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Direct observation of the intermediate in an ultrafast isomerization.
Using a combination of two-dimensional infrared (2D IR) and variable temperature Fourier transform infrared (FTIR) spectroscopies the rapid structural isomerization of a five-coordinate ruthenium complex is investigated. In methylene chloride, three exchanging isomers were observed: (1) square pyramidal equatorial, (1); (2) trigonal bipyramidal, (0); and (3) square pyramidal apical, (2). Exchange between 1 and 0 was found to be an endergonic process (ΔH = 0.84 (0.08) kcal mol-1, ΔS = 0.6 (0.4) eu) with an isomerization time constant of 4.3 (1.5) picoseconds (ps, 10-12 s). Exchange between 0 and 2 however was found to be exergonic (ΔH = -2.18 (0.06) kcal mol-1, ΔS = -5.3 (0.3) eu) and rate limiting with an isomerization time constant of 6.3 (1.6) ps. The trigonal bipyramidal complex was found to be an intermediate, with an activation barrier of 2.2 (0.2) kcal mol-1 and 2.4 (0.2) kcal mol-1 relative to the equatorial and apical square pyramidal isomers respectively. This study provides direct validation of the mechanism of Berry pseudorotation - the pairwise exchange of ligands in a five-coordinate complex - a process that was first described over fifty years ago. This study also clearly demonstrates that the rate of pseudorotation approaches the frequency of molecular vibrations
Evaluation of electric and magnetic fields distribution and SAR induced in 3D models of water containers by radiofrequency radiation using FDTD and FEM simulation techniques
In this study, two software packages using different numerical techniques
FEKO 6.3 with Finite-Element Method (FEM) and XFDTD 7 with Finite Difference
Time Domain Method (FDTD) were used to assess exposure of 3D models of square,
rectangular, and pyramidal shaped water containers to electromagnetic waves at
300, 900, and 2400 MHz frequencies. Using the FEM simulation technique, the
peak electric field of 25, 4.5, and 2 V/m at 300 MHz and 15.75, 1.5, and 1.75
V/m at 900 MHz were observed in pyramidal, rectangular, and square shaped 3D
container models, respectively. The FDTD simulation method confirmed a peak
electric field of 12.782, 10.907, and 10.625 V/m at 2400 MHz in the pyramidal,
square, and rectangular shaped 3D models, respectively. The study demonstrated
an exceptionally high level of electric field in the water in the two identical
pyramid shaped 3D models analyzed using the two different simulation
techniques. Both FEM and FDTD simulation techniques indicated variations in the
distribution of electric, magnetic fields, and specific absorption rate of
water stored inside the 3D container models. The study successfully
demonstrated that shape and dimensions of 3D models significantly influence the
electric and magnetic fields inside packaged materials; thus, specific
absorption rates in the stored water vary according to the shape and dimensions
of the packaging materials.Comment: 22 pages, 30 figures and 2 table
Studies of Histidine, Phenylalanine Complexes of Oxovanadium(IV) Derived from Acetylacetone
Schiff base complexes of oxovanadium(IV) with amino acids and acetylacetone were synthesized and characterized by elemental analysis, conductivity measurements, spectral and magnetic data. The complexes were found to be non-electrolytes and stoichiometry shown 1:1. The spectral and magnetic data were suggesting the square pyramidal geometr
Spectral properties of the two-dimensional Schrödinger Hamiltonian with various solvable confinements in the presence of a central point perturbation
We study three solvable two-dimensional systems perturbed by a point interaction centered at the
origin. The unperturbed systems are the isotropic harmonic oscillator, a square pyramidal
potential and a combination thereof. We study the spectrum of the perturbed systems. We show
that, while most eigenvalues are not affected by the point perturbation, a few of them are strongly
perturbed. We show that for some values of one parameter, these perturbed eigenvalues may take
lower values than the immediately lower eigenvalue, so that level crossings occur. These level
crossings are studied in some detail
Diiodido[4′-(4-pyridyl)-2,2′:6′,2′′-terpyridine-κ3 N,N′,N′′]copper(II)
The CuII atom in the title compound, [CuI2(C20H14N4)], has a distorted square-pyramidal coordination formed by the N atoms of the tridentate 4′-(4-pyridyl)-2,2′:6′2′′-terpyridine (pyterpy) ligand and two I atoms; one of the I atoms is in the apical position. In contrast to other known square-pyramidal diiodido- and dibromidocopper complexes of the pyterpy ligand in which metal–halogen distances are significantly different, in the title compound the apical and equatorial Cu—I bonds are almost identical [2.6141 (8) and 2.6025 (8) Å, respectively]
trans-Chlorido{3-chloro-2-[(1-naphthyl)iminomethyl]phenyl-κ2 C 1,N}bis(trimethylphosphane)nickel(II)
The title compound, [Ni(C17H11ClN)Cl(C3H9P)2], was obtained as a product of the reaction of [Ni(PMe3)4] with a molar equivalent of 2,6-dichloro-N-naphthylbenzaldehydeamine in diethyl ether. The τ parameter is 0.3, indicating that the coordination geometry is square-pyramidal. The NiII atom lies in the center of a square pyramidal in which one C, one Cl and two P atoms form the basal plane, with the imine N atom in an apical position. Two P-atom donors are located in trans positions
Investigation of a square-based pyramidal-sheet roof
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