Is Phenalenyl Aromatic?

The rings phenalenyl are determined using some quantitative aromatic indices to have around 40 % the aromaticity of benzene. The monocation, monoanion, and monoradical of phenalenyl are found to be equally aromatic. This work is licensed under a Creative Commons Attribution 4.0 International License

Chemical Graphs. XL.1 Three Relations Between the Fibonacci Sequence and the Numbers of Kekule Structures for Non-branched cata-Condensed Polycyclic Aromatic Hydrocarbons

Fo·r benze.notd or non-benzenoid ca:ta1fusenes having a non- ibranched string 01f cata-co.ndensed rings, the numbers K of Kekule structures (perfect matching·s) can be expressed vi<t the recurrence relationship (1); as a coa.-ollary when each annelated .segment has exactly two ring.s, the numbers O\u27f Kelm.le structures form the Fiibonacci sequence. Coro.nary 2 presents a second re.lationshi:p with Fiibonacci numbers. Algebraic expressions for the number of Kekule struc- 1tures in non-brainched cata.fusenes 1n terms of hexago.n numbers iJn each linearly condensed segment can be obtained. The numbers of terms in .such .a,,lgebraic expressivns lead to a new numerical triangle (Table I) which is related to Pascal\u27s triangle, and which pwvides a third link with the F ~bonacci numbers expressed either by relation (7) or by the equivalent relation (10)

Convexity deficit of benzenoids

In 2012, a family of benzenoids was introduced by Cruz, Gutman, and Rada, which they called convex benzenoids. In this paper we introduce the convexity deficit, a new topological index intended for benzenoids and, more generally, fusenes. This index measures by how much a given fusene departs from convexity. It is defined in terms of the boundary-edges code. In particular, convex benzenoids are exactly the benzenoids having convexity deficit equal to 0. Quasi-convex benzenoids form the family of non-convex benzenoids that are closest to convex, i.e., they have convexity deficit equal to 1. Finally, we investigate convexity deficit of several important families of benzenoids

Topological Ring Currents and Bond Currents in Some Neutral and Anionic Altans and Iterated Altans of Corannulene and Coronene.

The novel series of conjugated systems called altans, defined nearly a decade ago, was subsequently extended to multiple ("iterated") altans, and their magnetic properties were calculated by Monaco and Zanasi using the ab initio ipso-centric formalism. Such properties of the single ("mono") altans of corannulene and coronene, calculated by this sophisticated ab initio approach, had earlier been compared with those calculated via the rudimentary Hückel-London-Pople-McWeeny (HLPM) method-a parameter-free topological, quasi graph-theoretical approach requiring knowledge only of the conjugated system's molecular graph and the areas of its constituent rings. These investigations are here extended to double and triple altans. HLPM bond currents in several neutral mono altans are found to differ from those in the corresponding dianion only in those bonds that lie on the structures' perimeters, while the HLPM bond currents in all bonds in the neutral double and triple altans of corannulene and coronene are precisely the same as in the respective dianions. Some rationalization of these unexpected phenomena is offered in terms of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) nature of the role played by the lone nonbonding orbital in each of the neutral species and its respective dianion