Figure-6: TD-DFT calculated UV-Vis spectra of D1, D1A, D2, D2A, D3 and D3A (a) in Methanol and (b) in Water by using SCC-DFTB
In
order to get the understanding of the behavior of dyes in different
solvents of varied polarity, the absorption spectrum of all dye were
studied in methanol and water using TD-DFT at SCC-DFTB level of theory
by utilizing parameters set org/tiorg-0-1 and solute factor of 2.7. The
UV-Vis spectra calculated for all the dyes in methanol and water
solvents is given in figure 6. The analysis exhibited a red shift in
spectral peaks as the polarity of solvent is increased which depends
upon properties of solvents and hydrogen bonding between solvent-solute
and solute-solute molecules [42,
79, 80]. The amount of solvent has also
affected the oscillator strength in addition to excitation energy of the
photoactive species.