Electronic properties and aromaticity of substituted diphenylfulvenes in the ground (S0) and excited (T1) states

Sadlej-Sosnowska, Nina

doi:10.1007/s11224-017-0995-y

Cited by 7 publications

(9 citation statements)

References 39 publications

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“…The ring’s double to single bond lengths ratio could be a fair measure of the ring’s quinoidization degree. However, instead of introducing a new parameter, we use the harmonic oscillator model of aromaticity (HOMA) index, − which was shown to be not only a measure of geometrical aromaticity but also a simple structural descriptor of moleculesbe they aromatic or nonaromatic, cyclic or acyclic, or linear or branched. − Moreover, it was already successfully used to study diphenylfulvenes in the first excited triplet state . Fulvenes are antiaromatic in the ground singlet but aromatic in the T 1 state.…”

Section: Results and Discussionmentioning

confidence: 99%

Substituent Effect in the First Excited Triplet State of Monosubstituted Benzenes

Dobrowolski

Karpińska

2020

ACS Omega

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The structure of 30 monosubstituted benzenes in the first excited triplet T1 state was optimized with both unrestricted (U) and restricted open shell (RO) approximations combined with the ωB97XD/aug-cc-pVTZ basis method. The substituents exhibited diverse σ- and π-electron-donating and/or -withdrawing groups. Two different positions of the substituents are observed in the studied compounds in the T1 state: one distorted from the plane and the other coplanar with a quinoidal ring. The majority of the substituents are π-electron donating in the first group while π-electron withdrawing in the second one. Basically, U- and RO-ωB97XD approximations yield concordant results except for the B-substituents and a few of the planar groups. In the T1 state, the studied molecules are not aromatic, yet aromaticity estimated using the HOMA (harmonic oscillator model of aromaticity) index increases from ca. −0.2 to ca. 0.4 with substituent distortion, while in the S1 state, they are only slightly less aromatic than in the ground state (HOMA ≈0.8 vs ≈1.0, respectively). Unexpectedly, the sEDA(T1) and pEDA(T1) substituent effect descriptors do not correlate with analogous parameters for the ground and first excited singlet states. This is because in the T1 state, the geometry of the ring changes dramatically and the sEDA(T1) and pEDA(T1) descriptors do not characterize only the functional group but the entire molecule. Thus, they cannot provide useful scales for the substituents in the T1 states. We found that the spin density in the T1 states is accumulated at the Cipso and Cp atoms, and with the substituent deformation angle, it nonlinearly increases at the former while decreases at the latter. It appeared that the gap between singly unoccupied molecular orbital and singly occupied molecular orbital (SUMO-SOMO) is determined by the change of the SOMO energy because the former is essentially constant. For the nonplanar structures, SOMO correlates with the torsion angle of the substituent and the ground-state pEDA(S0) descriptor of the π-electron-donating substituents ranging from 0.02 to 0.2 e. Finally, shapes of the SOMO-1 instead of SOMO frontier orbitals in the T1 state somehow resemble the highest occupied molecular orbital ones of the S0 and S1 states. For several planar systems, the shape of the U- and RO-density functional theory-calculated SOMO-1 orbitals differs substantially.

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Section: Results and Discussionmentioning

confidence: 99%

Substituent Effect in the First Excited Triplet State of Monosubstituted Benzenes

Dobrowolski

Karpińska

2020

ACS Omega

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“…This allows the fulvene to function as a 6π component in reactions with electron-deficient dienes (Scheme 5) and fulvenes acting as dipolarophiles have been reported for enantioselective [6 + 3] and [3 + 2] cycloadditions [83–84 105]. In general, reactions with electron-rich alkenes will take place preferentially at the exocyclic C6 position while other less electron-rich species interact most strongly with the fulvene HOMO resulting in only [4 + 2] cycloadditions [101,103].…”

Section: Reviewmentioning

confidence: 99%

“…Pentafulvenes show dual capabilities in DACs, with documented examples of them functioning as both dienes and dienophiles [55,114,150–151 154,159,174–176 227–229]. The exact nature of the fulvene moiety is dependent mostly on its substituents (e.g., EWG or EDG) relative to the other reactants [6,42,45,67,103,153,230]. Maleimides (including maleic anhydride) [55,71,92,96,150,176–177 179–184 186,192,229,231], dimethyl acetylenedicarboxylate (DMAD) and p -benzoquinone [60,150,159,164,175,211] derivatives [174,183,200,229] are often used as the complementary dienophiles (Scheme 14, reaction pathways (i), (ii) and (iii), respectively), as well as mono- and disubstituted acetylene derivatives, such as methyl propiolate [229] and dibenzoylacetylene [150].…”

Section: Reviewmentioning

confidence: 99%

“…Although the stereochemistry of DACs can usually be predicted by the ‘endo rule’ [92,176,229,232], there are some exceptions, particularly when sterically-demanding fulvenes, such as norbornyl-fused fulvenes [229] or adamantilydenefulvene [174] are involved. In the literature, many cycloaddition reactions have been conducted with dimethylfulvene [52,97,106,118,133–134] or diphenylfulvene [20,103,114,133,163,180]. In each instance, the endo stereochemistry of the cycloadduct is dominant [91,176,180], indicating that the fulvene substituents in the exocyclic C6 position are too distal to impact the stereoselectivity [76,229].…”

Section: Reviewmentioning

confidence: 99%

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An overview of the cycloaddition chemistry of fulvenes and emerging applications

Swan¹,

Platts²,

Blencowe³

2019

Beilstein J. Org. Chem.

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The unusual electronic properties and unique reactivity of fulvenes have interested researchers for over a century. The propensity to form dipolar structures at relatively low temperatures and to participate as various components in cycloaddition reactions, often highly selectively, makes them ideal for the synthesis of complex polycyclic carbon scaffolds. As a result, fulvene cycloaddition chemistry has been employed extensively for the synthesis of natural products. More recently, fulvene cycloaddition chemistry has also found application to other areas including materials chemistry and dynamic combinatorial chemistry. This highlight article discusses the unusual properties of fulvenes and their varied cycloaddition chemistry, focussing on applications in organic and natural synthesis, dynamic combinatorial chemistry and materials chemistry, including dynamers, hydrogels and charge transfer complexes. Tables providing comprehensive directories of fulvene cycloaddition chemistry are provided, including fulvene intramolecular and intermolecular cycloadditions complete with reactant partners and their resulting cyclic adducts, which provide a useful reference source for synthetic chemists working with fulvenes and complex polycyclic scaffolds.

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“…Importantly, it was determined that among the sites available for substitution, atom C6 is the most responsive to substitution with electron-donating groups . The problem of the electronic structure of fulvene derivatives was taken up in several subsequent theoretical studies. − The composite picture, arising from the application of a range of aromaticity indices, is that of increased aromatic character with increasing electron-donating ability of the substituent at atom C6.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Study of Ground- and Excited-State Charge Transfer in Fulvene-Based Donor–Acceptor Systems

Kochman

Durbeej

2019

J. Phys. Chem. A

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Donor–acceptor systems based on fulvene as the electron-accepting moiety are typified by exotic, strongly polar electronic structures. In this contribution, ab initio calculations have been performed to explore the ground- and excited-state properties of an archetypal compound of this class, which incorporates the exocyclic carbon atom of fulvene into a tetramethylimidazoline-like five-membered ring. In the electronic ground state, the compound under study has a pronounced zwitterionic character and is best described as consisting of a negatively charged cyclopentadienyl ring linked covalently to a positively charged tetramethylimidazolium ring. Both of these rings can be considered as aromatic. The excess negative charge localized on the cyclopentadienyl ring is highly labile in the photochemical sense: the low-lying valence excited states exhibit varying degrees of reverse charge transfer, whereby electron density is transferred from the cyclopentadienyl ring back onto the tetramethylimidazolium ring. The topographies of the excited-state potential energy surfaces favor rapid and efficient internal conversion at an extended, fulvene-like S1/S0 conical intersection seam. As a consequence, the excited-state lifetime of this compound is predicted to be on the order of 100 fs.

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Electronic properties and aromaticity of substituted diphenylfulvenes in the ground (S0) and excited (T1) states

Cited by 7 publications

References 39 publications

Substituent Effect in the First Excited Triplet State of Monosubstituted Benzenes

Substituent Effect in the First Excited Triplet State of Monosubstituted Benzenes

An overview of the cycloaddition chemistry of fulvenes and emerging applications

Theoretical Study of Ground- and Excited-State Charge Transfer in Fulvene-Based Donor–Acceptor Systems

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