Double helix chain frameworks constructed from bis-benzotriazole building blocks: Syntheses, crystal structures and third-order nonlinear optical properties

Reactions of 1,1'-(1,3-propylene)bis-1H-benzotriazole (pbbt) and KSCN with Ni(II) or Co(II) salt lead to the formation of two new double helix chain coordination polymers {[Ni(pbbt)(2)(NCS)(2)]center dot H2O}(n) 1 and {[Co(pbbt)(2)(NCS)(2)]center dot H2O}(n) 2. Their third-order nonlinear optical (NLO) properties were determined with a 7 ns pulsed laser at 532 nm. The results show that polymer 2 exhibits large NLO absorptive effects (alpha(2) = 1.4 x 10(-9) mW(-1)),and both of them show strong NLO refractive behaviors with the refractive index n(2) of 3.02 x 10(-18) m(2) W-1 for 1 and 8.23 x 10(-18) m(2)W(-1) for 2. The hyperpolarizability |gamma| values of 1 and 2 were calculated to be 1.68 x 10(-29) esu and 4.58 x 10(-29) esu, respectively. This indicates that the third-order NLO properties of coordination polymers can be altered through metal ions manipulation. (C) 2008 Published by Elsevier B.V.