Magnetic response properties of carbon nano-onions

Orozco‐Ic, Mesías; Sundholm, Dage

doi:10.1039/d2cp02718f

Cited by 8 publications

(8 citation statements)

References 62 publications

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“…Our calculations on Ge12 2-, Sn12 2-, and Pb12 2reveal that these compounds show an inside paratropic and an outside spherical diatropic current, akin to all-carbon fullerenes. 94,95 The core-electron contribution to the total current density is significant, particularly near the nuclei where the current density pathways are markedly distorted (Figure 4). This is evident in the B ind z calculations, which show a considerable influence of core electrons on shielding.…”

Section: Moleculementioning

confidence: 99%

Core-electron contributions to the magnetic response of molecules with heavy elements and their significance in aromaticity assessments

Orozco Ic,

Soriano-Agueda,

Sundholm

et al. 2024

Preprint

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This study delves into the magnetic response of core electrons and their influence on the global magnetic response of systems planar and three-dimensional containing heavy elements, employing the removing valence electron (RVE) approximation. We also explore electronic aromaticity indices to understand the potential role of core electrons on electron delocalization in absence of an external perturbation. The study reveals that core electrons significantly contribute to the overall magnetic response, especially to the magnetic shielding, affecting the interpretation of aromaticity. In contrast, the calculation of the electronic aromaticity indices suggests a negligible participation of the core electrons to the electron delocalization. Despite its widespread use, the study emphasizes caution in labeling systems as strongly aromatic based solely on shielding function computations. It is noteworthy to emphasize the limitations associated with each aromaticity criterion, particularly in the context of magnetic shielding function calculations, the core-electron effect contamination is undeniable. Hence, the integration of various criteria becomes imperative for attaining a comprehensive understanding of magnetic responses within complex systems.

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Section: Moleculementioning

confidence: 99%

Core-electron contributions to the magnetic response of molecules with heavy elements and their significance in aromaticity assessments

Orozco Ic,

Soriano-Agueda,

Sundholm

et al. 2024

Preprint

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“…The hypothetical pseudo-π systems mimic accurately the magnetic response of the molecules exposed to an external magnetic field. The pseudo-π model that has been applied to hydrocarbons and all-carbon structures reduces dramatically the computational costs without significantly affecting the magnetic response. ,− …”

Section: Methodsmentioning

confidence: 99%

“…Computational studies of the MICD susceptibility (MICD or current density) of nanostructures are demanding since the molecules can consist of hundreds or even thousands of atoms. The pseudo-π approximation, which was originally introduced for studies of the MICD of small hydrocarbons, has successfully been used in current-density studies of large aromatic hydrocarbons and nanosized all-carbon structures. ,, Construction of a pseudo-π model for studies of the MICD of porphyrin nanostructures is not obvious because porphyrins contain nitrogen atoms, and a metal cation or eventually inner hydrogen atoms that have to be accounted for in the model because the orbitals of the inner hydrogen atoms or the valence electrons of the metal atom contribute to the conjugated bonding of the porphyrin.…”

Section: Introductionmentioning

confidence: 99%

Current-Density Calculations on Zn-Porphyrin₄₀ Nanorings

Mahmood,

Dimitrova,

Sundholm

2023

J. Phys. Chem. A

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Two porphyrinoid nanorings have been studied computationally. They were built by linking 40 Zn-porphyrin units with butadiyne bridges. The molecular structures belonging to the D 40h point group were fully optimized with the Turbomole program at the density functional theory (DFT) level using the B3LYP functional and the def2-SVP basis sets. The aromatic character was studied at the DFT level by calculating the magnetically induced current-density (MICD) susceptibility using the GIMIC program. The neutral molecules are globally non-aromatic with aromatic Zn-porphyrin units. Charged nanorings could not be studied because almost degenerate frontier orbitals led to vanishing optical gaps for the cations. Since DFT calculations of the MICD are computationally expensive, we also calculated the MICD using three pseudo-π models. Appropriate pseudo-π models were constructed by removing the outer hydrogen atoms and replacing all carbon and nitrogen atoms with hydrogen atoms. The central Zn atom was either replaced with a beryllium atom or with two inner hydrogen atoms. Calculations with the computationally inexpensive pseudo-π models yielded qualitatively the same magnetic response as obtained in the all-electron calculations.

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“…These calculations were performed with the Turbomole software . Given that hybrid long-range corrected functionals like CAM-B3LYP are well suited for describing electron delocalization in large organic molecules , and provide magnetic properties consistent with those obtained at the CCSD(T) level, we computed the electronic indices and the magnetic response at the CAM-B3LYP/def2-TZVP level. The magnetic response was determined by computing the magnetically induced current density − ( J ind ) and the induced magnetic field − ( B ind ) using the gauge including magnetically induced current (GIMIC) − and Aromagnetic programs, respectively.…”

Section: Computational Detailsmentioning

confidence: 99%

Understanding Aromaticity in [5]Helicene-Bridged Cyclophanes: A Comprehensive Study

Orozco-Ic,

Soriano-Agueda,

Escayola

et al. 2024

J. Org. Chem.

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This study explores the aromaticity of doubly [5]helicene-bridged (1,4)cyclophane and triply [5]helicenebridged (1,3,5)cyclophane via calculations of the magnetic response and of electronic aromaticity indices. The primary objective is to assess the π-electron delocalization to determine whether they sustain global ring currents associated with π aromaticity. The molecules show local ring currents in the presence of an external magnetic field. The ring currents flow diatropically in the stacked six-membered rings and in the helicene arms. However, these π currents are not interconnected due to the discontinuity of the π delocalization at the C−C single bonds connecting the central six-membered rings to the helicene arms. Electronic indices suggest that the helicene-arm systems have significantly smaller electron delocalization than benzene. The reduction in the delocalization does not compromise their ability to exhibit ring currents in the presence of an external magnetic field. The analysis provides further evidence that the magnetic criteria yield a different degree of aromaticity for the helicene arms than obtained in the calculation of the electronic aromaticity indices. However, both approaches confirm that the studied molecules are not globally aromatic.

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Magnetic response properties of carbon nano-onions

Abstract: The magnetic response of a number of double- and triple-layer carbon nano-onions (CNOs) is analyzed by calculating the magnetically induced current density and the induced magnetic field using the pseudo-π...

Cited by 8 publications

References 62 publications

Core-electron contributions to the magnetic response of molecules with heavy elements and their significance in aromaticity assessments

Core-electron contributions to the magnetic response of molecules with heavy elements and their significance in aromaticity assessments

Current-Density Calculations on Zn-Porphyrin₄₀ Nanorings

Understanding Aromaticity in [5]Helicene-Bridged Cyclophanes: A Comprehensive Study

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Magnetic response properties of carbon nano-onions

Abstract: The magnetic response of a number of double- and triple-layer carbon nano-onions (CNOs) is analyzed by calculating the magnetically induced current density and the induced magnetic field using the pseudo-π...

Cited by 8 publications

References 62 publications

Core-electron contributions to the magnetic response of molecules with heavy elements and their significance in aromaticity assessments

Core-electron contributions to the magnetic response of molecules with heavy elements and their significance in aromaticity assessments

Current-Density Calculations on Zn-Porphyrin40 Nanorings

Understanding Aromaticity in [5]Helicene-Bridged Cyclophanes: A Comprehensive Study

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Current-Density Calculations on Zn-Porphyrin₄₀ Nanorings