The photoelectron spectrum of 7b-methyl-7bH-cyclopent[cd]indene

Abstract

The He' photoelectron (p.e.) spectrum of 7b-methyl-7bH-cycIopent[cd) indene (1 ) has been recorded. The first four bands are assigned to ionization events from It-orbitals related to the perimeter of [lOIannulene. This assignment is based on model calculations using the HMO and the MIND0/3 model. The p.e. spectrum of ( 1) is compared with that of ?,6-methano [lO]annulene (3). The rearrangement of (1 ) t o its 2aH isomer (4) is also discussed.

Rees polycyanated hydrocarbons and related compounds are extremely powerful Brønsted superacids in the gas-phase and DMSO—a density functional B3LYP study

“…The CC bond lengths of the perimeter vary in a narrow range between 1.395-1.423 A ˚, which are close to the aromatic bond distances. Thus, they are consistent with the electrophilic activity of 1c, 44,45 its photoelectron spectra 49 and diatropicity of the NMR hydrogen chemical shifts. 43 The central CC bonds emanating from the C(sp 3 ) carbon are longer (B1.483 A ˚), because they are of the C(sp 3 )-C(sp 2 ) type.…”

“…27 This approach is in our view very promising, because the chemistry of the cyano group is known. [38][39][40][41] Continuing our efforts in this direction, we consider here Rees hydrocarbons, [42][43][44][45][46][47][48][49] deprived of the methyl group substituted at the central carbon atom (I-II) and a related fluoradene tautomer (III), which is not prepared as yet (Scheme 1). They will serve as molecular frameworks for powerful neutral organic superacids obtained after polycyanation.…”

Extremal acidity of Rees polycyanated hydrocarbons in the gas phase and DMSO – a density functional study

“…Thus, it is justified to characterize 1 as a quasi- [10]annulene system. This conjecture is in accordance with its electrophilic reactivity, 3,4 photoelectron spectra 19 and diatropicity reflected in the NMR H-chemical shifts d H . 2 The corresponding anion 1 2 is planar with C-C bond distances displayed in Scheme 1.…”

Annulenes, 1980–2000

“…Calculations making allowance for electron correlation predicted delocalised electronic systems in the periphery. 12,91,92 Photoelectronic spectra of 39 are in accord with this, 92 as are NMR spectra of 39, in which the peripheral hydrogen atoms provide signals at δ H 7.53-7.92 ppm and the methyl group a signal at δ H Ϫ1.67 ppm, 85 thus demonstrating the diatropicity of the annulene.…”