Multidimensionality of delocalization indices and nucleus‐independent chemical shifts in polycyclic aromatic hydrocarbons II: Proof of further nonlocality

Fias, Stijn; Damme, Sofie Van; Bultinck, Patrick

doi:10.1002/jcc.21520

Cited by 42 publications

(41 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Figures 4 and 6 on the one hand, and of Figures 4 and 7 on the other, inevitably invite the general conclusion that -despite its superficially intuitive appeal -the "ring-current" index is out of step with the other two indices considered here -π-electron partitions and Δ 6 -values -as an index of what might be regarded as "local aromaticity". This conclusion agrees with the idea that aromaticity is a multi-dimensional and scaledependent phenomenon [12][13][14][15][16][17][18][19] -but see Ref. 15 for the opposite viewpoint.…”

Section: A Third Kind Of Correlation Involv-ing Quantum-chemical Critsupporting

confidence: 88%

“…Of the characteristic properties associated with conjugated systems, diamagnetic susceptibilities arising from π-electron ringcurrents [1][2][3][4] have been considered as one of the main diagnostics of aromaticity [5][6][7] -albeit a controversial one. [8][9][10][11] However, because of the so-called multidimensional character of aromaticity, [12][13][14][15][16][17][18][19] a quantitative measure requires the presence of several attributes, and this complicates quantitative assessments of the concept. One should note, however, that this multidimensional character has been discussed mostly for conjugated heterocycles, [20][21][22] whilst the present paper is about benzenoid hydrocarbons.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Correlations between Topological Ring-Currents, π-Electron Partitions, and Six-Centre Delocalisation Indices in Benzenoid Hydrocarbons

Balaban¹,

Mallion²

2012

Croat. Chem. Acta

119

View full text Add to dashboard Cite

Abstract. Comparison is made between three different indices that characterise the individual rings of a wide range of condensed benzenoid hydrocarbons. Two of these ("π-electron partitions" and the six-centre delocalisation-indices that have been called "Δ 6 -values") have been introduced only recently as potential indicators of what might be called "local aromaticity", whilst the third ("topological π-electron ringcurrents") was suggested as a possible discriminator in this regard nearly fifty years ago. Whilst linear correlations between ring currents and π-electron partitions within certain restricted classes of ring types are good (with correlation coefficients of up to 0.998), agreement between the two indices over all classes of ring types is poor. Predictions arising from a consideration of π-electron partitions and Δ 6 -values seem, on the other hand, to be in somewhat better accord. It is therefore concluded that, despite its superficially intuitive appeal, the ring-current index is out of step both with π-electron partitions and Δ 6 -values as a general indicator of so-called "local aromaticity". (doi: 10.5562/cca1846)

show abstract

Section: A Third Kind Of Correlation Involv-ing Quantum-chemical Critsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Correlations between Topological Ring-Currents, π-Electron Partitions, and Six-Centre Delocalisation Indices in Benzenoid Hydrocarbons

Balaban¹,

Mallion²

2012

Croat. Chem. Acta

119

View full text Add to dashboard Cite

show abstract

“…Experience has shown that this leads to very similar current density maps as when using the true molecule 41,42 and even shows a remarkable numerical similarity for current densities but also NICS values and Multicenter Indices. [21][22][23]43,44 The Na 6 system thus can be considered to be a true experimental realization of a pseudo-π system.In the ipsocentric method, one can show that the current density in a molecule depends on three key elements. In the perturbation theory ansatz, one needs to have an appropriate combination of orbital symmetries with the symmetry corresponding to the angular and linear momentum operators.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

Ring Currents in Polycyclic Sodium Clusters

Radenković

Bultinck

2011

J. Phys. Chem. A

Self Cite

View full text Add to dashboard Cite

In the recent work by Khatua et al. [Khatua, S.; Roy, D. R.; Bultinck, P.; Bhattacharjee, M.; Chattaraj, P. K. Phys. Chem. Chem. Phys. 2008, 10, 2461-2474 the synthesis and structure of a fac-trioxo molybdenum metalloligand and its sodium complex containing 1D hexagonal chains of sodium ions was reported. In the same paper, the aromaticity of hexagonal Na-clusters was quantified by means of the nucleus-independent chemical shift and electronic multicentre indices. It was shown that the aromaticity of hexagonal Na-clusters is of the same order as the aromaticity of analogous benzenoid hydrocarbons. In the present study current density maps are used to rationalize the aromaticity of polycyclic Na-clusters. It is shown that although polycyclic Na-systems sustain a diatropic ring current, the induced current density is several times weaker than in analogous benzenoid hydrocarbons. A detailed analysis indicates that the current density in hexagonal Na-systems is almost completely determined by four HOMO σ-electrons. 1,2 the concept of aromaticity was extended from its usual organic realm to the field of all-metal inorganic clusters. Compared to the aromaticity encountered in organic molecules, primarily being of the traditional π-type, all-metal systems can exhibit a multifold aromaticity [3][4][5] and conflicting aromaticity, 2,3,[6][7][8][9] arising from their σ-, π-, δ- The problem with claims that a certain species is aromatic is that this conclusion may depend rather significantly on the property used to characterize aromaticity. As an example: a ring that exhibits bond length equalization as in benzene but does not sustain a ring current could be classified by some as aromatic but by others as not aromatic depending on the relative importance they attach to the property of bond lengths equalization or ring currents respectively. The same is true for e.g., electron delocalization and ring currents. Although one of us has previously shown that electron delocalization and ring currents in carbohydrates go hand in hand, 20-23 the more general and subtle interrelationship is that a delocalized system is a necessary but not sufficient requirement for a ring current. In previous work on Na 6 systems, electron delocalization was gauged by the multicentre index and information on a ring current was obtained indirectly from NICS values. The problem with NICS, however, is that although usually a negative (or aromatic) NICS value reflects the 3 existence of a ring current, there is no direct way to extract and thus beyond doubt prove the existence of an underlying ring current. INTRODUCTION COMPUTATIONAL METHODSThe structures of the Na 4n+2 (n = 1-5) entities (Figure1) were taken from the experimental structural data given by Khatua et al. 13,14 The molecular structures of the linear polyacenes C 4n+2 H 2n+4 (n = 1-5) were optimized at the B3LYP/6-311+G* level.Computed Hessian matrices showed the optimized structures to correspond to minima on the potential energy surface.The current density maps presented in this pap...

show abstract

“…permutations of the elements in the string {A}. The MCI index has been successfully applied to a broad number of situations, from simple organic compounds to complex all metal clusters with multiple aromaticity [8,[46][47][48][49][50][51][52][53][54][55][56]. For planar species, S ij (A k ) = 0 for i ∈ σ and j ∈ π orbital symmetries; thus, MCI can be exactly split into σ-and π-contributions, namely MCI σ and MCI π , respectively.…”

Section: π-Electron Delocalization Analysismentioning

confidence: 99%

Why 1,2-quinone derivatives are more stable than their 2,3-analogues?

et al. 2015

View full text Add to dashboard Cite

In this work, we have studied the relative stability of 1,2- and 2,3-quinones. While 1,2-quinones have a closed-shell singlet ground state, the ground state for the studied 2,3-isomers is open-shell singlet, except for 2,3-naphthaquinone that has a closed-shell singlet ground state. In all cases, 1,2-quinones are more stable than their 2,3-counterparts. We analyzed the reasons for the higher stability of the 1,2-isomers through energy decomposition analysis in the framework of Kohn–Sham molecular orbital theory. The results showed that we have to trace the origin of 1,2-quinones’ enhanced stability to the more efficient bonding in the π-electron system due to more favorable overlap between the SOMOπ of the ·C4n−2H2n–CH·· and ··CH–CO–CO· fragments in the 1,2-arrangement. Furthermore, whereas 1,2-quinones present a constant trend with their elongation for all analyzed properties (geometric, energetic, and electronic), 2,3-quinone derivatives present a substantial breaking in monotonicityThis work has been supported by the European Union in the framework of European Social Fund through the Warsaw University of Technology Development Programme. O.A. S., H. S. and T.M. K. gratefully acknowledge the Foundation for Polish Science for supporting this work under MPD/2010/4 project "Towards Advanced Functional Materials and Novel Devices-Joint UW and WUT International PhD Programme" and the Interdisciplinary Center for Mathematical and Computational Modeling (Warsaw, Poland) for providing computer time and facilities. Thanks are also to the Ministerio de Economia y Competitividad of Spain (Projects CTQ2011-23156/BQU and CTQ2011-25086) and the Generalitat de Catalunya (project numbers 2014SGR931, Xarxa de Referencia en Quimica Teorica i Computacional, and ICREA Academia 2014 prize for MS

show abstract

Multidimensionality of delocalization indices and nucleus‐independent chemical shifts in polycyclic aromatic hydrocarbons II: Proof of further nonlocality

Cited by 42 publications

References 38 publications

Correlations between Topological Ring-Currents, π-Electron Partitions, and Six-Centre Delocalisation Indices in Benzenoid Hydrocarbons

Correlations between Topological Ring-Currents, π-Electron Partitions, and Six-Centre Delocalisation Indices in Benzenoid Hydrocarbons

Ring Currents in Polycyclic Sodium Clusters

Why 1,2-quinone derivatives are more stable than their 2,3-analogues?

Contact Info

Product

Resources

About