title: UV and IR spectroscopy of cold 1,2-dimethoxybenzene complexes with alkali metal ions.
abstract: We report UV photodissociation (UVPD) and IR-UV double-resonance spectra of 1,2-dimethoxybenzene (DMB) complexes with alkali metal ions, M(+)·DMB (M = Li, Na, K, Rb, and Cs), in a cold, 22-pole ion trap. The UVPD spectrum of the Li(+) complex shows a strong origin band. For the K(+)·DMB, Rb(+)·DMB, and Cs(+)·DMB complexes, the origin band is very weak and low-frequency progressions are much more extensive than that of the Li(+) ion. In the case of the Na(+)·DMB complex, spectral features are similar to those of the K(+), Rb(+), and Cs(+) complexes, but vibronic bands are not resolved. Geometry optimization with density functional theory indicates that the metal ions are bonded to the oxygen atoms in all the M(+)·DMB complexes. For the Li(+) complex in the S(0) state, the Li(+) ion is located in the same plane as the benzene ring, while the Na(+), K(+), Rb(+), and Cs(+) ions are located off the plane. In the S(1) state, the Li(+) complex has a structure similar to that in the S(0) state, providing the strong origin band in the UV spectrum. In contrast, the other complexes show a large structural change in the out-of-plane direction upon S(1)-S(0) excitation, which results in the extensive low-frequency progressions in the UVPD spectra. For the Na(+)·DMB complex, fast charge transfer occurs from Na(+) to DMB after the UV excitation, making the bandwidth of the UVPD spectrum much broader than that of the other complexes and producing the photofragment DMB(+) ion.
authors.affiliation: Department of Chemistry, Graduate School of Science, Hiroshima University, Japan. y-inokuchi@hiroshima-u.ac.jp
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Inokuchi
authors.forename: Oleg V
authors.initials: OV
authors.lastname: Boyarkin
authors.forename: Takayuki
authors.initials: T
authors.lastname: Ebata
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Rizzo
mesh_terms: D000840:Anisoles / Q000737:chemistry*; D003080:Cold Temperature; D007477:Ions / Q000737:chemistry; D008672:Metals, Alkali / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000840:Anisoles; D007477:Ions; D008672:Metals, Alkali; D009942:Organometallic Compounds; C005299:veratrole