<i>Cis</i>−<i>Trans</i> Isomerism in Porphyrin Isomers

Ghosh, Abhik; Jynge, Knut

doi:10.1021/jp971446d

Cited by 22 publications

(14 citation statements)

References 6 publications

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“…A number of studies have focused on computational method assessment, [14±16] spectral details, [17±20] force fields, [21±23] and substituent effects [24±28] of porphyrins. Recently Ghosh and Jynge have made extensive local density functional (LDF) calculations on the cis ± trans isomerism in porphyrin isomers [29] and they also compared free-base porphyrin with various chlorins. [30] In this work we apply ab initio methods on bonellindimethylester, which is a multiply substituted free-base porphyrin possessing C 1 symmetry.…”

Section: Introductionmentioning

confidence: 99%

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An Ab Initio Study of Structure and Energetics of Free-Base Bonellin-Dimethylester Isomers and Transition States

Sundholm¹,

Konschin²,

Häser

1999

Chem. Eur. J.

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The molecular structures of bonellin-dimethylester isomers and transition states, for the hydrogen migration of the inner hydrogens, have been optimized at density functional level by the use of split-valence basis sets augmented with polarization functions. Accurate values for the relative energies of the six isomers and the eight transition states have been obtained by performing second-order Mùller ± Plesset calculations. The isomer energies obtained at density functional level are 2 ± 5 kcal mol À1 smaller than second-order Mùller ± Plesset values, while the isomer energies calculated at Hartree ± Fock level are typically 1 kcal mol À1 too small compared with second-order Mùl-ler ± Plesset values, except for one isomer whose Hartree ± Fock energy is 7 kcal mol À1 larger. Compared with the second-order Mùller ± Plesset values, the energy barriers for the transition between the isomers calculated at density functional level are 3 ± 7 kcal mol À1 too small, whereas those obtained at Hartree ± Fock level are 6 ± 8 kcal mol À1 too large. Nuclear magnetic shielding constants calculated at Hartree ± Fock level are also reported. The calculated nuclear magnetic shieldings are used for analyzing the aromaticity and the aromatic pathway of the porphyrin nucleus.

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Section: Introductionmentioning

confidence: 99%

“…[4,5,29,30] For bonellin-dimethylester there are two nondegenerate trans-isomers (isomer 1 and 6). Isomer 1 is lower in energy, since its aromatic resonance pathway is not affected by the substituents.…”

mentioning

confidence: 99%

An Ab Initio Study of Structure and Energetics of Free-Base Bonellin-Dimethylester Isomers and Transition States

Sundholm¹,

Konschin²,

Häser

1999

Chem. Eur. J.

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“…[55][56][57][58] The predominant existence of the trans tautomer in porphyrins, porphycenes, and dibenzotetraaza [14]annulenes is also supported by the calculations of relative energies of different tautomers. [59][60][61] The cis form has higher energy and could not be detected experimentally at standard conditions. It may require setting the molecule in a specific environment to detect different tautomers.…”

Section: Resultsmentioning

confidence: 97%

Correlations of geometric and spectroscopic parameters of intramolecular hydrogen bonds in porphyrin-like macrocycles

Gawinkowski

Prakash

2022

Preprint

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Chemical bond lengths and angles are characteristic structural parameters that describe a molecule. Likewise, the frequencies of the vibration modes and the NMR chemical shift are unique and referred to as "chemical fingerprints" specific to the compound. These are the basic parameters describing and allowing the identification of newly obtained compounds. In macrocyclic compounds with a porphyrin-like structure, intramolecular hydrogen bonding significantly influences the physicochemical properties. This paper presents the correlations between geometric and spectroscopic parameters related to hydrogen bonds in this type of macrocyclic compound. In particular, these relationships were demonstrated for a large group of porphyrin, porphycene, and dibenzotetraaza[14]annulene derivatives and the group of other macrocycles with a similar structure. A very strong linear relationship is found between the frequencies of vibrations of the NH groups of the hydrogen bond and the length of this bond, which is common for all macrocyclic compounds of this type. Several other relationships are shown between spectroscopic (IR, Raman, NMR) and geometric (X-ray) parameters indicating differences and similarities between different families of macrocycles. Apart from a better understanding of the nature of hydrogen bonds and their characteristics in porphyrin-like macrocyclic compounds, these relationships will facilitate the identification of new macrocycles and the extrapolation of their spectroscopic properties.

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“…8 The porphyrin isomers reported to date include, corrphycene, hemiporphycene, and isoporphycene obtained by shuffling the four pyrrolic subunits and the meso-carbon bridge. 5,[8][9][10][11][12] Many research groups have recently exploited some of the unique properties exhibited by the N-confused porphyrins because their remarkable ability to act as tetra-coordinate ligands to form transition metal complexes. 4 This led to a flurry of synthetic attempts toward novel porphyrin-like molecules, with structural variants such as ring or bridge extended, reshuffled, inverted, N-and C-fused, contracted and core-modified porphyrins.…”

Section: Introductionmentioning

confidence: 99%

“…9 Ghosh and Jynge reported BLYP/6-31G** calculations on cis and trans porphyrin isomers having [3⋅0⋅1⋅0], [3⋅1⋅0⋅0] and [4⋅0⋅0⋅0] connectivity. 10 Core modification in the skeleton by replacing one or two pyrrole nitrogens by other heteroatoms such as O and S alters the electronic structure and results in the formation of modified porphyrins. Introducing other heteroatoms yields new classes of compounds containing novel chelating properties.…”

Section: Introductionmentioning

confidence: 99%

A theoretical study of porphyrin isomers and their core-modified analogues:cis-trans isomerism, tautomerism and relative stabilities

2004

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Semiempirical (AM1 and PM3) and density functional theory (DFT) calculations were performed on about 50 porphyrin isomers with 25 each of 1,2 (syn) and 1,3 (anti) tautomeric forms. The corresponding oxa-and thia-core-modified analogues were also computed. The variations of relative energies and stabilities of the core-modified analogues were compared with parent porphyrin 1 and the corresponding oxa-and thia-analogues. The trends in relative energies are not significantly changed while going from parent system to oxa-and thia-core-modified porphyrins in case of both syn and anti tautomers. Isomers of types [2⋅2⋅0⋅0], [3⋅0⋅1⋅0], [3⋅1⋅0⋅0], and [4⋅0⋅0⋅0] are destabilized due to the absence of methine bridge, which results in angle strain for tetrapyrroles. Isomers having [2⋅1⋅1⋅0], [2⋅1⋅0⋅1], [2⋅0⋅2⋅0] and [2⋅2⋅0⋅0] connectivity, the Z isomers, are more stable compared to the corresponding E isomers in both syn and anti forms of parent and core-modified analogues.

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Cis−Trans Isomerism in Porphyrin Isomers

Cited by 22 publications

References 6 publications

An Ab Initio Study of Structure and Energetics of Free-Base Bonellin-Dimethylester Isomers and Transition States

An Ab Initio Study of Structure and Energetics of Free-Base Bonellin-Dimethylester Isomers and Transition States

Correlations of geometric and spectroscopic parameters of intramolecular hydrogen bonds in porphyrin-like macrocycles

A theoretical study of porphyrin isomers and their core-modified analogues:cis-trans isomerism, tautomerism and relative stabilities

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