Two cobalt(II) one-dimensional ribbon of rings polymers: Syntheses, structures and non-linear optical properties

Two cobalt(II) coordination polymers {[Co(SCN)2(3-bpit)2] · 2CH3OH}n (1) (3-bpit = N,N′-bis(3-pyridylformyl)imidazolidine-2-thione) and {[Co(SCN)2(4-bpit)2] · CH3OH · CH3CN}n (2) (4-bpit = N,N′-bis(4-pyridylformyl)imidazolidine-2-thione) have been synthesized for study of the third-order non-linear properties. X-ray crystal structural analyses reveal that the two polymers show the same topological motif: a ribbon of rings. Their third-order non-linear optical (NLO) properties in DMF solution have been studied by Z-scan techniques with a linearly polarized laser light (λ = 532 nm; pulse widths = 7 ns). Both of them exhibit strong self-focusing effect. The third-order NLO susceptibility χ(3) values are calculated to be 2.61 × 10−11 esu (1) and 2.76 × 10−11 esu (2), respectively. The values are comparable to those of the reported good NLO materials.