Time-dependent density functional theory (TDDFT) calculations have been used to understand the excited-state properties of modified chlorophyll (Chlide f), Chlide a, Chlide b, and axial ligated (with irnidazole, H2O, CH3OH, CH3COOH, C6H5OH) Chlide f molecules. The computed differences among the Q(x), B-x, and B-y band absorbance wavelengths of Chlide a, b, and f molecules are found to be comparable with the experimentally observed shifts for these bands in chlorophyll a (chl a), chl b, and chl f molecules. Our computations provide evidence that the red shift in the Q(y), band of chl f is due to the extended delocalization of macrocycle chlorin ring because of the presence of the -CHO group. The local contribution from the -CHO substituent to the macrocycle chlorin ring stabilizes the corresponding molecular orbitals (lowest unoccupied molecular orbital (LUMO) of the Chlide f and LUMO-1 of the Chlide b). All the absorption bands of Chlidef shift to higher wavelengths on the addition of axial ligands. Computed redox potentials show that, among the axial ligated Chlidef molecules, Chlide f- imidazole acts as a good electron donor and Chlidef CH3COOH acts as a good electron acceptor.