Nonlinear absorption properties of 'axial-bonding' type tin(IV) tetratolylporphyrin based hybrid porphyrin arrays

The nonlinear absorption properties of 'axial-bonding' type hybrid porphyrin arrays based on a tin(IV) tetratolylporphyrin (SnTTP) scaffold are studied with picosecond and nanosecond pulses. The effect of different central metal atoms substituted adjacent to the tin(IV) porphyrin in the oligomer structure is discussed. In the picosecond regime the lifetimes of the excited singlet states and two-photon absorption (TPA) processes dominate leading to interesting switching of nonlinear absorption behaviour. The TPA cross-section (σTPA) is found to be as high as 396 × 10-46 cm4 s photon-1 molecule-1, for an oligomer with Sn and Ni porphyrin macrocycles. However, in the nanosecond regime the optical limiting performance has increased considerably with increasing number of porphyrins in the array and excited state absorption is found to play a major role