Global and Local Aromaticity of Linear and Angular Polyacenes

Cyrański, Michał K.; Stępień, Beata T.; Krygowski, Tadeusz M.

doi:10.1016/s0040-4020(00)00919-4

Cited by 94 publications

(112 citation statements)

References 29 publications

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“…The global aromaticity (estimated on experimental geometry) of phenanthrene 22 is 0.750. This is in excellent agreement with the value estimated on B3LYP/6-311G** optimized geometry (HOMA=0.741 12 ). Despite high modifications of the system in 1,7-phenanthroline 7-oxide, 1,7-phenanthroline 1,7-dioxide, 1,8-phenanthroline 1,8-dioxide, 4,7-phenanthroline 4-oxide the extent of delocalization is higher: 0.821, 0.779, 0.768 and 0.794, respectively.…”

Section: Resultssupporting

confidence: 90%

How far is the pi-electron delocalization of phenanthrene moiety is modified in the aza-analogues and their N-oxides?

Stępień¹,

Krygowski²,

Cyrański³

et al. 2004

Arkivoc

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Dedicated to Professor Mieczysław AbstractThe consequences of the replacement of a CH fragment of phenantherene by N-aza, N-N-diaza and/or N-oxide groups for the cyclic π-electron delocalization are discussed. Despite substantial structural changes, the π-electron structure is modified only moderately. The aza-analogues usually exhibit more effective π-electron delocalization, while the N-oxidation leads to its decrease. Usually the presence of the nitrogen atom or N-O group lead to more efficient delocalization in neighboring fragment(s). The analysis is based on experimental geometries of four phenanthroline N-oxides and N,N-dioxides (4,7-phenanthroline 4-oxide, 1,7-phenanthroline 1,7-dioxide, 1,7-phenanthroline 7-oxide and 1,8-phenanthroline 1,8-dioxide) and is completed by the geometry optimizations with use of the DFT method at B3LYP/6-311G** level of theory.

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Section: Resultssupporting

confidence: 90%

How far is the pi-electron delocalization of phenanthrene moiety is modified in the aza-analogues and their N-oxides?

Stępień¹,

Krygowski²,

Cyrański³

et al. 2004

Arkivoc

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“…A molecular system satisfying specific energetic, geometric, magnetic, and chemical reactivity criteria could be called aromatic [45,46,[49][50][51][52][53][54]. Obviously, aromaticity is one of the most frequently used concepts in chemistry.…”

Section: Introductionmentioning

confidence: 99%

“…However, unlike chemical bonding, aromaticity is a multidimensional property. Therefore, in common practice are aromaticity studies including results obtained from various criteria [45,46,[49][50][51][52][53][54] and recently concentrating on two popular aromaticity indexes: HOMA [45,46,52] and NICS [47,49]. Thus, these parameters should reflect geometrical (HOMA) and magnetic (NICS) properties of three different ring subunits of phthalocyanine (see Fig.…”

Section: Introductionmentioning

confidence: 99%

Solvent impact on the planarity and aromaticity of free and monohydrated zinc phthalocyanine: a theoretical study

2017

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A theoretical investigation on the planarity of molecular structure of zinc phthalocyanine (ZnPc) and its aromaticity has been performed using B3LYP and M06-2X density functionals combined with selected Pople-type basis sets. The effect of the applied calculation method on the optimized structure of ZnPc and ZnPc•••H 2 O, both in the gas phase and in the polar solvent, was analyzed. To quantify the aromaticity of the ZnPc and ZnPc•••H 2 O complexes, both the geometric and magnetic criteria, i.e., Harmonic Oscillator Model of Aromaticity (HOMA) index and the nucleus-independent chemical shift (NICS) values at the centers or 1 Å above the centers of structural subunits, were calculated. The energies of highest energy occupied molecular orbital (HOMO) and lowest energy unoccupied molecular orbital (LUMO) and energy gaps were also estimated. The results show that the free ZnPC molecule is flat in the gas phase and nonplanar in the polar environments (DMSO and water). ZnPC•••H 2 O is nonpolar in the gas phase and polar solvent which is in agreement with recent X-ray reports. Both HOMA and NICS indexes indicate the presence of highly aromatic macrocycle and benzene rings while these parameters for pyrrolic ring are significantly smaller than in free pyrrole. The presence of polar solvents practically does not change aromaticity of the ring subunits of the studied compounds.

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“…25 These ASE values were determined as the difference between the group additivity values for the aromatic system and those for the olefinic reference. 10 Neither of these plots extrapolates well to naphthalene (ASEPE = 2.61) or benzene (ASEPE = 3.49). 26 for the linear and zigzag polyacenes.…”

Section: Dsmentioning

confidence: 90%

“…9 A comparison of the aromaticity of the linear and zigzag polyacenes was performed by the HOMA method. 10 By the topological measure of stability (TMS), the infinite zigzag polyacene is two times more stable than the infinite linear polyacene. 11 As an example chrysene has a TMS = 0.7292 and we calculated that triphenylene has a TMS = 0.7778 indicating it is more stable than is chrysene.…”

Section: Introductionmentioning

confidence: 99%

Correlations of the Number of Dewar Resonance Structures and Matching Polynomials for the Linear and Zigzag Polyacene Series

Dias¹

2013

Croat. Chem. Acta

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Abstract. Linear and zigzag polyacene series have been the subject of numerous studies because of their contrasting electronic and stability characteristics. The correlation of the properties of these series is examined in regard to their number of Dewar resonance structures (DS). Since resonance-theoretic methods require algorithms for determining the number of Dewar resonance structures (DS), recursion equations for calculating DS for these series are presented for the first time. Excellent correlations between DS and the absorption p-band, ionization energies, Hückel HOMO, Aihara's reduced HOMO-LUMO gap, topological resonance energy (TRE), aromatic stabilization energy (ASE), and the Klein and Randić innate degree of freedom are presented and rationalized. (doi: 10.5562/cca2292)

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Global and Local Aromaticity of Linear and Angular Polyacenes

Cited by 94 publications

References 29 publications

How far is the pi-electron delocalization of phenanthrene moiety is modified in the aza-analogues and their N-oxides?

How far is the pi-electron delocalization of phenanthrene moiety is modified in the aza-analogues and their N-oxides?

Solvent impact on the planarity and aromaticity of free and monohydrated zinc phthalocyanine: a theoretical study

Correlations of the Number of Dewar Resonance Structures and Matching Polynomials for the Linear and Zigzag Polyacene Series

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