Negative Ion Photoelectron Spectroscopy Confirms the Prediction that (CO)5 and (CO)6 Each Has a Singlet Ground State

Journal Article · Wed Mar 20 04:00:00 EDT 2013 · Journal of the American Chemical Society, 135(11):4291-4298

DOI:https://doi.org/10.1021/ja4005128· OSTI ID:1079738

Bao, Xiaoguang; Hrovat, David; Borden, Weston; Wang, Xue B.

Cyclobutane-1,2,3,4-tetraone has been both predicted and found to have a triplet ground state, in which a b2g MO and an a2u MO is each singly occupied. In contrast, (CO)5 and (CO)6 have each been predicted to have a singlet ground state. This prediction has been tested by generating the (CO)5 - and (CO)6 - anions in the gas-phase by electrospray vaporization of solutions of, respectively, the croconate (CO)52- and rhodizonate (CO)62- dianions. The negative ion photoelectron (NIPE) spectra of the (CO)5•- radical anion give electron affinity (EA) = 3.830 eV and a singlet ground state for (CO)5, with the triplet higher in energy by 0.850 eV (19.6 kcal/mol). The NIPE spectra of the (CO)6•- radical anion give EA = 3.785 eV and a singlet ground state for (CO)6, with the triplet higher in energy by 0.915 eV (21.1 kcal/mol). (RO)CCSD(T)/aug-cc-pVTZ//(U)B3LYP/6-311+G(2df) calculations give EA values that are only ca. 1 kcal/mol lower than those measured and EST values that are only 2 - 3 kcal/mol higher than those obtained from the NIPE spectra. Thus, the calculations support the interpretations of the NIPE spectra and the finding, based on the spectra, that (CO)5 and (CO)6 both have a singlet ground state.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1079738
• Report Number(s): PNNL-SA-91096; 44678; KC0301020
• Journal Information: Journal of the American Chemical Society, 135(11):4291-4298, Journal Name: Journal of the American Chemical Society, 135(11):4291-4298
• Country of Publication: United States
• Language: English

Related Subjects

Environmental Molecular Sciences Laboratory