title: Investigation of the excited state structure of DCM via ultrafast electronic pump/vibrational probe.
abstract: Time resolved visible pump, infrared probe transient absorption measurements of the solutes 4-dicyanomethylene-2-methyl-6-(p-(dimethylamino)styryl)-4H-pyran (DCM) and its isotopomer DCM-d6 are employed to probe the dynamics of charge transfer state formation in dimethyl sulfoxide (DMSO) and acetonitrile (MeCN). We observe a two stage charge transfer (CT): the first step is an instrument-response-limited charge separation to the dicyanomethylene group, and the second involves a structural evolution of the dimethylamino group. Theoretical calculations and isotopic substitution indicate that the observed vibration is due to the dimethylamino group twisting out of plane, stabilizing the charge separation.
authors.affiliation: Department of Chemistry, University of California, Berkeley, and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Van Tassle
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Prantil
authors.forename: Graham R
authors.initials: GR
authors.lastname: Fleming
mesh_terms: D000097:Acetonitriles; D004121:Dimethyl Sulfoxide; D004583:Electrons; D008958:Models, Molecular; D015394:Molecular Structure; D011714:Pyrans / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013343:Styrenes / Q000737:chemistry*; D013997:Time Factors
chemical_list: D000097:Acetonitriles; D011714:Pyrans; D013343:Styrenes; C082825:4-(dicyanomethylene)-2-methyl-6-(4-(dimethylamino)styryl)-4H-pyran; D004121:Dimethyl Sulfoxide; C032159:acetonitrile