Weak interactions in ion–ligand complexes of C3H+3 isomers: competition between H-bound and C-bound structures in c-C3H+3·L and H2CCCH+·L (L = Ne, Ar, N2, CO2, and O2)
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Explicitly correlated coupled cluster theory at the CCSD(T)-F12x level (T. B. Adler, G. Knizia, and H.-J. Werner, J. Chem. Phys. 127, 221106, 2007) has been employed to study structures and vibrations of complexes of type c-C3H+ 3 L and H2C3H+ L (L = Ne, Ar, N2, CO2, and O2). Both cations have different binding sites, allowing for the formation of weak to moderately strong hydrogen bonds as well as ‘‘C-bound’’ or ‘‘p-bound’’ structures. In contrast to previous expectations, the energetically most favourable structures of all H2C3H+ L complexes investigated are ‘‘C-bound’’, with the ligand bound to the methylenic carbon atom. The theoretical predictions enable a more detailed interpretation of infrared photodissociation (IRPD) spectra than was possible hitherto. In particular, the bands observed in the range 3238–3245 cm 1 (D. Roth and O. Dopfer, Phys. Chem. Chem. Phys. 4, 4855, 2002) are assigned to essentially free acetylenic CH stretching vibrations of the propargyl cation in ‘‘C-bound’’ H2C3H+ L complexes.
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