Synthesis, structure, and large optical limiting effect of the first coordination polymeric cluster based on an {I@[AgI(inh)]6} hexagram block.

In this paper, treatment of N-(isonicotinoyl)-N'-nicotinoylhydrazine (inh) and AgI with excess KI afforded a unique coordination polymeric cluster {[AgI(inh)]6(KI)}n (1) with the hexagram cluster units centered by mu6-I. In the polymer these hexagram units are parallel to the ab plane and are linked by separated K+ centers through inh. Polymer 1 represents the first example of coinstantaneous cation-anion-induced supramolecular self-assembly with nanoscale inner cavities. The polymer's third-order nonlinear optical (NLO) properties were determined by the Z-scan technique in DMF solution. The results show that the polymer has strong third-order optical nonlinearities. The nonlinear absorptive index a2 and refractive index n2 are calculated to be 1.044 x 10(-9) mW(-1) and 2.827 x 10(-11) esu, respectively. The values are comparable to those of the reported cluster polymers. The optical limiting experiments show that the present cluster exhibits a large optical limiting capacity. The value of the limiting threshold was measured as 0.53 J cm(-2) from the optical limiting experimental data. This value is three times better than 1.6 J cm(-2) of C60. This paper also gives a summary and comparison on the optical limiting properties of oligomeric and polymeric clusters.