PNNL

Abstract

The recently synthesized acetylide compound KSeCCH containing the main group element selenium within the novel [SeCCH]- anion was successfully investigated in the gas phase by high resolution velocity-map imaging (VMI) and magnetic-bottle (MB) photoelectron spectroscopy coupled with an electrospray ionization source. Both VMI and MB spectra exhibited identical electron affinities (EA, 2.517 ± 0.002 eV), spin–orbit coupling (SOC) splittings (1492 ± 20 cm-1), and Se-C stretching frequencies (573 ± 20 cm-1) of the corresponding neutral tetra-atomic radical [SeCCH] •, with the VMI spectrum possessing six times higher spectral resolution compared with the MB spectrum. These experimental values were well reproduced by calculations at the CCSD(T) level, in which both the isolated [SeCCH]- anion and [SeCCH]• radical adopted linear geometries. The simulated spectra based on the calculated Franck-Condon factors, the SOC splitting, and experimental line width matched well with the measured spectra. Furthermore, comparisons of the EA and SOC splitting values with the previously reported isolobal species [SeCN]• are also made and discussed. The decrease in the EA and SOC splitting of [SeCCH]• is ascribed to the differences in the electronegativities between C and N atoms, as well as the electron density on the Se atom in their singly occupied molecular orbital (SOMO). This work was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Bioscience and performed at the EMSL, a national scientific user facility sponsored by DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. U.R. and M.H. acknowledge the financial support of the German Science Foundation (DFG, Project RU 546/13-1).