Electronic spectroscopy of the HCCN radical

Abstract

The Ã(3)A"-X̃(3)Σ(-) electronic transition of the HCCN∕DCCN radical was observed by laser-induced fluorescence spectroscopy. Rotationally resolved excitation spectra were observed for HCCN and DCCN, and effective molecular constants of the upper state were determined. The observed intensities of the rotational lines were anomalous, probably due to a level-dependent non-radiative decay process in the excited state. Fluorescence depletion spectroscopy was applied in order to observe non-fluorescent vibronic levels. A dispersed fluorescence spectrum was also observed to determine the vibrational level structure in the ground electronic state. The observed vibrational structures in the fluorescence depletion and dispersed fluorescence spectra were tentatively assigned based on the results of ab initio calculations.

Phosphinidenes: Fundamental Properties and Reactivity

“…The bonding situation in HCCP slightly differs from the isovalent HCCN, as the latter displays a carbenic structure in the ground state with a very low barrier (~300 cm À 1 ) to linearity. [42] The calculated ΔE ST for HCCP was 17.9 kcal mol À 1 , much larger than that for HCCN (0.7 kcal mol À 1 ). In line with the electronic structure of HCCN, the O 2 -oxidation of HCCN proceeds by attacking the carbenic carbon atom in yielding the Criegee intermediate NCC(H)OO, [43] however, the yet unexplored O 2 -oxidation of HCCP might occur in a different manner by attacking the terminal phosphorus atom.…”

“…The experimental and theoretical results conclude that HCCP exists in a linear phospho‐allenic form with a significant contribution from the delocalized phosphorene structure (H−Ċ=C=$${{\dot {\rm P}}}$$ ), whereas, the bent carbenic form (H−C−C≡P) plays a negligible role. The bonding situation in HCCP slightly differs from the isovalent HCCN, as the latter displays a carbenic structure in the ground state with a very low barrier (~300 cm −1 ) to linearity [42] . The calculated Δ E ST for HCCP was 17.9 kcal mol −1 , much larger than that for HCCN (0.7 kcal mol −1 ).…”

Free Ethynylarsinidene and Ethynylstibinidene: Heavier Analogues of Nitrenes and Phosphinidenes

“…The corresponding origin bands are likely in the region of 350 to 370 nm (28 600 to 27 000 cm −1 ); if so, the corresponding theoretically predicted transition energies would be higher by about 0.7–0.8 eV (Table 3). In HCCN, the analogous π‐π* system (identified as X 3 Σ − →1 3 Σ − ), [18d] appears around 300 to 340 nm with a vibronic progression of ca. 550 cm −1 [18]…”