Two novel two-dimensional double-sheet layered manganese(ii) coordination polymers: synthesis, crystal structures and third-order nonlinear optical properties

Two novel Mn(II) coordination polymers [Mn(N3)2(bbp)2]n1 and {[Mn(NCS)2(bbp)2]·0.25H2O}n2 (bbp = 4,4′-trimethylenedipyridine) with 2D double-sheet layered structures were obtained by a normal synthesis method at room temperature. Interestingly, each layer contains two sheets; the double-sheet layer is formed around an octahedral coordination center, Mn(II), with bbp ligands knitted into each other. The structures both contain channels with dimensions of about 6.5 × 6.5 Å for 1 and 6.7 × 6.0 Å for 2. Both compounds have a similar construction, giving the same third-order nonlinear optical (NLO) behavior and weak antiferromagnetic properties. Their third-order NLO refractive indexes n2 are 1.21 × 10−18 m2 W−1 for 1 and 6.71 × 10−19 m2 W−1 for 2. The NLO susceptibilities χ(3) were calculated to be 4.78 × 10−12 esu and 2.40 × 10−12 esu, respectively.