Spin Density, Spin Population, Spin Polarization, and Spin Delocalization

2004 ◽  
pp. 49-82 ◽  
Keyword(s):  
Spin Density ◽  
Spin Polarization ◽  
Spin Population ◽  
Spin Delocalization

scholarly journals Insights on spin delocalization and spin polarization mechanisms in crystals of azido copper(II) dinuclear complexes through the electron spin density Source Function

2017 ◽  
Vol 73 (4) ◽  
pp. 565-583 ◽  
Author(s):  
Carlo Gatti ◽  
Giovanni Macetti ◽  
Leonardo Lo Presti
Keyword(s):  
Spin Density ◽  
Spin Polarization ◽  
Source Function ◽  
Reference Points ◽  
Dinuclear Complexes ◽  
Azido Group ◽  
Local Spin ◽  
Whole Space ◽  
Spin Delocalization ◽  
Spin Densities

The Source Function (SF) tool was applied to the analysis of thetheoreticalspin density in azido CuIIdinuclear complexes, where the azido group, acting as a coupler between the CuIIcations, is linked to the metal centres either in an end-on or in an end–end fashion. Results for only the former structural arrangement are reported in the present paper. The SF highlights to which extent the magnetic centres contribute to determine the local spin delocalization and polarization at any point in the dimetallic complex and whether an atom or group of atoms of the ligands act in favour or against a given local spin delocalization/polarization. Ball-and-stick atomic SF percentage representations allow for a visualization of the magnetic pathways and of the specific role played by each atom along these paths, at given reference points. Decomposition of SF contributions in terms of a magnetic and of a relaxation component provides further insight. Reconstruction of partial spin densities by means of the Source Function has for the first time been introduced. At variance with the standard SF percentage representations, such reconstructions offer a simultaneous view of the sources originating from specific subsets of contributing atoms, in a selected molecular plane or in the whole space, and are therefore particularly informative. The SF tool is also used to evaluate the accuracy of the analysed spin densities. It is found that those obtained at the unrestricted B3LYP DFT level, relative to those computed at the CASSCF(6,6) level, greatly overestimate spin delocalization to the ligands, but comparatively underestimate magnetic connection (spin transmission) among atoms, along the magnetic pathways. As a consequence of its excessive spin delocalization, the UB3LYP method also overestimates spin polarization mechanisms between the paramagnetic centres and the ligands. Spin delocalization measures derived from the refinement of Polarized Neutron Diffraction data seem in general superior to those obtained through the DFT UB3LYP approach and closer to the far more accurate CASSCF results. It is also shown that a visual agreement on the spin-resolved electron densities ραand ρβderived from different approaches does not warrant a corresponding agreement between their associated spin densities.

Salts of Ferricinium Cation and its Homologues: NMR Investigation, II EPR and NMR Spectra of sym-Polymethyl Substituted Ferricinium Cations

1980 ◽  
Vol 35 (11) ◽  
pp. 1415-1419 ◽  
Author(s):  
R. B. Materikova ◽  
V. N. Babin ◽  
S. P. Solodovnikov ◽  
I. R. Lyatifov ◽  
P. V. Petrovsky ◽  
...  
Keyword(s):  
Density Distribution ◽  
Spin Density ◽  
Spin Polarization ◽  
Nmr Spectra ◽  
General Pattern ◽  
Spin Density Distribution ◽  
Determining Factors ◽  
Spin Delocalization ◽  
C Nmr

Abstract The EPR, 1H and 13C NMR spectra of methylferricinium hexafluorophosphates, [(MenCp)2Fe]PF6, n = 0-5, have been recorded. HFS constants have been estimated for all the ligand atoms. The general pattern of the spin density distribution is shown to depend on the superposition of the various mechanisms of spin delocalization. For the majority of the cations the determining factors has been found to be represented by spin polarization over the π-skeleton.

ESR Studies on 205Tl Hyperfine Couplings in the Radical Cations of Tl(III)Porphyrins

1974 ◽  
Vol 29 (12) ◽  
pp. 1827-1833 ◽  
Author(s):  
Chr. Mengersen ◽  
J. Subramanian ◽  
J.-H. Fuhrhop ◽  
K. M. Smith
Keyword(s):  
Spin Density ◽  
Spin Polarization ◽  
Radical Cations ◽  
Esr Spectra ◽  
Cation Radicals ◽  
Bilinear Relation ◽  
Tetraphenyl Porphyrin ◽  
Pi Orbitals ◽  
Spin Densities ◽  
Hyperfine Couplings

The isotropic 205Tl hyperfine couplings obtained from the ESR spectra of the radical cations of Tl (III) meso tetraphenyl porphyrin (TPP), octaethyl porphyrin (OEP) and octaethyl chlorin (OEC) are reported. The radical cations were generated by electrooxidation in dichloromethane as solvent. A Karplus-Fraenkel type bilinear relation is used to interpret the 205Tl couplings, taking into account the sigma-pi spin polarization of Tl -N bonds by the spin density at the nitrogen atoms in the ligand as well as the direct pi interaction of the orbitals of Tl with the pi orbitals of the ligand. It is shown that for the cation radicals of Tl porphyrins, both these mechanisms contribute to the Tl couplings whereas for the cation radicals of Co- and Zn-porphyrins the sigma-pi polarization alone is sufficient to account for the metal hyperfine couplings. It is suggested that Tl-hyperfine couplings can be used to estimate the nitrogen spin densities of porphyrin radical systems when the nitrogen splittings are not resolved in the ESR spectra.

scholarly journals Design Considerations for Oligo(p-Phenyleneethynylene) Organic Radicals in Molecular Junctions

2020 ◽  
Author(s):  
Martin Sebastian Zöllner ◽  
Rukan Nasri ◽  
Haitao Zhang ◽  
Carmen Herrmann
Keyword(s):  
Spin Polarization ◽  
Single Molecule ◽  
Fermi Energy ◽  
Organic Radicals ◽  
Stable Radical ◽  
Design Consideration ◽  
Dispersion Interactions ◽  
Electron Transmission ◽  
Design Considerations ◽  
Spin Delocalization

Spin polarization in the electron transmission of radicals is important for understanding single-molecule conductance experiments focusing on shot noise, Kondo properties or magnetoresistance. We study how stable radical substituents can affect such spin polarization when attached to oligo(p- phenyleneethynylene) (OPE) backbones. We find that it is not straightforward to translate the spin density on a stable radical substituent into spin-dependent transmission for the para-connected wires under study here, owing to increased steric interactions compared with meta-connected wires, and a resulting twisting of the radical substituent and OPE π systems. The most promising example is a t-butyl nitroxide substituent, which, despite little pronounced spin delocalization onto the backbone, yields a spin-dependent transmission feature which one might be able to shift towards the Fermi energy by additional substituents. We also find that for bulkier substituents, dispersion interactions with the substituent can lead to twisting of one of the outer OPE rings, reducing the overall conductance. As a further potential design consideration, attaching radicals via linkers might increase the possibilities for spin-dependent intermolecular and molecule-electrode interactions.

scholarly journals Spin Density Calculations on the Tetraphenylverdazyl Radical and Two Nitroxide Radicals: First and Second Order Spin Polarization.

1996 ◽  
Vol 50 ◽  
pp. 458-461 ◽  
Author(s):  
Lars Öhrström ◽  
André Grand ◽  
Bernd Pilawa ◽  
Georg W. Jensen ◽  
Inge L. Møller ◽  
...  
Keyword(s):  
Spin Density ◽  
Spin Polarization ◽  
Second Order ◽  
Nitroxide Radicals

MAGNETIC COUPLING CONSTANTS AND SPIN DENSITY DISTRIBUTIONS FOR CYANO-BRIDGED Gd(III)-Fe(III) AND Gd(III)-Cr(III) COMPOUNDS: BROKEN-SYMMETRY AND DENSITY FUNCTIONAL THEORY CALCULATIONS

2005 ◽  
Vol 19 (15n17) ◽  
pp. 2538-2543 ◽  
Author(s):  
YI QUAN ZHANG ◽  
CHENG LIN LUO ◽  
ZHI YU
Keyword(s):  
Density Functional Theory ◽  
Spin Density ◽  
Spin Polarization ◽  
Density Functional ◽  
Population Analysis ◽  
Magnetic Coupling ◽  
Coupling Constants ◽  
Broken Symmetry ◽  
Functional Theory ◽  
Density Distributions

Magnetic coupling constants J for the complete structures of [ Gd(capro) 2( H 2 O )4 Cr(CN) 6]• H 2 O (capro represents caprolactam) (a) and trans-[ Fe(CN) 4(μ- CN )2 Gd ( H 2 O )4 (bpy) ]•4 H 2 O •1.5 bpy (b) have been calculated using hybrid density functional theory (DFT) B3LYP combined with a modified broken symmetry approach (BS). The calculated J value of -0.24 cm-1 for a is very close to the experimental -0.33 cm-1. They both show the antiferromagnetic interaction between Gd(III) and Cr(III) . For b, although the sign of the calculated J value of 4.24 cm-1 is different from that of the experimental -0.38 cm-1, the two values both show the weak magnetic coupling interaction between Gd(III) and Fe(III) . The spin density distributions are discussed on the basis of Mulliken population analysis. For complexes a and b, both transition metal ( Fe(III) or Cr(III) ) and rare earth Gd(III) display a spin polarization effect on the surrounding atoms, where a counteraction of the opposite polarization effects leads to a low spin density on the bridging ligand C1N1 . For the compounds Gd(III) - Cr(III) (a) and Gd(III) - Fe(III) (b) in the HS states, Cr(III) has stronger spin polarization influence on the bridging atoms than Fe(III) even causing the positive spin population on the bridging atom N1 .

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