A novel coordination polymer [Co(NCS)2(bpms)2]n (bpms=1,2-bis(4-pyridylmethyl)disulfenyl): synthesis, crystal structure and third-order nonlinear optical properties

A new 4,4′-bipyridyl-based ‘building block’, 1,2-bis(4-pyridylmethyl)disulfenyl (bpms) was synthesized. Treatment of the ‘building block’ with Co(NO3)2 and KSCN afforded a new type of one-dimensional (1-D) double zigzag chain coordination polymer [Co(NCS)2(bpms)2]n. Each Co ion is symmetrically bridged by four bpms ligands and also coordinates with two NCS− anions. The [Co(NCS)2(bpms)2]n can be regarded as a layered structure in the solid state. The 1-D parallel chains are stacked ABAB with a rotation of 90° between A and B. [Co(NCS)2(bpms)2]n in DMF solution also shows very strong third-order nonlinear optical (NLO) properties, its third-order susceptibility χ(3) is 1.07×10−11 esu in a 2.8×10−3 g cm−3 DMF solution. The data are comparable to those of C60, phthalocyanine derivations and inorganic clusters. To our knowledge, this is the first reported coordination polymer showing strong third-order NLO properties.