Mndo study of bond orders in some conjugated BI- and tri-cyclic hydrocarbons

Three closely related 1-(naphthalen-2-yl)prop-2-en-1-ones: pseudosymmetry, disorder and supramoleular assembly mediated by C—H...π and C—Br...π interactions

“…1-3),are always significantly shorter than the other C-C bonds in the naphthalene units, as expected from the bond orders calculated for naphthalene itself (Glidewell & Lloyd, 1984). The structures of the two independent molecules in compound (I), showing the atom-labelling scheme.…”

Exploring the validity of the Glidewell–Lloyd extension of Clar’s π-sextet rule: assessment from polycyclic conjugated hydrocarbons

“…Glidewell and Lloyd's rule [8] affirms that the total population of -electrons in conjugated polycyclic systems tends to form the smallest 4n+2 groups and to avoid the formation of the smallest 4n groups. Scheme 1 shows four non-benzenoid PCHs discussed by Glidewell and Lloyd [8] in which application of their rule leads to the conclusion that one of the resonance structures (in red in Scheme 1) is more relevant than the others to explain the electronic and molecular properties of these species.…”

“…In 1984, Glidewell and Lloyd [8] proposed to extent the Clar rule to non-benzenoid polycyclic conjugated hydrocarbons (PCHs).…”

“…Scheme 1 shows four non-benzenoid PCHs discussed by Glidewell and Lloyd [8] in which application of their rule leads to the conclusion that one of the resonance structures (in red in Scheme 1) is more relevant than the others to explain the electronic and molecular properties of these species. For instance, for bicyclodeca [6.2.0]pentaene (top left chart of Scheme 1), which is composed by fused cyclooctatetraene and cyclobutadiene rings, the resonance structure that better defines the molecular and electronic structure of this compound is the one that places eight -electrons in the 8-MR and two in the 4-MR. Glidewell and Lloyd [8]. We consider that the time is ripe to examine this rule in deeper detail.…”

“…Finally, let us mention that although we have considered only polycyclic conjugated hydrocarbons constituted by an even number of carbon atoms, it is likely that the rule applies to polycyclic conjugated hydrocarbons with an odd number of carbon atoms with 4n or 4n+2 -electrons like benzothienocyclobutadiene or the benzocycloheptatrienium or benzocycloheptatrienide ions [8]. Table 1.…”