The ligand N,N'-bis(1,3,4-thiobiazolyl)-2,6-pyridyldicarboxamide (btapca) has been synthesized and its coordination properties toward La(III) and Ce(III) in the presence of air have been investigated. The complexes [Ln(8)(tbzcapc)(12)-(H2O)(24)].6DMF (Ln = La, 1, Ce, 2; tbzcapc = 6-[2-N-(1,3,4-thiabiazolyl)carboxamido]-2-pyridylcarboxylate) show octameric ellipsoid structures. We found the starting ligand btapca had been altered into tbzcapc during the formation process of [Ln(8)(tbzcapc)(12)(H2O)(24)].6DMF. The NLO properties of complexes 1 and 2 were investigated via Z-scan techniques. It is interesting that the two isostructural complexes show completely different NLO properties. Complex 1 shows NLO refractive effects without absorption, while complex 2 possesses NLO absorptive behavior without refraction.