Two New 2-Benzoylbenzoate Metal Complexes with Bapen: Synthesis,Spectroscopic and Crystal Structures

Abstract  

Coordination compounds of compositions [Ni(bba)₂(bapen)] (1) and [Cu(bba)₂(bapen)]0.5H₂O (2), where bba = 2-benzoylbenzoate, bapen = N,N′-bis(3-aminopropyl)ethylenediamine, have been prepared. The crystal and molecular structure of (1) and (2) were determined by X-ray analysis. Nickel and copper atoms are six-coordinated by four N atoms of amine and O donor atoms of 2-benzoylbenzoate anions, whereas 0.5 water molecule is situated outside the coordination sphere in (2). The calculated ∆(OCO) values are consistent with presence of monodentate carboxylate. Thermal analysis show that the mass losses of 1 in the temperature ranges 240–343 °C correspond to the decomposition of bba ligands, while the mass losses of 2 in the temperature ranges 105–125 °C correspond to the decomposition of crystal lattice water molecule.     

DFT - based study of electronic structures and mechanical properties of LiTaO3: ferroelectric and paraelectric phases

Abstract

By applying ab initio calculation within density functional theory (DFT), we study the structure parameters, electronic band structure, elastic coefficients, polycrystalline elastic properties, anisotropy factors and Debye temperature of ferroelectric and paraelectric phases of LiTaO₃ within the generalised gradient approximation at ambient pressure. The atomic structure in both phases is fully relaxed and the lattice constant, angle and atomic positions are well consistent with experimental values. The computed single-crystal elastic coefficients indicate that mechanical stability of LiTaO₃ in both phases is confirmed using the generalised Born criteria. The shear, bulk and Young’s modulus, Poisson’s ratio, and Vickers hardness were computed according to theoretical elastic constants by Voight–Reuss–Hill method. Several anisotropy factors and indexes are computed to illustrate mechanical anisotropy. Both phases are shown to be weakly anisotropic. The Debye temperature is estimated using the longitude and transverse elastic wave velocity of the ideal polycrystalline LiTaO₃ aggregates. We have found that LiTaO₃ in both phases has an indirect energy band gap. The differences in the electronic structure and density of states for both phases are quite small. Our results indicate that the mechanical and bonding properties of both phases are very similar. The obtained results were compared with the available experimental and theoretical values.     

High-resolution beam steering using microlens arrays

Imaging or beam-steering systems employing a periodic array of microlenses or micromirrors suffer from diffraction problems resulting from the destructive interference of the beam segments produced by the array. Simple formulas are derived for beam steering with segmented apertures that do not suffer from diffraction problems because of the introduction of a moving linear phase shifter such as a prescan lens before the periodic structure. The technique substantially increases the resolution of imaging systems that employ microlens arrays or micromirror arrays. Theoretical, numerical, and experimental results demonstrating the high-resolution imaging concept using microlens arrays are presented.     

Impedance‐based viscoelastic flow cytometry

Elastic nature of the viscoelastic fluids induces lateral migration of particles into a single streamline and can be used by microfluidic based flow cytometry devices. In this study, we investigated focusing efficiency of polyethylene oxide based viscoelastic solutions at varying ionic concentration to demonstrate their use in impedimetric particle characterization systems. Rheological properties of the viscoelastic fluid and particle focusing performance are not affected by ionic concentration. We investigated the viscoelastic focusing dynamics using polystyrene (PS) beads and human red blood cells (RBCs) suspended in the viscoelastic fluid. Elasto‐inertial focusing of PS beads was achieved with the combination of inertial and viscoelastic effects. RBCs were aligned along the channel centerline in parachute shape which yielded consistent impedimetric signals. We compared our impedance‐based microfluidic flow cytometry results for RBCs and PS beads by analyzing particle transit time and peak amplitude at varying viscoelastic focusing conditions obtained at different flow rates. We showed that single orientation, single train focusing of nonspherical RBCs can be achieved with polyethylene oxide based viscoelastic solution that has been shown to be a good candidate as a carrier fluid for impedance cytometry.     

What determines the banking sector performance in globalized financial markets? The case of Turkey

This study attempts to give an insight into the trend in the performance of the Turkish banking sector by conducting a panel data fixed effects regression analysis. The results reveal that efficiency change is negatively related to the number of branches. We find a positive relationship between the loan ratio and the performance indices efficiency and efficiency change. Furthermore, bank capitalization is positively related to efficiency change. Interestingly however, return on equity is not statistically significant in explaining any of the efficiency measures. There is also no robust relationship between foreign ownership and efficiency. Finally, restructuring attempts in post-crises epoch robustly account for the improvement in efficiency scores in recent years.     

Copolymers Containing Phosphorescent Iridium(III) Complexes Obtained by Free and Controlled Radical Polymerization Techniques

A methacrylate‐functionalized phosphorescent Ir(III)‐complex has been synthesized, characterized, and applied as a monomer in radical copolymerizations. Together with methyl methacrylate, the complex has been copolymerized under free radical polymerization conditions. Aiming for host‐guest‐systems, applicable e.g. in organic light emitting devices (OLEDs), the complex was further copolymerized with a methacrylate‐functionalized carbazole derivative using the atom transfer radical polymerization technique. Applying gel permeation chromatography, in combination with a photodiode array detector, could clearly prove the formation of the copolymers. The optical properties of the photoactive monomers as well as the copolymers were investigated by absorption and emission spectroscopy (in solution). For the carbazole‐copolymer, the emission originates almost exclusively from the complex. This provides evidence of an efficient intrachain energy transfer, which makes the system an interesting candidate for potential OLED applications.

     

Solid-state Electrochemical Sensor Based on a Cross-linked Copper(II)-doped Copolymer and Carbon Nanotube Material for Selective and Sensitive Detection of Monohydrogen Phosphate

A novel solid-state electrochemical sensor based on a newly synthesized cross-linked copper(II) doped-copolymer and carbon nanotube material was developed for the direct determination of monohydrogen phosphate ions (HPO₄²⁻). The synthesized copolymers were characterized by FTIR, XPS, TG/DTG-DTA and SEM techniques. The sensor had a Nernstian slope:-30.7±0.4 mV/decade, linear concentrations range: 1.0×10⁻⁶ - 1.0×10⁻¹ M, detection limit: 6.5×10⁻⁷ M, response time: 4 s and life time: 17 weeks. The sensor displayed constant potentials in the pH range 7.0-9.5. The sensor was successfully used as an indicator electrode in potentiometric titration and the direct determination of HPO₄ ²⁻ in water samples.