Ultrafast Excited State Relaxation Dynamics of New Fuchsine- a Triphenylmethane Derivative Dye |
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Authors: | Chinmoy Biswas Prof. Venugopal Rao Soma Dr. Prabhakar Chetti Dr. Sai Santosh Kumar Raavi |
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Affiliation: | 1. Ultrafast Photophysics and Photonics Laboratory, Department of Physics, Indian Institute of Technology Hyderabad, Kandi 502285 Telangana, India;2. Advanced Centre of Research in High Energy Materials (ACRHEM), University of Hyderabad, Hyderabad 500046 Telangana, India;3. Department of Chemistry, National Institute of Technology, Kurukshetra 136119 Haryana, India |
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Abstract: | An all-inclusive investigation of the ultrafast excited state relaxation dynamics of a triphenylmethane derivative molecule, New Fuchsine (NF), using a combined approach of density functional theory (DFT), femtosecond transient absorption spectroscopy (fs-TAS), and photoluminescence spectroscopy is presented in this work. The DFT calculations confirmed the formation of twisted molecular structure in the excited state of NF in ethanol solution with bond rotation of ≈86°. TAS measurements of NF solution exhibited ultrafast ground state-recovery pathway via a conical intersection confirming an ultrafast structural reorientation. On the contrary, TAS measurements of NF thin-film exhibited a longer excited-state lifetime suggesting a hindered molecular twisted state formed as an intermediate step. Photophysical kinetic models are proposed to globally fit the fs-TAS data establishing the twisted intramolecular charge transfer (TICT) state mediated ground state recovery for NF in solution and thin film, respectively. Temperature-dependent photoluminescence study of NF film provided a clear insight into the effect of rotational motion of phenyl rings in NF molecules over the TICT mediated emission. |
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Keywords: | triphenylmethane femtosecond transient absorption spectroscopy photoluminescence low-temperature photoluminescence anisotropy |
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