Gas phase electronic structure of the 3d metal monoacetylides (MCCH, M = Sc .. Zn)

The physical properties of gas phase metal monoacetylide (M-CCH, where M=Sc-Zn) molecules have been evaluated with coupled cluster theory and multireference configuration interaction. Metal monoacetylides are isovalent to well-studied metal monocyanides (M-CN) and metal monoisocyanides (M-NC), which suggests the MCCH series will have similar electronic structure. Some of the MCCH molecules, such as ScCCH, FeCCH, and CoCCH share a trait with their isoelectronic MCN/MNC counterparts: profound multireference character and low-lying excited electronic states. Also like the MCN/MNC molecules, the M-CCH species have rather large ligand dissociation energies. Due to the prevalence of CnH polyyne molecules discovered in the interstellar medium, members of the MCCH series likely exist as relevant astrochemicals and could be involved in prebiotic reactions.