10-π-Electron arenes à la carte: structure and bonding of the [E–(CnHn)–E]n−6 (E = Ca, Sr, Ba; n = 6–8) complexes

Mondal, Sukanta; Cabellos, José Luis; Pan, Sudip; Osorio, Edison; Torres‐Vega, Juan J.; Tiznado, William; Restrepo, Albeiro; Merino, Gabriel

doi:10.1039/c6cp00671j

Cited by 31 publications

(12 citation statements)

References 44 publications

(59 reference statements)

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“…In the latter analysis, the size of the Δ E orb term is a very useful indicator to justify which fragmentation scheme is the best to represent the electronic structure of the overall molecule. The one, which results in the lowest Δ E orb value, is the best to describe the bonding of the molecule as it needs the least change in charge distribution to get the electronic structure of the molecule [120,121]. For both C-Ng and Ng-N bonds, we tested both neutral (electron-shared) and ionic schemes, and in either case the neutral scheme results in the lowest Δ E orb value.…”

Section: Discussionmentioning

confidence: 99%

How Far Can One Push the Noble Gases Towards Bonding?: A Personal Account

et al. 2019

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Noble gases (Ngs) are the least reactive elements in the periodic table towards chemical bond formation when compared with other elements because of their completely filled valence electronic configuration. Very often, extreme conditions like low temperatures, high pressures and very reactive reagents are required for them to form meaningful chemical bonds with other elements. In this personal account, we summarize our works to date on Ng complexes where we attempted to theoretically predict viable Ng complexes having strong bonding to synthesize them under close to ambient conditions. Our works cover three different types of Ng complexes, viz., non-insertion of NgXY type, insertion of XNgY type and Ng encapsulated cage complexes where X and Y can represent any atom or group of atoms. While the first category of Ng complexes can be thermochemically stable at a certain temperature depending on the strength of the Ng-X bond, the latter two categories are kinetically stable, and therefore, their viability and the corresponding conditions depend on the size of the activation barrier associated with the release of Ng atom(s). Our major focus was devoted to understand the bonding situation in these complexes by employing the available state-of-the-art theoretic tools like natural bond orbital, electron density, and energy decomposition analyses in combination with the natural orbital for chemical valence theory. Intriguingly, these three types of complexes represent three different types of bonding scenarios. In NgXY, the strength of the donor-acceptor Ng→XY interaction depends on the polarizing power of binding the X center to draw the rather rigid electron density of Ng towards itself, and sometimes involvement of such orbitals becomes large enough, particularly for heavier Ng elements, to consider them as covalent bonds. On the other hand, in most of the XNgY cases, Ng forms an electron-shared covalent bond with X while interacting electrostatically with Y representing itself as [XNg]+Y−. Nevertheless, in some of the rare cases like NCNgNSi, both the C-Ng and Ng-N bonds can be represented as electron-shared covalent bonds. On the other hand, a cage host is an excellent moiety to examine the limits that can be pushed to attain bonding between two Ng atoms (even for He) at high pressure. The confinement effect by a small cage-like B12N12 can even induce some covalent interaction within two He atoms in the He2@B12N12 complex.

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Section: Discussionmentioning

confidence: 99%

How Far Can One Push the Noble Gases Towards Bonding?: A Personal Account

et al. 2019

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“…This conclusion is supported by an energy decomposition analysis which was also reported by the authors. The orbital interactions ΔE orb between the neutral barium atoms and benzene in [Ba‐(C 6 H 6 )‐Ba] using different electronic states are large (between −322.4 and −475.7 kcal/mol) which is much larger than in [Ba(Cp) 2 ] (ΔE orb =‐86.2 kcal/mol) . We think that the intrinsic aromaticity in the systems [E‐(C 6 H 6 )‐E] is weaker than in free benzene, but this is compensated by the strong interactions with the metal atoms.…”

Section: Introductionmentioning

confidence: 90%

“…The finding that the cyclic planar molecules (N 6 H 6 ) 2+ and C 2 N 4 H 6 are energetically unfavourable appears to be in conflict with the results of a theoretical study of inverse sandwich complexes [E‐(C 6 H 6 )‐E] with E=Ca, Sr, Ba by Merino and coworkers . The workers found singlet structures with D 6h symmetry as energy minima where the atoms E carry large positive charges between 1.50 e (Ba) and 1.59 e (Ca).…”

Section: Introductionmentioning

confidence: 95%

Aromaticity, the Hückel 4 n+2 Rule and Magnetic Current

et al. 2017

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Quantum chemical calculations using density functional theory and correlated ab initio methods of the 10 π‐electron systems (N6H6)2+ and C2N4H6 show that the planar forms are no minima on the potential energy surfaces. The twisted ring structures of the two species are energy minima, but acyclic isomers are much lower in energy. The planar geometries sustain strong diamagnetic ring current comparable with that of benzene. In contrast, the calculated multicenter normalized Giambiagi electron delocalization index ING suggests that π‐delocalization in planar (N6H6)2+ and C2N4H6 is much weaker than in benzene. Since aromaticity is synonymous for a particular stability of cyclic delocalized systems, it may be stated that calculation or measurement of magnetic chemical shifts due to induced ring currents is not a reliable method to ascertain the aromatic character of a molecule. Aromatic compounds exhibit ring current induced magnetic shielding, but the reverse conclusion that ring current induced magnetic shielding identifies aromaticity is not justified. Furthermore, the 4n+2 rule as indicator of aromatic stabilization should only be used in conjunction with the ring size; the nature of the occupied π orbitals must always be examined.

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“…[24] All the previousc omputations were done using the Gaussian09program. [29][30][31][32][33][34] The EDA decomposes the instantaneous interaction energy, DE int ,b etween the helicene and E + into four terms;aq uasi-classical electrostatic interaction DV elstat ,aDE Pauli caused by repulsion between same spin electrons, and an orbital interaction DE orb term as ar esult of the stabilizing orbital interaction. [28] We have used EDA to study as eries of organometallicc omplexes before.…”

Section: Computationaldetailsmentioning

confidence: 99%

“…Additionally, the nature of the interactions was analyzed by the Energy Decomposition Analysis (EDA) at the PBE‐D3/TZ2P level using the previously optimized geometries via the ADF 2016 package . We have used EDA to study a series of organometallic complexes before . The EDA decomposes the instantaneous interaction energy, Δ E int , between the helicene and E + into four terms; a quasi‐classical electrostatic interaction Δ V elstat , a Δ E Pauli caused by repulsion between same spin electrons, and an orbital interaction Δ E orb term as a result of the stabilizing orbital interaction.…”

Section: Computational Detailsmentioning

confidence: 99%

Bonding and Mobility of Alkali Metals in Helicenes

Barroso

Murillo

Martínez‐Guajardo

et al. 2018

Chemistry A European J

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In this work, we analyze the interactions of alkali metal cations with [6]- and [14]helicene and the cation mobility of therein. We found that the distortion of the carbon skeleton is the reason that some of the structures which are local minima for the smallest cations are not energetically stable for K , Rb , and Cs . Also, the most favorable complexes are those where the cation is interacting with two rings forming a metallocene-like structure, except for the largest cation Cs , where the distortion provoked by the size of the cation destabilizes the complex. As far as mobility is concerned, the smallest cations, particularly Na , are the ones that can move most efficiently. In [6]helicene, the mobility is limited by the capture of the cation forming the metallocene-like structure. In larger helicenes, the energy barriers for the cation to move are similar both inside and outside the helix. However, complexes with the cation between two layers are more energetically favored so that the movement will be preferred in that region. The bonding analysis reveals that interactions with no less than 50 % of orbital contribution are taking place for the series of E -[6]helicene. Particularly, the complexes of Li show remarkable orbital character (72.5-81.6 %).

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10-π-Electron arenes à la carte: structure and bonding of the [E–(C_nH_n)–E]ⁿ⁻⁶ (E = Ca, Sr, Ba; n = 6–8) complexes

Cited by 31 publications

References 44 publications

How Far Can One Push the Noble Gases Towards Bonding?: A Personal Account

How Far Can One Push the Noble Gases Towards Bonding?: A Personal Account

Aromaticity, the Hückel 4 n+2 Rule and Magnetic Current

Bonding and Mobility of Alkali Metals in Helicenes

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