Optical limiting of pentaazadentate metal complexes for ps pulses in solution

Experimental results of optical limiting of five pentaazadentate metal complexes for ps pulses was reported, the mechanism was reverse saturable absorption. The samples do not be damaged when high energy laser (2.6 J/cm2) was used. The results show that the limiting thresholds of complexes [(APPC-COOH)Cd]Cl(I) and [APPC-np)Cd]Cl (II) at T/To=0.5 are 44.1 mJ/cm2 and 146 mJ/cm2 respectively. The lowest nonlinear transmittance of complex I is 9%. Electron withdrawing groups can enhance the limiting effect for this kind of complexes, but the effect of heavy atom acts opposite role.