Heterometallic polymeric clusters containing tetraselenotungstate anion:: One-dimensional helical chain {[La(Me2SO)8][μ-WSe4)3Ag3]}n and cyanide-bridged three-dimensional cross-framework {[Et4N]2[(μ4-WSe4)Cu4(CN)4]}n

[PPh4](2)[WSe4] reacts with an equivalent of [Ag(MeCN)(4)][ClO4] in DMF to afford a linear polymeric cluster {[Ph4P][(mu-WSe4)Ag]}(n) (1). Treatment of cluster 1 with excess La(NO3)(3). 3H(2)O in Me2SO solution resulted in the formation of a helical chain polymeric cluster {[La(Me2SO)(8)][(mu-WSe4)(3)Ag-3]}(n) (2) Cluster 2 crystallizes in the monoclinic space group P2(1)/n with four formula units in a cell of dimensions a = 12.7642(5) Angstrom, b = 24.1725(9) Angstrom, c = 19.4012(7) Angstrom and beta = 103.546(11)degrees. Refinement by full-matrix least-squares techniques gave final residuals R = 0.0540 and R-w = 0.1116 for 494 variables and 7593 reflections (F-o(2) > 2.0 sigma(F-o(2))). The anion {[(mu-WSe4)(3)Ag-3]}(n)(3n-) in 2 can be described as a butterfly-type SeWSe3Ag2 basic repeating unit linked through interactions with a Ag atom of one fragment and a Ag atom of another to form an intriguing helical array. The CuCN, KCN, and [Et4N](2)[WSe4] reaction system resulted in the formation of a novel three-dimensional cluster {[Et4N](2)[(mu(4)-WSe4)Cu-4(CN)(4)]}(n) (4) either in DMF/2-picoline or in solid at 80 degrees C. Cluster 4 crystallizes in the orthorhombic space group Fddd with cell constants a = 11.090(2) Angstrom, b = 23.206(5) Angstrom, c = 23.910(5) Angstrom, and Z = 8. Anisotropic refinement with 1510 reflections (F-o(2) > 2.0 sigma(F-o(2))) and 82 parameters for all non-hydrogen atoms yielded the values of R = 0.0428 and R-w = 0.0887. The anion structure of 4 is built up from a WSe4Cu4 unit bridged by cyanide ligands to form a three-dimensional cross framework. The air- and moisture-stable polymeric clusters easily decompose into small molecular clusters when treated with ligands such as PPh3 and pyridine (Py). Cluster 2 exhibits both strong optical absorption and an optical self-focusing effect (effective alpha(2) = 2.2 x 10(-9) m.W-1, n(2) = 6.8 x 10(-15) m(2).W-1; examined in a 0.13 mM DMF solution). Cluster 4 shows good photostability in the process of measurement and a large optical limiting effect (the limiting threshold is ca. 0.2 J.cm(-2)).