The Acenes:  Is There a Relationship between Aromatic Stabilization and Reactivity?

Schleyer, Paul von Ragué; Manoharan, Mariappan; Jiao, and Haijun; Stahl, Frank

doi:10.1021/ol016553b

Cited by 322 publications

(339 citation statements)

References 36 publications

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“…From Table 2 we can observe the negative slope values; the acidity increases (Δ acid G° decreases) when χ XC 6 H 4 increases, validating the proposal that the central ring exhibits more contribution to Δ acid G° than the edge rings and it behaves as a rather separated benzenoid ring or localized entity. This is a nice coincidence with the ambident nucleophilic character experimentally observed for the 9-anthrylmethyl carbanion and related intermediates [26], and the calculated aromaticity of the central ring of anthracene [27][28][29].…”

Section: F(osupporting

confidence: 86%

Understanding the Nucleophilic Character and Stability of the Carbanions and Alkoxides of 1-(9-Anthryl)ethanol and Derivatives

2013

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Abstract:The nucleophilic character and stability of the carbanions vs. alkoxides derived from 2,2,2-trifluoro-1-(9-anthryl)ethanol and 1-(9-anthryl)ethanol containing X electron-releasing and X electron-acceptor substituents attached to C-10, have been studied at the B3LYP/6-31+G(d,p) level of theory. Results analyzed in terms of the absolute gas-phase acidity, Fukui function, the local hard and soft acids and bases principle, and the molecular electrostatic potential, show that the central ring of the 9-anthryl group confers an ambident nucleophilic character and stabilizes the conjugated carbanion by electron-acceptor delocalization.

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Section: F(osupporting

confidence: 86%

Understanding the Nucleophilic Character and Stability of the Carbanions and Alkoxides of 1-(9-Anthryl)ethanol and Derivatives

2013

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“…In addition, the NICS at 1 Å above and below the center of the ring (NICS(1) out and NICS(1) in , respectively), considered to better reflect the π-electron effects [66,67], have also been calculated for these systems. The values in Table 1 show that NICS(0) and NICS(1) in follow the same trend, thus increasing the aromaticity with bending, however, NICS(1) out follows the expected opposite behavior, like HOMA and PDI.…”

Section: B) C) A)mentioning

confidence: 99%

“…Lazzeretti [62,63] and Aihara [64] have pointed out in several works that NICS's validity to indicate diamagnetic ring currents is limited by the potential spurious contributions from the in-plane tensor components that, at least in classical organic aromatic compounds, are not related to aromaticity. This effect is partially avoided by using NICS (1), that is considered to better reflect the π-electron effects [65][66][67][68], or with its corresponding out-of-plane tensor component (NICS(1) zz ) or even better with the π contribution to this component computed at the ring center or at 1 Å above (NICS(0) πzz and NICS(1) πzz , respectively). In 1997, the first dissected NICS were introduced by Schleyer et al [68] and were applied to study the aromaticity of some inorganic rings.…”

Section: Introductionmentioning

confidence: 99%

A Critical Assessment of the Performance of Magnetic and Electronic Indices of Aromaticity

et al. 2010

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Abstract:The lack of reference aromatic systems in the realm of inorganic aromatic compounds makes the evaluation of aromaticity in all-metal and semimetal clusters a difficult task. To date, calculation of nucleus-independent chemical shifts (NICS) has been the most widely used method to discuss aromaticity in these systems. In the first part of this work, we briefly review our previous studies, showing some pitfalls of the NICS indicator of aromaticity in organic molecules. Then, we refer to our study on the performance of some aromaticity indices in a series of 15 aromaticity tests, which can be used to analyze the advantages and drawbacks of aromaticity descriptors. It is shown that indices based on the study of electron delocalization are the most accurate among those analyzed in the series of proposed tests, while NICS(1) zz and NICS(0) πzz present the best behavior among NICS indices. In the second part, we discuss the use of NICS and electronic multicenter indices (MCI) in inorganic clusters. In particular, we evaluate the aromaticity of two series of all-metal and semimetal clusters with predictable aromaticity trends by means of NICS and MCI. Results show that the expected trends are generally better reproduced by MCI than NICS. It is concluded that NICS(0) π and NICS(0) πzz are the kind of NICS that perform the best among the different NICS indices analyzed for the studied series of inorganic compounds.

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“…Negative (diatropic) NICS values indicate aromaticity, while positive (paratropic) values imply antiaromaticity. NICS(0) is usually computed at the ring centers, but also can be calculated at certain distance above or below the center of the ring; the NICS obtained at 1 Å above the ring centroid, NICS(1) as well as the NICS zz (1) tensor component are considered to be better aromaticity indices than NICS(0) [23,24]. The NICS(0), NICS(1), NICS zz (0) and NICS zz (1) are given in Table 3.…”

Section: Stability Of the Cyclo-cu 4 (μ-) 4 L N (N = 1-4; Nuc = N 2 mentioning

confidence: 99%

“…However, the NICS zz component acquires negative values (in the range of -5.6 to -10.5 ppm) in a distance of 1.6 -1.8 Å above the ring plane. Considering that the NICS zz component is a better index of aromaticity [23,24] we could say that all planar structures keep the aromatic character of the parent cyclo-Cu 4 (μ-) 4 molecule.…”

Section: Stability Of the Cyclo-cu 4 (μ-) 4 L N (N = 1-4; Nuc = N 2 mentioning

confidence: 99%

How the Aromatic 4-Membered Hydrido-Bridged Copper Rings Respond to Successive Nucleophilic Attack?

Tsipis¹,

Charistos²

2008

TOMEJ

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Electronic structure calculations (B3LYP/6-311+G**) predict that nucleophilic attack of the aromatic cycloCu 4 (μ-) 4 ring yields ligand-stabilized tetranuclear Cu 4 clusters formulated as cyclo-Cu 4 (μ-) 4 Nuc n (n = 1-4; Nuc = N 2 , CO, H 2 O, NH 3 and PH 3 ). Depending on the number of added nucleophiles, the tetranuclear Cu 4 clusters adopt planar, bent or 3D tetrahedral geometries. These molecules exhibit aromatic character, which is primarily due to 4s and 3d cyclic electron delocalization over the Cu 4 framework (s and d-orbital aromaticity). The aromaticity of the novel ligand stabilized tetranuclear Cu 4 clusters was verified by a number of established criteria of aromaticity. In particular, the nucleusindependent chemical shift, NICS(0) and NICS(1) and their out-of-plane components NICS zz (0), NICS zz (1) and the NICS scan pictures are indicative for the aromaticity of the planar, bent and tetrahedral Cu 4 clusters. The effect of the substituents on the aromatic character of the Cu 4 clusters is also a main concern of the present work. It was found that increasing the number of the attacking nucleophiles increases the diatropic response of the aromatic tetranuclear Cu 4 clusters. Moreover, the aromaticity of the 3D structures (spherical aromaticity) is higher than the aromaticity of the planar and bent structures. The effect of the coordinated nucleophiles, Nuc, on the stability, geometry, electronic structure and bonding mode of the cyclo-Cu 4 (μ-) 4 Nuc n molecules is also thoroughly discussed.

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The Acenes: Is There a Relationship between Aromatic Stabilization and Reactivity?

Cited by 322 publications

References 36 publications

Understanding the Nucleophilic Character and Stability of the Carbanions and Alkoxides of 1-(9-Anthryl)ethanol and Derivatives

Understanding the Nucleophilic Character and Stability of the Carbanions and Alkoxides of 1-(9-Anthryl)ethanol and Derivatives

A Critical Assessment of the Performance of Magnetic and Electronic Indices of Aromaticity

How the Aromatic 4-Membered Hydrido-Bridged Copper Rings Respond to Successive Nucleophilic Attack?

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