Pentalene:  Formation, Electronic, and Vibrational Structure

Bally, Thomas; Chai, Steven K.; Neuenschwander, Markus; Zhu, Zhendong

doi:10.1021/ja963439t

Cited by 127 publications

(141 citation statements)

References 28 publications

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“…Simple arguments based on the second-order bond fixation in conjugated molecules [43,44] indicate that the symmetrical bond equalized D 2h structure corresponds to a maximum on the ground state energy surface and that the molecule distorts to C 2h symmetry with alternating single and double bonds. Bond alternation of the order of ≈ 0.15Å has been calculated by all ab initio methods for ground state C 2h pentalene [28,29,158] (see Table 8). …”

Section: Cyclooctatetraene: a Non Planar Cyclic Conjugated Systemmentioning

confidence: 99%

“…Cyclobutadiene has been considered the reference antiaromatic system [23,24] though recently criticism has been advanced to this view [25,26]. Going up with the ring size, while cyclooctatetraene is characterized by a non planar arrangement of the four π bonds [4,10,11], pentalene, where the ring is forced to planarity by crosslink [27,28], is equally well suited to model antiaromatic properties [29]. On the contrary, the more complex and formally antiaromatic structure of s-indacene peculiarly shows a bond equalized ring geometry [30,31].…”

Section: Introductionmentioning

confidence: 99%

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Structures of Annulenes and Model Annulene Systems in the Ground and Lowest Excited States

Gellini

Salvi

2010

Symmetry

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The paper introduces general considerations on structural properties of aromatic, antiaromatic and non-aromatic conjugated systems in terms of potential energy along bond length alternation and distortion coordinates, taking as examples benzene, cyclobutadiene and cyclooctatetraene. Pentalene, formally derived from cyclooctatetraene by cross linking, is also considered as a typical antiaromatic system. The main interest is concerned with [n]annulenes and model [n]annulene molecular systems, n ranging from 10 to 18. The rich variety of conformational and configurational isomers and of dynamical processes among them is described. Specific attention is devoted to bridged [10]-and [14]annulenes in the ground and lowest excited states as well as to s-indacene and biphenylene. Experimental data obtained from vibrational and electronic spectroscopies are discussed and compared with ab initio calculation results. Finally, porphyrin, tetraoxaporphyrin dication and diprotonated porphyrin are presented as annulene structures adopting planar/non-planar geometries depending on the steric hindrance in the inner macrocycle ring. Radiative and non-radiative relaxation processes from excited state levels have been observed by means of time-resolved fluorescence and femtosecond transient absorption spectroscopy. A short account is also given of porphycene, the structural isomer of porphyrin, and of porphycene properties.

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Section: Cyclooctatetraene: a Non Planar Cyclic Conjugated Systemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Structures of Annulenes and Model Annulene Systems in the Ground and Lowest Excited States

Gellini

Salvi

2010

Symmetry

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“…Unsubstituted pentalene (42) is very reactive 103 with a large negative TRE of ¹0.2152 «¢«. 78,101 This molecule can be viewed as perturbed cyclooctatetraene.…”

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confidence: 99%

Graph Theory of Aromatic Stabilization

Aihara¹

2016

BCSJ

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Aromaticity is very sensitive to the geometry of the π-system. Topological resonance energy (TRE), defined graphtheoretically, represents an aromatic stabilization energy (ASE) arising from cyclic conjugation in the π-system. TRE can be calculated for not only ground-state but also excited-state species. The TRE concept has since been extended analytically to solve many different problems concerning aromaticity and reactivity. Bond resonance energy (BRE), defined in harmony with TRE, is an excellent probe for exploring kinetic stability of cyclic π-systems. It represents the contribution of individual π-bonds to global aromaticity. The well-known isolated pentagon rule (IPR) for fullerenes was verified in terms of BRE. Superaromatic stabilization energy (SSE) defined for macrocyclic π-systems finally confirmed the absence of macrocyclic aromaticity in kekulene. A novel local aromaticity index for polycyclic aromatic hydrocarbons (PAHs) was devised by reinterpreting the definition of SSE. We then found that aromatic properties of some PAHs are not compatible with Clar's aromatic sextet rule. We now feel that many fundamental problems with regard to aromatic stabilization and related phenomena have been solved conceptually.

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“…125) The radical anion of cyclooctatetraene [COT (2b), this species may be the radical anion of pentalene, a prototypical Hückel antiaromatic molecule which eluded chemists for several decades. 127) With appropriate tuning of the injection energy, the Scheme 9. Cyclooctatetraene, its anionic derivatives, and their collision-induced transformations.…”

Section: ) 120)mentioning

confidence: 99%

Fundamental Aspects of Gas Phase Ion Chemistry Studied Using the Selected Ion Flow Tube Technique

Kato¹

2005

J. Mass Spectrom. Soc. Jpn.

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Gas phase ion chemistry using the selected ion flow tube (SIFT) technique is discussed with the focus on fundamental studies on ion structure, energetics, reactivity, and dynamics: Laser-induced fluorescence (LIF) kinetics/dynamics of N 2 ῍ (v) ions (vibrationally state-selected ion῎molecule reactions; energy transfer processes), mechanisms of prototypical organic ion reactions (S N 2 nucleophilic substitution and kinetic isotope e#ects; hydrogen/deuterium exchange; isotope e#ects in termolecular association), and ion῎molecule reactions with biological implications (S N 2 reactions at a nitrogen center; E CO 2 elimination reactions of alkyl hydroperoxides). Anion chemistry of small nitroalkanes is also presented. A powerful combination of SIFT and negative ion photoelectron spectroscopy is used to study thermochemistry and structure of energetic and exotic ions (alkyl peroxides; anionic derivatives of diazo and azole compounds, cyclooctatetraene, and cyclopentanone). Finally, some of the new directions in SIFT research are discussed, i.e., reactions of ions with polyatomic organic radicals, and chemical ionization mass spectrometry with new detection schemes.

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Pentalene: Formation, Electronic, and Vibrational Structure

Cited by 127 publications

References 28 publications

Structures of Annulenes and Model Annulene Systems in the Ground and Lowest Excited States

Structures of Annulenes and Model Annulene Systems in the Ground and Lowest Excited States

Graph Theory of Aromatic Stabilization

Fundamental Aspects of Gas Phase Ion Chemistry Studied Using the Selected Ion Flow Tube Technique

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