A new bidentate "building block", N,N'-bis(3-pyridylformyl)piperazine (bpfp), was synthesized. X-ray diffraction studies reveal that the piperazine ring in bpfp forms a chairlike structure conformation. bpfp self-assembled into two-dimensional layered rhombohedral grid polymers {[Mn(H2O)(2)-(SO4)(bpfp)](H2O)(3)(CH3OH)}(n) (1) and I[Zn(NCS)(2)(bpfp)(2)].2H(2)O}(n) (2) with Mn(II) and Zn(II), a three-dimensional polymer [Cd(N-3)(2)(bpfp)](n) (3) with Cd(II), and a one-dimensional zigzag polymer [HgI2(bpfp)](n) (4) with Hg(II). Each rhombohedral grid in polymer 1 is composed of four Mn, two bpfp, and two SO42-; the dimensions of the grid are 6.537 x 12.843 Angstrom. In polymer 2, each rhombohedral grid consists of 60-membered rings Zn-4(bpfp)(4) showing the dimensions of 14.231 x 15.586 Angstrom. Zn-4(bpfp)(4) grids are bridged by Zn ions and all pyridyl-N atoms of bpfp ligands into the 2-D network structure along a and c directions. Polymer 3 exhibits a 3-D layered structure with tetragonal prism channel viewing from a direction. The bpfp ligands occupy the four edges of tetragonal prism channel, which is cut off by layers consisting of rhombohedral grids Cd-4(N-3)(4). Polymer 4 is quite different from polymers 1-3; it exhibits a 1-D zigzag framework extending along the c axis. Polymers 1-3 possess a very strong NLO absorption and self-focusing effect. Their third-order NLO absorptive coefficients 0.2 are 9.2 x 10(-9), 6.9 x 10(-9), and 7.1 x 10(-9) m W-1. The third-order NLO hyperpolarizabilities gamma are 1.79 x 10(-28), 9.10 X 10(-29), and 9.66 x 10(-29) esu, respectively. The gamma values are comparable to those of the best NLO materials and coordination polymers. We found that the valence shell structures of central metal ions can influence the NLO properties of coordination polymers.