China
Africa
Explore chapters and articles related to this topic
Kekulé Structure
Published in Mihai V. Putz, New Frontiers in Nanochemistry, 2020
Marina A. Tudoran, Mihai V. Putz
Benzenoid hydrocarbons are defined as polycyclic conjugated molecules with six-membered rings, having each pair of carbon being connected by a single or double bond (Vukicevic & Zigert, 2008). When the double bonds are situated in a single ring, they represent the π electrons, whose distribution is represented by Kekulé structures. In mathematical literature, they are known as benzenoid graphs, defined as 2-connected subgraphs of the hexagonal lattice with the property that every bounded face is a hexagon. A benzenoid graph B in which all of its vertices lie on its perimeter is called catacondensed, and if not is called peri-condensed. The edge from B which does not belong to its perimeter is called inner edge, and a hexagon which contains only one inner edge is called terminal hexagon or a leaf. For a benzenoid graph B, the set of all of its hexagon is noted with H(B), and the set of the terminal hexagons with L(B). One can define a matching for a graph B as a set of pairwise independent edge, and a perfect matching or 1-factor, if the set covers all vertices of B. Studies in this area, revealed that there is a correspondence one-to-one between the 1-factor of benzenoid graph and Kekulé structure (Cyvin & Gutman, 1989).
Two-dimensional coronene fractal structures: topological entropy measures, energetics, NMR and ESR spectroscopic patterns and existence of isentropic structures
Published in Molecular Physics, 2022
Micheal Arockiaraj, Joseph Jency, Jessie Abraham, S. Ruth Julie Kavitha, Krishnan Balasubramanian
Benzenoid hydrocarbons are polycyclic, fully conjugated, unsaturated compounds comprised of six-membered rings with intriguing characteristics that continue to attract chemists to investigate their physico-chemical properties with respect to aromaticity and molecular structure. It is observed that the graphene segments [1] made up of these benzenoid compounds exhibit large π-conjugated systems with strong intermolecular interactions and high-order columnar packing [2,3], providing a suitable material for building organic semiconductors [4,5] and opto-electronic devices [6,7]. The skeletons of these benzenoid hydrocarbon molecules are represented as benzenoid systems. They possess a connected molecular graph structure similar to a honeycomb lattice without cut vertices and non-hexagonal interior faces [8]. Coronene is one such highly symmetrical, planar benzenoid compound consisting of seven aromatic, peri-fused benzene rings [9–11]. Though it was synthesised way back in 1940, it remains as one of the remarkable molecules in organic chemistry [12–14]. Its unique electronic structure, owing to the delocalisation of aromaticity among the outer six rings, and its six-fold structural symmetry assists in the formation of thin films and crystallisation of molecules [15] and enables enhanced electron mobility and better self-assembly to form stacks and ribbons inside nanotubes [16–18], resulting in nanomaterials with potential optical and electronic properties [19–22].