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Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
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Paramagnets are materials with unpaired electrons that possess a finite magnetic moment. In the absence of a magnetic field, these moments are randomly oriented, and thus the net moment is zero. Under an external field, a torque acting on the moments tends to align them along the field's direction. However, the random thermal motion of electrons produces a torque opposite to the external field and tries to disorient the moments. These two competing effects align only a few moments along the...
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Crystal Field Theory
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Closed-shell paramagnetic porphyrinoids.

Rashid R Valiev1, Heike Fliegl2, Dage Sundholm3

  • 1Tomsk State University, Lenina 36, Tomsk, Russian Federation. valievrashid@gmail.com and Department of Chemistry, University of Helsinki, P.O. Box 55 (A. I. Virtanens plats 1), FIN-00014, Finland. dage.sundholm@helsinki.fi.

Chemical Communications (Cambridge, England)
|August 22, 2017
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Summary
This summary is machine-generated.

Researchers found a linear relationship between magnetizabilities and ring-current strength in antiaromatic porphyrinoids. Molecules with strong ring currents exhibit closed-shell paramagnetism and positive magnetizabilities.

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Area of Science:

  • Computational Chemistry
  • Quantum Chemistry
  • Organic Chemistry

Background:

  • Porphyrinoids are macrocyclic compounds with diverse applications.
  • Understanding their magnetic properties is crucial for predicting molecular behavior.
  • Antiaromaticity in porphyrinoids can lead to unique electronic characteristics.

Purpose of the Study:

  • To investigate the relationship between magnetizabilities and ring-current strength in antiaromatic porphyrinoids.
  • To explore the magnetic properties of carbaporphyrins, carbathiaporphyrins, and isophlorins.
  • To determine the nature of paramagnetism in these systems.

Main Methods:

  • Calculations performed at Hartree-Fock (HF), density functional theory (DFT), and second-order Møller-Plesset perturbation theory (MP2) levels.
  • Analysis of magnetizabilities and magnetically induced ring-current strength susceptibilities.
  • Study of various antiaromatic closed-shell porphyrinoid structures.

Main Results:

  • A linear correlation was established between magnetizabilities and ring-current strength susceptibilities.
  • Porphyrinoids with high ring-current strength exhibited closed-shell paramagnetism.
  • Positive magnetizabilities were observed in these paramagnetic systems.

Conclusions:

  • Strong paratropic ring currents in antiaromatic porphyrinoids are responsible for their closed-shell paramagnetism.
  • The observed linear relationship provides a predictive tool for magnetic properties.
  • These findings contribute to the understanding of electronic structures in novel porphyrinoid systems.