Gas-phase electronic spectroscopy of the indene cation (C9H8+)

Abstract

The electronic spectrum of the indene radical cation has been investigated through resonance-enhanced photodissociation of the weakly bound C9H8(+)-He and C9H8(+)-Arn (n = 1, 2) complexes in a tandem mass spectrometer. The D2 ← D0 band origin for indene(+)-He is observed at 17,379 ± 15 cm(-1), while the D2 ← D0 and D4 ← D0 band origins for indene(+)-Ar appear at 17,353 ± 15 cm(-1) and 28,254 ± 15 cm(-1), respectively. The vibronic structure of the D2 ← D0 band system is assigned by comparison with a simulated spectrum based on time-dependent density functional theory calculations, and is due mainly to progressions in ring deformation vibrational modes. Possible correspondences between the stronger visible transitions of the indene cation and diffuse interstellar bands observed towards the heavily reddened star HD 204827 are discussed.

Rationalization of photo-detachment spectra of the indenyl anion (C9H7−) from the perspective of vibronic coupling theory

“…The presence of this molecule or its cationic, anionic or dehydrogenated forms in the circumstellar space is still unidentified, but the results obtained from different spectroscopic and pyrolytic techniques applied on different carbonaceous chondrites that originated either from the solar system or from the ISM indicate the presence of indene and its isomers in those chondrites. 42,43 The formation of closed-shell indene (C 9 H 8 ) and its dehydrogenated radical [indenyl (C 9 H 7 )] species has been predicted from the addition of acetylene to fulvenallene, 44 cyclopentadienyl radical, 45 and benzyl radical. 46 Along with these, the addition of propargyl to benzyne 47 and the oxidation of the naphthyl radical followed by decomposition [48][49][50] also suggest the possible mechanism of formation of indenyl.…”

Electronic spectrum and photodissociation chemistry of the linear methyl propargyl cation H2C4H3+

“…indene + -Ar, 18 indole + -Ar, 22 H 2 C 3 H + -N 2 and H 2 C 3 H + -Ne. 23 All calculations were performed with the Gaussian 09 program suite.…”

Electronic Spectroscopy of the 1,3-Cyclopentadiene Cation (C5H6+)

“…This level of theory, which includes empirical dispersion corrections, has been used in previous studies of similar noncovalently bound systems including quinoline + −Ar and isoquinoline + −Ar 29 and indene + −Ar. 30 The binding energy of the complex was calculated taking into account the zero-point vibrational energy and employing the counterpoise correction to deal with basis set superposition error. 31 All electronic structure calculations were performed using the Gaussian 09 package.…”