scholarly journals Three-Dimensional Fully pi-Conjugated Macrocycles: When Truly 3D-Aromatic and when 2D-Aromatic-in-3D?

2021 ◽  
Author(s):  
Henrik Ottosson ◽  
Ouissam El Bakouri ◽  
Dariusz Szczepanik ◽  
Kjell Jorner ◽  
Rabia Ayub ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Electron Delocalization ◽  
Conjugated Molecules ◽  
Aromatic Molecules ◽  
Pi Conjugated ◽  
Aromatic Character ◽  
Conjugated Macrocycles ◽  
Polycyclic Aromatic ◽  
Symmetric Structures ◽  
Macrocyclic Molecules

Recently, several fully pi-conjugated macrocycles with strongly puckered or cage-type structures have been synthesized and found to exhibit aromatic character according to both experiments and computations. Herein, we examine their electronic structures and put them in relation to truly 3D-aromatic molecules (e.g., closo-boranes and certain charged fullerenes) as well as 2D-aromatic polycyclic aromatic hydrocarbons. We use qualitative theory combined with quantum chemical calculations, and find that the macrocycles explored thus far should be described as 2D-aromatic with three-dimensional structures (abbr. 2D-aromatic-in-3D) instead of truly 3D-aromatic. Besides fulfilling the 6n + 2 pi-electron rule, 3D-aromatic molecules with highly symmetric structures (e.g., Td and Oh) have a number of molecular orbital (MO) levels that are (at least) triply degenerate. At lower symmetries, the triple (or higher) orbital degeneracies should be kept in approximate sense. This last criterion is not fulfilled by macrocyclic cage molecules that are 2D-aromatic-in-3D. Their aromaticity results from a fulfillment of Hückel’s 4n + 2 rule for each individual macrocyclic path, yet, their pi-electron counts are coincidentally 6n + 2 numbers for macrocycles with three tethers of equal lengths. We instead link the 3D-macrocyclic molecules explored earlier to naphthalene, motivating their description as 2D-aromatics albeit with 3D structures. It is notable that macrocyclic cages which are 2D-aromatic-in-3D can be aromatic also when the tethers are of different lengths, i.e., when their pi-electron counts differ from 6n + 2. Finally, we identify tetrahedral and cubic pi-conjugated molecules that fulfill the 6n + 2 rule and which exhibit significant electron delocalization. Yet, their properties are similar to those of analogous compounds with electron counts that differ from 6n + 2. Thus, despite that these tetrahedral and cubic molecules show substantial pi-electron delocalization they should not be classified as true 3D-aromatics.

scholarly journals Magnetically Induced Ring-Current Strengths of Planar and Nonplanar Molecules: New Insights from the Pseudo-π Model

2021 ◽  
Author(s):  
Mesías Orozco-Ic ◽  
Maria Dimitrova ◽  
jorge barroso ◽  
Dage Sundholm ◽  
Gabriel Merino
Keyword(s):  
Magnetic Fields ◽  
Ring Current ◽  
Three Dimensional ◽  
Molecular Structures ◽  
Response Analysis ◽  
Aromatic Character ◽  
Polycyclic Aromatic ◽  
Planar Molecules ◽  
Current Densities ◽  
Induced Currents

<p>The π-contribution to the magnetically induced current densities, ring-current strengths, and induced magnetic fields of large planar molecules (as kekulene) and three-dimensional molecules (as [10]cyclophenacene and chiral toroidal nanotubes C<sub>2016 </sub>and C<sub>2196</sub>) have been computed using the pseudo-π model with the gauge-including magnetically induced currents method. The magnetic response analysis shows that π-electrons are the main actors of the electron delocalization in carbon systems regardless of their size, suggesting that the π- component of the ring-current strengths can be used for assessing the aromatic character of this kind of molecules. Computations using the pseudo-π model yield current densities and induced magnetic fields that are not contaminated by contributions from core and σ-electrons allowing investigations of large molecular structures as polycyclic aromatic hydrocarbons and cylindrical or toroidal carbon nanotubes.</p>

scholarly journals Magnetically Induced Ring-Current Strengths of Planar and Nonplanar Molecules: New Insights from the Pseudo-π Model

2021 ◽  
Author(s):  
Mesías Orozco-Ic ◽  
Maria Dimitrova ◽  
jorge barroso ◽  
Dage Sundholm ◽  
Gabriel Merino
Keyword(s):  
Magnetic Fields ◽  
Ring Current ◽  
Three Dimensional ◽  
Molecular Structures ◽  
Response Analysis ◽  
Aromatic Character ◽  
Polycyclic Aromatic ◽  
Planar Molecules ◽  
Current Densities ◽  
Induced Currents

<p>The π-contribution to the magnetically induced current densities, ring-current strengths, and induced magnetic fields of large planar molecules (as kekulene) and three-dimensional molecules (as [10]cyclophenacene and chiral toroidal nanotubes C<sub>2016 </sub>and C<sub>2196</sub>) have been computed using the pseudo-π model with the gauge-including magnetically induced currents method. The magnetic response analysis shows that π-electrons are the main actors of the electron delocalization in carbon systems regardless of their size, suggesting that the π- component of the ring-current strengths can be used for assessing the aromatic character of this kind of molecules. Computations using the pseudo-π model yield current densities and induced magnetic fields that are not contaminated by contributions from core and σ-electrons allowing investigations of large molecular structures as polycyclic aromatic hydrocarbons and cylindrical or toroidal carbon nanotubes.</p>

A Three-Dimensional Tetraphenylethylene-Based Fluorescence Covalent Organic Framework for Molecular Recognition

2020 ◽  
Author(s):  
Junxia Ren ◽  
Yaozu Liu ◽  
Xin Zhu ◽  
Yangyang Pan ◽  
Yujie Wang ◽  
...  
Keyword(s):  
Molecular Recognition ◽  
Fluorescence Probe ◽  
Three Dimensional ◽  
Hazardous Substances ◽  
Covalent Organic Framework ◽  
Highly Sensitive ◽  
Volatile Organic ◽  
Polycyclic Aromatic ◽  
Better Than ◽  
Organic Framework

<p><a></a><a></a><a></a><a></a><a></a><a></a><a></a><a>The development of highly-sensitive recognition of </a><a></a><a></a><a></a><a></a><a>hazardous </a>chemicals, such as volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs), is of significant importance because of their widespread social concerns related to environment and human health. Here, we report a three-dimensional (3D) covalent organic framework (COF, termed JUC-555) bearing tetraphenylethylene (TPE) side chains as an aggregation-induced emission (AIE) fluorescence probe for sensitive molecular recognition.<a></a><a> </a>Due to the rotational restriction of TPE rotors in highly interpenetrated framework after inclusion of dimethylformamide (DMF), JUC-555 shows impressive AIE-based strong fluorescence. Meanwhile, owing to the large pore size (11.4 Å) and suitable intermolecular distance of aligned TPE (7.2 Å) in JUC-555, the obtained material demonstrates an excellent performance in the molecular recognition of hazardous chemicals, e.g., nitroaromatic explosives, PAHs, and even thiophene compounds, via a fluorescent quenching mechanism. The quenching constant (<i>K</i><sub>SV</sub>) is two orders of magnitude better than those of other fluorescence-based porous materials reported to date. This research thus opens 3D functionalized COFs as a promising identification tool for environmentally hazardous substances.</p>

scholarly journals The carbonization of aromatic molecules with three-dimensional structures affords carbon materials with controlled pore sizes at the Ångstrom-level

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Tomoki Ogoshi ◽  
Yuma Sakatsume ◽  
Katsuto Onishi ◽  
Rui Tang ◽  
Kazuma Takahashi ◽  
...  
Keyword(s):  
Porous Carbon ◽  
Carbon Materials ◽  
Carbon Sources ◽  
Three Dimensional ◽  
Chemical Vapor ◽  
Thermal Polymerization ◽  
Sodium Ion Battery ◽  
Pore Sizes ◽  
Aromatic Molecules ◽  
Template Methods

AbstractCarbon materials with controlled pore sizes at the nanometer level have been obtained by template methods, chemical vapor desorption, and extraction of metals from carbides. However, to produce porous carbons with controlled pore sizes at the Ångstrom-level, syntheses that are simple, versatile, and reproducible are desired. Here, we report a synthetic method to prepare porous carbon materials with pore sizes that can be precisely controlled at the Ångstrom-level. Heating first induces thermal polymerization of selected three-dimensional aromatic molecules as the carbon sources, further heating results in extremely high carbonization yields (>86%). The porous carbon obtained from a tetrabiphenylmethane structure has a larger pore size (4.40 Å) than those from a spirobifluorene (4.07 Å) or a tetraphenylmethane precursor (4.05 Å). The porous carbon obtained from tetraphenylmethane is applied as an anode material for sodium-ion battery.

Photophysics of polycyclic aromatic molecules on semiconductor powders

1983 ◽  
Vol 105 (21) ◽  
pp. 6383-6389 ◽  
Author(s):  
K. Chandrasekaran ◽  
J. K. Thomas
Keyword(s):  
Aromatic Molecules ◽  
Polycyclic Aromatic

Triplet state dynamics in polycyclic aromatic molecules

1974 ◽  
Vol 27 (4) ◽  
pp. 556-561 ◽  
Author(s):  
Richard H. Clarke ◽  
John M. Hayes
Keyword(s):  
Triplet State ◽  
Aromatic Molecules ◽  
Polycyclic Aromatic

Graphene in Titan

2021 ◽  
Author(s):  
Rahul Kumar Kushwaha ◽  
Ambresh Mallya ◽  
Dipen Sahu ◽  
Jaya Krishna Meka ◽  
Sheng-Lung Chou ◽  
...  
Keyword(s):  
Room Temperature ◽  
Laboratory Experiments ◽  
Vacuum Ultraviolet ◽  
Physical Nature ◽  
Potassium Bromide ◽  
Aromatic Molecules ◽  
Transmission Electron ◽  
Polycyclic Aromatic ◽  
Plasma Spectrometer ◽  
Electron Microscopes

&lt;p&gt;Benzene (C&lt;sub&gt;6&lt;/sub&gt;H&lt;sub&gt;6&lt;/sub&gt;) ice has been observed in the Titan&amp;#8217;s stratosphere [1], and benzonitrile (C&lt;sub&gt;6&lt;/sub&gt;H&lt;sub&gt;5&lt;/sub&gt;CN) is a possible constituent in the benzene and nitrogen-rich environment of Titan&amp;#8217;s atmosphere [2]. The energetic processing of such aromatic molecules can synthesize large and complex aromatic molecules such as the Polycyclic Aromatic Hydrocarbons (PAHs). To-date a number of laboratory experiments have reported the formation of complex organics from the energetic processing of aromatic molecules [3-6]. In particular, Scanning Electron Microscopy (SEM) micrographs of the residues resulting from irradiated benzene ices are found to contain geometrically shaped particles [6]. Therefore, by employing electron microscopes, we can understand the physical nature of the dust leftover from the aromatic molecule irradiation.&lt;/p&gt; &lt;p&gt;In the present investigation, we subjected benzonitrile ice made at 4 K to vacuum ultraviolet (9 eV) radiation at two beamlines, BL03 and BL21A2 of Taiwan Light Source at NSRRC, Taiwan. After irradiation, the ice was warmed to room temperature, which left a brownish residue on the Potassium Bromide (KBr) substrate. The VUV spectrum of the residue is observed to have characteristic aromatic signatures. The residue is then transferred to a quantifoil grid for High-Resolution Transmission Electron Microscope (HR- TEM) imaging. HR-TEM micrographs revealed the presence of graphene in the residue. This result suggests that N-graphene could be present in benzene and nitrogen-rich icy clouds of Titan. The high masses observed by the Cassini plasma spectrometer in Titan&amp;#8217;s atmosphere could then be attributed to the presence of N-graphene along with the more common tholins [7].&lt;/p&gt; &lt;p&gt;&lt;strong&gt;References&lt;/strong&gt;&lt;/p&gt; &lt;p&gt;[1] Vinatier S. et al. (2018) &lt;em&gt;Icarus, 310,&lt;/em&gt; 89.&lt;/p&gt; &lt;p&gt;[2] Loison J. C. et al. (2019) &lt;em&gt;Icarus 329,&lt;/em&gt; 55.&lt;/p&gt; &lt;p&gt;[3] Strazzulla G. et al. (1991) &lt;em&gt;A&amp;A, 241&lt;/em&gt;, 310.&lt;/p&gt; &lt;p&gt;[4] Callahan M. P. et al. (2013) &lt;em&gt;Icarus, 226&lt;/em&gt;, 1201.&lt;/p&gt; &lt;p&gt;[5] James R. et al. (2019) &lt;em&gt;RSC Adv. 9&lt;/em&gt; (10), 5453.&lt;/p&gt; &lt;p&gt;[6] Rahul K. K. et al. (2020) &lt;em&gt;Spectrochim. Acta A, 231, &lt;/em&gt;117797.&lt;/p&gt; &lt;p&gt;[7] Rahul K. K. et al. (2020) &lt;em&gt;arXiv:2008.10011&lt;/em&gt;.&lt;/p&gt;

scholarly journals The General (α,3)-Path Connectivity Indices of Polycyclic Aromatic Hydrocarbons

2018 ◽  
Vol 2018 ◽  
pp. 1-5
Author(s):  
Haiying Wang ◽  
Chuantao Li
Keyword(s):  
Applied Sciences ◽  
Polycyclic Aromatic Hydrocarbons ◽  
Aromatic Hydrocarbons ◽  
Molecular Graph ◽  
Three Dimensional ◽  
3D Qsar ◽  
Medical Sciences ◽  
Connectivity Indices ◽  
Polycyclic Aromatic ◽  
Extremal Values

The general (α,t)-path connectivity index of a molecular graph originates from many practical problems such as three-dimensional quantitative structure-activity (3D QSAR) and molecular chirality. It is defined as Rtα(G)=∑Pt=vi1vi2⋯vit+1⊆G[d(vi1)d(vi2)⋯d(vit+1)]α, where the summation is taken over all possible paths of length t of G and we do not distinguish between the paths vi1vi2⋯vit+1 and vit+1⋯vi2vi1. In this paper, we focus on the structures of Polycyclic Aromatic Hydrocarbons (PAHn), which play a role in organic materials and medical sciences. We try to compute the exact general (α,3)-path connectivity indices of this family of hydrocarbon structures. Furthermore, we exactly derive the monotonicity and the extremal values of R3α(PAHn) for any real number α. These valuable results could produce strong guiding significance to these applied sciences.

Sign in / Sign up

Export Citation Format

Share Document