Synthesis,characterization and 1,3‐butadiene polymerization behaviors of cobalt complexes bearing 2‐pyrazolyl‐substituted 1,10‐phenanthroline ligands

A series of cobalt(II) complexes containing tridentate 2‐pyrazolyl‐substituted 1,10‐phenanthroline ligands (L) with the general formula [LCoCl₂] have been successfully synthesized and fully identified by IR spectroscopy, elemental analysis and mass spectroscopy. Cobalt complexes Co4–Co8 were further confirmed by X‐ray crystallographic analysis, and all the complexes adopted distorted trigonal pyramid geometries around the cobalt center. In combination with methylaluminoxane, the complexes exhibit high cis‐1,4‐selectivity for 1,3‐butadiene polymerization. The catalytic activities of the complexes mainly depend on the nature of the substituent and its position at the pyrazolyl ring of the ligand. Complexes having a bulkier substituent on the pyrazolyl ring of the ligand show lower catalytic activity and the incorporation of electron‐withdrawing substituent enhances the activity. Polymerization behaviors were almost not affected with varying [Al]/[Co] ratio, but both activity and the cis‐1,4 content decrease slightly as polymerization temperature increasing. Copyright © 2013 John Wiley & Sons, Ltd.     

Investigating the effect of gravity on long pulsed laser drilling

With the aim of improving the efficiency of laser drilling, an upward drilling method is proposed. In the experiment, a long pulsed laser beam was arranged to propagate upwards, in the opposite direction to gravity, and was used to drill hole at the bottom of an aluminum slab. A semi-infinite axisymmetric model of this system was also established. The analytical solution for the hole shape was derived by assuming that material, once it melted, was removed from hole with the aid of gravity. The calculation results agreed well with the experimental results. For further verification of the effects of gravity, the removed molten material and the hole shape for the downward (along the gravity direction) and the upward drilling cases were compared experimentally. In addition, the relationships between gravity, the inertia force, the surface tension and the viscosity were discussed. The results show that more molten material is expelled with the assistance of the gravity, and the laser energy is used more efficiently to melt the aluminum slab in the upward drilling.     

Subsolidus binary phase diagram of the bilayer compounds [n-C_nH_(2n+1)N(CH_3)_3]_2ZnCl_4(n = 16, 18)

The bilayer compounds[n-CnH2n+1N(CH3)3]2Zn Cl4(n=16,18)experience solid-solid phase transition within the temperature range of 310 to 340 K.The low-temperature crystal structures of the pure compounds are characteristic of the piling effect in which a 2D macro-anion Zn Cl42- is sandwiched between two alkylammonium layers.These layers become conformationally disordered in the high-temperature phases.The structures can alternatively be viewed as a double layer of alkylammonium ions between Zn Cl42- sheets and can be considered as crystalline models of lipid bilayers.The experimental subsolidus binary phase diagram of[n-C16H33N(CH3)3]2Zn Cl4-[n-C18H37N(CH3)3]2Zn Cl4 has also been established over the whole composition range by differential scanning calorimetry(DSC)and X-ray diffraction.In the phase diagram,one intermediate compound[n-C16H33N(CH3)3][n-C18H37N(CH3)3]Zn Cl4 at WC16C3Zn%47.50 and two eutectoid invariants points at WC16C3Zn%35.10 and75.70 were observed;the respective temperatures of the two eutectoids are 320±1 and 315±1 K.In addition,there are three noticeable solid solution ranges in the phase diagram:α-phase at the left,β-phase at the right,andγ-phase in the middle.     

Fabrication of periodical structure and shape-induced modulating spectroscopy of Au nanoparticles

This paper presents optical property of the periodical bowties structure of Au nanoparticles on glass substrate fabricated by high-resolution electron beam lithography. Numerical calculation is used to examine the shape-induced surface plasmon enhancement and extinction spectroscopy by using Finite-Difference Time Domain algorithm and Lorentz model of surface plasmon. The calculated extinction spectra of the periodical nanoparticles are consistent with the experimental results. The influence of the geometrical shape on the spectral properties of bowtie nanoparticles is discussed. This investigation may help one to design plasmonic sub-wavelength devices with desired spectral properties.