Insights on the aromaticity of imidazolylidene carbenes by means of DFT calculations

Andres S. Urbina; Cesar H. Zambrano; F. Javier Torres; Luis Rincon

doi:10.1016/j.comptc.2016.09.007

Insights on the aromaticity of imidazolylidene carbenes by means of DFT calculations

Andres S. Urbina, Cesar H. Zambrano, F. Javier Torres, Luis Rincon

Research output: Contribution to journal › Article › peer-review

Abstract

The effect of sixteen substituents on the structure of imidazolylidene carbenes was studied using five aromaticity criteria: Singlet-Triplet energy gap (STG), a modified version of the Harmonic Oscillator Model of Aromaticity (HOMA) geometric descriptor, the Aromatic Stabilization Energy (ASE) based on the energy of hydrogenation of the carbenes, the Nuclear Independent Chemical Shift (NICS) and the Aromatic Fluctuation Index (FLU). These calculations were conducted at the B2PLYP/aug-cc-pVDZ//B3LYP/6-311+G^∗ level of theory. Even if these five descriptors are intended to quantify the “aromaticity” of the substituted carbenes, the correlation between them is far from being statistically significant. After excluding some “outliers”, a detailed analysis reveals three important correlations: (i) STG and ASE, (ii) HOMA and ASE and (iii) NICS(1)_zz and FLU. The first one supports the well-known connection between the STG and the energy of hydrogenation of carbenes. The second is strongly influenced by the interplay between energetic and “steric” factors associated with each substituent group. The last one is clearly due to the extent of the electronic delocalization in these heterocyclic compounds.

Original language	English (US)
Pages (from-to)	108-113
Number of pages	6
Journal	Computational and Theoretical Chemistry
Volume	1094
DOIs	https://doi.org/10.1016/j.comptc.2016.09.007
State	Published - Oct 15 2016
Externally published	Yes

All Science Journal Classification (ASJC) codes

Biochemistry
Condensed Matter Physics
Physical and Theoretical Chemistry

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10.1016/j.comptc.2016.09.007

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title = "Insights on the aromaticity of imidazolylidene carbenes by means of DFT calculations",

abstract = "The effect of sixteen substituents on the structure of imidazolylidene carbenes was studied using five aromaticity criteria: Singlet-Triplet energy gap (STG), a modified version of the Harmonic Oscillator Model of Aromaticity (HOMA) geometric descriptor, the Aromatic Stabilization Energy (ASE) based on the energy of hydrogenation of the carbenes, the Nuclear Independent Chemical Shift (NICS) and the Aromatic Fluctuation Index (FLU). These calculations were conducted at the B2PLYP/aug-cc-pVDZ//B3LYP/6-311+G∗ level of theory. Even if these five descriptors are intended to quantify the “aromaticity” of the substituted carbenes, the correlation between them is far from being statistically significant. After excluding some “outliers”, a detailed analysis reveals three important correlations: (i) STG and ASE, (ii) HOMA and ASE and (iii) NICS(1)zz and FLU. The first one supports the well-known connection between the STG and the energy of hydrogenation of carbenes. The second is strongly influenced by the interplay between energetic and “steric” factors associated with each substituent group. The last one is clearly due to the extent of the electronic delocalization in these heterocyclic compounds.",

author = "Urbina, {Andres S.} and Zambrano, {Cesar H.} and Torres, {F. Javier} and Luis Rincon",

note = "Funding Information: This work has been performed by employing the resources of the USFQ{\textquoteright}s High Performance Computing system (HPC-USFQ). The authors would like to thank USFQ{\textquoteright}s chancellor and collaboration grants programs for financial support. Publisher Copyright: {\textcopyright} 2016 Elsevier B.V.",

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AU - Urbina, Andres S.

AU - Zambrano, Cesar H.

AU - Torres, F. Javier

AU - Rincon, Luis

N1 - Funding Information: This work has been performed by employing the resources of the USFQ’s High Performance Computing system (HPC-USFQ). The authors would like to thank USFQ’s chancellor and collaboration grants programs for financial support. Publisher Copyright: © 2016 Elsevier B.V.

PY - 2016/10/15

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AB - The effect of sixteen substituents on the structure of imidazolylidene carbenes was studied using five aromaticity criteria: Singlet-Triplet energy gap (STG), a modified version of the Harmonic Oscillator Model of Aromaticity (HOMA) geometric descriptor, the Aromatic Stabilization Energy (ASE) based on the energy of hydrogenation of the carbenes, the Nuclear Independent Chemical Shift (NICS) and the Aromatic Fluctuation Index (FLU). These calculations were conducted at the B2PLYP/aug-cc-pVDZ//B3LYP/6-311+G∗ level of theory. Even if these five descriptors are intended to quantify the “aromaticity” of the substituted carbenes, the correlation between them is far from being statistically significant. After excluding some “outliers”, a detailed analysis reveals three important correlations: (i) STG and ASE, (ii) HOMA and ASE and (iii) NICS(1)zz and FLU. The first one supports the well-known connection between the STG and the energy of hydrogenation of carbenes. The second is strongly influenced by the interplay between energetic and “steric” factors associated with each substituent group. The last one is clearly due to the extent of the electronic delocalization in these heterocyclic compounds.

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Insights on the aromaticity of imidazolylidene carbenes by means of DFT calculations

Abstract

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