Supporting information for infrared multiple photon dissociation spectroscopy of cationized methionine: effects of alkali-metal cation size on gas-phase conformation

A description of the structures of Met and M+(Met) for M+ = Li+, Na+, K+, Rb+, and Cs+. Two figures (S1a and S1b) depicting the 298 K Gibbs free energies calculated at the R/6- 311+G(2d,2p)//B3LYP/6-311+G(d,p) (M+ = Li+, Na+, K+) and R/HW*/6-311+G(2d,2p)// B3LYP/HW*6-311+G(d,p) (M+ = Rb+ and Cs+) levels, where R = B3LYP (S1a) and B3P86 (S1b) for eight distinct conformations. One table (S1) providing 0 K relative energies calculated at the R/HW*/6-311+G(2d,2p) and R/Def2TZVP levels of theory, where R = B3LYP, B3P86, and MP2(full), for eight conformations of Rb+(Met) and Cs+(Met). Two tables (S2 and S3) providing geometric parameters (bond lengths, bond angles, and dihedral angles) for low-energy structures of M+(Met). Vibrational frequencies and IR intensities are calculated for M+(Met) at the B3LYP/6-311+G(d,p) (M+ = Li+, Na+, K+) and B3LYP/HW*/6-311+G(d,p) (M+ = Rb+ and Cs+) levels. Four tables (S4?S7) providing the vibrational frequencies and IR intensities for the [N,CO,S] tgcgt, tgcgg, tgggt, and tgggg conformers for all M+(Met). Two tables (S8 and S10) providing vibrational frequencies and IR intensties for the [CO2?] ctggg and [COOH] ctggg conformers for all M+(Met). Two tables (S9 and S11) providing vibrational frequencies and IR intensities for the [CO2?] cgtgg and ctggt and [COOH] cgtgg and ctggt conformers for K+(Met) to Cs+(Met). One table (S12) providing vibrational frequencies and IR intensities for the [COOH,S] cgggg conformers for Na+(Met) to Cs+(Met). One table (S13) providing vibrational frequencies and IR intensities for the [COOH,S] cgggt and cgcgg conformers for K+(Met) to Cs+(Met). Two tables (S14 and S15) providing the vibrational frequencies and IR intensities for four [N,CO,S] and four [N,OH,S] conformers of H+(Met) calculated at the B3LYP/6-311+G(d,p) level.