Photophysics of Fe(III)–sulfosalicylic acid complexes in aqueous solutions

Femtosecond pump-probe spectroscopy (λpump = 420 nm) was used to determine the photophysical processes of Fe(III) complexes with 5-sulfosalicylic acid (Fe(SSA)n, n = 2, 3) in aqueous solutions. The excitation of the Fe(SSA)n complexes in the charge transfer bands is followed by an ultrafast relaxation to the ground electronic state with two characteristic times. The shorter time constant is ascribed to internal conversion to the vibrationally hot electronic ground state of Fe(SSA)n and the second time constant is assigned to the vibrational cooling of the ground state.