in common polar aprotic solvents such as NMP,DMAc,DMF,DMSO,pyridine,HMPA,and even in less polar solvents such as THF and m-cresol at room temperature.Thermal properties of polyamides were evaluated by means of DSC,DMTA and TGA.These polymers showed glass transition temperatures（T_g） in the range of 138-210℃. Their initial decomposition temperature（T_i） varied from 265℃to 310℃under N₂.The dilute solution（0.2 g/dL） of polyamides in DMF exhibited fluorescence emission withλ_max in the range of 470-550 nm.     

Efficient Synthesis of Novel Coumarin‐3‐carboxamides (=2‐Oxo‐2H‐1‐benzopyran‐3‐carboxamides) Containing Lipophilic Spacers

The novel coumarin‐3‐carboxamides (=2‐oxo‐2H‐1‐benzopyran‐3‐carboxamides) 5a – 5g containing lipophilic spacers were synthesized through the Ugi‐four‐component reaction (Scheme 1). The reactions of aromatic aldehydes 1 , 4,4′‐oxybis[benzenamine] or 4,4′‐methylenebis[benzenamine] as diamine 2 , coumarin‐3‐carboxylic acid (=2‐oxo‐2H‐benzopyran‐3‐carboxylic acid; 3 ), and alkyl isocyanides 4 lead to the desired substituted coumarin‐3‐carboxamides 5a – 5g at room temperature with high bond‐forming efficiency. These novel coumarin derivatives exhibit brilliant fluorescence at 544 nm in CHCl₃.     

Investigation of Ternary Fission of <Stack><Subscript>98</Subscript><Superscript>252</Superscript></Stack>Cf Using Three-Cluster and Unified Ternary Fission Models

Using three-cluster and unified ternary fission models, the ternary fission of ₉₈²⁵²Cf is studied. We applied collinear and equatorial configurations to study the ternary fission of ₉₈²⁵²Cf when the third fragment is ₃¹⁰Li. The nuclear potential energy in the three-cluster model and unified ternary fission model is calculated respectively, using Yukawa plus exponential and proximity formalisms. The relative yields of different fragmentation channels are calculated. Our results reveal that the ternary fragmentation potential of the three fragments and the relative yields depend on the configuration of three fragments and usedmodel. Two models predict that the lowest driving potential and highest relative yield take place for the fragment combination ₅₁¹³²Sb + ₄₄¹¹⁰Ru + ₃¹⁰Li. Also, the values of driving potential and relative yield are not equal in the three-clustermodel and unified ternary fission model. For fragment combination ₅₁¹³²Sb + ₄₄¹¹⁰Ru + ₃¹⁰Li, the relative yield based on the three-cluster model in collinear configuration is maximum, whereas the unified ternary fission model in equatorial configuration predicts the lowest relative yield.     

Formation of Superheavy Elements: Study Based on Dynamical Approach

Using multi-dimensional Langevin equations for the probability distribution of the distance between the surfaces of two approaching nuclei, we have studied the formation of superheavy elements via calculation of evaporation and fission cross sections of these elements. Evaporation residue cross sections have been calculated for the 1n, 2n, 3n, 4n, and 5n evaporation channels using one and four dimensional Langevin equations for the ⁴⁸Ca+²²⁶Ra, ²³²Th, ²³⁸U, ²³⁷Np, ^{239,240,242,244}Pu, ²⁴³Am, ^245,248Cm, ²⁴⁹Bk, and ²⁴⁹Cf reactions. Our results show that with increasing dimension of Langevin equations the evaporation residue cross section is increased. Also, obtained results based on fourdimensional Langevin are in better agreement with experimental data in comparison with one-dimensional model.