Pentaazadentate metal complexes are a macrocyclic ligand containing 22 $pi@-electrons, which coordinate with numerous metal ions to form near coplanar configurations with excellent thermal and light stabilities. A more extended optical window between Soret (420 nm) and Q (760 nm) band in visible region provides a condition for requiring high transmittances at low incident light intensity and they are of also large third- order nonlinear optical susceptibilities comparing with porphyrin's and phthalocyanine's metal complexes. The third- order optical susceptibilities $chi$+(3)$/$-1111$/ are determined at 647 nm in methanol by pump-probed procedure and the molecular second hyperpolarizabilities $gamma$-1111$/ which are of approximately 10$+$MIN@31$/ esu are also obtained. Optical limiting based on reverse saturable absorption are observed for ns pulses laser. The optical limiting behaviors may be alternated by introduce different substituents onto the benzene ring or/and different metal ion into the center of macrocylic ligands The limiting threshold at T/T$-0$/ equals 0.5 is 131 mJ/cm$+2$/ for complex $LB@(PL-NO$-2$/)Cd$RB@Cl, the corresponding clamped energy is 34 mJ/cm$+2$/. The optical limiting performance may be influenced by solution concentrations.
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