Spectroscopy of the Free Phenalenyl Radical

Abstract

After benzene and naphthalene, the smallest polycyclic aromatic hydrocarbon bearing six-membered rings is the threefold-symmetric phenalenyl radical. Despite the fact that it is so fundamental, its electronic spectroscopy has not been rigorously scrutinized, in spite of growing interest in graphene fragments for molecular electronic applications. Here we used complementary laser spectroscopic techniques to probe the jet-cooled phenalenyl radical in vacuo. Its spectrum reveals the interplay between four electronic states that exhibit Jahn-Teller and pseudo-Jahn-Teller vibronic coupling. The coupling mechanism has been elucidated by the application of various ab initio quantum-chemical techniques.

On the electronic spectroscopy of closed-shell cations derived from resonance-stabilized radicals: Insights from theory and Franck-Condon analysis

“…Of the known gas-phase spectra of neutral, closed-shell PAHs, including up to C 42 H 18 , there is no match with a DIB (Salama et al 2011). Fewer neutral radicals have been studied, but there is an emerging body of work on resonance-stabilized radicals (RSRs) containing up to 13 carbon atoms which suggests that these species are also not DIB carriers (Reilly et al 2008(Reilly et al , 2009Troy et al 2009;Sebree et al 2010;Troy et al 2011;Chalyavi et al 2010;Sebree et al 2011;O'Connor et al 2011). …”

Aromatic changes in isoelectronic derivatives of phenalenyl radicals by central carbon replacement

“…13 The phenalenyl radical, the smallest open shell graphene, 14 was first prepared by Reid 6 and independently detected by Calvin. 15 It is a resonance-stabilised radical 16 that can be generated and observed at room temperature in solution, showing thermodynamic high stability but some kinetic instability. 7,14 Since then, a number of simple derivatives have been generated 17 and the literature reviewed.…”

Electronically Stabilized Nonplanar Phenalenyl Radical and Its Planar Isomer

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] These compounds are of great fundamental interest and yet they also have a range of potential applications in photochemistry, 14,15 synthesis, 16,17 materials science, 18-21 spintronics [22][23][24] and biology. 25,26 In particular, open-shell polycyclic aromatic hydrocarbons have been shown to be promising molecular conductors and spin carriers in the emerging field of organic spin chemistry.…”

“…These compounds were characterized crystallographically, and also by NMR, EPR, electrochemistry and electronic spectra. The synthesis of the previously reported compound benzo [5,6]naphthaceno[1,12,11,10-jklmna]xanthylium (5 + ), the largest oxygen-containing polycyclic hydrocarbon, was undertaken for comparison with 8 + and 9 + , allowing us to report its crystal structure here for the first time. The different properties of these compounds and their radicals are explained by considering their differing aromaticities using in-depth computational methods.…”

“…We also prepared the previously reported cation of benzo [5,6]naphthaceno-[1,12,11,10-jklmna]xanthylium (5 + ) -the largest polycyclic hydrocarbon containing a pyrylium moiety yet synthesized -in order to compare the differences in its structural and electronic properties with those of 8 + and 9…”