Ultrafast
Solvation Dynamics and Vibrational Coherences
of Halogenated Boron-Dipyrromethene Derivatives Revealed through Two-Dimensional
Electronic Spectroscopy
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Abstract
Boron-dipyrromethene (BODIPY) chromophores
have a wide range of
applications, spanning areas from biological imaging to solar energy
conversion. Understanding the ultrafast dynamics of electronically
excited BODIPY chromophores could lead to further advances in these
areas. In this work, we characterize and compare the ultrafast dynamics
of halogenated BODIPY chromophores through applying two-dimensional
electronic spectroscopy (2DES). Through our studies, we demonstrate
a new data analysis procedure for extracting the dynamic Stokes shift
from 2DES spectra revealing an ultrafast solvent relaxation. In addition,
we extract the frequency of the vibrational modes that are strongly
coupled to the electronic excitation, and compare the results of structurally
different BODIPY chromophores. We interpret our results with the aid
of DFT calculations, finding that structural modifications lead to
changes in the frequency, identity, and magnitude of Franck–Condon
active vibrational modes. We attribute these changes to differences
in the electron density of the electronic states of the structurally
different BODIPY chromophores