We present results of the nonlinear refractive index and nonlinear absorption coefficient [Fe-III(3-pyha)(3)] and [Fe-III(4-pyha)(3)] water solutions, using Z-scan technique with a low power continuous wave laser at 633 nm. No qualitative differences were observed in absorption and refractive index nonlinear processes for both samples. We propose that the nonlinear absorption involves two photon absorption. The two photon absorption cross sections for both samples at 633 nm were calculated. Pump and probe technique was used to record triplet state absorption spectrum. The band gap of the triplet state was estimated from the spectrum. The use of these complexes in photo-dynamic therapy is discussed. (C) 2012 Elsevier B.V. All rights reserved.