title: Direct observation and control of ultrafast photoinduced twisted intramolecular charge transfer (TICT) in triphenyl-methane dyes.
abstract: Femtosecond time-resolved infrared spectroscopy was employed to study intramolecular charge transfer in triphenylmethane dyes, including malachite green (MG), malachite green carbinol base (MGCB), and leucomalachite green (LMG). A local excited state (LE) and a twisted intramolecular charge-transfer (TICT) state have been observed directly in MG. Furthermore, solvent-controlled TICT measurements in a series of linear alcohols indicate that the transition time (4-11 ps) from LE to TICT is strongly dependent on alcohol viscosity, which is due to rotational hindrance of dimethylaniline in high-viscosity solvents. For LMG, no TICT is observed due to steric hindrance caused by the sp(3)-hybridized central carbon atom. However, for MGCB, TICT is rescued by the addition of the electron-donating hydroxyl group to the bridge. These results for MG and its analogues provide new insight regarding the dynamics and mechanism of twisted intramolecular charge transfer (TICT) in triphenylmethane dyes.
authors.affiliation: Department of Chemistry, Emory University, Atlanta, Georgia, 30322, United States.
authors.forename: Guifeng
authors.initials: G
authors.lastname: Li
authors.forename: Donny
authors.initials: D
authors.lastname: Magana
authors.forename: R Brian
authors.initials: RB
authors.lastname: Dyer
mesh_terms: D004396:Coloring Agents / Q000737:chemistry*; D015394:Molecular Structure; D055668:Photochemical Processes; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013997:Time Factors; D014320:Triphenylmethyl Compounds / Q000737:chemistry*
chemical_list: D004396:Coloring Agents; D014320:Triphenylmethyl Compounds; C046945:triphenylmethane