Reactions of 1,1′-(1,4-butanediyl)bis-1H-benzimidazole (bbbm) with Cd(II), Ni(II), or Co(II) afford three organic–metal polymers: {[Cd(bbbm)(SO 4 )(H 2 O) 2 ]CH 3 OH} n (1), {[Ni(bbbm) 2 (H 2 O) 2 ](NO 3 ) 2 ·2CH 3 OH·6H 2 O} n (2) and {[Co(bbbm) 2 (H 2 O) 2 ](NO 3 ) 2 ·2CH 3 OH·6H 2 O} n (3). In 1, bbbm and SO42- coordinate to Cd(II) simultaneously leading to a 3-D structure. In 2 and 3, each bridging bbbm ligand links two Ni(II) or Co(II) ions forming the 2-D layered structure with (4, 4) grid units. Each (4, 4) grid unit is a 44-membered ring and constructed by four bbbm ligands acting as four sides and four Ni(II) or Co(II) ions representing four corners. Their third-order nonlinear optical (NLO) properties in DMF solution have been studied by Z-scan technique. The results show that the DMF solution of 2 possesses both the large third-order NLO absorptive and strong refractive behaviors; and 3’s shows large NLO absorptive effect and weak NLO refractive behavior. A reasonably good fit between the experimental data and the theoretical curve suggests that the experimentally obtained NLO effects are effective third-order in nature.