scholarly journals Electronic Structures of Purine Bases Studied by Electrochemical-ESR Techniques. Spin Distribution in Purine Anion Radical

1980 ◽  
Vol 53 (5) ◽  
pp. 1252-1256 ◽  
Author(s):  
Hiroaki Ohya-Nishiguchi ◽  
Yasunori Shimizu ◽  
Noboru Hirota ◽  
Kohji Watanabe
Keyword(s):  
Electronic Structures ◽  
Anion Radical ◽  
Spin Distribution ◽  
Purine Bases

scholarly journals Light-Induced Control of the Spin Distribution on Cu–Dithiolene Complexes: A Correlated Ab Initio Study

Molecules ◽  
2019 ◽  
Vol 24 (6) ◽  
pp. 1088 ◽  
Author(s):  
Jhon Zapata-Rivera ◽  
Carmen Calzado
Keyword(s):  
Excited States ◽  
Electronic Structures ◽  
Crystal Packing ◽  
Building Blocks ◽  
Electronic Transitions ◽  
Ab Initio Study ◽  
Spin Distribution ◽  
Conducting Materials ◽  
Dmit Ligand ◽  
Adequate Analysis

Metal dithiolene complexes—M(dmit)2—are key building blocks for magnetic, conducting, and optical molecular materials, with singular electronic structures resulting from the mixing of the metal and dmit ligand orbitals. Their use in the design of magnetic and conducting materials is linked to the control of the unpaired electrons and their localized/delocalized nature. It has been recently found that UV–Vis light can control the spin distribution of some [Cu(dmit)2]−2 salts in a direct and reversible way. In this work, we study the optical response of these salts and the origin of the differences observed in the EPR spectra under UV–Vis irradiation by means of wave function-based quantum chemistry methods. The low-lying states of the complex have been characterized and the electronic transitions with a non-negligible oscillator strength have been identified. The population of the corresponding excited states promoted by the UV–Vis absorption produces significant changes in the spin distribution, and could explain the changes observed in the system upon illumination. The interaction between neighbor [Cu(dmit)2]−2 complexes is weakly ferromagnetic, consistent with the relative orientation of the magnetic orbitals and the crystal packing, but in disagreement with previous assignments. Our results put in evidence the complex electronic structure of the [Cu(dmit)2]−2 radical and the relevance of a multideterminantal approach for an adequate analysis of their properties.

Modulation of the optical properties of chiral porphyrin dimers by introducing bridged chiral amide-bonds

2020 ◽  
Vol 25 (01) ◽  
pp. 37-46
Author(s):  
Mingfeng Qin ◽  
Zhen Zhang ◽  
Weihua Zhu ◽  
John Mack ◽  
Rodah C. Soy ◽  
...  
Keyword(s):  
Optical Properties ◽  
Amino Acid ◽  
Electronic Structures ◽  
Anion Radical ◽  
Cd Spectra ◽  
Radical Species ◽  
Amide Bonds ◽  
Band Region ◽  
Porphyrin Dimers

The d/l-enantiomers of a series of three Zn(II)tetraarylporphyrin dimers were synthesized and isolated by incorporating a bridging amide-bonded xanthene moiety at the para-position of one of the meso-aryl rings. The electronic structures and optical properties were modulated by incorporating chiral amino acid moieties into the amide-bonding moieties of the xanthene bridge that contain methyl, tolyl and 2-methylindole substituents. A cofacial dimer was formed in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) resulting in a significant red shift of the B band, due to a relative destabilization of the HOMO, which has large MO coefficients on the pyrrole nitrogens. The sign sequences observed in the B band region of the CD spectra due to the presence of the chiral amino acid moieties were modified due to this change in geometry. Significant CD intensity is also observed in the B band region of the CD spectra of anion radical species during in situ spectroelectrochemical measurements.

The phenylcyclooctatetraene anion radical and dianion: an intramolecular charge and spin distribution isotope effect

1992 ◽  
Vol 114 (2) ◽  
pp. 399-403 ◽  
Author(s):  
Gerald R. Stevenson ◽  
Richard D. Burton ◽  
Richard C. Reiter
Keyword(s):  
Isotope Effect ◽  
Anion Radical ◽  
Spin Distribution

The Nature of Oxide Surfaces: Topographic and Electronic Structure

1993 ◽  
Vol 51 ◽  
pp. 966-967
Author(s):  
Dawn A. Bonnell ◽  
Yong Liang
Keyword(s):  
Transition Metal Oxides ◽  
Electronic Structures ◽  
Recent Progress ◽  
Spatial Localization ◽  
Level Of Detail ◽  
Scanning Tunneling ◽  
Oxide Surfaces ◽  
Tunneling Microscopy ◽  
Considerable Effort ◽  
Complete Understanding

Recent progress in the application of scanning tunneling microscopy (STM) and tunneling spectroscopy (STS) to oxide surfaces has allowed issues of image formation mechanism and spatial resolution limitations to be addressed. As the STM analyses of oxide surfaces continues, it is becoming clear that the geometric and electronic structures of these surfaces are intrinsically complex. Since STM requires conductivity, the oxides in question are transition metal oxides that accommodate aliovalent dopants or nonstoichiometry to produce mobile carriers. To date, considerable effort has been directed toward probing the structures and reactivities of ZnO polar and nonpolar surfaces, TiO2 (110) and (001) surfaces and the SrTiO3 (001) surface, with a view towards integrating these results with the vast amount of previous surface analysis (LEED and photoemission) to build a more complete understanding of these surfaces. However, the spatial localization of the STM/STS provides a level of detail that leads to conclusions somewhat different from those made earlier.

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