Cyclometallated ruthenium(III) complexes: Synthesis,structure and properties

Reactions of Schiff bases (H₂apahR) derived from acetophenone and acid hydrazides, triethylamine and [Ru(PPh₃)₃Cl₂] (1:2:1 mole ratio) in methanol provide cyclometallated ruthenium(III) complexes of formula trans-[Ru(apahR)(PPh₃)₂Cl] in 74–81% yields. The complexes have been characterized by elemental analysis, magnetic susceptibility, spectroscopic (infrared, electronic and EPR) and electrochemical measurements. X-ray crystal structures of two representative complexes have been determined. In each complex, the metal centre is in distorted octahedral CNOClP₂ coordination sphere assembled by the C,N,O-donor meridionally spanning apahR^2?, the chloride and the two mutually trans-oriented PPh₃ molecules. All the complexes are one-electron paramagnetic (μ_eff. = 1.85–1.98 μ_B) and display rhombic EPR spectra in frozen (120 K) dichloromethane-toluene (1:1) solution. Electronic spectra of the complexes display several absorptions within 470–270 nm due to ligand-to-metal charge transfer and ligand centred transitions. The complexes are redox active and display a Ru(III) → Ru(II) reduction and a Ru(III) → Ru(IV) oxidation in the potential ranges ?0.66 to ?0.70 V and 0.75 to 0.80 V (vs. Ag/AgCl), respectively.     

Synthesis of the methylene bis-tetrahydropyran motif of (−)-exiguolide

A chiral-pool approach for the construction of methylene bis-tetrahydropyran subunit, C₁-C₁₆ fragment, of (−)-exiguolide is described. The synthesis was efficiently accomplished starting from l-glutamic acid and l-aspartic acid involving oxa-Michael reaction and an aldol-driven-reductive etherification as key steps for the formation of tetrahydropyran ring.     

A new proof of the transformation law of Jacobi's theta function

We present a new proof, using Residue Calculus, of the transformation law of the Jacobi theta function defined in the upper half plane. Our proof is inspired by Siegel's proof of the transformation law of the Dedekind eta function.

     

Quasiclassical trajectory study of the vibrational quenching of hydroxyl radicals through collision with O atoms

The collisional removal of vibrationally excited OH radicals by O atoms is studied by the quasiclassical trajectory method. To evaluate the effect of different topological features on the scattering processes two different global potential energy surfaces, DMBE IV and TU, are used. Results for reactive, exchange, and inelastic scattering probabilities are reported for central collisions (with zero total angular momentum) with a fixed relative translational energy for vibrational levels of OH ranging from nu=1 to v=8. Vibrational state distributions of product molecules are also compared on the two potential energy surfaces. Both surfaces predict higher probabilities for reaction than for exchange or inelastic scattering. The vibrational state distributions of the product diatomic molecules are different on the two surfaces. In particular, the two surfaces give substantially different probabilities for multiquantum OH vibrational relaxation transitions OH(v)+O-->OH(v')+O.     

Discrete pattern recognition by fitting onto a continuous function

This article outlines an original method for matching discrete structures when atom correspondences are unknown. This method avoids the current atom-by-atom treatment (and its inherent combinatorial problems) and considers the structures to be compared in their totality. The basic idea is to first obtain the atom correspondences by fitting one of the two discrete structures onto a spline approximation of the other, rather than optimizing in discrete space, and, second, to overlap the two discrete structures on the basis of the proposed assignment. As starting data, the method requires only the Cartesian coordinates of the two structures. No connectivity information, neither atom labeling nor matching tolerance is required. This method can readily handle matches of molecules with a few hundred atoms. It is able to search for a given 3D pattern as well as for a pattern common to two structures. © 1997 John Wiley & Sons, Inc. J Comput Chem 18 : 1875–1892, 1997     

Photoacoustic studies on the thermal properties of the NLO compound: L‐alaninium maleate

Studies on thermal and optical properties are very essential for a nonlinear optical material. Photoacoustics (PA) is a recently developed non‐destructive testing (NDT) tool for studying such properties. L‐Alaninium maleate (C₃H₈NO₂⁺·C₄H₃O₄^‐), an organic non‐linear optical (NLO) material was synthesized using submerged seed solution method and was characterized by single crystal X‐ray diffraction (XRD) and density. PA technique was used to determine the thermal parameters of LAM crystals. Moreover, possible phase transition analysis was conducted to ascertain the thermal stability. Scanning electron microscopic (SEM) studies were also carried out and crystal‐packing features discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Photoacoustic study of the thermal and optical properties of hippuric acid

Photoacoustic spectroscopy (PAS) is a recently developed, non‐destructive testing (NDT) tool, used for analyzing the physical properties of materials. This method is used here to determine the thermal diffusivity and conductivity of the gel‐grown single crystals of hippuric acid, a minor constituent of urinary calculi and also a non‐linear optical (NLO) material. Optical absorption of the specimen was studied using its PA spectrum and compared with UV‐visible absorption spectra. Second harmonic generation (SHG) conversion efficiency was also carried out. Characterization of the crystals was made using X‐ray powder diffraction and density determination. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Photoacoustic and X‐ray Studies on H+ Ion Implanted n‐GaAs

Qualitative and quantitative analysis on the defects in H⁺ ion implanted (30keV with doses 10¹⁴, 10¹⁵, 10¹⁶ and 10¹⁷ ions/cm²) n‐GaAs are carried out here by Atomic Force Microscopy (AFM), XRD and Photoacoustic measurements, for various doses. The close agreement between these measurements reveal that even the microscopic strain parameter ∈₁ (from XRD) can be viewed microscopically with photoacoustics. Various thermal parameters are computed for the 30 keV H⁺ ion implanted n‐GaAs and reported for the first time.     

On generalized modular forms supported on cuspidal and elliptic points

Suppose N∈{13,17,19,21,26,29,31,34,39,41,49,50}. In this paper, we extend previous results of Kohnen–Mason (On the canonical decomposition of generalized modular functions, 2010) to prove that generalized modular forms for Γ ₀(N) with rational Fourier expansions whose divisors are supported only at the cusps and at the elliptic points are actually classical modular forms. We discuss possible limitations to this extension and pose questions about possible zeroes for modular forms of prime level.