On the bifurcation analysis of a three‐dimensional non‐autonomous model of molecular systems

Bifurcations and stability of a molecular system are analyzed via a method which combines a perturbation skim with Harmonic Balancing. This revised version was published online in July 2006 with corrections to the Cover Date.     

4,5-, 3,6-, and 3,4,5,6-tert-Butylsulfanylphthalonitriles: synthesis and comparative structural and spectroscopic analyses

Three tert-butylsulfanylphthalonitriles have been prepared with optimized synthetic procedures. Their comparative structural analyses have been completed, with a focus on IR and NMR spectroscopy and refined X-ray structural data. Miscellaneous parameters such as UV absorption, melting points, and related polarity of the compounds are summarized.     

Orthogonal multifunctionalization of aliphatic polycarbonate via sequential Michael addition and radical‐thiol‐ene click reactions

Aliphatic polycarbonate (PC) copolymer is synthesized by ring opening copolymerization of acrylate‐ and allyl‐functional cyclic carbonate monomers. The post‐polymerization functionalization of the resulting copolymer is performed quantitatively using a variety of thiol compounds via sequential Michael addition and photo‐induced radical thiol‐ene click reactions within relatively short reaction time at ambient temperature. This metal‐free click chemistry methodology affords the synthesis of biocompatible PC copolymer with multifunctional groups. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1581–1587     

Analog active filter component selection with nature inspired metaheuristics

The most crucial design step for analog active filter design is the optimal selection of passive component values due to manufactured constants. Since the search on possible combinations in preferred values for capacitors and resistors is an exhaustive process, it has to be automated with high accuracy within short computation time. In this work, two nature inspired metaheuristics, differential evolution (DE) and harmony search (HS) algorithms are utilized for optimal filter design considering different topologies and manufacturing series. Simulation results show that as global optimization methods both DE and HS minimize the total design error and reduce the elapsed time with respect to previously utilized methods.     

Synthesis,characterization, aggregation and thermal properties of a novel polymeric metal-free phthalocyanine and its metal complexes

A novel polymeric metal-free phthalocyanine (M = 2H) and its metal complexes (M = Zn, Cu, Co and Ni) were prepared by the tetramerization reaction of 3,6,9-Tris(p-tolylsulfonyl)-1,11-bis(3,4-dicyanophenoxy)-3,6,9-triazaundecane 5 with the appropriate materials. The electrical conductivities of the metal-free phthalocyanine and the metal complexes, measured in air, were found to be ∼10⁻⁶–10⁻⁵ S m⁻¹. The aggregation property of the zinc complex 7 was investigated with Ni²⁺, Cu²⁺, Co²⁺, Pb²⁺, Cd²⁺ and Ag⁺ cations. Thermal analysis of the polymers were done by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) at a heating rate of 10 °C min⁻¹ under a nitrogen atmosphere. All the novel compounds were characterized by using elemental analysis, UV–Vis, FT–IR, NMR and MS spectral data and DSC, DTA/TG techniques.     

Spectroscopic,electrochemical, theoretical characterization and biological evaluation of a ferrocenyl-substituted unsymmetric azine ligand and its Cu(II) complex

Ferrocenyl-substituted unsymmetrical azine and its Cu(II) complex were prepared. The redox active ferrocene-based azine was obtained by condensation of 1-[(E)-hydrazono]-5-bromo-2-hydroxybenzene with ferrocene carboxaldehyde. The ferrocenyl ligand and its Cu(II) complex were characterized by IR, UV–vis, NMR, X-ray, magnetic susceptibility, molar electrical conductivity measurements, and TG techniques. The redox behaviors of the ferrocene compounds were investigated by cyclic voltammetry. Structural parameters and spectroscopic properties of the ligand and the Cu(II) complex were calculated by employing density functional theory (DFT) and time-dependent DFT and compared with available experimental data. We found slightly stronger binding ability for Cu(II) complex than the free ligand. DNA binding abilities for ferrocenyl-substituted unsymmetrical azine ligand and its Cu(II) complex are higher than some reported ferrocene compounds. We also studied DNA cleavage, superoxide and DPPH radical scavenging abilities of the compounds. Furthermore, the synthesized organometallic compounds can be bound to DNA through an intercalative mode.     

Morphological evolution in dewetting polystyrene/polyhedral oligomeric silsesquioxane thin film bilayers

Morphological evolution in dewetting thin film bilayers of polystyrene (PS) and a polyhedral oligomeric silsesquioxane (POSS), trisilanolphenyl-POSS (TPP), was studied as a function of annealing temperature and annealing time. The results demonstrate unique dewetting morphologies in PS/TPP bilayers at elevated temperatures that are significantly different from those typically observed in dewetting polymer/polymer bilayers. During temperature ramp studies by optical microscopy (OM) in the reflection mode, PS/TPP bilayers form cracks with a weak optical contrast at approximately 130 degrees C. The crack formation is attributed to tensile stresses within the upper TPP layer. The weak optical contrast of the cracks observed in the bilayers for annealing temperatures below approximately 160 degrees C is consistent with the cracking and dewetting of only the upper TPP layer from the underlying PS layer. The optical contrast of the morphological features is significantly enhanced at annealing temperatures of >160 degrees C. This observation suggests dewetting of both the upper TPP and the lower PS layers that results in the exposure of the silicon substrate. Upon annealing the PS/TPP bilayers at 200 degrees C in a temperature jump experiment, the upper TPP layer undergoes instantaneous cracking as observed by OM. These cracks in the upper TPP layer serve as nucleation sites for rapid dewetting and aggregation of the TPP layer, as revealed by OM and atomic force microscopy (AFM). X-ray photoelectron spectroscopy (XPS) results indicated that dewetting of the lower PS layer ensued for annealing times >5 min and progressed up to 90 min. For annealing times >90 min, OM, AFM, and XPS results revealed complete dewetting of both the layers with the formation of TPP encapsulated PS droplets.     

Excess molar volumes,viscosity, refractive index,and Gibbs energy of activation of binary biodiesel + benzene,and biodiesel + toluene mixtures at 298.15 and 303.15 K

Excess molar volumes (V ^E), viscosities, refractive index, and Gibbs energies were evaluated for binary biodiesel + benzene and toluene mixtures at 298.15 and 303.15 K. The excess molar volumes V ^E were determined from density, while the excess Gibbs free energy of activation G*^E was calculated from viscosity deviation Δη. The excess molar volume (V ^E), viscosity deviation (Δη), and excess Gibbs energy of activation (G*^E) were fitted to the Redlich-Kister polynomial equation to derive binary coefficients and estimate the standard deviations between the experimental data and calculation results. All mixtures showed positive V ^E values obviously caused by increased physical interactions between biodiesel and the organic solvents.     

Vapor Phase Synthesis of SnS Facilitated by Ligand-Driven “Launch Vehicle” Effect in Tin Precursors

Extraordinary low-temperature vapor-phase synthesis of SnS thin films from single molecular precursors is attractive over conventional high-temperature solid-state methods. Molecular-level processing of functional materials is accompanied by several intrinsic advantages such as precise control over stoichiometry, phase selective synthesis, and uniform substrate coverage. We report here on the synthesis of a new heteroleptic molecular precursor containing (i) a thiolate ligand forming a direct Sn-S bond, and (ii) a chelating O^N^N-donor ligand introducing a “launch vehicle”-effect into the synthesized compound, thus remarkably increasing its volatility. The newly synthesized tin compound [Sn(SBu^t)(tfb-dmeda)] 1 was characterized by single-crystal X-ray diffraction analysis that verified the desired Sn:S ratio in the molecule, which was demonstrated in the direct conversion of the molecular complex into SnS thin films. The multi-nuclei (¹H, ¹³C, ¹⁹F, and ¹¹⁹Sn) and variable-temperature 1D and 2D NMR studies indicate retention of the overall solid-state structure of 1 in the solution and suggest the presence of a dynamic conformational equilibrium. The fragmentation behavior of 1 was analyzed by mass spectrometry and compared with those of homoleptic tin tertiary butyl thiolates [Sn(SBu^t)₂] and [Sn(SBu^t)₄]. The precursor 1 was then used to deposit SnS thin films on different substrates (FTO, Mo-coated soda-lime glass) by CVD and film growth rates at different temperatures (300–450 °C) and times (15–60 min), film thickness, crystalline quality, and surface morphology were investigated.