LANTHANIDE COMPLEXES WITH REGIOISOMERS OF CHLORO-SUBSTITUTED TETRAPHENYLPORPHYRIN

N. N. Semenishyn

doi:10.18524/2304-0947.2021.3(79).240750

LANTHANIDE COMPLEXES WITH REGIOISOMERS OF CHLORO-SUBSTITUTED TETRAPHENYLPORPHYRIN

Odesa National University Herald Chemistry ◽

10.18524/2304-0947.2021.3(79).240750 ◽

2021 ◽

Vol 26 (3(79)) ◽

pp. 27-36

Author(s):

N. N. Semenishyn

Keyword(s):

Lanthanide Complexes ◽

Heavy Atoms

Several isomeric complexes of Yb (III) and Lu(III) with H2tpp and its tetrachloro-substituted derivatives were synthesized. Symmetrical ortho-, meta- and para-positioning of four heavy atoms allows to study their effect on emission features of complexes. Obtained results show the rise of 4f-luminescence effectiveness in the row ortho-meta-para isomers.

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Object Wave Determination by Single-Sideband Methods

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100071776 ◽

1973 ◽

Vol 31 ◽

pp. 266-267

Author(s):

Kenneth H. Downing ◽

Benjamin M. Siegel

Keyword(s):

Phase Shift ◽

Carbon Films ◽

Object Wave ◽

Electron Wave ◽

Phase Object ◽

Heavy Atoms ◽

Single Sideband ◽

Thin Carbon ◽

Additional Phase Shift ◽

Additional Phase

Under the “weak phase object” approximation, the component of the electron wave scattered by an object is phase shifted by π/2 with respect to the unscattered component. This phase shift has been confirmed for thin carbon films by many experiments dealing with image contrast and the contrast transfer theory. There is also an additional phase shift which is a function of the atomic number of the scattering atom. This shift is negligible for light atoms such as carbon, but becomes significant for heavy atoms as used for stains for biological specimens. The light elements are imaged as phase objects, while those atoms scattering with a larger phase shift may be imaged as amplitude objects. There is a great deal of interest in determining the complete object wave, i.e., both the phase and amplitude components of the electron wave leaving the object.

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Single Atom Image Contrast in Fixed Beam Dark Field Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100051840 ◽

1974 ◽

Vol 32 ◽

pp. 366-367

Author(s):

Wah Chi

Keyword(s):

Scattering Amplitude ◽

Present Report ◽

Dark Field ◽

Image Contrast ◽

Single Atom ◽

Optical Theorem ◽

Hartree Fock ◽

Heavy Atoms ◽

Beam Stop ◽

Fixed Beam

Resolution and contrast are the important factors to determine the feasibility of imaging single heavy atoms on a thin substrate in an electron microscope. The present report compares the atom image characteristics in different modes of fixed beam dark field microscopy including the ideal beam stop (IBS), a wire beam stop (WBS), tilted illumination (Tl) and a displaced aperture (DA). Image contrast between one Hg and a column of linearly aligned carbon atoms (representing the substrate), are also discussed. The assumptions in the present calculations are perfectly coherent illumination, atom object is represented by spherically symmetric potential derived from Relativistic Hartree Fock Slater wave functions, phase grating approximation is used to evaluate the complex scattering amplitude, inelastic scattering is ignored, phase distortion is solely due to defocus and spherical abberation, and total elastic scattering cross section is evaluated by the Optical Theorem. The atom image intensities are presented in a Z-modulation display, and the details of calculation are described elsewhere.

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Relative Intensities in ED Patterns From Thin Gold Films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100096436 ◽

1972 ◽

Vol 30 ◽

pp. 636-637

Author(s):

R. H. Morriss ◽

J. D. C. Peng ◽

C. D. Melvin

Keyword(s):

Theoretical Calculations ◽

Diffraction Theory ◽

Gold Films ◽

Reasonable Accuracy ◽

Experimental Conditions ◽

Crystal Perfection ◽

Heavy Atoms ◽

Fine Focus ◽

Convergent Beam ◽

Beam Diffraction

Although dynamical diffraction theory was modified for electrons by Bethe in 1928, relatively few calculations have been carried out because of computational difficulties. Even fewer attempts have been made to correlate experimental data with theoretical calculations. The experimental conditions are indeed stringent - not only is a knowledge of crystal perfection, morphology, and orientation necessary, but other factors such as specimen contamination are important and must be carefully controlled. The experimental method of fine-focus convergent-beam electron diffraction has been successfully applied by Goodman and Lehmpfuhl to single crystals of MgO containing light atoms and more recently by Lynch to single crystalline (111) gold films which contain heavy atoms. In both experiments intensity distributions were calculated using the multislice method of n-beam diffraction theory. In order to obtain reasonable accuracy Lynch found it necessary to include 139 beams in the calculations for gold with all but 43 corresponding to beams out of the [111] zone.

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A Base Specific Single Heavy Atom Stain for Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100094176 ◽

1972 ◽

Vol 30 ◽

pp. 184-185

Author(s):

J. P. Langmore ◽

N. R. Cozzarelli ◽

A. V. Crewe

Keyword(s):

Electron Microscopy ◽

Electron Microscope ◽

High Resolution ◽

Elastic Scattering ◽

Heavy Atom ◽

High Vacuum ◽

Heavy Atoms ◽

Large Movement ◽

Base Sequencing ◽

Scanning Electron

A system has been developed to allow highly specific derivatization of the thymine bases of DNA with mercurial compounds wich should be visible in the high resolution scanning electron microscope. Three problems must be completely solved before this staining system will be useful for base sequencing by electron microscopy: 1) the staining must be shown to be highly specific for one base, 2) the stained DNA must remain intact in a high vacuum on a thin support film suitable for microscopy, 3) the arrangement of heavy atoms on the DNA must be determined by the elastic scattering of electrons in the microscope without loss or large movement of heavy atoms.

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The Interpretation of Crystal Lattice Images

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010009600x ◽

1972 ◽

Vol 30 ◽

pp. 550-551

Author(s):

J. M. Cowley ◽

Sumio Iijima

Keyword(s):

Crystal Orientation ◽

Diffraction Theory ◽

Phase Changes ◽

Electron Wave ◽

Crystal Lattices ◽

Heavy Atoms ◽

Lattice Images ◽

The Right ◽

Intuitive Interpretation ◽

Suitable Approximation

The imaging of detailed structures of crystal lattices with 3 to 4Å resolution, given the correct conditions of microscope defocus and crystal orientation and thickness, has been used by Iijima (this conference) for the study of new types of crystal structures and the defects in known structures associated with fluctuations of stoichiometry. The image intensities may be computed using n-beam dynamical diffraction theory involving several hundred beams (Fejes, this conference). However it is still important to have a suitable approximation to provide an immediate rough estimate of contrast and an evaluation of the intuitive interpretation in terms of an amplitude object.For crystals 100 to 150Å thick containing moderately heavy atoms the phase changes of the electron wave vary by about 10 radians suggesting that the “optimum defocus” theory of amplitude contrast for thin phase objects due to Scherzer and others can not apply, although it does predict the right defocus for optimum imaging.

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Synthesis of Some Lanthanide Complexes Derived From o-Vanphen

Polytechnic Journal ◽

10.25156/ptj.2018.8.2.180 ◽

2018 ◽

Vol 8 (2) ◽

pp. 264-276

Author(s):

Muharram Yaseen

Keyword(s):

Lanthanide Complexes

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Intrinsic Stacking Interactions of Natural and Artificial Nucleobases

10.26434/chemrxiv.11400405 ◽

2019 ◽

Author(s):

Drew P. Harding ◽

Laura J. Kingsley ◽

Glen Spraggon ◽

Steven Wheeler

Keyword(s):

Gas Phase ◽

Electrostatic Interactions ◽

Density Functional ◽

Molecular Descriptors ◽

Stacking Interactions ◽

Interaction Energies ◽

Functional Theory ◽

Binding Partner ◽

Heavy Atoms ◽

Wide Range

The intrinsic (gas-phase) stacking energies of natural and artificial nucleobases were explored using density functional theory (DFT) and correlated ab initio methods. Ranking the stacking strength of natural nucleobase dimers revealed a preference in binding partner similar to that seen from experiments, namely G > C > A > T > U. Decomposition of these interaction energies using symmetry-adapted perturbation theory (SAPT) showed that these dispersion dominated interactions are modulated by electrostatics. Artificial nucleobases showed a similar stacking preference for natural nucleobases and were also modulated by electrostatic interactions. A robust predictive multivariate model was developed that quantitively predicts the maximum stacking interaction between natural and a wide range of artificial nucleobases using molecular descriptors based on computed electrostatic potentials (ESPs) and the number of heavy atoms. This model should find utility in designing artificial nucleobase analogs that exhibit stacking interactions comparable to those of natural nucleobases. Further analysis of the descriptors in this model unveil the origin of superior stacking abilities of certain nucleobases, including cytosine and guanine.

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