Configurational Properties of N,N′-Dimethyl-1,3-Diazacyclohexane and Its Analogues Containing P and As Atoms: A Hybrid-DFT Study and NBO Interpretation

Abstract

The configurational properties of N,N′-dimethyl-1,3-diazacyclohexane (1), N,N′-dimethyl-1,3-diphosphacyclohexane (2), and N,N′-dimethyl-1,3-diarsenacyclohexane (3) have been analyzed by means of hybrid density functional theory (B3LYP/6-311+G**)–based method and NBO interpretation. The NBO analysis of donor–acceptor (bond?antibond) interactions revealed that the calculated generalized anomeric effects (GAE) between the equatorial ee-ae, ea-aa, and ee-aa configurations decrease from compound 1 to compound 3. Contrary to the decrease of the GAE values for ee-ea configurations, the ea configuration stability increases from compound 1 to compound 3. This could be explained reasonably by the decrease of the nonbonded steric repulsions (by lengthening of the C?M bond lengths increase from compound 1 to compound 3) between the ee, ea, and aa configurations from compound 1 to compound 3. The correlations between the GAE, Wiberg bond indexes (WBI), natural bond orders (NBOs), dipole moments, orbital integrals, structural parameters, and Gibbs free energy difference (G _ee–G _ea, G _ea–G _aa G _ee–G _aa) values (i.e., ΔG _ee-ea, ΔG _ea-aa, ΔG _ee-aa) values between the ee, ea, and aa configurations of compounds 1–3 have investigated.

GRAPHICAL ABSTRACT     

Ab Initio Study of the Dehydrogenation of 3-Pyrroline, 2,5-Dihydrofuran and 2,5-Dihydrothiophene

Abstract

The nature of the transition state structures of the decomposition of 3-pyrroline (1), 2,5-dihydrofuran (2) and 2,5-dihydrothiophene (3) were investigated usingab initio Molecular Orbital (MO) and Density Factional Theory (DFT) methods. The energy barrierof the decomposition of compound 1 is smaller than compound 2 and compound 2 is smaller than compound 3. The energy barriers for the decomposition of compounds 1–3 are 46.20, 50.17, and 61.34 kcal mol^?1, respectively, which is calculated by B3LYP/6-31G^*//HF/6-31G^* level of theory. Which is ingood agreement with reported experimental data. Contrary to the previously reported data, the distance between the cis-2-and-5-hydrogen atoms in compound 1 is greater than compound 2. The transition-state structures of the decomposition of compounds 1–3 are formed by interaction of the cis-2-and-5-hydrogen atoms. Also, the rings of compounds 1–3 in the transition state structures are puckered.     

Development and evaluation of a 166holmium labelled porphyrin complex as a possible therapeutic agent

Porphyrins are interesting derivatives with low toxicity, tumor avidity and rapid wash-out suggested as potential radiopharmaceuticals in radiolabeled form. In this work, [¹⁶⁶Ho] labeled 5,10,15,20-tetrakis(phenyl) porphyrin ([¹⁶⁶Ho]-TPP) was prepared using [¹⁶⁶Ho]HoCl₃ and 5,10,15,20-tetrakis(phenyl)porphyrin (H₂TPP) for 12 h at 50 °C (radiochemical purity: >95 ± 2 % ITLC, >99 ± 0.5 % HPLC, specific activity: 0.9–1.1 GBq/mmol). Stability of the complex was checked in final formulation and human serum for 48 h. The partition coefficient was calculated for the compound (log P = 2.01). The biodistribution of the labeled compound in vital organs of wild-type rats was studied using scarification studies and SPECT. A detailed comparative pharmacokinetic study performed for ¹⁶⁶Ho cation and [¹⁶⁶Ho]-TPP performed up to 24 h. The complex is mostly washed out from the circulation through kidneys and in less extends from the liver. The kidney:blood, kidney:liver and kidney:muscle ratios 4 h post injection were 14, 3.6 and 7.38 respectively.     

Synthesis of gem-Dihydroperoxides from Ketones and Aldehydes Using Silica Sulfuric Acid as Heterogeneous Reusable Catalyst

Silica sulfuric acid (SSA) was found to efficiently catalyze the conversion of aldehydes and ketones directly into the corresponding gem-dihydroperoxides (DHPs) on treatment with aqueous 30% H₂O₂ at room temperature. Mild reaction conditions, good to excellent yields, short reaction times, low environmental impact, and recyclability of the catalyst are the main advantages of this synthetic method.     

Enhancement of Nanoclay Dispersion and Exfoliation in Epoxy Using Aminic Hardener Treated Clay

Exfoliation and dispersion of nanoclays in epoxy matrices plays an important role in achieving better physical and mechanical properties of resultant nanocomposites. In this article, modification of clay with an aminic hardener for the increment of dispersion and exfoliation into the epoxy matrix has been investigated. In the solvent media, a slurry of hydrophilic Na-Montmorrilonite was mixed and treated with isophoronediamine (IPDA). The nanocomposites containing epoxy and IPDA-modified clay were produced through a recently developed “slurry compounding” method. Dispersion and exfoliation of the modified clay and the microstructure of the resultant nanocomposite were studied by optical microscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared (FTIR) spectroscopy. The samples were then compared with the high shear mixed and sonicated nanocomposites containing commonly used quaternary ammonium modified clays. The comparison showed that dispersion and exfoliation of hardener-modified organoclays in epoxy have been improved due to the treatment of clay and the compounding method.     

Efficient Synthesis of Urea Derivatives via a Sequential One-Pot Nucleophilic Addition/Ugi Five-Component Reaction Under Solvent-Free Conditions

Urea polyfunctional derivatives were successfully synthesized via a one-pot, five-component nucleophilic addition/Ugi reaction sequence. Simplicity, solvent-free conditions, and good yields of products are advantages of this method.     

Locally convex quotient lattice cones

Walter Roth has investigated certain equivalence relations on locally convex cones in [W. Roth, Locally convex quotient cones, J. Convex Anal. 18, No. 4, 903–913 (2011)] which give rise to the definition of a locally convex quotient cone. In this paper, we investigate some special equivalence relations on a locally convex lattice cone by which the locally convex quotient cone becomes a lattice. In the case of a locally convex solid Riesz space, this reduces to the known concept of locally convex solid quotient Riesz space. We prove that the strict inductive limit of locally convex lattice cones is a locally convex lattice cone. We also study the concept of locally convex complete quotient lattice cones.     

Heat and fluid flow analysis of metal foam embedded in a double-layered sinusoidal heat sink under local thermal non-equilibrium condition using nanofluid

The present study aims to enhance the hydrothermal performance of a porous sinusoidal double-layered heat sink using nanofluid. The optimum thickness of metal foam (nickel) for different Reynolds numbers ranging from 10 to 100 for the laminar regime and Darcy numbers ranging from 10^?4 to 10^?2 is obtained. At the optimum porous thicknesses, nanofluid (silver–water) with three volume fractions of nanoparticles equal to 2, 3, and 4% is employed to enhance the heat sink thermal performance. Darcy–Brinkman–Forchheimer model and the local thermal non-equilibrium model or two equations method are employed to model the momentum equation and energy equations in the porous region, respectively. It was found that in the cases of Darcy numbers 10^?4, 10^?3, and 10^?2 the dimensionless optimum porous thicknesses are 0.8, 0.8, and 0.2, respectively. It was also obtained that the maximum PEC number is 2.12 and it corresponds to the case with Darcy number 10^?2, Reynolds number 40, and volume fraction of nanoparticles 0.04. The validity of local thermal equilibrium (LTE) assumption was investigated, and it was found that increasing the Darcy number which results in an enhancement in porous particle diameter leads to some errors in results, under LTE condition.

     

Nonlinear harmonic vibration analysis of a plate-cavity system

Nonlinear harmonic oscillation of a plate-cavity system is analytically studied in this paper. Von-Karman theory is used to model a rectangular plate backed by an air cavity. Coupled nonlinear differential equations of system are analytically derived using Galerkin’s approach. The Multiple Scales Method (MSM) is then employed to solve the corresponding nonlinear equations. Primary, secondary, and combinational resonance conditions are taken into account and the corresponding closed-form frequency-amplitude relationships are derived. A parametric study is carried out and effects of different parameters on the frequency responses are investigated.     

Hydrothermal synthesis of star-like and dendritic PbS nanoparticles from new precursors

Lead sulfide (PbS) nanostructures with different morphologies and particle sizes were obtained via a simple hydrothermal reaction between lead (II) salicylate (Pb(Hsal)₂) and thiourea (tu). Reaction products were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible (UV–vis) and Fourier transform infrared (FT-IR) spectroscopy. Morphology of the product, varying from star-like to dendritic, depends on the mole ratio of tu to (Pb(Hsal)₂), pH, and reaction time.