Third-order nonlinear optical properties of three Mn(II)-4,4′-bpy coordination polymers and crystal structure of three-dimensional network [Mn(SO4)(4,4′-bpy)(H2O)2]n

We determined the third-order nonlinear optical (NLO) properties of coordination polymers [Mn(SO4)(4,4′-bpy)(H2O)2]n (1), and [Mn(N3)2(4,4′-bpy)]n (2) and [{Mn(NCS)2(4,4′-bpy)(H2O)2}(4,4′-bpy)]n (3) by Z-scan technique. Polymers 1 and 2 show strong self-defocusing effects. Their third-order NLO susceptibility χ(3) are 5.0×10−12 esu in a 4×10−4 g cm−3 DMF solution for 1 and 1.2×10−11 esu in a 1.6×10−3 g cm−3 DMF solution for 2, respectively. These data are comparable to those of cluster polymers. Polymer 3 exhibits weaker self-defocusing behavior than polymer 1 and 2. The crystal structure of polymer 1 shows that the compound exhibits three-dimensional (3-D) layered structure. Every layer is formed in the ac plane by connecting Mn centers via bridging bpy ligands to generate parallel MnbpyMn chains, whereas between adjacent layers the MnbpyMn chains have an angle of 45°. MnbpyMn chains in different layers are joined by zigzag MnSO42−MnSO42 chains leading to the 3-D framework.