A PHP Error was encountered
Severity: Warning
Message: fopen(/var/lib/php/sessions/ci_session3jbv9i8u7je9hpjble06dmblfufod97s): Failed to open stream: No space left on device
Filename: drivers/Session_files_driver.php
Line Number: 177
Backtrace:
File: /var/www/html/index.php
Line: 316
Function: require_once
A PHP Error was encountered
Severity: Warning
Message: session_start(): Failed to read session data: user (path: /var/lib/php/sessions)
Filename: Session/Session.php
Line Number: 137
Backtrace:
File: /var/www/html/index.php
Line: 316
Function: require_once
Aromatic character of coronoid hydrocarbons is greatly influenced by the shapes of outer and inner peripheries. The most aromatic rings in coronoids are jutting benzene rings on the armchair edges, if any. Clar formulas of many coronoids conform to the aromaticity patterns. However, placement of all aromatic sextets on highly aromatic rings is sometimes forbidden by the presence of the central cavity. The magnitude of aromatic stabilization energy due to macrocyclic conjugation [SSE(mc)] and the NICS(1) value at the center of the cavity strongly depend on the structure of the superposed Clar formula. Localization of π-electrons in fixed aromatic sextets effectively suppresses macrocyclic conjugation. The sign of SSE(mc) is determined by the number of carbon atoms that form the hub cycle.
Publication Analysis
Top Keywords
macrocyclic conjugation
8
Similar Publications
Multiple zigzag chains Zm,n of length and width constitute an important class of regular graphene flakes of rectangular shape. The physical and chemical properties of these basic pericondensed benzenoids can be related to their various topological invariants, conveniently encoded as the coefficients of a combinatorial polynomial, usually referred to as the ZZ polynomial of multiple zigzag chains Zm,n. The current study reports a novel method for determination of these ZZ polynomials based on a hypothesized extension to John-Sachs theorem, used previously to enumerate Kekulé structures of various benzenoid hydrocarbons.
View Article and Find Full Text PDF
The efficient synthesis and electronic properties of two large-size cove-edged nanographenes (NGs), CN1 and CN2, are presented. X-ray crystallographic analysis reveals a contorted backbone for both molecules owing to the steric repulsion at the inner cove position. Noticeably, the dominant structures of these molecules contain four (for CN1) or six (for CN2) localized C=C double bonds embedded in nine (for CN1) or twelve (for CN2) aromatic sextet rings according to Clar's formula, which is supported by bond length analysis and theoretical (NICS, ACID) calculations.
View Article and Find Full Text PDF
In our recent paper, the effects of molecular planarity on the local aromaticity in several series of increasingly planar fully benzenoid hydrocarbons were examined. It was found that the Clar formulas can provide correct information on the local aromaticity distribution even in nonplanar fully benzenoid systems. In the present work, the influence of molecular planarity on the ab initio magnetically induced current densities was examined for the same sets of molecules.
View Article and Find Full Text PDF
J Phys Chem A
April 2019
Department of Chemistry , University of Missouri, Kansas City , Kansas City , Missouri 64110-2499 , United States.
Because the effect of a benzenoid perimeter edge on a sextet pattern is of paramount importance, trends in the degree of sextet aromaticity are determined. The spectacular structural isomorphism between the total set of benzenoid hydrocarbons and its strain-free total resonant sextet (TRS) subset as described herein is an unequivocal demonstration of the validity of the Clar sextet principle. Aromaticity and the Clar's sextet principle are intricately related which form the basis of this isomorphism.
View Article and Find Full Text PDF
J Phys Chem A
April 2016
Department of Chemistry, Faculty of Science, Shizuoka University, Oya, Shizuoka 422-8529, Japan.
We found that the Clar sextet formula with the maximum number of sextet rings cannot always be defined meaningfully for large irregular-shaped PAHs. It is true that edge structure is always a primary determinant of the PAH aromaticity pattern. In large PAH molecules, every edge structure modifies the aromaticity pattern near the edge, but its influence fades on going away from the edge.
View Article and Find Full Text PDF
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!
