Threshold Photoelectron Spectroscopy of Cyclopropenylidene, Chlorocyclopropenylidene, and Their Deuterated Isotopomeres

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2010-10, Vol.114 (42), p.11269-11276
• Main Authors: Hemberger, Patrick, Noller, Bastian, Steinbauer, Michael, Fischer, Ingo, Alcaraz, Christian, Cunha de Miranda, Bárbara K, Garcia, Gustavo A, Soldi-Lose, Héloïse
• Format: Article
• Language: English
• Subjects: Chemical Sciences; Cyclopropanes - chemistry; Deuterium - chemistry; Hydrocarbons, Cyclic - chemistry; Mass Spectrometry; Molecular Dynamics Simulation; Molecular Structure; or physical chemistry; Photoelectron Spectroscopy; Quantum Theory; Theoretical and
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp104019d

Cyclopropenylidene (c-C3H2), chlorocyclopropenylidene (c-C3HCl), and their deuterated isotopomers were studied by the threshold photoelectron-photoion coincidence (TPEPICO) technique using VUV synchrotron radiation. The carbenes were generated via flash pyrolysis. In all species a change in geometry is visible upon ionization, with significant activity in the CC, CC-stretching mode and, in the case of c-C3H2/D2, the CH-bending mode. The electron is removed from an sp2 like hybrid orbital centered on the carbene C atom. The mass selected threshold photoelectron (TPE) spectra were fitted by a Franck−Condon simulation, yielding the equilibrium geometry of the cation ground state (1A1). The adiabatic ionization energy IEad of c-C3H2 was determined to be 9.17 eV, in good agreement with calculations and literature values. Two vibrational wavenumbers of the cation were determined experimentally (ν3 + = 1150 cm−1 and ν2 + = 1530 cm−1). Chlorocyclopropenylidene was also studied by TPE spectroscopy and has a similar IEad of 9.17 eV. The spectrum also shows a vibrational progression that corresponds to the CC- and CC-stretching modes of the cation. The equilibrium geometry was also determined by a Franck−Condon fit. The IEad of the deuterated isotopomers, c-C3D2 and c-C3DCl, were also determined to be 9.17 eV. The spectra confirm the assignments for the nondeuterated species.